Reproductive biology of the nonnative oyster, Crassostrea gigas (Thunber, 1793) as a key for its successful spread along the rocky shores of Northern Patagonia, Argentina

Crassostrea gigas was introduced in Anegada Bay (North Patagonia, Argentina), in 1981 for aquaculture purposes. The species has, since established in the field, covered all available hard substrata in the bay and gradually expanded south along the coast of the neighboring province of Río Negro, 90 km away from its original introduction site. Our work focused on the reproductive dynamics of the species at the introduction site, with emphasis on the thermal thresholds needed for each stage of gonad development. During early spring, the oysters in Anegada Bay go through active gonad proliferation. Maturity extends mainly from October to January. The first spawning occurs in November, when seawater temperature exceeds 17°C, and peaks from December to February, when seawater temperature lies in the range ot 19–21.5°C. The timing of gonad development is size dependent. Larger (≥70 mm) and medium-size oysters begin spawning first, whereas small oysters ( 17°C), and spawning only occurs in those sites where this threshold is reached.Versión del editor

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

Modelling Seasonal Dynamics of Biomasses and Nitrogen Contents in a Seagrass Meadow (Zostera noltii hornem). Application to the Thau Lagoon (French Mediterranean Coast).

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Distribution of mercury and other trace metals in the cockle Cerastoderma glaucum from the Mediterranean Lagoon Etang de Thau

8 páginas, 7 figuras, 2 tablasThe concentrations of Ag, Cd, Co, Cr, Cu, Ni, Pb, Zn, Mn, and Fe in the soft tissue of the cockle Cerastoderma glaucum from six sites along the Mediterranean Lagoon Etang de Thau were determined by AAS; Hg was determined by the cold-vapor technique. Significant spatial variations in metal concentrations within the lagoon were recorded. Elevated levels of tissue Pb, Cr, and Hg in the Etang des Eaux Blanches, an area adjacent to the harbor and highly industrialized region, are likely of anthropogenic origin. Seasonally dependent variations in the tissue concentrations of trace elements at Crique de l’Angle were observed. The highest levels of Cr and Pb in the tissue were identified in March 1992, of Hg, Co, and Fe in period August 1990–January 1991, of Mn in August 1992, and Ag in January 1991. The gills contained the maximum amounts of Co and Ni, the mantle the most Fe and Hg, and the digestive gland (hepatopancreas) had most Cu.One of the authors (P.S.) wishes to thank the Embassy of France, which founded his scientific stay in France (IFREMER). This work was carried out within the framework of the Polish-French cooperation program (ATP E01) and was supported by French Government Postdoctoral Fellowship (to M.W.) and by a grant (to P.S.) from the Polish National Committee of Scientific Research (Komitet Badan Naukowych) in Warsaw as part of the LOICZ Programme: grant no. 6 P202 034 06.Peer reviewe

Changes in point and non-point sources phosphorus loads in the Thau catchment over 25 years (Mediterranean Sea -France)

International audienceIn Thau coastal lagoon, phosphate concentrations have decreased by 89% from 1971 to 1994. The present relatively long term (over 25 years) study compares changes in the contribution of point (PS) and non-point sources (NPS) total phosphorus (P) loads. The analysis of the distribution of the sources in comparison with the changes in the phosphate concentrations in the Thau lagoon aims to point out their relative impact in order to create a sustainable management plan for this system. This is needed, firstly because water quality supports shellfish farming, which is the main economical activity of the basin. Secondly, because the population is planned to increase by 40% between 1995 and 2020 thus leading to an increase of urban pressures. PS P loads, represented by discharges by wastewater treatment plants, have increased by 143% while NPS P loads, both represented by export from lands and loads from non-connected population, have decreased by 64%. Despite important changes in land-use by an exceptional decrease of vineyards areas (−12.5%), domestic effluents main contribute (>60%) to both PS and NPS P loads and seem to be more implicated in the decrease of phosphate concentrations in the Thau lagoon, probably because of the different phosphorus forms engaged

Modelling of Oxygen and Nitrogen Cycling as a Function of Macrophyte Community in the Thau Lagoon.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra