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This thesis is concerned with an investigation into the effects of food concentration, temperature and turbidity on the life cycle characteristics such as growth, body size, development and reproduction of species of planktonic Cladocera brought to the U.K. from a shallow turbid Lake Jacaretinga, Amazonia. The species studied were Daphnia gessneri, Moina reticulata and Diaphanosoma sarsi. Long term growth experiments were performed using both batch and continuous flow culture under controlled laboratory conditions using various combinations of temperature (22°, 27°, and 32°C),concentration of algal food Scenedesmus acutus (0.03, 0.05, 0.1, 0.25, 0.5, and 1.OmgC.1) and turbidity (10, 20, and 50 NTU). Animals were examined daily throughout their cycle from the newborn (neonate) to 3rd adult instars. The ecology of planktonic animals in Lake Jacaretinga was studied intensively during a three month period (February, March and April 1986). This period of study included two ecologically/limnologically important periods, namely, before the flooding of the River Amazon and after the river flooding, when the lake became more turbid due to suspended particles. Weekly samples of zooplankton providedinformation on the species composition and numerical density of the cladoceran populations as well as their horizontal distribution in five stations. Information was also obtained on environmental condition in the lake (temperature, dissolved oxygen concentration, Secchi disc transparency, chlorophyll-a and particulate carbon concentration). Population of Diaphanosoma sarsi, Ceriodaphnia cornuta and Daphniagessneri, decreased during the flood, and populations of Moinareticulata increased and became a dominant species. Life cycle experiments shows that growth and reproduction are greatly influenced by food concentration and turbidity. Consistent differences were found between Daphnia gessneri and Moina reticulata,being Moina reticulata more successful in survival, growth and reproduction. Application of the experimental results on the effects of food, temperature and turbidity on the life cycle characteristics of the planktonic cladocerans are used to interpret the changes in the cladoceran population in Lake Jacaretinga during this period of floading. This is a significant contribution to our knowledge since Lake Jacaretinga is one of the characteristic varzea lakes in Central Amazonia whose limnology is largely determined by the annual flooding of Amazon River.

The problems of penetration into brackish water by echinoderms are reviewed. A comparison is made between Loch Etive and the Baltic Sea with respect to their individual hydrographies. Experiments indicate that ophiuroids behave as osmo conformers and that while Ophiocomina nigra is stenohaline, Ophiura albida is potentially euryhaline. It is argued that the perivisceral fluid of ophiuroids is similar, ionically and functionally, to the ambulacral fluids of asteroids and echinoids. Salinity tolerance experiments confirm that O. albida is potentially euryhaline. Differences in tolerance between O. albida and Amphiura chiajei are related to their modes of life. Evidence suggests that acclimatisation by O. albida can extend the tolerance to diluted sea water. It is shown that O. albida, from Loch Etive, can be adapted to full strength sea water rapidly and without subsequent morphological deleterious effects. Possibilities resulting in the presence and maintenance of O. albida at the head of Loch Etive are discussed. It is considered that an increase in the percentage of skeleton in ophiuroids is important in the development of tolerance to reduced salinity. A proposal that O. albida from the Oresund may represent a more advanced stage than O. albida from Loch Etive in adaptation to brackish water is made. Evidence suggests that smaller animals have higher Sr/Ca atom ratios than larger individuals of the same species. This may be manifested by a faster growth rate in young animals or by the physical constraints of the incorporation of the strontium ion into the calcite lattice. Data from O. albida (Loch Etive) demonstrates that there may be some concentrating mechanism in these ophiuroids. Discrimination ratios between the Sr/Ca atom ratio in ophiuroids and the ambient medium are calculated. In an elevated ambient strontium level ophiuroids may take up the 'extra' available strontium to different degrees which may partly reflect the original ambient strontium concentration to which the particular species are adapted.

Haptophytes are renowned for the most prominent and biogeochemically important group of marine calcifiers: coccolithophores. The unexpected discovery of a unique, silicifying member of this clade - Prymnesium neolepis - prompted questions regarding mechanisms of silicification and their origin in the calcifier-dominated haptophytes. To address these questions I used cell physiology, biochemistry and molecular approaches, investigating cellular and molecular mechanisms involved in silicification in haptophytes. Comparisons of this system with calcification in coccolithophores and other silica-based systems in eukaryotes were also made. Here I report that P. neolepis is an obligate silicifier, producing silica scales in a process fundamentally different to that observed in coccolithophores. Scale deposition and secretion in P. neolepis is localized in the posterior, vacuolar part of the cell rather than in the anterior part near the flagellar roots as in calcifying coccolithophores. The organic matrix underlying silica scales in P. neolepis was found to be non-homologous with organic scales, which in coccolithophores serve as coccolith baseplates. This suggests, that silica scales and coccoliths arise from two distinct, most likely non-homologous processes, which is further supported by the comparative investigation of the role of cytoskeleton in silica scale production in P. neolepis and coccolithogenesis in a representative calcifier, Coccolithus pelagicus. Using cytoskeleton inhibitors I established, that the cytoskeleton components used for morphogenesis and secretion of biomineralised structures are different in these two systems. Analysis of P. neolepis biosilica revealed the presence of an intimately associated organic fraction consisting of a putatively chitin-containing material, potentially serving as an organic matrix underlying silica scales. Further biochemical investigation of the biosilica-associated organics confirmed the presence of long chain polyamines (LCPAs) dissimilar to those previously reported in diatoms and sponges. Additionally, a potentially novel, proline and lysine-rich protein sharing a weak homology with lipocalins was recovered, suggesting that this silicification system is unique to haptophytes. Several theories concerning acquisition of the ability to silicify in haptophytes were proposed. Overall, the findings presented in this study provide a detailed description of Si biomineralisation system in this unique, silicifying haptophyte and supply novel information on biomineralisation systems in marine haptophytes. This study contributes a basis on which the phenomenon of silicification in haptophytes can be further investigated, as well as novel information which can be further used in elucidation of origins of silicification in algae and other Eucarya.

Coral reefs are highly diverse and economically important. Despite this, a confluence of anthropogenic threats endangers reefs globally. The diving tourism industry is an important beneficiary of coral reefs, especially reefs located within the tropical latitudes. With a recent increase in popularity of diving tourism concomitant with a global expansion of marine coastal tourism, reef managers and policy makers are presented with fresh challenges. This study explores the potential economic, social and conservation impacts of artificial reefs as recreational scuba diving resources and investigates their use as a reef management strategy within a marine protected area. A majority of the study was conducted on the Caribbean island of Barbados, West Indies. In the first part of the thesis, I estimate the economic benefits of recreation-orientated artificial reefs through a synthesis of data, and find that artificial reefs have a substantial recreation value. The need for more detailed, high-quality artificial reef valuation studies, that use a standard reporting protocol, is recommended. The second part of the thesis is based on field work using questionnaires to solicit information from users of artificial reefs. Interviews reveal novice divers have a preference for artificial reefs for local diving in contrast to experienced divers who have an overriding preference to dive on natural reefs. Moreover, an inverse relationship exists between diver experience and satisfaction of artificial reef diving, with novices being very satisfied with the experience. Using 24 variables to measure diver enjoyment between artificial and natural reef sites, I establish participants experience significantly higher levels of enjoyment at artificial reefs. Further, it was shown that enjoyment of artificial reefs is attributed to the challenge of the dive, new experiences and photographic opportunities. Irrespective of reef type, I find novices are significantly more influenced by personal incentive attributes of the dive (e.g. updating diving skills), while biophysical aspects of the reef and photography contribute significantly more to experienced divers enjoyment. A contingent valuation study of visitors to pay a daily marine park entrance fee reveals a higher mean willingness to pay (US$18.33) for natural reef conservation than for protecting and maintaining artificial reefs (US$17.58). Variables that exhibit significant explanatory power of willingness to pay include the number of species viewed, age of respondent and level of concern for coral reefs.

Exposure of artificial surfaces such as ship hulls to a marine environment leads to the attachment of assorted biomolecules, single celled organisms and marine invertebrates such as barnacles or mussels. Together, they form a structure known as a biofilm. These films lead to higher fuel consumption and add considerable expense to the operation of ships used by industrial and naval organisations. The work presented in this thesis describes the surface analysis of a novel poly(dimethylsiloxane) (PDMS) based foul-release coating. The coating also contains poly(ethylene glycol) groups (PEG). The differing chemical properties between these two domains led to an observed surface modification effect in water, whereby contact angle measurements decreased from ~110o to ~65 o over a period of five minutes. This effect was rapidly reversible on drying. Time of Flight-Secondary Ion Mass Spectrometry cryogenic depth profiling experiments confirmed this change in surface chemistry where the frozen surface of the coating was shown to have a higher intensity of ions associated with PEG groups at the surface compared to that in the bulk. Water immersion also led to a swelling of the surface seen by a change in the surface topography by Atomic Force Microscopy investigations. When applied to glass surfaces the coatings were flat and generally defect free regardless of the application method used. On exposure to Pseudomonas aeruginosa the coatings were found to be ten times more effective at preventing bacterial adhesion in the first instance than a PDMS standard. The mechanism of action was shown to be non-toxic by live/dead staining and did not appear to affect the way in which bacteria move on a surface. A flow adhesion assay demonstrated that a flow rate of almost two orders of magnitude lower was required to remove fifty percent of bacteria from a coated surface than on a glass standard, demonstrating the foul-release ability of the switching coating. Sea trials in a French coastal region highlighted the importance of exposing candidate coatings to a true marine environment for a suitable duration in order to determine their potential for use. Ultimately we show that the coating presented is a candidate for use as an effective coating for preventing marine biofouling and surface analysis was deemed to be an appropriate methodology to analyse coatings that have changing properties on exposure to water.

Purely qualitative investigations of the plankton of an area cannot provide sufficient information for the full understanding of the seasonal changes that oocur nor of the interrelation of the various planktonic plants and animals. Quantitative data must be obtained before these can be properly described. Except for the qualitative records by Scott (1906, 19(7) and Hiddell (1914) the plankton of waters off the north ooast of Wales, and of the Menai Straits in particular, has tended to be neglected. The unusual hydrographic conditions of the Menai Straits, which connect areas whose fauna and flora show considerable differences (Crisp & Knight-Jones, 1953) suggested such studies would be rewarding. In describing the various populations the policy in the present work has been to give the details of the most numerous species of both plants and animals individually and to summarize the others in various groups. This simplified the description and discussion of the dynamics of the population, which would be difficult to follow if all species were described in detail. At an early stage in the investigations it became obvious that the plankton of these coastal waters differed considerably from that of the Irish Sea in general, which has been described by Williamson (1956). In particular tho copepods Oithonina nana (Giesbrecht) and Euterpina acutifrons (Dana) were prominent species in the Menai Straits. Euterpina acutifrons was found to have several points of interest. Firstly, dimorphism occurs in the male; this has received considerable attention and has been found to be of some significonce in the biology of the species. Secondly, Euterpina is pelagic, while most other harpacticoid copepods are benthic or littoral. Investigations of its development (which was inadequately described by Tesch (1915)) in culture allowed a consideration of the adaptive modifications of Euterpina to a pelagic existence, of its rate of growth and development, and of the developmental aspects of dimorphism in the male. The latter has been a controversial subject in previous studies of copepod development (Sewell, 1912, 1929, 1940; Gurney, 1929; Coker, 1934) . Thirdly, Euterpina has a world-wide distribution, mainly centered in the warmer seas. Consideration of this led to investigations of some aspects of the relationship between the environment and the development of the species and also to a comparison of its breeding season in the waters round Anglesey with those reported in other latitudes . The present work also includes studies of the larval development of Oithonina nana, another warm water form. Despite its being a very common plankton animal, the larval. development of this species has tended to be neglected. In the work as now presented the studies of these species are given a considerable proportion of the total space, since the data provided on their development, growth and breeding illuminate the general study of the plankton which, in turn, forms a background to the detailed studies. The form of presentation of this thesis may perhaps call for some explanation. The sections into which it is divided have been prepared in the form of separate papers intended for publication. This means that figures and tables are numbered oonsecutively within each section and not continuously throughout the thesis, and also that a separate bibliography will be found at the end of each section. It is hoped that this method of presentation will cause no inconvenience to the reader.

Climate change has a profound impact on the phenology and abundance of plankton in the NE Atlantic and North Sea. There is concern that harmful algal bloom (HAB) species may increase, accompanied by negative socio-economic impacts, including threats to human health and marine harvesting. We reviewed historical major UK outbreaks of poisoning and attempted to examine the epidemiology on a finer scale by linkage of hospital admissions, GP and pathology records. As expected the incidence of shellfish poisonings was very low but accurate identification of poisoning was generally unreliable. The current UK shellfish monitoring programme is the key indicator for monitoring trends in the risk of human exposure. Using the Continuous Plankton Recorder (CPR) survey, we mapped spatial and temporal trends of various phytoplankton, including HAB species, and zooplankton (Tintinnids and Calanus). We found fundamental shifts in the relative abundance of diatoms versus dinoflagellates, with a dramatic dinoflagellate decline in recent years. Northward shifts in abundance were found for some Tintinnid and Calanus taxa. Using criteria of statistical causality, these changes were linked to climate, in particular sea surface temperature and increasingly windy conditions in the summer, with a notable non-linear interaction between these factors. Focusing on Calanus, we showed the strength of statistical links between abundance and climate variables can wax and wane as the time series lengthens. We found tentative evidence for adaptation of Calanus to climate change, but not at a level that could reverse overall long-term patterns. Links with climate are often argued to be proxies for unobserved mechanisms that determine species abundance, such as stratification. We developed a new stratification index, covering the whole NE Atlantic from 1970 to 2009. We propose that this has wide applicability in marine climate change studies. Throughout, our work demonstrates the importance of consistent long-term ecological survey data.