Spatial heterogeneity in the food web of a heavily modified Mediterranean coastal lagoon: stable isotope evidence

Aquatic Biology

Antoine Grémare¹  Jean-Michel Amouroux¹  Jean-Yves Bodiou¹  Pascal Riera¹  Antoine Carlier¹  Martin Desmalades¹ 

关键词: Food web;    Lagoon;    δ13C;    δ15N;    Spatial heterogeneity;    Trophic plasticity;    Shellfish aquaculture;    Northwestern Mediterranean;   

DOI  :  10.3354/ab00147

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: We investigated the food web structure of the Salses-Leucate Lagoon (northwestern Mediterranean) through δ¹³C and δ¹⁵N analysis of its benthic macrofauna and potential food sources. This lagoon was heavily human-modified during the 1970s, allowing permanent exchange with the open sea and an increase in salinity from that time. As a result, it exhibits a much less marked salinity gradient than the neighbouring lagoon ecosystems, which suggests a priori that its food web structure is more homogeneous. In this environmental context, we assessed spatial variability in the isotopic composition of non-vagrant macrofauna in Salses-Leucate in relation to degree of connection with the open sea, anthropogenic inputs and the presence of oyster aquaculture. Overall, the main trophic pathway is based on suspended particulate organic matter and sedimented organic matter. However, there were marked spatial differences (at different scales) in both δ¹³C and δ¹⁵N values of macrofauna, which suggests an important feeding plasticity within each category of primary consumers at a small spatial scale. δ¹³C data showed that the contributions of the different food sources to the diet of primary consumers changed depending on distance from continental inputs, connection with the open sea and local primary producer coverage. Small-scale δ¹⁵N variability revealed a very localised influence of anthropogenic nitrogen output. Regarding the possible effect of aquaculture, the isotopic ratios of sediment and macrobenthos were not modified underneath the oyster lines with respect to the neighbouring area. Conversely, the isotopic signature of consumers living on the oyster lines contrasted with those living underneath. Therefore, our results suggest that a decoupling exists between the trophic pathways that occur in the water column and on the soft bottom of this shallow water ecosystem.

【 授权许可】

Unknown