Comparative analysis of the food webs of two intertidal mudflats during two seasons using inverse modelling: Aiguillon Cove and Brouage Mudflat, France

Abstract

Inverse analysis was used to model the food webs of two intertidal mudflat ecosystems: Aiguillon Cove (AC) and Brouage Mudflat (BM) (south-western Atlantic coast, France). The aim of the present study is to describe and compare the functioning of these two ecosystems. The method of inverse analysis has been adapted in order to take into account, in a single calculation, two seasons: spring/summer (mid-March to mid-October) and autumn/winter (the rest of the year). Gathering all available data on the two sites, the most important gaps in knowledge were identified with the help of sensitivity analyses: they concerned mainly the exports of material by grazing fish (such as mullet Liza ramada), resuspension of microphytobenthos, and fluxes linked to microfauna which is poorly known for the two systems. The two sites presented the same overall type of functioning (net import of detritus, export of living organic material and higher faunal activity during spring/summer). In both ecosystems, primary production was dominated by the microphytobenthic production, of which a great part was exported via water-column advection and biotic vectors (grazing fish), while many secondary producers also used detritus as a food resource. Each system also had its own characteristics, one BM being much more seasonally driven than the other AC. It appeared essential to take the seasons into account, as variations in microphytobenthos production and in meiofauna, macrofauna and biotic vectors led to great differences in the food-web organisation Résumé

Trophic relationships among fish assemblages in a mudflat within Brazilian marine protected area

“…DEGRÉ et al (2006) found that the grazing fish, which kept a roughly equilibrated diet between microphytobenthos and detritus, changed their exclusively herbivorous diet during summer to prey on nematofauna during winter in a mudflat. This fluidity among guilds exists because ecological interactions among species are intensified at certain periods, with the less competitive species or species more susceptible to predation being excluded or replaced by species with greater adaptability to environmental pressures (ARAÚJO et al, 2006).…”

Experimental estimation of assimilation rates of meiofauna feeding on 14C-labelled benthic diatoms

“…The Brouage mudflat has become the best-studied mudflat of Marennes-Oléron Bay and an important experimental site due to its exceptional morpho-sedimentological features (Bassoullet et al, 2000) and high primary productivity (Guarini et al, 1997). Most of the components of the Brouage ecosystem have been studied: the abundances and diversity of macrofauna, meiofauna and flora (Cariou-Le Gall and Blanchard, 1995;Rzeznik-Orignac et al, 2003;Sauriau et al, 1989) and numerous data are available on its benthic ecology (Degré et al, 2006;Leguerrier et al, 2003;.…”

“…Meiofauna can contribute up to 30% of the living biomass in sediment, and it is assumed that their contribution to the food of deposit-feeding macrofauna is of similar magnitude (Coull, 1990(Coull, , 1999Degré et al, 2006;Gerlach, 1978;Leguerrier et al, 2003). Meiofauna feed on bacteria, diatoms and protozoa as well as other small organisms.…”

The Devil Lies in Details: New Insights Into the Behavioural Ecology of Intertidal Foraminifera

“…They play a key role in the trophic web of intertidal mudflats (Degré et al, 2006). There are about 4000 benthic species, with hundreds of living individuals being easily found in a few cubic centimetres of sediment (Schö nfeld et al, 2012).…”