Biogeochemical response of an intact coastal sediment to organic matter input:: a multivariate approach

We tested the effect of additions of organic matter of different quality (C:N ratio) and quantity on benthic fluxes of ammonium, nitrate, silicate, oxygen and dissolved inorganic carbon (DIC). Additions were made to intact sediment boxes, according to a 2-level factorial design, and the magnitude and temporal scale of the response were evaluated with Partial Least Square (PLS) regression analysis. Response patterns were followed over a 40 d period following the addition, but only fluxes of ammonium, nitrate, silicate and oxygen for the first 2 d after addition, and nitrate fluxes for the first 8 d after addition, could be used for predictive modelling. The results showed that the response of the microbial community to different qualities and quantities of organic matter may initially be related to its capacity to sequester organic matter, and in the long term, to its growth in response to the respective nutritional supply. The results also suggest that such an experimental approach can be a useful tool for classification of areas with potential risk of eutrophication.