Ostrea edulis has become considerably depleted throughout its range in areas of former abundance through disease, overexploitation, habitat loss and interactions with introduced species. 0. edulis has been included in the UK Species Biodiversity Action Plan and efforts towards its regeneration have shown potential for success. The Come estuary has a long history of oyster cultivation, is part of the Essex Estuaries European Marine Site, a controlled area for Bonamia ostreae and contains designated shellfish waters. Fragmented patches of 0. edulis were sparsely distributed in the estuary, within the species' range of acceptable salinity. Maximum densities were lower than those observed historically in Essex estuaries and the Solent, but slightly greater than former fishery areas in Northern Ireland. Ostrea appeared to form part of an extensive, but declining metapopulation of oysters in the region. Availability of hard substrata was found to be an important driver of spatial variation on a local scale. Key areas for settlement of 0. edulis were identified close to the estuary mouth, however, modification of the benthos by dredging to resuspend fine particulates and increasing coarse sediment by planting out cultch did not increase recruitment. Larval densities were low during the reproductive season and were concluded to be limiting recruitment. Biodiversity increased in association with 0. edulis density and availability of coarse substrata, demonstrating the value of the 0. edulis habitat for settlement and recruitment of sessile and epizootic macrofauna in an estuary composed substantially of fine sediments. Crepidula Jornicata dominated the sublittoral zone of the Come on coarse substrata and Polychaetae were abundant on fine sediments. Despite habitat overlap between C. Jornicata and O. edulis, no evidence was apparent of spatial competition between the species. Crassostrea gigas dominated large areas within the littoral zone, however the habitats of C. gigas and 0. edulis overlapped minimally in shallow subtidal areas. Adoption of strategies to increase broodstock and therefore larval supply was recommended to promote natural regeneration of 0. edulis in the Colne estuary.

No description available.

There is a constant and increasing need for sensitive and relevant information regarding the effects of the chronic exposure of coastal and marine ecosystems to anthropogenically derived chemicals and stressors. If these environments are to be preserved and maintained then an increased availability of techniques to aid in the understanding of pollutant effect will be of significant advantage. This work examines the use of a suite of biomarkers of marine pollution exposure and effect to determine environmental quality and the effect of pollutants on marine organisms. The aim is to examine the sensitivity of a range of techniques and their applicability to field monitoring. The blue mussel Mytilus edulis and the shore crab, Carcinus maenas, were chosen as test organisms. A range of techniques, including lysosomal membrane tests, cardiac monitoring, histopathology, and embryonic bioassays have been utilised. The robustness of the neutral red test in mussels is demonstrated in a range of laboratory and field studies. Confounding factors, such as variability and operator bias, are discussed. Significant advances have been made in the application of the lysosomal neutral red test to crabs. Laboratory and field test data are presented demonstrating the application of this test. Significant new linkages are shown between the biomarkers under test. Field data are presented showing links between subcellular membrane disruption, increased tissue abnormalities and the consequences of this on reproductive ability. Additional data are presented on the use of a freshwater mussel, Anodonta cygnea, as a sentinel animal. Links between cardiac activity and sub-cellular disruption are shown. Finally, field data are presented demonstrating the application of the methods under test as a rapid method of establishing environmental quality. Fieldwork conducted in the Black Sea region shows a significant correlation with inventories of land based emissions and biological proof of suspected poor areas of environmental quality.

No description available.

Cilia are of particular importance to the planktonic veliger larva, fulfilling feeding, locomotory and sensory roles. This study concentrates on the ciliation of the larval mantle and velum. The mantle is an important adult organ yet one scarcely studied in the larval form. The larval velum is the characteristic swimming and feeding organ of the veliger larval form. Knowledge of the ciliary arrangement of larval bivalves, especially in relation to different life history strategies, provides important information for arguments over the phylogeny of such characteristics within the Mollusca. Anatomical work explored the possibility of ciliary sense organs being found on the mantle and further elucidates the pattern of distribution of cilia on the velum. Larval ciliary swimming in varying water temperatures has been investigated via the development of a filming methodology, revealing the thermal tolerance of swimming using velar ciliation and the ability of the larva to detect and respond to temperature stimuli. Cilia were investigated throughout larval development from veliger stage to metamorphosis in two bivalve families, the Ostreidae (Crassostrea gigas and Ostrea edulis) and the Teredinidae (Lyrodus pedicellatus). The three larvae represented three developmental modes with C. gigas planktonic, O. edulis partly brooded and L. pedicellatus long-term brooded. Scanning electron microscopy (SEM) and light microscopy was used for anatomical investigations. Confocal laser scanning microscopy was used to locate catecholamines and serotonin in C. gigas larvae, with reference to the cilia locations identified by SEM. Swimming larvae were filmed in fixed and changing temperatures to identify behavioural or physiological reactions. The mantle of the ostreid larvae had 13 different cilia groups which have been identified and photographed in C. gigas and O. edulis. Two of these groups appear to be sensory. One group is associated with the developing gill bud, and the other is located directly under the posterodorsal shell notch. The location of this group under the shell notch also was the location for several cells containing catecholamines. The ventral inner mantle rim of ostreid larvae has large tracts of cilia, probably primitive larval versions of adult rejection tracts. There were several flask-shaped cells with catecholamines and two long serotonin containing fibres in the mantle where these tracts were found. The mantle of L. pedicellatus had 2 distinct groups of cilia. One of these groups formed discrete clumps on the inner mantle fold and featured sensory structures. The velar ciliation of both the ostreid species larvae was almost identical, and both revealed a previously unreported band of cilia. This band may increase the efficiency of the opposed band particle capture system. The velum of L. pedicellatus was different from the ostreid larvae; its velar ciliature was similar to other long-term brooded larvae recorded in the literature with a large adoral tract and the loss of the post-oral band. Larval swimming velocity increased with increasing water temperature. Acclimated larvae were able to swim in water temperatures where larval activity stopped during sudden temperature changes. Changes in larval swimming during sudden temperature changes are probably due to an interaction of three factors: water viscosity changes affecting cilia efficiency, the physiological effect of temperature and behavioural responses. The additional ciliary band on the ostreid velum probably increases particle capture efficiency, and further investigations are needed to determine if this is a characteristic unique to the ostreids. The velar ciliation of the brooded L. pedicellatus is, by the pediveliger stage, similarly modified to the velum of other brooded larvae from widely separated taxonomic groups. Mantle ciliation is more extensive in ostreids than in teredinids, but both have sensory stereocilia on the mantle. The presence of catecholamines and serotonin suggests that the larva has a measure of control both of mantle and velar ciliary beat, seen in the variation in swimming patterns and particle rejection. The filming and analytical techniques developed offer an accessible method for gathering laboratory data on larval behaviours. Analysis of swimming suggested larvae can sense changes in temperature and effect a behavioural response to it. Such responses may enable larvae to control their vertical position in the water column when encountering environmental discontinuities or heterogeneities such as thermoclines. Variation in larval swimming velocity between larval batches suggests this method could also be used as a quick assay to determine the fitness of different larval batches within a hatchery.

Στην παρούσα διδακτορική διατριβή μελετήθηκε η βιολογία του είδους Ruditapes decussatus (Linnaeus, 1758) από τη λιμνοθάλασσα του Αράξου και το εκβολικό σύστημα του Ευήνου. Ο στόχος της μελέτης ήταν η βαθύτερη γνώση της βιολογίας του R. decussatus στα δύο ελληνικά οικοσυστήματα, η οποία δύναται να συμβάλει τόσο στην ορθολογική αλιευτική του διαχείριση, όσο και σε μια ενδεχόμενη συστηματική καλλιέργειά του στην Ελλάδα. Για το σκοπό αυτό πραγματοποιήθηκαν τυχαίες δειγματοληψίες σε δεκαπενθήμερη βάση επί τρία χρόνια. Τα αποτελέσματα έδειξαν ότι οι δύο πληθυσμοί διαφέρουν σε σημαντικό βαθμό σε ό,τι αφορά την αύξηση και τη θνησιμότητα, ενώ οι διαφορές στην αναπαραγωγική τους συμπεριφορά είναι μικρότερης έκτασης. Ειδικότερα ο πληθυσμός στη λιμνοθάλασσα του Αράξου εμφανίζει άριστα χαρακτηριστικά αύξησης και αναπαραγωγής, ενισχύοντας την άποψη ότι μια απόπειρα εντατικής καλλιέργειας του είδους στη χώρα μας θα στεφόταν με επιτυχία. Επίσης αποκομίστηκαν σημαντικά συμπεράσματα που αφορούν την ηθολογία του είδους και τη συμπεριφορά του σε καταστάσεις κινδύνου. / In the present doctoral thesis we studied the biology of two populations of the bivalve Ruditapes decussatus, one located in the lagoon of Araxos and the other in the estuary of Evinos River. The objective of the study was the use of the results in order to contribute in the species’ rational and successful management and in the development of an aquaculture industry in Greece. For this aim species were randomly sampled every two weeks in a three-year period. The results showed that the two populations differ significantly regarding increase and mortality, while the differences in their reproductive behaviour are less important. Specifically the population in the lagoon of Araxos shows excellent characteristics regarding increase and reproduction, supporting the opinion that an attempt of intensive culture of this species in our country would be crowned with success. Also we obtained important informations that concern the ethology of the species and its behavior in stress situations.

Le but de ce travail de doctorat est d’évaluer la possibilité d’utiliser Haslea ostrearia et la marennine en ostréiculture. Les objectives de ce projet sont : (1) l'évaluation du comportement alimentaire de l'huître creuse Crassostrea gigas sur des cellules d’H. ostrearia de différentes tailles et les conséquences potentielles sur les populations algales; (2) la caractérisation du verdissement par la marennine et ses conséquences sur la physiologie de C. gigas; (3) les conséquences du verdissement sur les traits comportementaux, physiologiques et biochimiques de plusieurs espèces de bivalves; (4) l'utilisation conjuguée d’H. ostrearia avec d'autres microalgues d’importance en aquaculture. Nos résultats suggèrent que la taille des cellules affecte considérablement le processus de selection d’H. ostrearia par l’huître. Cette étude démontre également que la forme extracellulaire de la marenninne contribue significativement au verdissement dans les mucocytes des branchies. Mis à part le verdissement des organes palléaux des bivalves, une concentration modérée de marennine (2 mg L-1) affecte les performances comportementales, physiologiques et biochimiques des bivalves. Néanmoins, ces effets pourraient être compensés par ses activités biologiques comme agent antibactérien naturel et source d’alimentation mixte d’algues en conchyliculture. / This Ph.D. thesis focuses on several assessments to achieve the optimum benefit of utilization of marennine in the field of aquaculture. The study covers: (1) the assessment in feeding behavior of the Pacific oyster Crassostrea gigas on different sizes of Haslea ostrearia and its ecological consequence; (2) the characterization of the greening by marennine and its consequences on some physiological traits of on C. gigas. (3) the consequence of greening by marennine on behavioral, physiological and biochemical traits of bivalves; (4) the utilization of H. ostrearia and marennine in a combination diet with other microalgae relevant to aquaculture.Our results suggest that cell size impacts considerably the selection process of H. ostrearia by oyster. This study also demonstrates that the extracellular form of marennine contributes significantly to the greening in the mucocytes of the gills. Apart from greening the pallial organs of bivalves, marennine (2 mg L-1) affects the behavioural, physiological and biochemical performance. Nevertheless, these effects can be compensated for its biological activities such as natural antibacterial agent and use as a mixed algal diet for bivalve aquaculture.

The freshwater pearl mussel (FPM) is an iconic bivalve mollusc whose presence in rivers is assumed to indicate a healthy, bio-diverse ecosystem, capable of providing a range of goods and services. However, excessive sedimentation has been shown consistently to have detrimental effects on FPM, at both the juvenile and adult life stages. As a major source of diffuse river pollution, previous studies have shown erosion rates rising with increasing precipitation, suggesting also increased risk under wetter, future climates. So far, however, most erosion studies have been at the small plot scale and hence it is not possible to make predictions at the catchment scale where risk assessments for FPM are most relevant. Furthermore, little research has focussed on how work to remediate sediment delivery might affect public appreciation of rivers as highly valued landscape features. This research focussed on three typical FPM rivers in the UK: the Ehen catchment in Northern England; the Conwy in North Wales and the Dee in East Scotland and asked 1) How will climate change predictions for the period 2010 – 2039 affect soil erosion at the catchment scale? 2) What factors influence public attitudes towards rivers, the FPM, and mitigation measures to control sediment movement? and 3) Can habitat management for FPMs take into account climate-driven environmental change and social values when constructing conservation goals? In respect of the first aim, the Pan-European Soil Erosion Risk assessment model, PESERA, showed that whilst soil erosion rates increased with rising precipitation, land cover was a more dominant driver of erosion rates over the period studied (2010-2039). Despite being flatter, arable land had higher erosion rates than those from forested portions of each catchment, which were in regions of steeper topography. Secondly, based on a mixture of qualitative focus groups and quantitative surveys, the majority of people had positive attitudes toward rivers, both in a general and local sense. The FPM was not a well-known aquatic species but information about possible human or ecological beneficiaries of mitigation to control sediment delivery into rivers did not affect how acceptable these measures were perceived to be. Factors increasing acceptability of mitigation measures included natural looking scenes that were accessible. In contrast, concerns about impacts on agriculture and food production led to lower levels of acceptability. Finally, this research highlighted crossovers between FPM habitat needs and ideal river scenes from a public perspective and concluded that social values of riverscapes can be included in habitat management plans for the FPM, without compromising conservation goals. A case study exemplifying the methodology used to do this, using the Dee catchment, Scotland and future scenarios from the National Ecosystem Assessment showed that conservation measures in aid of the FPM can accommodate different land management priorities and societal needs. As one of the first studies to assess interactions between evidence from physical sciences, ecology and public perception for an iconic species, this research is expected to have far reaching consequences for public policy, land management practices and river conservation. At a policy level, this includes the ways in which environmental practices can accommodate the social values identified within this research to allow a more holistic approach to ecosystem management; for on the ground practitioners, this research will influence how ecologically important but socially unfamiliar species are managed and how the impacts of land management are assessed both temporally, (to include the impacts of future climate change), spatially, (to take account of catchment wide effects) and socially (to examine social acceptability of different management options).

Les écosystèmes côtiers sont parmi les plus vulnérables aux changements globaux actuels, qui entraînent notamment une augmentation de la température de l'eau, ainsi que de la fréquence des épisodes hypoxiques. La coquille Saint-Jacques, Pecten maximus, est une espèce subtidale évoluant à des profondeurs de 2 à 210 m. Malgré son intérêt commercial et un intérêt écologique majeur, cette espèce n'a fait l'objet que de peu d'études au niveau moléculaire. L'objectif de cette thèse était de caractériser les mécanismes moléculaires régissant l'acclimatation de cette espèce aux contraintes thermique et hypoxique. Nous avons dans un premier temps caractérisé les modifications d'expression des gènes/protéines, par des approches transcriptomiques (RNAseq) et protéomiques (2-DE), dans un tissu, le manteau, d'animaux exposés à une contrainte thermique prolongée (56 jours). Nous avons ainsi pu identifier les voies majeures de régulation (eg., AP-1), les grandes fonctions (eg., cytosquelette) et processus (eg., apoptose) impliqués dans la réponse, mais également d'observer les grandes orientations du métabolisme (eg., dégradation des lipides de réserve). La réponse des organismes à l'hypoxie dépend de leur manière de gérer les faibles teneurs en oxygène. Nous avons d'abord, par une approche comparative avec une espèce intertidale, la moule (Mytilus spp.), caractérisée la réponse physiologique de la coquille Saint-Jacques à l'hypoxie. Nous avons pu ainsi déterminer ses paramètres d'oxyregulation, plus particulièrement son Point critique en 02 (Pc02). Le développement d'une approche protéomique, couplant l'effet de la température et de l'hypoxie, nous a ensuite permis d'identifier plusieurs protéines (CK2, GLN, etc.) potentiellement impliquées dans la réponse au niveau moléculaire. Enfin, dans l'optique de mieux comprendre la physiologie particulière de ces mollusques dans leur environnement naturel, nous avons comparé les signatures protéomiques de deux populations de P. maximus évoluant dans des écosystèmes contrastés, i.e. en limite nord- (Norvège) et au centre- (Brest) de l'aire de répartition de l'espèce. Les résultats suggèrent des différences majeures entre les deux populations au niveau du cytosquelette. En conclusion, ce travail ouvre des perspectives nouvelles pour la compréhension des mécanismes moléculaires régissant l'adaptation des mollusques aux contraintes thermiques et hypoxiques, deux stress particulièrement importants pour les organismes marins dans le contexte du changement global. / Coasts are among the most vulnerable ecosystems to the ongoing global changes, which result in increased water temperatures and frequencies of hypoxic episodes. The great scallop, Pecten maximus, is a subtidal species living at depths of 2-210 m. In spite of its commercial and major ecological values, only few studies at the molecular level were performed on this species. This thesis aimed at characterizing the molecular mechanisms implied in acclimation of this species to thermal and hypoxia stresses. We first characterized the changes of expression of the genes / proteins in response to a long-term thermal stress (56 days), by using both a transcriptomic- (RNAseq) and a proteomic- (2-DE based) approaches, in the mantle tissue of scallops. This allowed us to identify key regulatory pathways (eg., AP-1), the major functions (eg., cytoskeleton) and processes (eg., apoptosis) involved in the response, but also to observe the main orientations of metabolism (eg., degradation of lipid reserves). The response of organisms to hypoxia depends on how they cope with low oxygen availability. Therefore, we first carried out a comparative approach with an intertidal species, the mussel (Mytilus spp.) to characterize the physiological response of P. maximus to hypoxia. Of note, we could determine its oxyregulatory parameters, particularly its critical point in 02 (Pc02). Then, coupling the effects of temperature and of hypoxia, we developed a proteomic approach that allowed us to identify several proteins (CK2, GLN, etc.) potentially involved in the response at the molecular level. Finally, in an effort to better understand the particular physiology of these mollusks in their natural environment, we compared the proteomic signatures of two populations of P. maximus living in highly contrasted ecosystems, ie in the northern limit- (Norway) and the center- (Brest) of the biogeographical distribution of this species. The results suggest major differences between the two populations, especially at the cytoskeleton level. In all, this work opens new avenues for understanding the molecular mechanisms governing the adaptation of mollusks to heat and hypoxia, two stresses that will most probably greatly influence the lifestyle of marine organisms and populations in future years.

Le “coût de la reproduction” est un concept qui définit qu’un investissement à la reproduction élevé a un prix qui se paye ultérieurement par une accélération de la sénescence. Cela peut notamment traduire des compromis entre la reproduction et d’autres fonctions physiologiques comme la défense antioxydante. Chez l’huître creuse Crassostrea gigas, la reproduction représente une fonction physiologique majeure. Dans le cadre des études effectuées pour comprendre les mortalités estivales affectant cette espèce, une corrélation négative entre effort reproducteur et survie a été observée. D’autre part, des gènes antioxydants ont été mis en évidence comme différentiellement exprimés entre les lignées d’huîtres sélectionnées pour leur résistance ou leur sensibilité aux mortalités estivales. Certaines études proposent que la susceptibilité au stress oxydant puisse représenter un coût de la reproduction participant au processus de sénescence. Dans ce contexte, nous avons analysé la capacité antioxydante des huîtres en fonction de leur investissement reproducteur. Pour cela, la technique d’ARN interférence a été utilisée pour manipuler l’effort reproducteur des huîtres. L’expression des principales enzymes antioxydantes (taux de transcrits et activités enzymatiques) et le dosage de dommages oxydatifs ont ensuite été mesurés dans différents tissus et cellules de l’organisme (branchies, gonade, hémocytes et gamètes). Les résultats obtenus dans le cadre de cette thèse suggèrent que la capacité antioxydante de C. gigas est particulièrement efficace et que la reproduction seule n’est pas suffisante pour induire un stress oxydant. Cette capacité antioxydante apparaît comme tissu-spécifique voire cellule-spécifique et le métabolisme du glutathion semble jouer un rôle majeur dans cette protection. Cette grande résistance au stress oxydant contribuerait à faire de C. gigas une espèce particulièrement adaptée à la vie dans des environnements stressants. / The “cost of reproduction” is a concept defining that a high reproductive investment has a price that is paid later by an acceleration of senescence. That may translate tradeoff between reproduction and other physiological functions such as antioxidant defense. In the Pacific oyster Crassostrea gigas, reproduction is a major physiological function. In a study led to understand the summer mortalities affecting this species, a negative correlation between reproductive effort and survival was observed. Moreover, some antioxidant genes were identified as differentially expressed between lines of oysters selected for resistance or susceptibility to summer mortalities. Some studies suggest that the susceptibility to oxidative stress may represent a cost of reproduction taking part to the process of senescence. In this context, we analyzed the antioxidant capacity of oysters according to their reproductive investment. For this, the technique of RNA interference was used to manipulate the reproductive effort of oysters. The expression of the main antioxidant enzymes (transcript levels and enzyme activities) and the dosage of oxidative damages were then measured in different tissues and cells of the organism (gills, gonad, hemocytes and gametes). The results obtained in this thesis suggest that the antioxidant capacity of C. gigas is particularly effective and that reproduction alone is not sufficient to induce oxidative stress. This antioxidant capacity appears to be tissue-specific even cell-specific and glutathione metabolism would to play a major role in this protection. This resistance to oxidative stress would make C. gigas be a species particularly adapted to life in stressful environments.