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

The importance of nonnative Pacific oyster reefs as supplementary feeding areas for coastal birds on estuary mudflats

1. A combined empirical and modelling approach was used to investigate the value of a Pacific oyster reef to feeding shorebirds and to observe and predict the impact of reef clearance on bird populations in the Colne Estuary, a protected area in south‐east England. Macro‐invertebrate biomass and numbers of feeding birds were measured on a Pacific oyster reef, an adjacent uncolonized mudflat, and an area of mudflat that had been cleared of oysters 6 months previously. These data were used to parameterize an individual‐basedmodel (MORPH) to predict the impact of clearance of the reef on winter bird survival. Feeding success and intake rates of Eurasian oystercatcher, Eurasian curlew, and Eurasian common redshank were also recorded during the course of a winter. 2. Themacro‐invertebrate diversity and biomass within both the oyster reef and the cleared area were significantly greater than the adjacent uncolonized mudflat. The density and biomass of large invertebrate prey in the mudflat were low, yet the Pacific oyster reef hadmuch higher densities and biomass of large prey, especially annelids and shore crabs. 3. The winter assemblage of feeding birds differed significantly between each of the areas. The mean total number of feeding birds was significantly greater on the uncolonized mudflat; however, mean peak counts, feeding success rate and prey intake rate of Eurasian oystercatcher were greater on the reef. Significantly greater intake rates and feeding success rates were also observed on the reef for Eurasian curlew, a species of conservation concern. 4. Field data and model predictions show that Pacific oyster reefs can provide valuable supplementary feeding areas for some shorebirds, yet other species avoided the reef. However, as estuaries vary in available feeding resources, it is important that the value of reefs and their management is determined regionally

Spatial variation of trace metals within intertidal beds of native mussels (Mytilus edulis) and non-native Pacific oysters (Crassostrea gigas): implications for the food web?

Abstract Pollution is of increasing concern within coastal regions and the prevalence of invasive species is also rising. Yet the impact of invasive species on the distribution and potential trophic transfer of metals has rarely been examined. Within European intertidal areas, the non-native Pacific oyster (Crassostrea gigas) is becoming established, forming reefs and displacing beds of the native blue mussel (Mytilus edulis). The main hypothesis tested is that the spatial pattern of metal accumulation within intertidal habitats will change should the abundance and distribution of C. gigas continue to increase. A comparative analysis of trace metal content (cadmium, lead, copper and zinc) in both species was carried out at four shores in south-east England. Metal concentrations in bivalve and sediment samples were determined after acid digestion by inductively coupled plasma-optical emission spectrometry. Although results showed variation in the quantities of zinc, copper and lead (mg m-2) in the two bivalve species, differences in shell thickness are also likely to influence the feeding behaviour of predators and intake of metals. The availability and potential for trophic transfer of metals within the coastal food web, should Pacific oysters transform intertidal habitats, is discussed

Ecological impacts of non-native Pacific oysters (Crassostrea gigas) and management measures for protected areas in Europe

Pacific oysters are now one of the most ‘globalised’ marine invertebrates. They dominate bivalve aquaculture production in many regions and wild populations are increasingly becoming established, with potential to displace native species and modify habitats and ecosystems. While some fishing communities may benefit from wild populations, there is now a tension between the continued production of Pacific oysters and risk to biodiversity, which is of particular concern within protected sites. The issue of the Pacific oyster therefore locates at the intersection between two policy areas: one concerning the conservation of protected habitats, the other relating to livelihoods and the socio-economics of coastal aquaculture and fishing communities. To help provide an informed basis for management decisions, we first summarise evidence for ecological impacts of wild Pacific oysters in representative coastal habitats. At local scales, it is clear that establishment of Pacific oysters can significantly alter diversity, community structure and ecosystem processes, with effects varying among habitats and locations and with the density of oysters. Less evidence is available to evaluate regional-scale impacts. A range of management measures have been applied to mitigate negative impacts of wild Pacific oysters and we develop recommendations which are consistent with the scientific evidence and believe compatible with multiple interests. We conclude that all stakeholders must engage in regional decision making to help minimise negative environmental impacts, and promote sustainable industry development

How Do They Do It? – Understanding the Success of Marine Invasive Species

From the depths of the oceans to the shallow estuaries and wetlands of our coasts, organisms of the marine environment are teeming with unique adaptations to cope with a multitude of varying environmental conditions. With millions of years and a vast volume of water to call their home, they have become quite adept at developing specialized and unique techniques for survival and – given increasing human mediated transport – biological invasions. A growing world human population and a global economy drives the transportation of goods across the oceans and with them invasive species via ballast water and attached to ship hulls. In any given 24-hour period, there are about 10,000 species being transported across different biogeographic regions. If any of them manage to take hold and establish a range in an exotic habitat, the implications for local ecosystems can be costly. This review on marine invasions highlights trends among successful non-indigenous species (NIS), from vectors of transport to ecological and physiological plasticity. Apart from summarizing patterns of successful invasions, it discusses the implications of how successfully established NIS impact the local environment, economy and human health. Finally, it looks to the future and discusses what questions need to be addressed and what models can tell us about what the outlook on future marine invasions is

Characterisation of the role of the protein Ten-eleven translocation 1 (TET1) in the dynamic of chromatin organisation

La chromatine, composée d’ADN et de protéines histones, possède une structure multi-échelle complexe et dynamique participant notamment à la régulation de la transcription. Son état de compaction peut être régulé par des modifications épigénétiques trouvées sur la queue des histones et sur l’ADN. Les enzymes Ten-eleven translocation (TET) sont responsables de l’oxydation des 5-methylcytosines. Parmi les formes oxydées, l’accumulation de la 5-hydroxyméthylcytosine au sein de régions régulatrices géniques est associée à l’activation de la transcription et à un état ouvert de la chromatine. Outre leur activité catalytique, les protéines TET sont aussi impliquées dans le recrutement de facteurs de remodelage chromatinien. Les protéines TET participent donc à la régulation de la structure chromatinienne via différents mécanismes qui restent cependant à être mieux caractérisés. En analysant l’état de structuration de la chromatine en microscopie confocale et électronique, j’ai pu démontrer qu’indépendamment de l’activité enzymatique de TET1, la surexpression de la région N-terminale de TET1 dans les cellules humaines est responsable d’une réorganisation chromatinienne aboutissant à une démixion entre phase chromatinienne et nucléoplasme. Cette réorganisation est aussi associée à une modification de la dynamique d’échange des histones au niveau du nucléosome. Au niveau fonctionnel, le remodelage chromatinien induit par le domaine N-terminal de TET1 est associé à un enrichissement d’une marque d’histone répressive, H3K27me3 et une diminution globale du niveau transcriptionnel. L’ensemble de ces données suggère que le domaine N-terminal de TET1, pourrait participer à la régulation de la transcription via son rôle dans le remodelage de la structure chromatinienne.The chromatin, composed of DNA and histone proteins, dysplays a complex and dynamic multiscale structure involved in the regulation of transcription. The chromatin compaction state is regulated by epigeneic tags found on both histones and DNA. Ten-eleven translocation (TET) enzymes are responsible for the oxidation of 5-methylcytosines. Among the oxidized forms, the accumulation of the the 5-hydroxymethylcytosine at regulatory regions is associated with transcriptional activation and an open chromatin state. Besides their catalytic activity, TET proteins are also involved in the recruitment of chromatin remodelers. Therefore, TET proteins participate in the regulation of the chromatin structure via several pathways that still need further investigations. By analysing the structural state of the chromatin by electron and confocal microscopy, I demonstrated that independently of the activity of TET1, the overexpression of the N-terminal domain of TET1 in human cells is responsible for a chromatin reorganisation leading to an unmixing of the chromatin phase from the nucleoplasm. This reorganisation is also associated with a change of histone turnover at the nucleosome. The chromatin reorganisation induced by the presence of the N-terminal domain of TET1 is associated with an enrichment in the repressive histone mark, H3K27me3 and a global shut down of the transcription. All these data suggest that the N-terminal domain of TET1 could participate in transcription regulation via its role in chromatin remodeling

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

Caractérisation du rôle de la protéine Ten-Eleven Translocation 1 (TET1) dans la dynamique de l'organisation de la chromatine

The chromatin, composed of DNA and histone proteins, dysplays a complex and dynamic multiscale structure involved in the regulation of transcription. The chromatin compaction state is regulated by epigeneic tags found on both histones and DNA. Ten-eleven translocation (TET) enzymes are responsible for the oxidation of 5-methylcytosines. Among the oxidized forms, the accumulation of the the 5-hydroxymethylcytosine at regulatory regions is associated with transcriptional activation and an open chromatin state. Besides their catalytic activity, TET proteins are also involved in the recruitment of chromatin remodelers. Therefore, TET proteins participate in the regulation of the chromatin structure via several pathways that still need further investigations. By analysing the structural state of the chromatin by electron and confocal microscopy, I demonstrated that independently of the activity of TET1, the overexpression of the N-terminal domain of TET1 in human cells is responsible for a chromatin reorganisation leading to an unmixing of the chromatin phase from the nucleoplasm. This reorganisation is also associated with a change of histone turnover at the nucleosome. The chromatin reorganisation induced by the presence of the N-terminal domain of TET1 is associated with an enrichment in the repressive histone mark, H3K27me3 and a global shut down of the transcription. All these data suggest that the N-terminal domain of TET1 could participate in transcription regulation via its role in chromatin remodeling.La chromatine, composée d’ADN et de protéines histones, possède une structure multi-échelle complexe et dynamique participant notamment à la régulation de la transcription. Son état de compaction peut être régulé par des modifications épigénétiques trouvées sur la queue des histones et sur l’ADN. Les enzymes Ten-eleven translocation (TET) sont responsables de l’oxydation des 5-methylcytosines. Parmi les formes oxydées, l’accumulation de la 5-hydroxyméthylcytosine au sein de régions régulatrices géniques est associée à l’activation de la transcription et à un état ouvert de la chromatine. Outre leur activité catalytique, les protéines TET sont aussi impliquées dans le recrutement de facteurs de remodelage chromatinien. Les protéines TET participent donc à la régulation de la structure chromatinienne via différents mécanismes qui restent cependant à être mieux caractérisés. En analysant l’état de structuration de la chromatine en microscopie confocale et électronique, j’ai pu démontrer qu’indépendamment de l’activité enzymatique de TET1, la surexpression de la région N-terminale de TET1 dans les cellules humaines est responsable d’une réorganisation chromatinienne aboutissant à une démixion entre phase chromatinienne et nucléoplasme. Cette réorganisation est aussi associée à une modification de la dynamique d’échange des histones au niveau du nucléosome. Au niveau fonctionnel, le remodelage chromatinien induit par le domaine N-terminal de TET1 est associé à un enrichissement d’une marque d’histone répressive, H3K27me3 et une diminution globale du niveau transcriptionnel. L’ensemble de ces données suggère que le domaine N-terminal de TET1, pourrait participer à la régulation de la transcription via son rôle dans le remodelage de la structure chromatinienne

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)

Cytosine hydroxymethylation by TET enzymes: From the control of gene expression to the regulation of DNA repair mechanisms, and back

Chromatin is a complex multi-scale structure composed of DNA wrapped around nucleosomes. The compaction state is finely regulated mainly by epigenetic marks present not only on nucleosomes but also on the DNA itself. The most studied DNA post-transcriptional modification is 5-methylcytosine (5-mC). Methylation of the cytosine at CpG islands localized at the promoter is associated with repression of transcription. On the contrary, enrichment of 5-hydroxymethylcytosine (5-hmC), one of the oxidation products of 5-mC by TET (ten-eleven translocation) enzymes, on promoters and enhancers promotes transcription activation. Recently, a new role of 5-hmC has been proposed in the context of DNA repair. 5-hmC was found to be enriched at DNA lesions and knockdown of TET led to impaired repair efficiency. Here, we review our current knowledge regarding the role of the regulation of the 5-mC/5-hmC balance by TET enzymes in the context of transcription modulation as well as DNA repair processes. In a final section, we speculate on the potential involvement of TET proteins in DNA repair mechanisms associated with transcription activation