Main Ecological Features of Benthic Macrofauna in Mediterranean and Atlantic Intertidal Eelgrass Beds: A Comparative Study

Abstract

The present study compares the intertidal eelgrass macrofauna in two geographically and ecologically disparate localities (central Mediterranean and eastern Atlantic). Both coastal ecosystems are developed on extensive large mudflats with eelgrass beds, hosting a great diversity of water birds and providing important socioeconomic assets. These two distinct and distant geographical ecosystems are affected by numerous anthropogenic pressures. By reflecting the response of the structure and functioning of benthic communities to climate change, the two eelgrass ecosystems provide a natural laboratory to investigate global warming. The macrobenthic fauna community of Zostera (Zosterella) noltei eelgrass beds was studied by sampling 34 stations in the Kneiss Islands and 48 stations in Arcachon Bay. A total of 148 species are identified in the Kneiss islands and 117 species in Arcachon Bay, but only 23 species are common to both ecosystems. Diversity, abundance and community structure are significantly different between the two study areas, which could be explained by differences between Mediterranean and Atlantic climatic conditions and by anthropic factors (e.g. fishing pressure, pollution, nutrient inputs) affecting each ecosystem. Multidimensional scaling (n-MDS) analysis identifies two distinct geographical station groups on the basis of species and familylevel abundance. On the contrary, three assemblages are identified on the basis of trophic groups distributed between the separate ecosystems. In terms of ecological quality status, the Kneiss site appears to have a good ecological condition and hosts a variety of sensitive species. On the other hand, biotic indices indicate that the Arcachon site is moderately perturbed and that the benthic communities are unbalanced. It is expected that the present-day functioning of the Kneiss Islands ecosystem will become typical of the situation in Arcachon Bay in several decades time, with the development of warmer and drier conditions.

Strength May Lie in Numbers: Intertidal Foraminifera Non-Negligible Contribution to Surface Sediment Reworking

“…277 ind•m −2 , [37]) and A. ovata (i.e. 592 ind•m −2 , [38]) in soft-sediment intertidal substrates, population-level surface sediment reworking rates SSRR p would respectively range from 277 to 1523 cm 2 •m −2 •day −1 from 11,840 and 59,200 cm 2 •m −2 •day −1 . For A. ovata, these figures have the same order of magnitude as the population-level SSRR p estimated here for Quinqueloculina seminula and Ammonia tepida (Figure 2).…”

Latitudinal Variation into the Macrofaunal Assemblages Associated to Zostera noltei Seagrass along the Atlantic Coast of Morocco

“…Comparison of mean species richness with previous studies was difficult because of variance of the sampling design (core dimensions, number of replicates, and number of selected sites). However, given the number of sampling size used in this analysis, the Z. noltei beds of our studied sites (96) were less than those recorded on the same ecosystem in the Kneiss Islands, Tunisia (148), and Arcachon Bay, France (117) [55]. e less diverse Z. noltei beds reported in the different studies where the seagrass is annual [56] or shows large annual fluctuations due to the grazing pressure by migrating seabirds (Table 9).…”

Molluscs from Tidal Channels of the Gulf of Gabès (Tunisia): Quantitative Data and Comparison with Other Lagoons and Coastal Waters of the Mediterranean Sea

“…Despite recent studies mainly in Tunisia waters [3,5,11,14,16,17] (see Figure 8), there is still relatively little published research on molluscs from the coastal waters of southern Tunisia, including the Gulf of Gabès [6,7,[28][29][30][31][32][33][34][35][36][37].…”

“…Nevertheless, it is recognized that the species richness of a particular area (whether of large extent or within a small zone) is related not only to the intrinsic global diversity of the considered area but also the sampling effort and the mesh sieve mesh used during a given campaign [76]. Consequently, it is difficult to compare the species richness of different sites where different sampling coverage; nevertheless, Table 5 reports the taxonomic richness and abundance of molluscs and the total sampling surface for lagoons and shallow waters in the Gulf of Gabès as well as other Tunisian and Mediterranean sites [1][2][3]7,8,17,[29][30][31]33,34,37,[41][42][43][77][78][79][80].…”