This study deals with the application of macrozoobenthos-based biotic indices (BI) within the frame of the implementation of the European Water Framework Directive. More precisely, this study aimed at assessing the performance of five recently developed methodologies (BI) for the assessment of ecological quality status (EcoQ) in two semi-enclosed, sheltered coastal ecosystems and in one transitional water body situated along the Western French coast, namely Marennes-Oléron Bay, Arcachon Bay, and the Seine Estuary. This study showed that these five indices rarely agreed with each other, describing very different pictures of the overall EcoQ of the three study sites. This work also clearly underlined the limitations of these approaches, notably the dependency of most of these BI and the resulting EcoQ classifications on habitat characteristics, more particularly to natural levels of sediment silt-clay content and the location of stations in the subtidal or the intertidal. The implication of our observations concerning the use of these BI for implementation of the WFD is discussed in terms of definition of habitat-specific reference conditions and necessity to adjust thresholds to the particular habitat occurring in semi-enclosed ecosystems. Meanwhile, the unmodified use of these BI severely impaired accurate assessment of EcoQ and decision-making on the managers' point of view.

Sabellaria alveolata is a gregarious polychaete that uses sand particles to build three-dimensional structures known as reefs, fixed atop rocks or built on soft sediments. These structures are known to modify the local grain-size distribution and to host a highly diversified macrofauna, altered when the reef undergoes disturbances. The goal of this study was to investigate the different sedimentary and biological changes associated with the presence of a S. alveolata reef over two contrasting seasons (late winter and late summer), and how these changes were linked. Three different sediments were considered: the engineered sediment (the actual reef), the associated sediment (the soft sediment surrounding the reef structures) and a control soft sediment (i.e. no reef structures in close proximity). Univariate and multivariate comparisons of grain-size distribution, soft sediment characteristics (organic matter content, chlorophyll a, pheopigments and carbohydrate concentrations) and macrofauna were conducted between the different sediment types at both seasons and between the two seasons for each sediment type. A distance-based redundancy analyses (dbRDA) was used to investigate the link between the different environmental parameters and the macrofauna assemblages. Finally, we focused on a disturbance continuum of the engineered sediments proxied by an increase in the mud present in these sediments. The effects of a continuous and increasing disturbance on the associated fauna were investigated using pairwise beta diversity indices (Sørensen and Bray-Curtis dissimilarities and their decomposition into turnover and nestedness). Results showed a significant effect of the reef on the local sediment distribution (coarser sediments compared to the control) and on the benthic primary production (higher in the associated sediments). At both seasons, S. alveolata biomass and sediment principal mode were the environmental parameters which best differentiated the engineered, associated and control sediment assemblages. These two parameters are under the ecosystem engineer's influence stressing its importance in structuring benthic macrofauna. Furthermore, in late summer but not in late winter, presence/absence and abundance based beta diversity were positively correlated to our disturbance proxy (mud content) a tendency driven by a species replacement and a rise in the associated fauna density. Our first set of results highlight the importance of S. alveolata reefs as benthic primary production enhancers via their physical structure and their biological activity. The results Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. obtained using beta diversity indices emphasize the importance of recruitment in structuring the reef's macrofauna andparadoxicallythe ecological value of S. alveolata degraded forms as biodiversity and recruitment promoters.

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.Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

ABSTRACT1. Reefs built by the annelid worm Sabellaria alveolata in the Bay of Mont-Saint-Michel (France) are the most extensive intertidal biogenic structures within Europe. Before and after mussel farming extensions, a study designed to provide a biological health index of the Sainte-Anne reef (223 ha) was carried in 2001 and 2007 to serve as an easy-to-use management tool and to ensure endangered reef portions were properly targeted and protected.2. Coupled physical and biological parameters were included in a spatial Health Status Index (HI). A spatial and temporal mapping survey of the HI showed a continuous deterioration of the reef's state of health, particularly in its central part. This degradation correlates with the colonization of the Pacific oyster Crassostrea gigas and with increasing silt deposits on the reef.3. A combination of several factors is likely to explain such rapid reef deterioration: (1) an increase in trophic competition between cultivated and wild suspension-feeders that is detrimental to the annelids; (2) a modification in the hydrodynamics and consequently in sedimentary patterns leading to an increase in silt deposition; and most importantly (3) an increase in recreational harvesting of oysters and associated reef trampling, resulting in reef fragmentation.4. Understanding the parameters that influence the reef dynamics is necessary in order to help efficient and effective management and policy focusing on the conservation status of large biogenic structures.

The North Sea Benthos Project 2000 was initiated as a follow-up to the 1986 ICES North Sea Benthos Survey with the major aim to identify changes in the macrofauna species distribution and community structure in the North Sea and their likely causes.The results showed that the large-scale spatial distribution of macrofauna communities in the North Sea hardly changed between 1986 and 2000, with the main divisions at the 50 m and 100 m depth contours. Water temperature and salinity as well as wave exposure, tidal stress and primary production were influential environmental factors on a large (North Sea-wide) spatial scale.The increase in abundance and regional changes in distribution of various species with a southern distribution in the North Sea in 2000 were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. This