Microphytobenthic response to organic matter enrichment: Does the same stressor lead to identical communities?

Abstract Microphytobenthos is a major factor in the functioning of shallow ecosystems as it is an essential component of primary productivity in coastal areas. Organic matter enrichment is a stressor that affects the microphytobenthic community of the marine sediments. However, it is unclear to what extend the microphytobenthic response to organic enrichment depends on the stressor itself (i.e. the nature of organic matter enrichment) or on the origin of the community in general (i.e. the pool of photosynthetic organisms present in the sampling site). Hence, an ex-situ organic matter enrichment experiment was used to examine changes in microphytobenthic communities when incubated under the same organic matter addition stress, using sedimentary pigment content as a proxy. Specifically, sediment samples from two different locations were incubated under the same stressor in the laboratory, i.e. presence/absence of organic matter enrichment. Our results suggested that the sediment biogeochemical response to organic matter enrichment was different between the two sites, and also the microphytobenthic communities that grew in both sediments differed.