Effects of epibionts on Sabellaria alveolata (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel     

Stanislas Dubois  John A. Commito  Frdric Olivier  Christian Retire 《Estuarine, Coastal and Shelf Science》2006,68(3-4):635

Biogenic structures built by ecosystem engineers such as corals, bivalves, polychaetes, and sea grasses provide habitat for benthic vertebrates and invertebrates. The polychaete Sabellaria alveolata is an important foundation species whose reef structure adds topographic complexity and high levels of biodiversity to the otherwise low-relief, low diversity, soft-bottom environments in the Bay of Mont Saint-Michel, France, where the largest such reef formations in Europe are found. In this bay, reefs are being increasingly colonised by oysters (Crassostrea gigas) from local aquaculture operations and by green algae (Ulva sp.) due to the increasing inputs of nitrates from terrestrial origin. The purpose of this study was to investigate the possible impacts of epibiotic oysters and green algae on the S. alveolata population and reef community structure in the Bay of Mont Saint-Michel, France. Univariate and multivariate comparisons of macrofauna were conducted for five reef types: controls (no epibionts), low oyster density, high oyster density, green algae, and oyster and green algae. Results showed that all the three reef types with oysters had significantly higher species richness and diversity values than control and algae-only reef types. Pairwise ANOSIM and SIMPER comparisons of controls versus the four reef types with epibionts revealed that all three of the reef types with oysters were significantly different from controls, but there was no significant difference between controls and algae-only reef types. A striking feature of the reef comparisons is that no single species in this species-rich system contributed more than 8.86% to the dissimilarity between the reef types. Thus, k-dominance curves for species abundances were not effective in revealing differences among the reef types. Our results demonstrate that recent anthropogenic inputs of oysters affect the reef species assemblage more strongly than algal epibionts. In addition, epibionts, especially green algae, alter S. alveolata population structure, causing a reduction in new recruits that over the long run may cause significant damage to the reef structure itself. These results are a first step towards understanding anthropogenic threats to S. alveolata reefs and may be useful in the development of strategies for their protection and management.  相似文献   

The need for a better characterization of a sediment commonly called “mud”     

Stanislas Wartel 《Geo-Marine Letters》1991,11(3):110-112

Of all known sediments “mud” is probably the one attracting the most attention today. It is certainly the only type of sediment being studied by investigators of a wide variety of scientific and technological disciplines. The experts in the latter category deal with it very actively because of the great number of problems that have emerged during the past decades as a consequences of the expansion of many harbors and of an increasing pollution of surface waters. Besides th geologist, for whom “mud” is the basic material for clay, shale, and slate, the sidementologist, hydraulic engineer, harbor-manager, soil scientist, biologist, the ecologist, and many other professionals are very much interested in this particular sediment. Indeed, its importance does not only lie in its geological meaning nor in the fact that it is a substratum for living organisms and vegetation, but as a result of its high adsorption and cation exchange capacity making it one of the most active carriers of many adsorbed pollutants, causing a troublesome, fast accumulating cohesive spoil in waterways accessing to major harbors.  相似文献   

Textural Characterization Using Gy’s Heterogeneity Functions     

Luc Barbanson  Stanislas Sizaret  Olivier Rozembaum  Jean Louis Rouet 《Mathematical Geosciences》2009,41(8):855-868

A solid can be regarded as a set of contiguous elementary units. The distribution within the solid of any properties, measurable within each elementary unit, can be characterized using two parameters. These parameters are built using the constitution and distribution heterogeneities of Gy. The former account for the granularity of the elementary units, whereas the latter assess the spatial distribution of the property. A texture which definition involves several properties can be described using a diagram where both parameters work as variables. Potential applications encompass (i) the textural classification of soils, ore, breccia, and concrete and (ii) the monitoring of textural transformation during process like dolomitization, metamorphism, weathering, deformation, or annealing.  相似文献