Influence of benthic macroinvertebrates on the erodability of estuarine cohesive sediments: Density- and biomass-specific responses

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• 作者：Erik Kristensen ; Jo茫o Magalh茫es Neto ; Morten Lundkvist ; Lars Frederiksen ; Miguel 脗ngelo Pardal ; Thomas Valdemarsen ; Mogens Rene Flindt
• 关键词：erosion threshold ; erosion rate ; behaviour ; macrofauna feeding ; microphytobenthos ; biostabilization
• 刊名：Estuarine, Coastal and Shelf Science
• 出版年：1 December, 2013
• 年：2013
• 卷：134
• 期：Complete
• 页码：80-87
• 全文大小：719 K

文摘

The impact of three dominating benthic invertebrates on sediment stability and erosion conditions of cohesive sediments in the Mondego Estuary, Portugal, was examined in laboratory annular flume experiments. The purpose was to test how the life habits and body size of the three involved species (Hydrobia ulvae, Nereis diversicolor and Scrobicularia plana) in terms of density or biomass influence sediment erosion. All three species decreased the free-stream erosion threshold (u_c) and increased erosion rate (E), since their feeding activities diminished the surface stabilizing effect of extracellular polymeric substances (EPS) produced by microphytobenthos. S. plana had the highest and H.聽ulvae the lowest impact when related to density (factor of 29 for u_c and factor of 19 for E), while H.聽ulvae was more important than S.聽plana when related to biomass (factor of 4 for u_c and factor of 6 for E). N. diversicolor had intermediate density-specific (4-6 times higher than H.聽ulvae) and lowest biomass-specific (2-3 times lower than S.聽plana) effects on erosion. It appears that faunal erosion impacts preferably should be reported in biomass units for comparative purposes because individual behavioural effects of a small-bodied species like H.聽ulvae functionally can be relatively more important than those of a 100 times heavier S.聽plana individual. This is clearly evidenced from the strongly diminished response in suspended Chlorophyll-a content in the presence of the former than the latter species, which is caused by an efficient microphytobenthos grazing by H.聽ulvae. It is also important to emphasize that the total faunal impact on erosion threshold in a certain area is dictated by combination of contributions from individual species. The total outcome is unpredictable and controlled by synergistic and antagonistic species-specific effects, species interactions as well as environmental and sediment conditions.