Abiotic and biotic patterns across Mediterranean coastal wetland systems, North East Aegean, Greece

Abstract

1 - Coastal wetlands are regarded as transitional ecosystems regulating fluxes of materials and energy between the land and the sea and are protected habitats under the NATURA 2000 European network of protected areas. Description of spatial heterogeneity in abiotic and biotic constituents of coastal wetland systems is a prerequisite for the establishment of long-term monitoring programs and a first step in elucidating their functional role in the landscape; both of particular significance to management. Spatial variability of water and substratum physicochemical variables and of substratum macroinvertebrate fauna composition and abundance across five sea-coastal wetland-land systems, Kalloni bay, Lesvos Island, Greece, were quantified during the growing season of 2005. 2 - The studied coastal wetlands develop on an alluvial flat plain of mineral soils as indicated by low values of percent organic matter, circumneutral pH, and high values of bulk density. Trends in physicochemical variables of substratum varied among the five coastal wetland systems studied even when the same variable was examined. Canonical discriminant analysis indicated that the most important substratum physicochemical variable in differentiating among the sea-wetland-land units of the studied gradients was electrical conductivity (salt influence) in four out of the five coastal wetland systems. Total nitrogen concentration of substratum was the only variable among the ones studied which was related positively either with total phosphorus concentration or/and percent organic matter of substratum in all wetland systems studied; the highest values occurred where vegetation was present. 3 - Distribution and abundance of substratum macroinvertebrate taxa across the sea-wetland-land gradients studied reflected the interaction between the marine and terrestrial environment. Gasteropoda, bivalvia and schaphopoda were found in higher abundances at sea and sea-influenced stations, which gradually decreased towards the land. On the other hand, insecta appeared at stations further away from the shore and their abundance progressively increased towards land. Gasteropoda and insecta were the taxa responsible for the identification of at least three clusters of stations across all five coastal systems studied. Two clusters contained clearly "terrestrially-influenced" or "sea-influenced" stations while intermediate clusters contained stations with varying degree of salt influence. 4 - Distribution and abundance of gasteropoda and insecta, however, were found to be directly related to nutrient status and not to electrical conductivity of substratum.