The Importance of Food Pulses in Benthic-Pelagic Coupling Processes of Passive Suspension Feeders

Sergio Rossi,Lucia Rizzo

doi:10.3390/w13070997

Abstract

Benthic-pelagic coupling processes and the quantity of carbon transferred from the water column to the benthic suspension feeders need multiple intensive sampling approaches where several environmental variables and benthos performance are quantified. Here, activity, dietary composition, and capture rates of three Mediterranean gorgonians (Paramuricea clavata, Eunicella singularis, and Leptogorgia sarmentosa) were assessed in an intensive cycle considering different variables such as the seston concentration and quality (e.g., carbon, nitrogen, and zooplankton), the colony branch patterns, and the energetic input of the single species (i.e., mixotrophic and heterotrophic). The three species showed clear differences in their impact on the seston concentration. Paramuricea clavata, the most densely distributed, showed a greater impact on the near bottom water column seston. The lowest impact of E. singularis on the seston could be explained by its mixotrophy and colony branching pattern. Leptogorgia sarmentosa had a similar impact as E. singularis, having a much more complex branching pattern and more than an order of magnitude smaller number of colonies per meter square than the other two octocorals. The amount of carbon ingested in the peaks of the capture rates in the three species may cover a non-neglectable proportion of the potential carbon fluxes.

Highlights

During the last decades, much attention has been paid to the role of megabenthic invertebrate structures composed mainly by invertebrates in benthic-pelagic coupling processes [1]
Biogenic structures produced by sponges, cnidarians, bryozoans, etc., known as marine animal forests [3,4], may even potentially change, depending on their structure, patch size, and current regime, the seston concentration [5]
The dependence on currents and seston concentration has been claimed as an essential point to understand benthic-pelagic coupling processes [6,7]; there are few studies highlighting the role of short-time cycles as energy providers in marine animal forests

Summary

Introduction

Much attention has been paid to the role of megabenthic invertebrate structures composed mainly by invertebrates in benthic-pelagic coupling processes [1]. The dependence on currents and seston concentration has been claimed as an essential point to understand benthic-pelagic coupling processes [6,7]; there are few studies highlighting the role of short-time cycles as energy providers in marine animal forests. It is well known that in a brief time (i.e., few hours), the seston concentration in near bottom water layers may suddenly change in concentration and quality [8,9,10,11] Such changes may have an immediate response to the energy fluxes in terms of activity of the benthic community [12,13,14,15]. When the benthic activity or the abundance of meiofauna has been analyzed in the deep sea, for example, a fast response to the primary productivity have been found according to different areas of the world, suggesting that the quantity and quality of the organic material transferred from the pelagic to the benthic domain is a crucial step to understand the energetic implications of these transfer processes [16,17,18,19]

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