Ecological-network models link diversity, structure and function in the plankton food-web.

Domenico D'Alelio,Timothy Wyatt,Simone Libralato,Maurizio Ribera D'Alcalà

doi:10.1038/srep21806

Abstract

A planktonic food-web model including sixty-three functional nodes (representing auto- mixo- and heterotrophs) was developed to integrate most trophic diversity present in the plankton. The model was implemented in two variants - which we named ‘green’ and ‘blue’ - characterized by opposite amounts of phytoplankton biomass and representing, respectively, bloom and non-bloom states of the system. Taxonomically disaggregated food-webs described herein allowed to shed light on how components of the plankton community changed their trophic behavior in the two different conditions, and modified the overall functioning of the plankton food web. The green and blue food-webs showed distinct organizations in terms of trophic roles of the nodes and carbon fluxes between them. Such re-organization stemmed from switches in selective grazing by both metazoan and protozoan consumers. Switches in food-web structure resulted in relatively small differences in the efficiency of material transfer towards higher trophic levels. For instance, from green to blue states, a seven-fold decrease in phytoplankton biomass translated into only a two-fold decrease in potential planktivorous fish biomass. By linking diversity, structure and function in the plankton food-web, we discuss the role of internal mechanisms, relying on species-specific functionalities, in driving the ‘adaptive’ responses of plankton communities to perturbations.

Highlights

Components and interactions, should be integrated in realistic models, either conceptual or numerical, to better reconstruct plankton functioning in time and space
We constructed a food-web model (FWM) to simulate a highly resolved plankton community, which includes sixty-three linked functional nodes (FN). This number of FNs greatly exceeds the minimum resolution considered sufficient for ecological network studies[32], but enables us to represent most of the trophic diversity in the plankton community
We studied the plankton community monitored at the Long-Term-Ecological Research station MareChiara in the Gulf of Naples (LTER-MC in GoN, depth = − 75 m36) during summer

Summary

Introduction

Components and interactions, should be integrated in realistic models, either conceptual or numerical, to better reconstruct plankton functioning in time and space. We constructed a food-web model (FWM) to simulate a highly resolved plankton community, which includes sixty-three linked functional nodes (FN). This number of FNs greatly exceeds the minimum resolution considered sufficient for ecological network studies[32], but enables us to represent most of the trophic diversity in the plankton community. We studied the plankton community monitored at the Long-Term-Ecological Research station MareChiara in the Gulf of Naples (LTER-MC in GoN, depth = − 75 m36) during summer At this coastal site, bloom and non-bloom ( named ‘green’ and ‘blue’) states alternated during most of the Mediterranean summer (mid-June-late August, years 2002–2009)[37]. This assumes mass-balance (i.e. consumption equals outflows in terms of production, respiration and unassimilated food for each FN) and computes biomass flows between nodes[34] (see M&M and SI for the derivation of physiological rates)

Methods

Results

Conclusion