Structure of a suprabenthic shelf sub-community of gammaridean Amphipoda in the Bay of Fundy compared with similar sub-communities in the Gulf of St. Lawrence

Abstract

A conceptual model of the adaptive structure of offshore bottom communities through seasonal patterns of pelagic-benthic coupling is tested by comparing the success of suprabenthic, shelf sub-communities of gammarideans selected in three areas differing in trophic status: the eutrophic Baie des Chaleurs and two oligotrophic ecosystems, the Bay of Fundy and the Lower St. Lawrence Estuary.The relative amount of primary production appears to affect both species richness and total density. It is higher in the very productive Baie des Chaleurs, implying tightly coupled pelagic-benthic links. In the Bay of Fundy, gammaridean density, although lower than in the Baie des Chaleurs, is higher than in the Lower St. Lawrence Estuary, but it appears to be characterized by smaller size at maturity or selection of smaller species of the same taxa. The Baie des Chaleurs community may be more biologically accommodated than those of the Lower St. Lawrence Estuary and the Bay of Fundy, which are physically less stable. In the latter, all trophic guilds appear less abundant, but scavengers-predators retain a similar relative success in all three ecosystems, presumably from being more remote from the seasonal pelagic food supply in the trophic chain. In both oligotrophic systems, slope species compete efficiently with shelf species in their preferred depth zone, presumably because of their natural adaptation to food scarcity.The amplitude of vertical migrations by suprabenthic gammarideans appears to be higher in the Bale des Chaleurs, possibly to favor horizontal redistribution to new patches of 'first-quality food' on the very stable and homogeneous mud basin of the Baie. Trends of seasonal abundance for ten gammaridean species in the Bay of Fundy confirm the reality of swimming guilds previously observed in the Baie des Chaleurs.

When season does not matter: summer and winter trophic ecology of Arctic amphipods

“…Enequist (1949) described oedicerotids as detritus-feeders that ingest accumulations of organic detritus in the mud-water interface, but they do not consume living multicellular organisms. This opinion was later well established in the literature (e.g., Chevrier et al, 1991;Buhl-Mortensen, 1996); however, detailed studies on mandible morphology and gut content analyses provide evidence that many species of the family prey on meiofauna (Beare & Moore, 1998;Yu et al, 2003). Similar to the oedicerotids studied by Dauby et al (2001) in the Weddell Sea, A. phyllonyx and P. lynceus, can be classified as deposit-feeders/ predators.…”

Circalittoral suprabenthic coarse sand community from the western English Channel

“…As suggested by Chevrier et al (1991), the suprabenthic fauna could play an important role in pelagic-benthic coupling, and more data were needed to develop the benthic-pelagic carbon flux models. The renewed interest was due both to the improved performance of the sledges and to the understanding of the role of suprabenthic communities in the trophic chain.…”

The Life Histories of the Offshore Oedicerotids Westwoodilla Caecula and Monoculodes Packardi (Crustacea: Amphipoda) From Loch Fyne, Scotland

“…Huberdeau & Brunei, 1982;Sainte-Marie & Brunei, 1985;Chevrier et al, 1991;Wildish et al, 1992). Thus no demarcation between swimming animals and those buried in the surface sediment was possible presently due to the unstratified net configuration of the gear we used.…”

“…Population densities of M. packardi at the Baie des Chaleurs were 283-2 ind 100 m~3 (Sainte-Marie & Brunei, 1985) while in the Bay of Fundy, Chevrier et al (1991) reported mean densities of 35-87 ind 100 m" 3 (mean value for 1987). Our 190 m station in Loch Fyne was intermediate between these two extremes; the mean density of M. packardi (all tows in daylight) during 1992, being 48 ind 100 m 3 .…”