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1
O'Brien, Allyson L., Liz Morris, and Michael J. Keough. "Multiple sources of nutrients add to the complexities of predicting marine benthic community responses to enrichment." Marine and Freshwater Research 61, no. 12 (2010): 1388. http://dx.doi.org/10.1071/mf10085.
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Understanding biological responses to nutrient enrichment under different environmental conditions is integral for the effective management of eutrophication in coastal environments. However, current conceptual models of nutrient enrichment are limited as they are based on studies that only consider a single source of nutrients, when in reality it is more likely that enrichment is a result of multiple sources. Here, we test the hypothesis that biological responses to nutrient enrichment in intertidal mudflat assemblages depend on the source by comparing enrichment from a controlled release fertilizer with that from decomposing macroalgae. Sediment at two sites in Port Phillip Bay, Victoria, were dosed with the different nutrient sources and monitored through time. After six weeks, the macroalgae-enriched plots had significantly higher abundances and biomass of some taxa of deposit-feeding polychaetes. In the fertilizer-enriched plots, the porewater nutrients increased but there was no detectable change in abundances or biomass of infauna, suggesting that the nutrients did not assimilate into the foodweb. The rate of assimilation of anthropogenic nutrients potentially occurs over longer time scales compared with the rapid assimilation and biological responses to decomposing macroalgae. Responses to the different nutrient sources provide new insights into the complexity of nutrient enrichment models that are applied to the management of aquatic ecosystems worldwide.
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Wyatt, Kevin H., Jill S. Bange, Andrea S. Fitzgibbon, Melody J. Bernot, and Allison R. Rober. "Nutrients and temperature interact to regulate algae and heterotrophic bacteria in an Alaskan poor fen peatland." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 3 (March 2015): 447–53. http://dx.doi.org/10.1139/cjfas-2014-0425.
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Permafrost thaw associated with warmer temperatures is expected to elevate nutrient levels in northern aquatic ecosystems, including peatlands. To evaluate these effects on algae and heterotrophic bacteria, we manipulated nutrients (nitrogen (N) and phosphorus (P)) and temperature (ambient and warmed) in a factorial design using nutrient diffusing substrates inside warming chambers in an Alaskan peatland. After 16 days, there was no effect of warming on the abundance of algae or heterotrophic bacteria in the absence of nutrient enrichment. Algal production and bacterial biomass were substantially elevated by N with and without P (NP and N, respectively), independent of warming. Warming significantly enhanced the effect of nutrient enrichment on the abundance of algae and heterotrophic bacteria compared with ambient temperatures. Rates of N fixation increased with the presence of heterocyst-forming cyanobacteria, which represented a greater proportion of algal taxonomic composition in the absence of N enrichment in both ambient and warmed conditions. Our results indicate that warmer temperatures and nutrient enrichment will elevate algal and heterotrophic metabolism in northern peatlands, and the magnitude of increase will depend on the combination of nutrients available during periods of inundation.
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Chrzanowski, T. H., R. W. Sterner, and J. J. Elser. "Nutrient enrichment and nutrient regeneration stimulate bacterioplankton growth." Microbial Ecology 29, no. 3 (May 1995): 221–30. http://dx.doi.org/10.1007/bf00164886.
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Pringle, Catherine M. "Effects of Water and Substratum Nutrient Supplies on Lotic Periphyton Growth: An Integrated Bioassay." Canadian Journal of Fisheries and Aquatic Sciences 44, no. 3 (March 1, 1987): 619–29. http://dx.doi.org/10.1139/f87-075.
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Effects of substratum and water nutrient perturbations on periphyton growth were assessed in a nutrient-poor stream by combining a substratum enrichment technique with a flow-through bioassay system. Periphyton growth (chlorophyll a, total biovolume) responded to combined influences of water and substratum enrichment in an additive manner when both compartments were amended with N and P to yield an optimal ratio [Formula: see text]. When NO3-N was added to the substratum and PO4-P to the water, algal growth response was synergistic. Analysis of the vertical distribution of P fractions in cores taken from nutrient-diffusing substrata indicates that attached microorganisms mediate P release from underlying substrata, acting as a filter or temporary sink. Nutrient-diffusing substrata are useful detectors of limiting nutrients in aquatic systems; however, their function and application differ from water enrichment assays where nutrients are added at a constant rate. Differences are partially attributed to spatial and temporal variability of nutrient release and the strictly localized influence of substratum flora on ambient water chemistry.
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Corstanje, R., and K. R. Reddy. "Microbial Indicators of Nutrient Enrichment." Soil Science Society of America Journal 70, no. 5 (September 2006): 1652–61. http://dx.doi.org/10.2136/sssaj2004.0070.
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Kennish, Michael J., and Alan R. Townsend. "Nutrient Enrichment and Estuarine Eutrophication1." Ecological Applications 17, sp5 (July 2007): S1—S2. http://dx.doi.org/10.1890/06-1623.1.
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Meador, Michael R. "Nutrient Enrichment and Fish Nutrient Tolerance: Assessing Biologically Relevant Nutrient Criteria1." JAWRA Journal of the American Water Resources Association 49, no. 2 (December 26, 2012): 253–63. http://dx.doi.org/10.1111/jawr.12015.
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Ning, Z., K. Yu, Y. Wang, F. Wei, Z. Liao, B. Yang, C. Fang, R. Xia, X. Huang, and G. Song. "Effects of nutrient enrichment and skewed N:P ratios on physiology of scleractinian corals from Weizhou Island in the northern South China Sea." Marine Ecology Progress Series 682 (January 20, 2022): 111–22. http://dx.doi.org/10.3354/meps13933.
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The availability of nitrogen (N) and phosphorus (P) is crucial for maintaining coral-dinoflagellate symbiosis, whereas excess nutrients and skewed N:P ratios are often associated with coral reef decline. It is thus essential to understand the general patterns of species-specific as well as dose-dependent responses of corals to elevated nutrient concentrations and skewed N:P ratios. Here, we found that the impacts of nutrient enrichment on the corals Acropora millepora and Platygyra crosslandi from Weizhou Island, South China Sea, were highly dependent on nutrient dose, N:P ratios, and coral species. Moderate nutrient enrichment (N: 19-140 µmol l-1 and P: 0.5-1.5 µmol l-1) did not lead to bleaching of either coral species, but their metabolic processes (calcification, nutrient uptake, and dinitrogen fixation) were affected. More depleted δ13C and lower dinitrogen fixation rates of A. millepora than of P. crosslandi indicated that A. millepora was more vulnerable to the disturbance of nutrient enrichment. However, N:P ratios (±SD) as high as 106 ± 10 decreased the photosynthetic efficiency and nutrient uptake rates of P. crosslandi, indicating that this species may be vulnerable to high N:P ratios, although it was one of the dominant coral assemblages at Weizhou Island. The results provide an important basis for understanding coral reef degradation triggered by nutrients and a suggestion that coastal management should focus not only on the concentrations but also on the ratios of nutrients.
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Sarri, Jurmin H., Yusop A. Abdulmutalib, Melapearl E. Mohammad Tilka, Ertuğrul Terzi, and Albaris B. Tahiluddin. "Effects of inorganic nutrient enrichment on the carrageenan yield, growth, and ice-ice disease occurrence of red alga Kappaphycus striatus." Aquatic Research 5, no. 2 (2022): 99–109. http://dx.doi.org/10.3153/ar22009.
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One of the problems in Kappaphycus farming is the slow growth in some farms due to nutrient insufficiency caused by overstocking. In the southern Philippines, most seaweed farmers practice inorganic nutrient enrichment of Kappaphycus to boost growth and decrease ice-ice disease occurrence using ammonium phosphate at an average concentration of 8.82 g L-1. In this study, experiments with Kappaphycus striatus enriched with inorganic nutrients were carried out at Pasiagan, Bongao, Tawi-Tawi, southern Philippines, using different inorganic nutrients (T1=8.82 g L-1 of urea, T2=8.82 g L-1 of phosphorus, and T3=control) within 45 days. Seaweeds were enriched in these three inorganic solutions for 30 seconds, placed into a large mat, covered with canvas, and left overnight. After 15 days, findings showed that the specific growth rates of T1 (6.99% day-1) and T3 (6.72% day-1) groups were significantly higher than the T2 (5.84% day-1) group (p<0.05). Inorganic nutrient enrichment did not significantly influence the occurrence of ice-ice disease. Moreover, inorganic nutrient enrichment did not affect the carrageenan yield after 45 days. K. striatus nutrient-enriched with urea could increase growth at day 15, but no effect on the occurrence of ice-ice disease and carrageenan yield. Hence, inorganic nutrient enrichment using urea provides a positive effect to farmed K. striatus by enhancing its growth without affecting its health and carrageenan yield.
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Mills, Anthony J., and Clélia Sirami. "Nutrient enrichment of ecosystems by fungus-growing versus non-fungus-growing termites." Journal of Tropical Ecology 34, no. 6 (October 31, 2018): 385–89. http://dx.doi.org/10.1017/s0266467418000330.
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Abstract:Fungus-growing termites (Macrotermitinae) collect water to air-condition their fungi and have been recorded tunnelling deeper than 80 m for groundwater. This collection of water ultimately results in solute accumulation and nutrient enrichment of their termitaria. We consequently hypothesized that nutrient enrichment of termitaria constructed by fungus-growing termites would be greater than by non-fungus-growing termites. To test this, we compared nutrient enrichment of termitaria of fungus-growingMacrotermesspp. in Namibia and termitaria of two non-fungus-growing termites –Trinervitermes trinervoidesin South Africa andNasutitermes triodiaein Australia. Compared with adjacent topsoils,Macrotermestermitaria were significantly enriched in 18 elements whereasT. trinervoidesandN. triodiaetermitaria were enriched in only one and five elements, respectively. Nutrients particularly enriched inMacrotermitestermitaria included Ca (an enrichment factor of 12), Mg (2.9), Co (2.8), Fe (2.4), Mn (2.3), Se (2.2) and Cu (2.0). We suggest that fungus-growing termites that collect water for air-conditioning their fungi have the potential to inadvertently boost – to a far greater degree than non-fungus-growing termites – the availability of nutrients to local plants and herbivores.
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Cortelezzi, Agustina, Carolina Ocón, María V. López van Oosterom, Rosana Cepeda, and Alberto Rodrigues Capítulo. "Nutrient enrichment effect on macroinvertebrates in a lowland stream of Argentina." Iheringia. Série Zoologia 105, no. 2 (June 2015): 228–34. http://dx.doi.org/10.1590/1678-476620151052228234.
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ABSTRACT One of the most important effects derived from the intensive land use is the increase of nutrient concentration in the aquatic systems due to superficial drainage. Besides, the increment of precipitations in South America connected to the global climate change could intensify these anthropic impacts due to the changes in the runoff pattern and a greater discharge of water in the streams and rivers. The pampean streams are singular environments with high natural nutrient concentrations which could be increased even more if the predictions of global climate change for the area are met. In this context, the effect of experimental nutrient addition on macroinvertebrates in a lowland stream is studied. Samplings were carried out from March 2007 to February 2009 in two reaches (fertilized and unfertilized), upstream and downstream from the input of nutrients. The addition of nutrients caused an increase in the phosphorus concentration in the fertilized reach which was not observed for nitrogen concentration. From all macroinvertebrates studied only two taxa had significant differences in their abundance after fertilization: Corbicula fluminea and Ostracoda. Our results reveal that the disturbance caused by the increase of nutrients on the benthic community depends on basal nutrients concentration. The weak response of macroinvertebrates to fertilization in the pampean streams could be due to their tolerance to high concentrations of nutrients in relation to their evolutionary history in streams naturally enriched with nutrients. Further research concerning the thresholds of nutrients affecting macroinvertebrates and about the adaptive advantages of taxa in naturally eutrophic environments is still needed. This information will allow for a better understanding of the processes of nutrient cycling and for the construction of restoration measures in natural eutrophic ecosystems.
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Järvinen, Marko, and Kalevi Salonen. "Influence of changing food web structure on nutrient limitation of phytoplankton in a highly humic lake." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 12 (December 1, 1998): 2562–71. http://dx.doi.org/10.1139/f98-137.
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We determined the potential nutrient limitation of summer phytoplankton production using 2 × 2 × 2 factorial design of enrichment bioassays both before and after the introduction of planktivorous whitefish (Coregonus lavaretus) in a polyhumic lake with an abundant population of the large cladoceran Daphnia longispina. After the fish introduction, Daphnia disappeared and was substituted by the rotifer Keratella cochlearis. During the dominance of Daphnia, additions of nutrients had little or no effect on primary production of phytoplankton in short-term (1-day) incubations. However, 5-day incubations suggested that P most likely was the limiting nutrient. After the fish introduction, both 1- and 5-day enrichment bioassays indicated potential N limitation of phytoplankton production. The strong response of phytoplankton production to combined enrichments with P and N also suggested colimitation by P and N, but this was probably forced by the relatively high additions of nutrients. Consistently low primary production after the combined addition of P and glucose suggests that in the presence of a labile organic C source, epilimnetic bacteria were superior to algae in the uptake of P. Our results suggest that changes in the food web structure may determine the limiting nutrient also in a highly humic lake.
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Wei, Lili, Shuh-Ji Kao, and Chaoxiang Liu. "Mangrove species maintains constant nutrient resorption efficiency under eutrophic conditions." Journal of Tropical Ecology 36, no. 1 (December 23, 2019): 36–38. http://dx.doi.org/10.1017/s0266467419000336.
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AbstractMangrove species have developed nutrient conservation mechanisms to adapt to oligotrophic intertidal environments. However, nutrient enrichment occurs worldwide, particularly in estuarine and coastal regions. Mangrove species may change their adaptive strategies if nutrient availability increases substantially. To understand how nutrient resorption (a major nutrient conservation strategy) responds to nutrient enrichment, a common mangrove species in China, Aegiceras corniculatum (black mangrove), was selected, and saplings were cultivated in nutrient-enriched soils. After one year, neither N nor P resorption efficiency showed significant variations with nutrient availability and there was no difference between N and P resorption efficiency. Overall, nutrient resorption efficiency of A. corniculatum remained at ∼40%, lower than the global average levels of evergreen plants (∼50%), indicating incomplete resorption of nutrients. Incomplete resorption was also evidenced by the nutrient concentrations, resorption proficiency and N: P ratio of plant leaves. Collectively, these results indicate that black mangrove can maintain constant nutrient resorption efficiency under eutrophic conditions.
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Greenwood, Jennifer L., and Amy D. Rosemond. "Periphyton response to long-term nutrient enrichment in a shaded headwater stream." Canadian Journal of Fisheries and Aquatic Sciences 62, no. 9 (September 1, 2005): 2033–45. http://dx.doi.org/10.1139/f05-117.
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We maintained elevated but moderate concentrations of nitrogen and phosphorus continuously for 2 years in a heavily shaded headwater stream and compared effects on stream periphyton with a reference stream. Both streams were sampled for 1 year before treatment. Some measures of periphyton biomass (ash-free dry mass and chlorophyll a) responded positively to enrichment. Increased chlorophyll a was likely a result of higher chlorophyll per cell, as total algal biovolume did not change with enrichment. These differences were greatest during high-light months (November-May), when cellular growth rates (a proxy for production) were also highest with enrichment. Algal assemblages were dominated by diatoms and remained similar between the treatment and reference streams throughout the enrichment period. Although nutrients stimulated algal growth rates, the long-term effects of nutrient addition on periphyton biomass were small in magnitude compared with other published values and were potentially suppressed by light availability and invertebrate consumption. These and other factors may have also been important in limiting the algal species pool and thus a taxonomic response to enrichment. Our results indicate that in headwater streams with intact tree canopies, chronic nutrient enrichment at moderate concentrations may have little detectable effect on benthic algal composition or periphyton biomass. Although nutrients stimulated algal growth rates, the long-term effects of nutrient addition on periphyton biomass were small in magnitude compared with other published values and were potentially suppressed by light availability and invertebrate consumption. These and other factors may have also been important in limiting the algal species pool and thus a taxonomic response to enrichment. Our results indicate that in headwater streams with intact tree canopies, chronic nutrient enrichment at moderate concentrations may have little detectable effect on benthic algal composition or periphyton biomass.
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Elsdon, Travis S., and Karin E. Limburg. "Nutrients and their duration of enrichment influence periphyton cover and biomass in rural and urban streams." Marine and Freshwater Research 59, no. 6 (2008): 467. http://dx.doi.org/10.1071/mf07085.
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Although it is well known that land use affects nutrient dynamics and algal growth in streams, the responses to different durations of nutrient supply are poorly understood. The associations of benthic (periphyton-dominated) biomass with concentrations of dissolved nitrogen and phosphorus in rural and urban streams in New York were quantified. Biomass was significantly greater (2-fold) in the urban compared with the rural stream, which was associated with differences in dissolved nutrients. Experimental field enrichment of nutrient concentrations and duration of exposure altered benthic periphyton. Increasing nutrients by 60–99% of ambient concentrations increased periphyton percentage cover and biomass. Periphyton abundance also increased with increasing duration of exposure to nutrients (2, 4 and 8 weeks); however, short-term pulses of nutrients (2 weeks) had no significant effect in the rural stream. These results indicate that effective management of nutrient delivery, by reducing time periods of high nutrient load, will minimise impacts to benthic environments.
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Ezzat, Leïla, Jean-François Maguer, Renaud Grover, and Christine Ferrier-Pagès. "New insights into carbon acquisition and exchanges within the coral–dinoflagellate symbiosis under NH 4 + and NO 3 − supply." Proceedings of the Royal Society B: Biological Sciences 282, no. 1812 (August 7, 2015): 20150610. http://dx.doi.org/10.1098/rspb.2015.0610.
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Anthropogenic nutrient enrichment affects the biogeochemical cycles and nutrient stoichiometry of coastal ecosystems and is often associated with coral reef decline. However, the mechanisms by which dissolved inorganic nutrients, and especially nitrogen forms (ammonium versus nitrate) can disturb the association between corals and their symbiotic algae are subject to controversial debate. Here, we investigated the coral response to varying N : P ratios, with nitrate or ammonium as a nitrogen source. We showed significant differences in the carbon acquisition by the symbionts and its allocation within the symbiosis according to nutrient abundance, type and stoichiometry. In particular, under low phosphate concentration (0.05 µM), a 3 µM nitrate enrichment induced a significant decrease in carbon fixation rate and low values of carbon translocation, compared with control conditions (N : P = 0.5 : 0.05), while these processes were significantly enhanced when nitrate was replaced by ammonium. A combined enrichment in ammonium and phosphorus (N : P = 3 : 1) induced a shift in nutrient allocation to the symbionts, at the detriment of the host. Altogether, these results shed light into the effect of nutrient enrichment on reef corals. More broadly, they improve our understanding of the consequences of nutrient loading on reef ecosystems, which is urgently required to refine risk management strategies.
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Zhao, Lei, Hua Yong Zhang, Fang Zhao, and Wang Tian. "Effects of Nutrient Enrichment on a Realistic Food Web." Applied Mechanics and Materials 700 (December 2014): 711–14. http://dx.doi.org/10.4028/www.scientific.net/amm.700.711.
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Nutrients supplies play a crucial role in population distribution of food webs, and it is one of the most important challenges in both theoretical and applied ecology to better understand the ‘bottom-up’ effect. Here we analyzed a realistic food web containing one limiting nutrient and two producer-consumer interactions. Through the simulations of the mean population size and the variability of each species, we found that 1) in infertile environment the coexistence of species increases with nutrient supply; 2) the mean values of species abundance increase dramatically at then remain constant with the increase of nutrient supply; and 3) the stability of each population also increases and then remains constant. These results are inconsistent with the traditional predictions known as the ‘paradox of enrichment’, and our analysis may provide a solution to this paradox.
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Qin, Le-Zheng, Zhaxi Suonan, Seung Hyeon Kim, and Kun-Seop Lee. "Growth and reproductive responses of the seagrass Zostera marina to sediment nutrient enrichment." ICES Journal of Marine Science 78, no. 3 (February 21, 2021): 1160–73. http://dx.doi.org/10.1093/icesjms/fsab031.
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Abstract Nutrient loading into coastal sediments is increasing due to anthropogenic activity and climate change. We examined the effects of sediment nutrient enrichment on the growth and reproduction of Zostera marina by adding nitrogen (N) and phosphorus (P) fertilizers into sediments. Areal productivity and shoot density increased by ca. 60% in N and N + P enrichment plots and by ca. 20% in the P enrichment plots. Biomass and shoot height were also higher in the N and N + P enrichment plots than in the P enrichment and control plots. These results suggest that sediment N availability was more important than P availability in stimulating the vegetative growth of Z. marina . The density and morphology of reproductive shoots and seed production increased in only the N enrichment plots. The sediment N enrichment stimulated both the vegetative growth and sexual reproduction, improving the meadow resilience through both sexual and asexual mechanisms. The P enrichment slightly increased only the vegetative growth and might have limited influence on seagrass reproduction. According to these results, the alteration of the sediment nutrient regimes might shift the balance between the vegetative growth and sexual reproduction of Z. marina. These findings may have important implications for the management of seagrass meadows under fluctuations in sediment nutrients caused by anthropogenic activity and climate change.
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Teixeira, Leonardo Henrique, and José Luiz Attayde. "Synergistic effects between omnivorous filter-feeding fish and nutrient enrichment on algal biomass." Acta Limnologica Brasiliensia 27, no. 2 (June 2015): 223–27. http://dx.doi.org/10.1590/s2179-975x6913.
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Aim: The Nile tilapia - Oreochromis niloticus(Linnaeus 1758) - is an exotic omnivorous filter-feeding fish that has been stocked for three decades in man-made lakes of Northeastern Brazil. Most experiments manipulating omnivorous filter-feeding fish in eutrophic lakes and reservoirs shows that their presence tends to increase phytoplankton biomass and primary production. In this study, we tested the hypothesis that tilapia interact synergistically with nutrient enrichment so that the effects of omnivorous fish on phytoplankton biomass becomes more intense with increasing nutrient concentration.MethodsA field experiment with a 2×3 factorial design was performed during four weeks in twenty-four mesocosms (0.25 m3) to which six treatments were randomly allocated: fingerling addition (F), juvenile tilapia addition (J), nutrient addition (NP), nutrient and fingerling addition (NPF), nutrient and juvenile tilapia addition (NPJ) and a control treatment with no tilapia or nutrients addition (C). A two-way repeated measures ANOVA was done to test for time (t), tilapia and nutrients effects and their interaction on total phosphorus, total nitrogen and chlorophyll-a concentrations.ResultsThe results showed a positive effect of nutrient addition on total phosphorus, total nitrogen and chlorophyll-a concentrations and a positive effect of tilapia on the concentration of chlorophyll-a. As expected, we found a synergistic interaction between the positive effect of Nile tilapia and nutrient enrichment on phytoplankton biomass.ConclusionsThe above results suggest that controlling tilapia abundance through fisheries management is a potential tool to improve water quality and mitigate the effects of lake and reservoir eutrophication.
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Noori, Roohollah, Elmira Ansari, Yong-Wook Jeong, Saber Aradpour, Mohsen Maghrebi, Majid Hosseinzadeh, and Sayed M. Bateni. "Hyper-Nutrient Enrichment Status in the Sabalan Lake, Iran." Water 13, no. 20 (October 14, 2021): 2874. http://dx.doi.org/10.3390/w13202874.
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Lakes/reservoirs are rapidly deteriorating from cultural eutrophication due to anthropogenic factors. In this study, we aimed to (1) explore nutrient levels in the Sabalan dam reservoir (SDR) of northwest Iran, (2) determine the reservoir water fertility using the total phosphorus (TP) based and total nitrogen (TN) based Carlson trophic state indices, and (3) specify primary limiting factors for the reservoir eutrophication. Our field observations showed a state of hyper-nutrient enrichment in the SDR. The highest variation of TN in the reservoir water column happened when the reservoir was severely stratified (in August) while the highest variation of TP took place when the thermocline was attenuated with the deepening of the epilimnion (in October). Both TP and TN based trophic indicators classified the SDR as a hypereutrophic lake. TN:TP molar ratio averaged at the epilimnion indicated a P–deficiency in the reservoir during warm months whilst it suggested a co–deficiency of P and N in cold months. Given the hyper-nutrient enrichment state in the reservoir, other drivers such as water residence time (WRT) can also act as the main contributor of eutrophication in the SDR. We found that WRT in the SDR varied from hundreds to thousands of days, which was much longer than that of other reservoirs/lakes with the same and even much greater storage capacity. Therefore, both hyper-nutrient enrichment and WRT mainly controlled eutrophication in the reservoir. Given time consuming and expensive management practices for reducing nutrients in the watershed, changes in the SDR operation are suggested to somewhat recover its hypereutrophic state in the short-term. However, strategic long-term recovery plans are required to reduce the transition of nutrients from the watershed to the SDR.
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Tewfik, Alexander, Joseph B. Rasmussen, and Kevin S. McCann. "Simplification of seagrass food webs across a gradient of nutrient enrichment." Canadian Journal of Fisheries and Aquatic Sciences 64, no. 7 (July 1, 2007): 956–67. http://dx.doi.org/10.1139/f07-071.
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Anthropogenic nutrient enrichment has resulted in significant changes in food web structure. Although such changes have been associated with the loss of diversity and ecosystem services, little empirical work has been done to study food webs of similar systems across a nutrient enrichment gradient. We examined 11 seagrass beds along a gradient of increasing δ15N of primary consumers, where δ15N is used as an indicator of sewage-derived nutrients. Observations across this gradient revealed corresponding increases in consumer density and changes in distinct functional groups, whereas consumer diversity, seagrass canopy, and macrodetrital biomass decreased. However, maximum overall primary consumer diversity and minimum density occurred at intermediate levels along the nutrient gradient. We hypothesize that higher species diversity at low to moderate levels of nutrient enrichment depends on the persistence of grazer-resistant seagrass. This seagrass canopy, and the significant macrodetritus it generates, facilitates a variety of food and shelter resources. Overgrazed and simplified habitats may occur when densities of generalist urchins, capable of direct producer consumption, are no longer controlled through competition, predation, and intraguild predation. We hypothesize that high and stable urchin populations appear possible with the increased availability of allochthonous phytoplankton and associated particulate detritus that is a well-known consequence of nutrient enrichment in aquatic systems.
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Lovelock, Catherine E., Marilyn C. Ball, Katherine C. Martin, and Ilka C. Feller. "Nutrient Enrichment Increases Mortality of Mangroves." PLoS ONE 4, no. 5 (May 19, 2009): e5600. http://dx.doi.org/10.1371/journal.pone.0005600.
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Vaudrey, Jamie M. P., James N. Kremer, Brett F. Branco, and Frederick T. Short. "Eelgrass recovery after nutrient enrichment reversal." Aquatic Botany 93, no. 4 (November 2010): 237–43. http://dx.doi.org/10.1016/j.aquabot.2010.08.005.
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Su, Xiaomei, Alan D. Steinman, Yunlin Zhang, Hong Ling, and Dan Wu. "Significant Temporal and Spatial Variability in Nutrient Concentrations in a Chinese Eutrophic Shallow Lake and Its Major Tributaries." Water 14, no. 2 (January 12, 2022): 217. http://dx.doi.org/10.3390/w14020217.
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Sediment nutrients can be released to the surface water when hydraulic disturbance becomes strong in shallow lakes, which contributes to nutrient enrichment and subsequent lake eutrophication in the water column. To explore the seasonal variations and spatial distributions exhibited by nutrients in the water column, surface sediment, and pore water of Lake Yangcheng and its major tributaries, we determined the concentrations of nitrogen (N) and phosphorus (P) throughout the lake in different seasons of 2018. Total N (TN) and total P (TP) concentrations in the connected rivers were much greater than those in the lake, indicating that external loading greatly contributed to the nutrient enrichment. TN concentration in the water column was highest in the winter, whereas TP peaked in the summer. A similar temporal pattern was observed for TN and TP in the sediment with maxima in the winter and minima in the summer; however, nutrients in the pore water were highest in the summer, in contrast to the temporal variation in the sediment. Additionally, high TN values in the water column and high TP in the three compartments were distributed primarily in the west part of the lake, while high TN concentrations in the sediment and pore water were observed mainly in the east portion of the lake. According to the enrichment factor index (an indicator evaluating the nutrient enrichment by comparing the detected contents and standard values), nutrients in the lake sediment were severely enriched with TN and TP averaging 2195.8 mg/kg and 543.0 mg/kg, respectively. The vertical distribution of TN and TP generally exhibited similar decreasing patterns with an increase in sediment depth, suggesting mineralization of TN and TP by microbes and benthic organisms. More attention and research are needed to understand the seasonality of nutrient exchange across the sediment–water interface, especially in eutrophic lakes.
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Young, Hillary S., Douglas J. McCauley, Robert B. Dunbar, and Rodolfo Dirzo. "Plants cause ecosystem nutrient depletion via the interruption of bird-derived spatial subsidies." Proceedings of the National Academy of Sciences 107, no. 5 (January 19, 2010): 2072–77. http://dx.doi.org/10.1073/pnas.0914169107.
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Plant introductions and subsequent community shifts are known to affect nutrient cycling, but most such studies have focused on nutrient enrichment effects. The nature of plant-driven nutrient depletions and the mechanisms by which these might occur are relatively poorly understood. In this study we demonstrate that the proliferation of the commonly introduced coconut palm, Cocos nucifera, interrupts the flow of allochthonous marine subsidies to terrestrial ecosystems via an indirect effect: impact on birds. Birds avoid nesting or roosting in C. nucifera, thus reducing the critical nutrient inputs they bring from the marine environment. These decreases in marine subsidies then lead to reductions in available soil nutrients, decreases in leaf nutrient quality, diminished leaf palatability, and reduced herbivory. This nutrient depletion pathway contrasts the more typical patterns of nutrient enrichment that follow plant species introductions. Research on the effects of spatial subsidy disruptions on ecosystems has not yet examined interruptions driven by changes within the recipient community, such as plant community shifts. The ubiquity of coconut palm introductions across the tropics and subtropics makes these observations particularly noteworthy. Equally important, the case of C. nucifera provides a strong demonstration of how plant community changes can dramatically impact the supply of allochthonous nutrients and thereby reshape energy flow in ecosystems.
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Tsoi, Wing Ying, Wade L. Hadwen, and F. Sheldon. "Identifying diatom indicator species of nutrient enrichment: An in situ nutrient enrichment experiment in subtropical upland streams." Ecological Indicators 119 (December 2020): 106744. http://dx.doi.org/10.1016/j.ecolind.2020.106744.
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Lakshmi, Ch S. Rama, T. Sreelatha, DV Ramana Reddy, and P. Surendrababu. "Nutrient fortification approaches for enrichment of zinc enrichment in rice grain." ORYZA- An International Journal on Rice 54, no. 4 (2017): 420. http://dx.doi.org/10.5958/2249-5266.2017.00057.1.
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Levi, Peter S., Jennifer L. Tank, Scott D. Tiegs, Janine Rüegg, Dominic T. Chaloner, and Gary A. Lamberti. "Does timber harvest influence the dynamics of marine-derived nutrients in Southeast Alaska streams?" Canadian Journal of Fisheries and Aquatic Sciences 68, no. 8 (August 2011): 1316–29. http://dx.doi.org/10.1139/f2011-067.
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Streams often rely on nutrient subsidies, and variation in nutrient delivery may alter the ecosystem response. Pacific salmon (Oncorhynchus spp.) provide marine-derived nutrients to their natal streams but also cause benthic disturbance, with the net effect determined by watershed and stream characteristics. To understand the factors contributing to variation in salmon-derived nutrients (SDN), we studied nutrient concentration and export in seven streams with varying physical characteristics due to timber harvest (e.g., channel complexity) over three years in Southeast Alaska, USA. Salmon increased concentrations and export of dissolved and particulate nitrogen, phosphorus, and carbon, but the magnitude of increase varied up to 41-fold among streams. The density of live salmon best predicted the increase in nutrient concentration and export, whereas the density of carcasses had a negligible effect. Nutrient export was predicted by transient storage before and after the salmon run. Streams in harvested watersheds with simplified channels had greater nutrient export than those in pristine watersheds with complex channels. However, enrichment from salmon overrode the effect of timber harvest on export during the run. Our study demonstrates that enrichment via SDN is short-lived and related to run size, whereas timber harvest and carcasses exert little influence on SDN dynamics.
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Luyima, Deogratius, Michael Egyir, Yeo-Uk Yun, Seong-Jin Park, and Taek-Keun Oh. "Nutrient Dynamics in Sandy Soil and Leaf Lettuce Following the Application of Urea and Urea-Hydrogen Peroxide Impregnated Co-Pyrolyzed Animal Manure and Bone Meal." Agronomy 11, no. 8 (August 20, 2021): 1664. http://dx.doi.org/10.3390/agronomy11081664.
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There is a paucity of data regarding the effect of nutrient-enriched biochar amendments on nutrient dynamics in both soil and crops. This is important because unlike pristine biochar, nutrient-enriched biochar is applied to the soil in minute quantities as large amounts may led to over application of the nutrients loaded in it. The current study examined the effects of both phosphorus- and nitrogen-enriched biochars on the dynamics of both macro and micronutrients in the sandy soil and leaf lettuce grown thereon. The phosphorus enrichment followed co-pyrolysis of animal manure (cow dung) with 25% and 50% bone meal (w/w), while the nitrogen enrichment was achieved by soaking the co-pyrolyzed biochar into urea and urea-hydrogen peroxide. The performances of the nutrient-enriched biochar were compared with the conventional amendment of urea and triple superphosphate (TSP) in the production of leaf lettuce over a period of two seasons in a pot experiment. The nutrient-enriched biochar amendments resulted into higher microbial biomass carbon and carbon to nitrogen ratios than the conventional amendment. The conventional amendment caused more phosphorus, potassium, and magnesium accumulations in the leaf lettuce than the nutrient-enriched biochar amendments. The nutrient-enriched biochar amendments led to more accumulations of nitrogen, calcium, and micronutrient elements in the leaf lettuce and availabilities of all the nutrient elements in the soil and thus, nutrient-enriched biochar acted as a reservoir that could provide nutrients to the growing lettuce beyond a single growing season.
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Meirinawati, Hanny, and A'an Johan Wahyudi. "Deepening Knowledge of Nutrient Dynamics in Coastal Waters." ASEAN Journal on Science and Technology for Development 39, no. 1 (April 28, 2022): 23–33. http://dx.doi.org/10.29037/ajstd.747.
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Nutrients are important compounds in waterbodies that regulate primary productivity and phytoplankton growth, the basis of food webs. Increased nutrient concentration has become a serious concern because it causes eutrophication and threatens the sustainability of ecosystems. Eutrophication is the process of nutrient enrichment in water bodies that affects their productivity and decreases water quality. Although information about nutrient distribution, limiting nutrients, and nutrient budgets is important for coastal water management, studies of wide-scale nutrient dynamics in Indonesian waters remain limited. To provide comprehensive data on nutrients, this review summarized the concentrations and compositions of nutrients in coastal waters, compared the limiting nutrients in various coastal waters based on the Redfield ratio, and described the factors affecting nutrient budgets using the database in ScienceDirect and Google Scholar. Curation was performed to summarize the nutrient dynamics in coastal waters. Results showed that nutrient concentration differed in each region due to many factors. Anthropogenic inputs greatly affected nutrients in tropical areas, such as Jakarta Bay (Indonesia). Understanding the quality and characteristics of water can help in managing waterbodies. This study provided knowledge related to nutrient dynamics in Indonesian waters and global biogeochemistry.
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Charan, Harshna, Eri Inomata, Hikaru Endo, Yoichi Sato, Yutaka Okumura, and Masakazu N. Aoki. "Decreased Irradiance and Nutrient Enrichment Mitigate the Negative Effect of Ocean Warming on Growth and Biochemical Compositions of a Canopy-Forming Marine Macroalga." Journal of Marine Science and Engineering 10, no. 4 (March 30, 2022): 479. http://dx.doi.org/10.3390/jmse10040479.
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Heatwaves under global warming have negative impacts on ecosystem primary producers. This warming effect may be synergized or antagonized by local environments such as light and nutrient availability. However, little is known about the interactive effects of warming, irradiance, and nutrients on physiology of marine macroalgae, which are dominant in coastal ecosystems. The present study examined the combined effects of warming (23 and 26 °C), irradiance (30 and 150 µmol photon m−2 s−1), and nutrients (enriched and non-enriched) on specific growth rate (SGR) and biochemical compositions of the canopy-forming marine macroalga Sargassum fusiforme. The negative effect of warming on SGR and ratio of chlorophyll (Chl) c to Chl a was antagonized by decreased irradiance. Moreover, the negative effect of temperature elevation on carbon content was antagonized by nutrient enrichment. These results suggest that the effect of warming on the growth and carbon accumulation of this species can be mitigated by decreased irradiance and nutrient enrichment.
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Tsai, An-Yi, and Vladimir Mukhanov. "Response of Growth and Grazing Rate of Nanoflagellates on Synechococcus spp. to Experimental Nutrient Enrichment." Water 13, no. 19 (September 28, 2021): 2686. http://dx.doi.org/10.3390/w13192686.
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As important bacterivores in planktonic food webs, mixotrophic nanoflagellates cancause mortality in marine Synechococcus spp. Our previous study found that the pigmented nanoflagellate (PNF) has a significant grazing impact on Synechococcus spp. In the current study, we applied the dilution approach to test the growth and grazing rates of nanoflagellates on Synechococcus spp. We then compared the differences between experimental nutrient additions and in situ conditions in the coastal waters of the East China Sea during the summer season from July to September. The growth rates of Synechococcus spp. in the ambient environment were between 0.54 and 0.62 day−1, which were slightly higher than the 0.56 and 0.66 day−1 with nutrient enrichment in summer. In contrast, our nutrient enrichment experiments produced a marked decline approximately from 21% to 58% in the nanoflagellate grazing rate on Synechococcus spp. The reason was that the mixotrophic PNFs directly used the added nutrients and reduced their supply of nutrients from prey during the incubation experiments.
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Yang, Ruirui, Junyu Dong, Changchao Li, Lifei Wang, Quan Quan, and Jian Liu. "The decomposition process and nutrient release of invasive plant litter regulated by nutrient enrichment and water level change." PLOS ONE 16, no. 5 (May 3, 2021): e0250880. http://dx.doi.org/10.1371/journal.pone.0250880.
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Wetlands are vulnerable to plant invasions and the decomposition of invasive plant litter could make impacts on the ecosystem services of wetlands including nutrient cycle and carbon sequestration. However, few studies have explored the effects of nutrient enrichment and water level change on the decomposition of invasive plant litter. In this study, we conducted a control experiment using the litterbag method to compare the decomposition rates and nutrient release in the litter of an invasive plant Alternanthera philoxeroides in three water levels and two nutrient enrichment treatments. This study found that the water level change and nutrient enrichment showed significant effects on the litter decomposition and nutrient dynamic of A. philoxeroides. The increase of water level significantly reduced the decomposition rate and nutrient release of litter in the nutrient control treatment, whereas no clear relationship was observed in the nutrient enrichment treatment, indicating that the effect of water level change on litter decomposition might be affected by nutrient enrichment. At the late stage of decomposition, the increase of phosphorus (P) concentration and the decrease of the ratio of carbon to P suggested that the decomposition of invasive plant litter was limited by P. Our results suggest that controlling P enrichment in water bodies is essential for the management of invasive plant and carbon sequestration of wetlands. In addition, the new index we proposed could provide a basis for quantifying the impact of invasive plant litter decomposition on carbon cycle in wetlands.
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Martínez-Crego, B., I. Olivé, and R. Santos. "CO<sub>2</sub> and nutrient-driven changes across multiple levels of organization in <i>Zostera noltii</i> ecosystems." Biogeosciences 11, no. 24 (December 17, 2014): 7237–49. http://dx.doi.org/10.5194/bg-11-7237-2014.
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Abstract. Increasing evidence emphasizes that the effects of human impacts on ecosystems must be investigated using designs that incorporate the responses across levels of biological organization as well as the effects of multiple stressors. Here we implemented a mesocosm experiment to investigate how the individual and interactive effects of CO2 enrichment and eutrophication scale-up from changes in primary producers at the individual (biochemistry) or population level (production, reproduction, and/or abundance) to higher levels of community (macroalgae abundance, herbivory, and global metabolism), and ecosystem organization (detritus release and carbon sink capacity). The responses of Zostera noltii seagrass meadows growing in low- and high-nutrient field conditions were compared. In both meadows, the expected CO2 benefits on Z. noltii leaf production were suppressed by epiphyte overgrowth, with no direct CO2 effect on plant biochemistry or population-level traits. Multi-level meadow response to nutrients was faster and stronger than to CO2. Nutrient enrichment promoted the nutritional quality of Z. noltii (high N, low C : N and phenolics), the growth of epiphytic pennate diatoms and purple bacteria, and shoot mortality. In the low-nutrient meadow, individual effects of CO2 and nutrients separately resulted in reduced carbon storage in the sediment, probably due to enhanced microbial degradation of more labile organic matter. These changes, however, had no effect on herbivory or on community metabolism. Interestingly, individual effects of CO2 or nutrient addition on epiphytes, shoot mortality, and carbon storage were attenuated when nutrients and CO2 acted simultaneously. This suggests CO2-induced benefits on eutrophic meadows. In the high-nutrient meadow, a striking shoot decline caused by amphipod overgrazing masked the response to CO2 and nutrient additions. Our results reveal that under future scenarios of CO2, the responses of seagrass ecosystems will be complex and context-dependent, being mediated by epiphyte overgrowth rather than by direct effects on plant biochemistry. Overall, we found that the responses of seagrass meadows to individual and interactive effects of CO2 and nutrient enrichment varied depending on interactions among species and connections between organization levels.
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Martínez-Crego, B., I. Olivé, and R. Santos. "CO<sub>2</sub> and nutrient-driven changes across multiple levels of organization in <i>Zostera noltii</i> ecosystems." Biogeosciences Discussions 11, no. 4 (April 3, 2014): 5239–74. http://dx.doi.org/10.5194/bgd-11-5239-2014.
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Abstract. Increasing evidence emphasizes that the effects of human impacts on ecosystems must be investigated using designs that incorporate the responses across levels of biological organization as well as the effects of multiple stressors. Here we implemented a mesocosm experiment to investigate how the effects of CO2 enrichment and its interaction with eutrophication, scale-up from changes in primary producers at the individual- (biochemistry) or population-level (production, reproduction, and/or abundance) to higher levels of community (macroalgae abundance, herbivory, and global metabolism) and ecosystem organization (detritus release and carbon sink capacity). The responses of Zostera noltii seagrass meadows growing in low- and high- nutrient field conditions were compared. In both meadows, the effect of elevated CO2 levels was mediated by epiphyte proliferation (mostly the cyanobacterium Microcoleus spp.), but not through changes in plant biochemistry or population-level traits. In the low-nutrient meadow, epiphyte proliferation suppressed the CO2 benefits on Z. noltii leaf production and led to increased detritus and decreased organic matter in sediment. Faster and stronger responses to nutrients than to CO2 were observed. Nutrient addition enhanced the nutritional quality of Z. noltii (high N, low C : N and phenolics) and the loss of leaves and shoots, while promoted the proliferation of pennate diatoms and purple bacteria. These changes led to a reduced sediment organic matter, but had no significant effects on herbivory nor on community metabolism. Interestingly, the interaction with CO2 attenuated eutrophication effects. In the high-nutrient meadow, a striking shoot decline caused by amphipod overgrazing was observed, with no response to CO2 and nutrient additions. Our results reveal that under future scenarios of CO2, the responses of seagrass ecosystems will be complex, being mediated by epiphyte proliferation rather than by effects on plant biochemistry. The multi-level responses of the system to nutrients overwhelmed those to CO2 enrichment, but the interaction between stressors reduced the effects of eutrophication. Both, CO2 and nutrient enrichments can reduce the carbon sink capacity of seagrass meadows.
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Cresswell, G. "Nutrient enrichment of the Sydney continental shelf." Marine and Freshwater Research 45, no. 4 (1994): 677. http://dx.doi.org/10.1071/mf9940677.
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Nutrient-rich waters arrived at the continental shelf at Sydney in late January 1992 in two ways: as an intrusion from the nearby continental slope and as a cold upwelled plume originating several hundred kilometres farther north. With the former, an undercurrent flowed northward on the upper continental slope south of where the nearshore edge of a warm anticyclonic eddy separated from the shelf and curved out to sea. The undercurrent rose onto the floor of the shelf and spread shoreward at least to the 60-m isobath as an intrusion of slope water. The other source of nutrients, the upwelled plume from the north, probably resulted from the East Australian Current spreading onto the shelf and driving an Ekman bottom boundary layer shoreward, where it upwelled to the surface and was then advected southward. Very high values of fluorescence at 20-40 m depth in the plume suggested a significant phytoplankton bloom. The plume was not continuous at the surface for the final 100 km of its passage to Sydney, rather taking the form of 40-km-long 'slugs' moving at -0.3 m s-1. It was, however, continuous beneath the surface. From Sydney it was carried out to sea around the perimeter of the anticyclonic eddy.
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MALONE, G. W. "Nutrient Enrichment in integrated Broiler Production Systems." Poultry Science 71, no. 7 (July 1992): 1117–22. http://dx.doi.org/10.3382/ps.0711117.
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Decaestecker, Ellen, Dino Verreydt, Luc De Meester, and Steven A. J. Declerck. "Parasite and nutrient enrichment effects onDaphniainterspecific competition." Ecology 96, no. 5 (May 2015): 1421–30. http://dx.doi.org/10.1890/14-1167.1.
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Milbrink, Göran, and Staffan Holmgren. "Nutrient enrichment and increase in fish growth." SIL Proceedings, 1922-2010 23, no. 3 (October 1988): 1730–36. http://dx.doi.org/10.1080/03680770.1987.11898094.
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Boesch, Donald F., Walter R. Boynton, Larry B. Crowder, Robert J. Diaz, Robert W. Howarth, Laurence D. Mee, Scott W. Nixon, et al. "Nutrient Enrichment Drives Gulf of Mexico Hypoxia." Eos, Transactions American Geophysical Union 90, no. 14 (April 7, 2009): 117–18. http://dx.doi.org/10.1029/2009eo140001.
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McCauley, Mark, and Tamar L. Goulet. "Caribbean gorgonian octocorals cope with nutrient enrichment." Marine Pollution Bulletin 141 (April 2019): 621–28. http://dx.doi.org/10.1016/j.marpolbul.2019.02.067.
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Grabau, Zane J., Danielle D. Treadwell, Jose J. Perez Orozco, David N. Campbell, and Robert C. Hochmuth. "Organic or conventional production system and nutrient rate affect the nematode community in carrot production." Journal of Nematology 53, no. 1 (January 1, 2021): 1–18. http://dx.doi.org/10.21307/jofnem-2021-082.
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Abstract Organic and conventional production are common in horticulture crops and each system may exert a different influence on the soil ecosystem, particularly the nematode community. Crop nutrient rate is an important choice in both production systems. The objectives of this study were to assess the impacts of (i) organic and conventional production systems and (ii) nutrient rate in both systems on the nematode community in carrot production. To investigate these objectives, field studies in organic and conventional production – which included fumigation with 1,3-dichloropropene – were conducted in North-Central Florida. In both production systems, nutrient rate treatments were 168, 224, 280, 336, and 392 kg N/ha. Poultry litter was the nitrogen source in organic production whereas synthetic, inorganic fertilizer was used in conventional production. All nematode trophic groups were consistently more abundant in organic than conventional production. The nematode community was more diverse and had greater trophic structure in organic production. Greater rates of organic nutrients increased enrichment opportunists (bacterivores and fungivores), but inconsistently across years. Conventional production had similar results except that only moderate nutrient rates increased fungivore abundances. Extreme enrichment opportunists (Rhabditis spp.) drove bacterivore trends in organic production whereas moderate enrichment opportunists (Cephalobus spp.) drove trends in conventional production. Nutrient rates did not affect omnivore-predators, herbivores, nematode community diversity, or structure in either system. In summary, type of production system, organic or conventional, exerts a strong influence on the nematode community, but nutrient rate has less consistent effects in horticulture production.
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Pereira, Danielle Goeldner, Fábio Amodêo Lansac-Tôha, Gustavo Mayer Pauleto, Luis Mauricio Bini, and Luiz Felipe Machado Velho. "Effects of nitrogen and phosphorus on the abundance and cell size of planktonic nanoflagellate communities." Acta Limnologica Brasiliensia 24, no. 4 (April 19, 2013): 427–37. http://dx.doi.org/10.1590/s2179-975x2013005000009.
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AIM: We experimentally investigated the effects of nutrients (Nitrogen and Phosphorus) enrichment on the density, biomass, and cell size of pigmented and heterotrophic plankton nanoflagellates communities. METHODS: The experiment was done in mesocosms in a tropical reservoir during a 19-day period. Four different treatments were carried out: Control (non-nutrient addition - C), phosphorus additions (P), nitrogen addition (N) and phosphorus + nitrogen addition (N + P). Each treatment was performed in triplicate, sorted randomly, thus giving a total of 12 experimental carboys, which were placed transversely in the middle of the reservoir. RESULTS: In general, pigmented and heterotrophic nanoflagellates fractions responded to nutrient addition, increasing densities and biomass values at the fertilized treatments. Opposed to expected, enriched treatments resulted in a slight decrease in mean cell size of the pigmented fraction. Moreover, in nutrient-rich treatments, pigmented nanoflagellates had higher relative abundance than in the control. CONCLUSIONS: Our results indicate that: i) the density and biomass of nanoflagellates responded to the nutrient enrichment, mainly when N and P were added together; ii) the pigmented and heterotrophic fractions showed distinct time responses to fertilization; iii) the growth of nanoflagellate community seems to be co-limited by N and P; iv) the nutrient enrichment led to a greater pigmented than heterotrophic fraction contribution; and v) among the analyzed variables, nanoflagellate densities seem to be more sensitive to changes in nutrient availability than biomass or mean cell size.
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Han, Ji Hoon J., Matthew P. Stefanak, and Ku‘ulei S. Rodgers. "Low-level nutrient enrichment during thermal stress delays bleaching and ameliorates calcification in three Hawaiian reef coral species." PeerJ 10 (July 14, 2022): e13707. http://dx.doi.org/10.7717/peerj.13707.
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Terrestrial-based nutrient pollution has emerged as one of the most detrimental factors to coral health in many reef habitats. Recent studies have shown that excessive dissolved inorganic nutrients can reduce coral thermal tolerance thresholds and even exacerbate bleaching during thermal stress, yet the effects of minor nutrient enrichment under heat stress have not been extensively studied. In this study, Lobactis scutaria, Montipora capitata, and Pocillopora acuta colonies under heated conditions (~30.5 °C) were exposed to low and balanced nitrogen and phosphorous concentrations over a 31-day heating period. Coral colonies were collected from Kāne‘ohe Bay, O‘ahu, which has a unique history of nutrient pollution, and held in mesocosms that allowed for environmental manipulation yet are also influenced by local field conditions. Principal findings included delays in the bleaching of nutrient-enriched heated colonies as compared to heated-only colonies, in addition to relatively greater calcification rates and lower proportions of early-stage paling. Species-specific outcomes were prevalent, with L. scutaria demonstrating no difference in calcification with enrichment under heat stress. By the end of the heating stage, however, many heated colonies were at least partially impacted by bleaching or mortality. Despite this, our findings suggest that low levels of balanced nutrient enrichment may serve as a mitigative force during thermal events. Further field-based studies will be required to assess these results in different reef habitats.
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Morris, Kay, Paul I. Boon, Paul C. Bailey, and Leesa Hughes. "Alternative stable states in the aquatic vegetation of shallow urban lakes. I. Effects of plant harvesting and low-level nutrient enrichment." Marine and Freshwater Research 54, no. 3 (2003): 185. http://dx.doi.org/10.1071/mf02002.
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Shallow urban lakes are often subject to chronic nutrient enrichment and their submerged plants are sometimes harvested to facilitate recreational use. The theory of alternative stable states predicts that: (i) low levels of nutrient enrichment should have little effect on the existing communities of submerged macrophytes in such lakes; but (ii) harvesting the plants should facilitate a shift to phytoplankton dominance. These two predictions were tested with large (3000 L), replicated mesocosms in a shallow urban lake densely colonized by the submerged angiosperm, Vallisneria americana Michaux. Harvesting V. americana substantially increased light penetration through the water column, but did not significantly increase phytoplankton biomass. Vallisneria americana regrew rapidly after harvesting and Chara species, which were previously absent, appeared in the harvested mesocosms. Chronic low-level nutrient enrichment significantly increased phytoplankton biomass (>100 μg chlorophyll a L–1) but not epiphyte biomass on the leaves of V. americana or on plastic leaf surrogates. The aboveground biomass and leaf area index of V. americana were not affected significantly by nutrient enrichment. The theory of alternative stable states successfully predicted the resilience of the submerged angiosperm community to low-level nutrient enrichment, but did not accurately predict the response to plant harvesting. The response of the lake vegetation to higher levels of nutrient enrichment is reported.
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Yadav, Arpana, Dhananjay Kumar, Ram Sharan Singh, Lalit K. Pandey, and Jyoti Rai. "Seasonal variations in response of periphytic algal community to nutrient enrichment in the river Ganga (Varanasi, India)." Annales de Limnologie - International Journal of Limnology 54 (2018): 32. http://dx.doi.org/10.1051/limn/2018025.
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Effect of nutrient enrichment on periphyton was studied using chemical diffusing substrates that released, singly or in combination, PO43−-P and nitrogen, both NO3−-N and NH4+-N. The study was carried out in March and June 2014 as these two time periods showed abundance of different groups of algae. Whereas diatoms and green algae were abundant in March, cyanobacteria dominated in June. Nitrogen was primarily growth limiting in river water as its enrichment enhanced the growth of periphyton. Phosphate limitation was secondary in nature. Enrichment of NH4+-N caused greater enhancement of periphytic growth than that of NO3−-N. Nutrient enrichment reduced species diversity, further enhancing total biovolume of the periphytic group that was predominant at that particular point of time. Nutrient enrichment markedly increased cyanobacterial populations in June due inter alia to high temperature. In spite of nutrient enrichment, the periphytic biomass did not reach the level (chla≥ 100–150 mg m−2) considered as the nuisance, except in March when combined enrichment of PO43−-P and NO3−-N greatly enhanced the periphytic biomass.
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Brown, Joseph K., Ashley Moulton, and Julie C. Zinnert. "Plant community re-organization and increased productivity due to multi-year nutrient enrichment of a coastal grassland." PLOS ONE 17, no. 7 (July 28, 2022): e0270798. http://dx.doi.org/10.1371/journal.pone.0270798.
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Nutrient enrichment alters plant community structure and function at a global scale. Coastal plant systems are expected to experience increased rates of nitrogen and phosphorus deposition by 2100, caused mostly by anthropogenic activity. Despite high density of studies investigating connections between plant community structure and ecosystem function in response to nutrient addition, inconsistencies in system response based on the ecosystem in question calls for more detailed analyses of nutrient impacts on community organization and resulting productivity response. Here, we focus on nutrient addition impacts on community structure and organization as well as productivity of different lifeforms in a coastal grassland. We established long-term nutrient enrichment plots in 2015 consisting of control (C), nitrogen (N), phosphorus (P), and nitrogen + phosphorus (NP) treatments. In 2017 we collected graminoid and forb productivity, root productivity, and community composition for each plot. We found no N x P interaction, but N enrichment was a significant main effect on productivity, highlighting N limitation in coastal systems. Importantly, nutrient enrichment treatments did not alter root productivity. However, all treatments caused significant differences in community composition. Using rank abundance curves, we determined that community composition differences were driven by increased dominance of nitrophilous graminoids, re-organization of subordinate species, and species absences in N and NP plots. Results of this study highlight how coastal grassland communities are impacted by nutrient enrichment. We show that community re-organization, increased dominance, and absence of critical species are all important mechanisms that reflect community-level impacts of nutrient enrichment in our coastal grassland site.
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Niu, Lixia, Pieter van Gelder, Xiangxin Luo, Huayang Cai, Tao Zhang, and Qingshu Yang. "Implications of Nutrient Enrichment and Related Environmental Impacts in the Pearl River Estuary, China: Characterizing the Seasonal Influence of Riverine Input." Water 12, no. 11 (November 19, 2020): 3245. http://dx.doi.org/10.3390/w12113245.
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The Pearl River estuary is an ecologically dynamic region located in southern China that experiences strong gradients in its biogeochemical properties. This study examined the seasonality of nutrient dynamics, identified related environmental responses, and evaluated how river discharge regulated nutrient sink and source. The field investigation showed significant differences of dissolved nutrients with seasons and three zones of the estuary regarding the estuarine characteristics. Spatially, nutrients exhibited a clear decreasing trend along the salinity gradient; temporally, their levels were obviously higher in summer than other seasons. The aquatic environment was overall eutrophic, as a result of increased fluxes of nitrogen and silicate. This estuary was thus highly sensitive to nutrient enrichment and related pollution of eutrophication. River discharge, oceanic current, and atmospheric deposition distinctly influenced the nutrient status. These factors accordingly may influence phytoplankton that are of importance in coastal ecosystems. Phytoplankton (in terms of chlorophyll) was potentially phosphate limited, which then more frequently resulted in nutrient pollution and blooms. Additionally, the nutrient sources were implied according to the cause–effect chains between nutrients, hydrology, and chlorophyll, identified by the PCA-generated quantification. Nitrogen was constrained by marine-riverine waters and their mutual increase-decline trend, and a new source was supplemented along the transport from river to sea, while a different source of terrestrial emission from coastal cities contributed to phosphate greatly.
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Schelske, Claire L. "Historical Nutrient Enrichment of Lake Ontario: Paleolimnological Evidence." Canadian Journal of Fisheries and Aquatic Sciences 48, no. 8 (August 1, 1991): 1529–38. http://dx.doi.org/10.1139/f91-181.
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Recent studies of Lake Ontario show four periods of nutrient enrichment that can be identified from the sediment record in this phosphorus-limited system: pristine phosphorus loads (early 1800s before European settlement), moderate increase in phosphorus loading after settlement (beginning approximately 1850), exponential increase in phosphorus loading from urban sources (approximately 1940–70), and decreased phosphorus loading as the result of phosphorus abatement strategies (beginning in mid-1970s). Paleolimnological data are used to infer new paradigms about historical dynamics and cycling of major nutrients. The temporal pattern of organic carbon production closely parallels changes in phosphorus loading. Silica supplies which were replete for diatom production before forest clearance in the mid-1800s became limiting for diatom production in the summer epilimnion after 1865 and in the water column after 1950. Silica reserves were depleted by increased diatom production and sedimentation that resulted from increased phosphorus loading. Biologically induced precipitation of calcite began after 1940 as an indirect effect of increased urban phosphorus loading on primary productivity. Calcite began to be precipitated when historical increases in CO2 utilized for primary productivity increased epilimnetic pH and the calcium carbonate saturation product was exceeded.
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Liu, Ao, Aixi Han, and Li Chai. "Assessing the Nutrient Adequacy in China’s Food Supply from 1965 to 2018." Nutrients 13, no. 8 (August 9, 2021): 2734. http://dx.doi.org/10.3390/nu13082734.
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Nutritional intake has important impacts on human health. A sufficient supply of nutrients is required to ensure high-level nutrition in a population. Assessment of nutrient supply adequacy can help to develop evidence-based policies and thereby promote public health. This study estimates the supply adequacy of nutrients in China’s food system from 1965 to 2018 at the national level, aiming to reveal whether the supply of nutrients meets the demand. The results show that the nutrient supply in China’s food system has experienced a sharp increase in the past five decades, and the deficiency in nutrient supply has been greatly mitigated. Although most nutrients such as potassium are already sufficiently supplied in China’s current food system, some nutrients, especially calcium and zinc, still need a further enlarged supply to improve the nutrition condition of the Chinese population. Besides encouraging a healthy diet, supply-side regulation, e.g., fortification and enrichment, is also needed to improve nutrient availability. This study helps people better understand the development and current situation of nutrient adequacy in China’s food supply, thereby providing information and implications for policymakers.