Phytoplankton food quality effects on gammarids: benthic–pelagic coupling mediated by an invasive freshwater clam

Abstract

Benthic–pelagic coupling mediated by bivalves has been shown to increase the flow of energy towards the benthos. To assess the capability of clams to process and therewith modify the quality of pelagic food sources for subsequent use by benthic invertebrates, we conducted a growth experiment in which juvenile Gammarus roeselii were raised either directly on sedimented pelagic autotrophs (algae, cyanobacteria) or on the same autotrophs biodeposited by the invasive freshwater clam Corbicula fluminea either as feces or pseudofeces. We show that growth and survival of G. roeselii are significantly improved when autotrophs are offered as biodeposition material and suggest that this clam-mediated upgrading of food quality is due to both an increased bioavailability of pelagic food particles, which are packed in mucus during clam processing, and an increased dietary provisioning with essential lipids (sterols and (or) polyunsaturated fatty acids) originating from the clams. Hence, filter-feeding bivalves provide a crucial link between the pelagic and benthic food web not only by deflecting energy fluxes, but also by processing and upgrading pelagic food (increased bioavailability, improved biochemical composition) for benthic invertebrates.

Nitrogen Fixed By Cyanobacteria Is Utilized By Deposit-Feeders

“…Also, bivalves performed better if fed cyanobacteria than when food deprived [23]. Moreover, cyanobacteria partially processed by, for example, clams were found to become more palatable and nutritiously upgraded for amphipods [23], thus facilitating usage of cyanobacteria-derived organic matter by benthic communities. Whether settled cyanobacteria could be eaten when relatively fresh or only after some decomposition remains, however, unclear and may differ among species.…”

“…In copepods, positive effects on recruitment were observed when cyanobacteria were offered as a supplementary food source [22]. Also, bivalves performed better if fed cyanobacteria than when food deprived [23]. Moreover, cyanobacteria partially processed by, for example, clams were found to become more palatable and nutritiously upgraded for amphipods [23], thus facilitating usage of cyanobacteria-derived organic matter by benthic communities.…”

Impact of food type on respiration, fractionation and turnover of carbon and nitrogen stable isotopes in the marine amphipod Gammarus aequicauda (Martynov, 1931)

“…One last hypothesis concerning the low assimilation of litter treatment lies in the experimental protocol itself: coprophagy was avoided throughout the experiment. Coprophagy is a very common strategy in marine invertebrates to cope with poorly nutritive and digestible food (Zimmer and Topp, 2002) and it has been proved that if it is given the choice, Gammarus roeselii preferred ingesting fecal biodeposited material rather than the original food source (Gergs and Rothhaupt, 2008;Basen et al, 2013). This coprophagy strategy is also a means of "gardening" bacterial flora on the feces, allowing bacterial development and enzyme action before re-ingestion, increasing food quality and digestibility (Zimmer and Topp, 2002;Córdova-Murueta et al, 2003).…”

Compound‐specific δ13C analyses reveal sterol metabolic constraints in an aquatic invertebrate

“…Considering the high plasticity in their feeding strategies, gammarids are best characterized as omnivores . Recent findings indicate that Gammarus roeselii is able to exploit deposited phytoplankton as a food source and that the growth and survival of G. roeselii feeding on deposited phytoplankton are affected by the phytoplankton sterol composition …”

“…[26,27] Recent findings indicate that Gammarus roeselii is able to exploit deposited phytoplankton as a food source and that the growth and survival of G. roeselii feeding on deposited phytoplankton are affected by the phytoplankton sterol composition. [28,29] The approach that we applied here is based on the finding that juvenile G. roeselii feeding on the green alga Scenedesmus obliquus exhibit a significantly higher mortality than those feeding on other deposited algae, indicating that this green alga is of poor nutritional quality. [29] Green algae, such as S. obliquus, are characterized by a deficiency in long-chain polyunsaturated fatty acids and often contain only Δ 7 -sterols, which have been shown to constrain growth and/or development of several arthropod species.…”