The pelagic ecosystem plays an important role in cycling carbon between ocean and atmospheric reservoirs. This study explores the hypothesis that widespread extinctions experienced by the pelagic ecosystem at the Cretaceous/Paleogene (K/Pg) resulted in a reduction in surface-to-deep ocean organic carbon (C-org) flux, followed by a long period of recovery (3-4 myr). This hypothesis, coined the ‘living ocean’ model by previous authors, has potential problems. Firstly, benthic foraminifera, which are believed to be dependent on surface-exported food, do not show widespread extinction.

Experimental work has shown the importance of grazing by patellid limpets in structuring intertidal assemblages. Little is known, however, about the effects of a largescale and chronic removal of limpets. Here I investigate the ecology of Patella candei, a seldom-studied limpet endemic to Macaronesia, and how its long-term fishery impacts the Azorean rocky intertidal. The specific aims of this thesis are to: examine the processes that affect the distribution of limpets in the Azores at a range of spatial scales; investigate the role of grazing by P. candei in structuring the Azorean rocky intertidal and if its harvesting has impacted the dynamics and functioning of this ecosystem. The distribution of limpets was variable at a range of spatial scales. At the scale of islands, inter-island variation in harvesting intensity affected the abundance and size structure of populations of limpets as well as the balance between grazers, algae and barnacles. Stocks of limpets showed clear signs of exploitation and there was evidence that current legislation, including limpet protected zones, have been largely ineffective in protecting these populations. At smaller spatial scales, substratum micro-topography influenced the distribution and sui-vival of limpets. I also showed that the experimental provision of microhabitats could be used as a measure to mitigate the effects of coastal urbanisation, whilst promoting a local enhancement of the stocks of limpets. Overall my results provide evidence for the population and community level effects of limpet harvesting and show that limpet harvesting has a strong impact on the structure and fiinctioning of the Azorean rocky intertidal.

No description available.

Climate change is likely to have profound effects on marine animals due to the predicted increases in water temperature and acidity. Many studies have examined the effects of these elevated temperatures and decreased pH at the extreme temperatures expected in the summer season, but few studies have investigated how climate change may affect animals in the winter. In this study, we investigate the effects of both winter and summer temperatures on the growth rates, body composition and metabolic rate of four species of intertidal marine invertebrates: two calcified (common mussel - Mytilus edulis and edible periwinkle – Littorina littorea) and two non-calcified (beadlet anemone – Actinia equina and sea squirts – Ascidiella aspersa) species. Samples divided to two groups, one group exposed to winter temperature condition and the second group exposed to summer temperature condition. Following a period of acclimatization during which temperature was gradually increased and pH decreased, animals were exposed to the predicted climatic conditions of 2050 (TR 2050) and 2100 (TR 2100) for six weeks. During the study period, the mortality rates were monitored as well as growth rates by taking body weight, buoyant weight and body morphometrics (length and Width). At the end of experiments, body composition were measured by taking water content, dry shell and dry body weight weight, fat content and C:N ratio. In addition, metabolic rates were measured using a closed-system respirometry. During the experiments, seawater parameters such as acidity, temperature, salinity and dissolved oxygen were measured. The results of the experiments found that there was a significant increase in mortality of A. aspersa at the higher temperatures and water acidity in winter. Furthermore, growth rates of A. equina and A. aspersa were significantly reduced at TR 2050. On the other hand, it was observed that the C:N ratio of L. littorea was significantly increased at TR 2050 and that metabolic rate was significantly higher at TR 2100. However, under summer conditions, L. littorea there was a significant decrease in buoyant weight at TR 2050. While there was no mortality amongst A. equina, a significant reduction growth was found at elevated temperature and decreased pH level. The results in this study indicate that inter-species responses to environmental changes are likely to differ but also that the inter-species response will also vary depending on the season and life stage of the animal.

No description available.

Within hours, any undefended structure immersed in the marine environment will become fouled: a term known as biofouling. This phenomenon causes substantial economic losses and affects not only shipping vessels but also static structures. Although metal biocides added to coatings have proved very effective against biofouling, there were increasing concerns about the detrimental effects these were having on non-target species. The problem facing manufacturers of these coatings is the lack of available testing methods for non-biocidal antifouling coatings. This thesis aims to develop a framework for a suite of behavioural bioassays to investigate the efficiency of non-biocidal coatings. The research represents methodological investigations coupled to pilot studies. Three fouling species were investigated, Spirorbis borealis, Balanus amphitrite, and Balanus improvisus. All three species showed significant differences in behaviour on nonbiocidal coatings supplied by Akzo Nobel and these behaviours could be used to discriminate between coatings. Immersion trials were carried out in Sweden, Singapore and the UK, in order to ascertain whether behavioural parameters of the larvae in the laboratory could be used to predict fouling observed in the field. All three species demonstrated that aspects of their behaviour could be used to predict fouling at least at one location, with both Spirorbis borealis and Balanus amphitrite displaying behaviour that could be used to predict fouling in all three sites. The research showed that the behavioural bioassays have the potential to be developed into an acceptable commercial screening test. From the conclusions a final protocol for filming, digitising and analysing larval behaviour, in order to predict field fouling is presented. Development of this protocol could lead to a rapid commercial screening test for non-biocidal antifouling coatings.

No description available.

Large-scale photographic surveys present an opportunity to quantify variation in benthic megafaunal community structure and dynamics on the undersampled abyssal plains, a habitat covering ~70% of the global seabed. The aims were to examine the method, and to use it to improve estimates of megafaunal abundance, biomass and functional groups (e.g. feeding types and rates) at the Porcupine Abyssal Plain (PAP, 4850m depth, NE Atlantic), and also at Station M (4000m, NE Pacific), with the resulting data combined into a food web model. Method investigations included testing the quality of photo-derived ecological data by comparing three experts’ annotations of a large set of images. Greater consensus was attained in the identification than in detection of megafauna, and variation in the detection of common taxa resulted in significant differences in estimated density and community composition. Randomisation of images should be used to combat annotation bias. Secondly, relationships between measured body dimensions and preserved and fresh wet weights were compiled and applied to dimensions measured in seabed images. Size spectra estimated from photos were similar to those of trawl-caught specimens, but the total fresh wet weight biomass of holothurians and cnidarians in the photos was ~20 times the estimates from trawl catches, suggesting that seabed photography may improve biomass estimates. Seabed imagery was applied to the ecology of abyssal hills and adjacent plain at the PAP, with substantial impacts to prior estimates of abundance, biomass and community composition. Biomass was 3 times greater on the hills than the plain, and assemblage and trophic compositions (by density and biomass) were significantly different, correlated with environmental conditions. A burrowing anemone, Iosactis vagabunda, was newly found to be the most abundant animal, likely important to carbon cycling with its newly-observed predatory and deposit feeding behaviours. Mobile deposit feeding rates were linked to body size, scaling at a power predicted by the Metabolic Theory of Ecology. This rate appears to increase in response to the deposition of detritus in only one taxon tested, while others remained constant. These findings all have impacts to carbon cycling. The fate of detritus input on abyssal hills and the plain was examined using a model of carbon flow through the food web, and the improved quantification of biomass and knowledge of feeding modes. Suspension feeding dominated carbon processing on the hill, removing nearly all labile detritus input. On the plain, half the labile detritus was used by deposit feeders. The community on the plain is dependent on a more stable carbon supply than the hill. This represents a substantial improvement to prior assessments of benthic biogeochemistry in the abyss.

Calcium carbonate precipitation by marine organisms is an acknowledged contributor to the global carbon cycle. Coccolithophores are unicellular marine phytoplankton, that by excreting calcium scales and performing photosynthesis, contribute largely to the flux of atmospheric carbon to the surface and deeper oceans. The impact of elevated future ocean temperature and ocean acidity on the mechanism and rates, by which coccolithophores secret their calcium carbonate scales internally and contribute to the global carbon cycle, has been widely studied. However, biomineralisation in coccolithophores, the expression of molecular pathways, and the timing of gene expression related to calcification are still poorly understood. To better understand the process of calcification the transcriptome and proteome of calcifying G1-phase Emiliania huxleyi cells were investigated in the light and dark using next generation techniques. The results showed clear differences in both the transcriptomic and proteomic profiles between the photosynthetically enhanced calcification and the dark calcification phase. Interestingly, the bulk of the biomineralisation genes were higher expressed in the dark calcification phase at low calcification rates, suggesting that a large proportion of the molecular calcification machinery is bound to the Golgi apparatus and endoplasmic reticulum, which are complemented in the early G1-phase following cytokinesis. Furthermore, the results suggest that a set of biomineralisation genes exhibits continuous expression in both conditions of the G1 phase, whereas other genes are more abundantly expressed in the calcification phase. The importance of the calcium binding proteins calreticulin, calnexin, and calmodulin in the calcification phase was confirmed by transcriptomic and proteomic data. Proton pumping V-type ATPases were found higher expressed in dark phase but was still highly expressed in the enhanced calcification phase in the light. Calcium transport related gene expression of members of the NCKX (Na+/Ca2+-K+ exchanger), NCX (Na+/Ca2+exchanger), and CAX (calcium exchanger) were stronger in the low calcification phase, whereas SERCA-type calcium transporting ATPases were nearly equally expressed in both condition but originating from different genes that were expressed in either the light or the dark. Furthermore, transcriptome exploration suggested syntaxin and synaptobrevin could play an important role in calcification related vesicle fusion. The results have important implications for better understanding the timing of calcification related gene expression throughout the E. huxleyi cell cycle and for potential transcriptomic plasticity in response to changing environmental conditions.

Dimethylsulphoniopropionate (DMSP) is the most abundant sulphur molecule in the oceans. Catabolism of DMSP by marine organisms is important both for the global movement of sulphur and as a carbon and sulphur source for microbial life. The molecular basis of DMSP catabolism had been revealed by the discovery of a DMSP demethylase and six different lyases in marine bacteria. However, at the start of this study in 2009 no eukaryotic DMSP lyase had been isolated, purified or characterized from axenic cultures, and there was little information on the enzymology of any of the bacterial DMSP lyase enzymes. The work presented in this thesis identifies the requirement of the three bacterial cupin DMSP lyases DddL, DddQ and DddW for metal cofactors, and also establishes the enzymology and biochemistry of these cupin-containing DMSP lyases. The presence of a typical DMSP lyase in the coccolithophore Emiliania huxleyi RCC1217 is also demonstrated for the first time from bacteria-free cultures by application of previously successful techniques used in the purification of bacterial ddd genes. Combined these findings provide new insights into the mechanisms of cleavage of DMSP by bacteria and phytoplankton and expand our understanding of the enzyme diversity involved in this process.