A review of potential impacts of submarine power cables on the marine environment:Knowledge gaps, recommendations and future directions

Submarine power cables (SPC) have been in use since the mid-19th century, but environmental concerns about them are much more recent. With the development of marine renewable energy technologies, it is vital to understand their potential impacts. The commissioning of SPC may temporarily or permanently impact the marine environment through habitat damage or loss, noise, chemical pollution, heat and electromagnetic field emissions, risk of entanglement, introduction of artificial substrates, and the creation of reserve effects. While growing numbers of scientific publications focus on impacts of the marine energy harnessing devices, data on impacts of associated power connections such as SPC are scarce and knowledge gaps persist. The present study (1) examines the different categories of potential ecological effects of SPC during installation, operation and decommissioning phases and hierarchizes these types of interactions according to their ecological relevance and existing scientific knowledge, (2) identifies the main knowledge gaps and needs for research, and (3) sets recommendations for better monitoring and mitigation of the most significant impacts. Overall, ecological impacts associated with SPC can be considered weak or moderate, although many uncertainties remain, particularly concerning electromagnetic effects

Etude du processus invasif de Crassostrea gigas en Bretagne: Etat des lieux, dynamique et conséquences écologiques

The Pacific oyster, Crassostrea gigas, was introduced in France at the end of the sixties to replace the Portuguese oyster, Crassostrea angulata, decimated by disease. But only since the nineties that wild populations established on Brittany's shores. The first part of this study shows all Brittany coasts now to be colonized by C. gigas. Stocks of wild oysters are estimated at 10 000 and 6 420 tons in the Bay of Brest, and the Morbihan Bay, respectively. The second part of this study concerns factors determining C. gigas invasive process dynamics. The responsibility of climate change in the establishment of C. gigas in Brittany is confirmed. Results also highlight that C. gigas does not recruit in the subtidal zone, which refutes accusations of European oyster, Ostrea edulis, exclusion. Finally, monitoring of the summer 2008 massive mortalities reveals that wild populations were little impacted. Analysis of ecological consequences of C. gigas invasion on Brittany shores is done in the last part of this study. Impacts on communities become marked when colonization intensifies with the creation of oyster reefs, which increase macrofaunal abundance and diversity. Studies on respiration and calcification processes show that total annual carbon production of rocky intertidal communities is increased twenty fold, reaching 761,77 g C m-2 year-1 when high density populations of C.gigas establish (nearly 700 ind. m-2).L'huître creuse du Pacifique, Crassostrea gigas a été introduite en France à la fin des années 60 pour remplacer l'huître portugaise, Crassostrea angulata, décimée par des maladies. Ce n'est cependant qu'à partir des années 90 que des populations sauvages se sont établies sur les estrans bretons. La première partie de cette étude a permis de montrer, qu'à l'exception de la zone nord-Finistère et des baies de Douarnenez et Audierne, l'ensemble des côtes bretonnes est actuellement colonisé par C. gigas. Des stocks de 10 000 et 6 420 tonnes ont été recensés en Rade de Brest et dans le Golfe du Morbihan. La seconde partie de cette étude a permis de préciser les facteurs déterminant la dynamique du processus invasif de C. gigas. La responsabilité du changement climatique dans l'établissement de C. gigas en Bretagne a ainsi été confirmée. Aucun recrutement de C. gigas n'a été observé dans la zone subtidale, réfutant ainsi les accusations d'exclusion de l'huître plate, Ostrea edulis. Enfin, l'impact de l'épisode de mortalité estivale massive des huîtres cultivées pendant l'été 2008 a été très faible dans les populations sauvages. L'analyse des conséquences écologiques de la prolifération de C. gigas sur les estrans bretons a été réalisée dans la dernière partie de cette étude. L'impact de C. gigas sur la communauté est net lorsque la colonisation s'intensifie et que de véritables récifs se forment, augmentant alors l'abondance et la diversité de la macrofaune. Les mesures de la production annuelle de carbone de la communauté intertidale rocheuse ont montré qu'elle est multipliée par plus de 20, lorsque C. gigas colonise le substrat en forte densité, atteignant 761,77 g C m-2 an-1

Differential response of benthic macrofauna to the formation of novel oyster reefs (Crassostrea gigas, Thunberg) on soft and rocky substrate in the intertidal of the Bay of Brest, France

International audienceWhen the Pacific oyster (Crassostrea gigas, Thunberg) was introduced into France for aquaculture in the mid-sixties, it was initially confined to the sites where it was farmed. Subsequent global warming most likely facilitated the establishment of wild populations throughout the French coastline. This phenomenon of spread has become so great that oyster reefs have recently appeared in sheltered estuaries, on both soft and hard substrate. The present study examined two such sites in the Bay of Brest, Brittany. It is the first to investigate the impacts of this new substrate on the biocoenosis of uncolonised intertidal habitats in France. Increased species richness and abundance of intertidal macrofauna were observed in the presence of oyster reefs on both, mud (4 and 20 fold respectively) and rock (5 fold for both). The dominance of suspension feeders in mud changed to carnivores in reefs and their underlying sediment. Calculation of biotic coefficients (BC) of the soft-bottom fauna revealed only a slight organic enrichment, and the organic and silt composition in the sediment beneath oyster reefs were not significantly different from that on bare sites. On rock, the dominance of grazers remained unchanged between bare rock and oyster reef, while reef on rock was also characterised by deposit and detritic feeders. C. gigas is suspected to cause a homogenisation of coastal habitats with an impoverishment of overall quality but we detected only 11 common species between reefs on mud (60 species) and those on rock (55 species)

High-Resolution Melting of 18S rDNA sequences (18S-HRM) for discrimination of bivalve’s species at early juvenile stage: application to a spat survey

International audienceIt is particularly difficult to identify bivalve species at early development stages (larvae and spat) by morphological examination. Targeting genetic marker commonly used for species identification, we developed a cheap and user friendly tool for bivalve identification through High-Resolution Melting (HRM) analysis. Based on the polymorphism of the nuclear 18S ribosomal RNA gene among 11 orders of bivalve, the 18S-HRM method allowed discriminating species of the Ostreida, Mytilida and Pectinida orders. In this study, this method proved to be a very sensitive tool able to authenticate one species that differed by only one mutation from another one. We applied the method by identifying bivalve species in spat collections from different benthic substrates moored at subtidal and intertidal areas in euhaline conditions. This field survey showed that the settlement of the invasive species Crassostrea gigas was limited vertically to intertidal substrates. In conclusion, the 18S-HRM analysis is a fast, closed-tube method with high resolution and cost effectiveness, and is thus a good alternative method to identify bivalve species. This HRM assay can by applied for species identification of bivalves in the context of ecological management as well as food traceability for bivalves with economical interests

Respiration and Calcification of Crassostrea gigas: Contribution of an Intertidal Invasive Species to Coastal Ecosystem CO2 Fluxes

International audienceRespiration and calcification rates of the Pacific oyster Crassostrea gigas were measured in a laboratory experiment in the air and underwater, accounting for seasonal variations and individual size, to estimate the effects of this exotic species on annual carbon budgets in the Bay of Brest, France. Respiration and calcification rates changed significantly with season and size. Mean underwater respiration rates, deducted from changes in dissolved inorganic carbon (DIC), were 11.4 μmol DIC g−1 ash-free dry weight (AFDW) h−1 (standard deviation (SD), 4.6) and 32.3 μmol DIC g−1 AFDW h−1 (SD 4.1) for adults (80-110 mm shell length) and juveniles (30-60 mm), respectively. The mean daily contribution of C. gigas underwater respiration (with 14 h per day of immersion on average) to DIC averaged over the Bay of Brest population was 7.0 mmol DIC m−2 day−1 (SD 8.1). Mean aerial CO2 respiration rate, estimated using an infrared gas analyzer, was 0.7 μmol CO2 g−1 AFDW h−1 (SD 0.1) for adults and 1.1 μmol CO2 g−1 AFDW h−1 (SD 0.2) for juveniles, corresponding to a mean daily contribution of 0.4 mmol CO2 m−2 day−1 (SD 0.50) averaged over the Bay of Brest population (with 10 h per day of emersion on average). Mean CaCO3 uptake rates for adults and juveniles were 4.5 μmol CaCO3 g−1 AFDW h−1 (SD 1.7) and 46.9 μmol CaCO3 g−1 AFDW h−1 (SD 29.2), respectively. The mean daily contribution of net calcification in the Bay of Brest C. gigas population to CO2 fluxes during immersion was estimated to be 2.5 mmol CO2 m−2 day−1 (SD 2.9). Total carbon release by this C. gigas population was 39 g C m−2 year−1 and reached 334 g C m−2 year−1 for densely colonized areas with relative contributions by underwater respiration, net calcification, and aerial respiration of 71%, 25%, and 4%, respectively. These observations emphasize the substantial influence of this invasive species on the carbon cycle, including biogenic carbonate production, in coastal ecosystems

CO2 generation by calcified invertebrates along rocky shores of Brittany, France

International audienceMany autochthonous and alien macroinvertebrates of the intertidal zone are biocalcifiers, and the present study proposes a first assessment of their calcimass and their annual calcium carbonate (CaCO3) production at a regional scale, along 500 km of the coastline of Brittany, France, which represents a wide range of the rocky-shore habitats commonly encountered in the north-eastern Atlantic region. All sites considered together gave a mean calcimass estimate of 5327 g m-2. The corresponding mean CaCO3 gross production was 2584 g m-2 year-1. The net production (including dissolution) by biocalcification was 2384 g CaCO3 m-2 year-1. Estimations of CO2 production via both calcification and respiration were carried out in particular for the phylum Mollusca and for crustacean barnacles, dominating in terms of calcimass. Mean CO2 production obtained by summing CO2 fluxes related to net CaCO3 production and respiration for all sampled sites was 22.9 mol m-2 year-1. These results illustrate the significance of CO2 production during biogenic CaCO3 precipitation of intertidal invertebrates in such temperate coastal environment compared with tropical zones and the contribution of the shelves to the global CaCO3 budget

Analyse spatiale de la prolifération de C. gigas en Bretagne

After its massive introduction in the seventies in France Crassostrea gigas has become the main production of French oyster farming. From the early 1990’s, C. gigas has started to spread to many sites of Brittany and Normandy and, thanks to climate warming, its population has dramatically increased leading to a general invasion and to deep changes in ecosystems and biodiversity. A research program called PROGIG has been set up to evaluate the dynamic of this proliferation on French Channel and Atlantic coasts, and to identify its interactions with marine ecosystems and human activities. This paper presents the GIS implemented to integrate the data collected during field surveys of oyster populations, and the results of a spatial analysis of its potential interactions with human activities on coastal zone

Un SIG dédié à la prolifération de l'huître creuse du Pacifique Crassostrea Gigas

International audienceAfter its massive introduction in the seventies in France Crassostrea gigas has became the main production of French oyster farming. From the early 1990's, C. gigas has started to spread many sites of Brittany and Normandy and, thanks to climate warming, its population has dramatically increased leading to a general invasion and to deep changes in ecosystems and biodiversity. A research program called PROGIG has been set up to evaluate the dynamic of this proliferation on French Channel and Atlantic coasts, and to identify its interactions with marine ecosystems and human activities. This paper presents the GIS implemented to integrate the data collected during field surveys of oyster populations, and the results of a spatial analysis of its potential interactions with human activities on coastal zone.L'huître creuse du Pacifique Crassostrea gigas est une espèce introduite massivement dans les années 70 en France pour les besoins de l'ostréiculture. Elle représente aujourd'hui l'essentiel de la production conchylicole française. Depuis le début des années 90, l'espèce a commencé à s'installer durablement sur de nombreux sites de Bretagne et de Normandie. Le processus de colonisation s'est accéléré depuis 2000, induisant des modifications profondes dans les écosystèmes et des changements dans la biodiversité. Ce phénomène d'invasion biologique a pour origine probable le réchauffement climatique qui favorise l'extension spatiale des zones dans lesquelles les huîtres peuvent pondre. Un programme de recherche a été mis en œuvre pour évaluer et quantifier la dynamique de cette prolifération au niveau des façades Manche et Atlantique et pour identifier les interactions réalisées avec les écosystèmes marins et les activités humaines. L'objet de cet article est de présenter le système d'information géographique (SIG) mis en œuvre pour intégrer les données de suivi de cette prolifération sur les côtes Manche-Atlantique de la Bretagne et pour l'analyse spatiale de ses interactions potentielles avec les activités humaines du littoral

Underwater operational noise level emitted by a tidal current turbine and its potential impact on marine fauna

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Sex-, gametogenesis, and tidal height-related differences in levels of HSP70 and metallothioneins in the Pacific oyster Crassostrea gigas

International audiencePacific oysters, Crassostrea gigas, living at a range of tidal heights, routinely encounter large fluctuations in temperature. We demonstrate that levels of heat shock proteins (HSP) and other stress proteins (metallothioneins, MTs) quantified by ELISA, remained similar in gills, mantle and digestive gland between oysters inhabiting low and high tidal heights. In contrast, endogenous HSPs and MITs levels in gonad changed significantly during gametogenesis. In female gonads, the constitutive form of HSP70 and the MTs increased from immature (or resting) to mature stages (about more than 3-fold) and decreased after spawning. In male gonads, the same expression patterns were observed, whereas Proteins levels decreased once fully mature. Females presented higher concentration of HSP70 and MTs than males during the spawning period. No significant difference in HSPs and MTs patterns was found among oysters sampled at low and high tidal heights. We hypothesize that the high level of stress proteins in eggs may increase survival of oyster progeny