Food web structures of subtidal benthic muddy habitats: evidence of microphytobenthos contribution supported by an engineer species
|Author(s)||Rigolet Carinne1, 2, Thiebaut Eric2, 3, Dubois Stanislas1|
|Affiliation(s)||1 : IFREMER, Dynam Environ Cotier DYNECO, Lab Ecol Benthique, F-29280 Plouzane, France.
2 : CNRS, UMR 7144, F-29280 Plouzane, France.
3 : Univ Paris 06, F-29680 Roscoff, France.
|Source||Marine Ecology Progress Series (0171-8630) (Inter-research), 2014 , Vol. 500 , P. 25-U49|
|WOS© Times Cited||18|
|Keyword(s)||Stable isotopes, Gregarious amphipod, Source contribution, Haploops, Benthic diatoms, Navicula|
|Abstract||Stable carbon and nitrogen isotopic composition (delta C-13 and delta N-15) of benthic organisms was investigated to understand the effects of a gregarious tubicolous amphipod species (Haploops nirae) on benthic food web structures and test whether drastic changes in species composition cause changes in food web structure. The habitat engineered by this species was sampled and compared with the adjacent uncolonized Amphiura filiformis muddy habitat in winter and summer. The isotopic signatures of macrofaunal and megafaunal species associated with both habitats were analysed along with potential food sources at each sampling period. Similar food web structures for each habitat (and each season), with high delta N-15 ranges spanning over 3 trophic levels, were reported although omnivory was less frequent in the H. nirae habitat. The amphipod H. nirae appears to play a baseline role, with the lowest delta N-15 values and delta C-13 values indicating that it primarily feeds on phytoplankton. Bayesian mixing models were used to estimate the contributions of potential food sources to the diet of the species accounting for most of the biomass in each habitat and showed that the epibionts covering tube mats are a key contribution to the food webs of both habitats. Identified as benthic diatoms, they may minimize interspecific food competition between dominant suspension feeders such as Polititapes virgineus or H. nirae within a habitat. This finding highlights the contribution of microphytobenthic producers to subtidal (similar to 30 m deep) muddy habitat food webs, suggesting that the mucopolysaccharides composing the H. nirae tubes support the growth of a heterotrophic diatom population. As an engineer species, H. nirae acts as a facilitator for diatoms which ultimately sustain the secondary production of the H. nirae habitat as well as the immediate surrounding habitats.|