Academic literature on the topic 'Barnacle larvae'

Investigations into the supply, settlement and recruitment of the barnacle Semibalanus balanoides (L.) to shores in Fife, East Scotland were undertaken over three consecutive years (2004 – 2006). Several designs of a passive larval trap, based on earlier published designs, were employed to quantify the delivery (supply) of cyprids to the substratum. Pump samples from the water column were collected to provide a measure of intertidal cyprid concentration. Cyprid concentration was found to exhibit both spatial and temporal variation, but was also found to be significantly correlated with cyprid supply, as quantified by the traps. In some years, pump and trap samples suggested that cyprid abundance in the intertidal was mediated by wind-driven processes. An artificial substratum was used to quantify cyprid settlement, allowing investigations into the supply-settlement relationship. Supply and settlement were found to be two very distinct biological phases. Supply describes the flux of larvae to the substratum. Settlement provides a measure of the amount of larvae that decide to settle on the substratum, as initial attachment for barnacle larvae is not permanent. Whilst supply saturation is unfeasible, daily saturation of the substratum by settlers was observed at many sites along the Fife coast. Levels of settlement saturation were found to vary both temporally, between years, and spatially, over scales of km. Varying levels of the desperation of larvae to settle, mediated by dwindling energy reserves, was thought to explain some of this variation. The supply data also provided some evidence of the possible movement of cyprids along the Fife coast from Fife Ness to Tentsmuir. However, wind-induced transport may also play a dominant role on the Fife coast. A comparison of supply and recruitment of larvae into adult populations revealed that both pre- and post-settlement events may influence recruitment. The relative importance of these factors was shown to be density-dependent. Negative intraspecific interactions were only seen in denser aggregations of adults. In less crowded aggregations, recruitment reflected initial patterns of larval supply.

In the past half century, a number of studies have described the general composition of the mesozooplankton of Southampton Water, highlighting aspects about the seasonality of the major components and identifying calanoid copepods and barnacle larvae as the major elements. Despite the number of studies, almost all knowledge about species composition, dominance and succession patterns of the mesozooplankton as a whole, is described from only a few studies, usually located at stations in the mid and lower estuary. It is clear that generalizations made for these stations will not reflect other parts of this estuary. Because of this, a 120 μm net-haul study comprising upper, mid and lower stations within Southampton Water was conducted over a period of 19 months, from 12/01/01 until 16/07/02, in order to critically re-evaluate the mesozooplankton community of the estuary, as well as to assess the importance of copepods and barnacle larvae to pelagic carbon fluxes. Additional biological and non-biological water column parameters were measured concurrently. A total of 144 different taxa were recorded within the zooplankton of Southampton Water during this study, with 92 identified to species, 30 to genus and 22 identified at a higher level. From these 31 were identified as holoplankton, 72 as meroplankton and 41 as tycoplankton, with 90 taxa recorded for the first time in Southampton Water. Numerically the zooplankton community was mainly composed of holoplankton forms (~69%), followed by meroplankton (~30%) and tycoplankton (~1%). Copepod nauplii were the most abundant holoplanktonic taxa, averaging 38% of all forms, followed by the calanoid Acartia spp. (31%), the cyclopoid Oithona nana (11%), the harpacticoid Euterpina acutifrons (11%) and the appendicularia Oikopleura sp. (5%). Barnacle larvae averaged 53% of the meroplanktonic forms, followed by polychaete (19%), gastropod (13%), bivalve (9%) and bryozoan larvae (3%). Harpacticoid copepods comprised 97% of the tycoplanktonic forms recorded. One unexpected finding of this study was the significant occurrence of the cyclopoid Oithona nana within the upper estuary, contrasting with previous studies where calanoids of the genus Acartia were considered the only dominant copepod form. Although present throughout the estuary, O.nana was clearly most abundant in the upper estuary where it presented a clear seasonal pattern, and was numerically the most abundant form from late-summer until early-winter, then replaced by copepod nauplii and Acartia spp. during mid-winter to late-spring, and by copepod nauplii, Acartia spp. and E.acutifrons during early to mid-summer. Barnacle larvae presented the same composition and seasonality reported in the past, with Elminius modestus the most abundant and frequent, and occurring throughout the year although it was outnumbered by Balanus crenatus from February to May. Of the remaining barnacle species found only Balanus improvisus, Semibalanus balanoides and Verruca stroemia were present in substantial numbers. Production of several copepod components was calculated, and an overall averaged production of 253.48 mg C m-3 yr-1 was estimated, with Acartia accounting for 55.6% of the production followed by E.acutifrons (16.0%), copepod nauplii (15.2%) and O.nana (13.2%). This previously unaccounted production may assist in readdressing the relatively low copepod secondary production previously estimated for Southampton Water. Production of barnacle larvae was also calculated and an overall averaged production of 32.80 mg C m-3 yr-1 was estimated, with E.modestus alone accounting for 54.7% followed by B.crenatus (35%), B.improvisus (6.7%), S.balanoides (3.1%) and V.stroemia (0.5%). Overall, production of barnacle larvae within Southampton Water is significantly lower than that of calanoid copepods contradicting previous assumptions that barnacle larvae could provide as much secondary production as calanoids. A new set of simple linear regression equations applicable to a range of crustacean zooplankton types are proposed for the preliminary estimation of production based primarily on the total number of organisms. Abundance, in conjunction with temperature, salinity and chlorophyll a pattern were also employed in the elaboration of multiple regression equations. Production values calculated by this new method were usually ±20% of the averaged value obtained by more conventional methods. When applied to an independent data set, differences of only ±7% were observed between production estimates using conventional and the new equations. The new estimated production values for barnacle larvae (meroplankton), Acartia (calanoid), Oithona (cyclopoid), Euterpina (harpacticoid) and copepod nauplii components of the mesozooplankton are integrated into an existing carbon-flux box-model for Southampton Water.