<p>Eutrophication is a current problem on coastal lines worldwide. Cirripedia like the northern acorn barnacle Semibalanus balanoides actively help to prevent high amounts of plankton in the coastal zones by filtering plankton out of the surrounding water. This investigation focuses on the movements of Semibalanus balanoides in comparison to increasing concentrations of plankton in the water (between 33mg and 110 mg particles per litre) which simulate eutrophication. The four factors feeding activity, pumping activity, isolation time and clogging of the feeding apparatus in relation to the plankton concentration of the water were examined. </p><p>The results show significant interaction between pumping movement and the plankton concentration. The feeding activity, the isolation time and the clogging compared to the plankton concentration get no statistical results. </p><p>Less feeding activity and an increase in pumping behaviour will not decrease the amount of plankton in the coastal waters which will increase the problems of eutrophication. The paper shows that more investigation on suspension feeders and their surroundings needs to be done to be able to understand the dangers fully.</p>

Eutrophication is a current problem on coastal lines worldwide. Cirripedia like the northern acorn barnacle Semibalanus balanoides actively help to prevent high amounts of plankton in the coastal zones by filtering plankton out of the surrounding water. This investigation focuses on the movements of Semibalanus balanoides in comparison to increasing concentrations of plankton in the water (between 33mg and 110 mg particles per litre) which simulate eutrophication. The four factors feeding activity, pumping activity, isolation time and clogging of the feeding apparatus in relation to the plankton concentration of the water were examined. The results show significant interaction between pumping movement and the plankton concentration. The feeding activity, the isolation time and the clogging compared to the plankton concentration get no statistical results. Less feeding activity and an increase in pumping behaviour will not decrease the amount of plankton in the coastal waters which will increase the problems of eutrophication. The paper shows that more investigation on suspension feeders and their surroundings needs to be done to be able to understand the dangers fully.

Techn. Universiẗat, Diss., 2003--Braunschweig.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), February 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 136-146). / The environmental cues for synchronous reproduction were investigated for two highly abundant, ecologically important crustacean species: the temperate acorn barnacle, Semibalanus balanoides, and the tropical terrestrial crab, Gecarcinus quadratus. Larval ecology of these two species was also studied to determine potential sources of larval mortality and recruitment success. High-frequency observations revealed that early-stage larval abundance of S. balanoides was related to storms, and possibly turbidity. Field observations and experiments studied the effect of turbidity and phytoplankton on larval release response. Release coincided with increased turbidity at three sites along the northeast coast of the United States. A three-year time series of phytoplankton and zooplankton data showed that larval release was not consistently related to phytoplankton abundance (total or single species). When gravid barnacles were exposed to phytoplankton or synthetic beads, they released in response to both, suggesting that presence of particles is more important than identity of particles. Feeding experiments showed that adult cannibalism on newly released larvae is lower in highly turbid conditions. It is suggested here that S. balanoides synchronizes its reproduction with the onset of phytoplankton blooms, but turbidity may fine-tune the timing if it provides predation refuge for larvae. Adult G. quadratus females undertake synchronized breeding migrations to the ocean after the first rains of the rainy season, presumably when the risk of desiccation is lowest. They wait for darkness and an ebbing tide before releasing their eggs into the water. First-stage zoeas have dark pigmentation, long dorsal and rostral spines, and a pair of lateral spines. Hatching in darkness may help zoeas avoid predation from planktivorous diurnal fish, and the zoeal spines may deter predation from planktivorous nocturnal fish. In the laboratory, a G. quadratus zoea reached the megalopa stage in 21 days. A mass migration of megalopae and juveniles out of the water was observed 30 days after adult females released their eggs. Plankton pump samples taken near the island suggest that zoea abundance and distribution may be related to the phase of the internal tide. Synchronous reproduction in these two species appears to be the result of predator avoidance behaviors. / by Joanna Gyory. / Ph.D.

This thesis describes the results of a three year study which collected larvae of the acorn barnacles Semibalanus balanoides on a rocky coastline in Fife, East Scotland. The nauplii larvae of S. balanoides are released from their parent in springtime in the United Kingdom and develop in the plankton for approximately one to two months. During this period they are transported some distance from the parent population and eventually return to the intertidal shoreline as a cyprid larval stage. The ‘decision’ to settle is a crucial point in the life history of the organism as most sessile organisms cannot move once this has occurred. The supply of larvae to intertidal shorelines was historically neglected until the 1980s. Patterns of settlement were largely considered irrelevant to distribution patterns of adults relative to postsettlement processes such as predation and competition. Despite the resurgence in “supply-side ecology” in the past 20 years there has been little development towards the measurement of larval supply. Consequently there has been very little description of fine scale or large spatio-temporal studies involving larval supply. This study demonstrates the first study directly addressing larval supply independently from larval settlement at mesoscales (metres to kilometres; days to years). Improvements were made to the passive larval trap described by Todd (2003). A conical opening was combined with the spiral trap design and a number of inlet areas were trialled (0.25cm², 0.5cm², 1cm² and 2cm²). These were tested across typical wave regimes measured with a new autonomous pressure sensing wave transducer and the 1cm² inlet was selected as the most appropriate trap design due to a balance between an increased per unit inlet larval capture and sufficient absolute larval capture so as to identify daily variation in larval supply to a site. Larval settlement has been studied extensively and is often used as a direct measure of rates of larval supply. It is widely assumed therefore that rates of settlement are a direct reflection of rates of supply, as long as settlement substrates and adult conspecific responses remain uniform. This thesis provides a means of accurately characterising the supply-settlement relationship for S. balanoides independent of substrate based responses and demonstrates that this is not the case. The relationship was found to be asymptotic, even at sites where there was low larval supply. It was concluded that density-dependent larva-larva interactions were present during the settlement of larvae and were relevant at daily temporal scales, limiting the rates of larval settlement proportional to larval density. There was no obvious effect on this relationship due to wave action however differences were observed between sites and years. Saturation of preferential environments within the tiles was observed resulting in a settlement preference cascade, with larvae being forced to settle in increasingly less preferable areas of the tiles with increasing larval density. Larva-larva interactions are demonstrated as having a considerable effect on the rates of settlement of S. balanoides.