Benthic-pelagic coupling mediates interactions in Mediterranean mixed fisheries: An ecosystem modeling approach

Abstract

Benthic—pelagic coupling plays a pivotal role in aquatic ecosystems but the effects of fishery driven interactions on its functioning has been largely overlooked. Disentangling the benthic—pelagic links including effects of mixed fisheries, however, needs sketching a whole description of ecosystem interactions using quantitative tools. A holistic food web model has been here developed in order to understand the interplay between the benthic-pelagic coupling and mixed fisheries in a Mediterranean system such as the Strait of Sicily. The reconstruction of the food web required review and integration of a vast set of local and regional biological information from bacteria to large pelagic species that were aggregated into 72 functional groups. Fisheries were described by 18 fleet segments resulting from combination of fishing gears and fishing vessel size. The input-output analysis on the food web of energy pathways allowed identifying effects of biological and fishery components. Results showed that the structure of the Strait of Sicily food web is complex. Similarly to other Mediterranean areas, the food web of the Strait of Sicily encompasses 4.5 trophic levels (TLs) with the highest TLs reached by bluefin tuna, swordfish and large hake and largely impacted by bottom trawling and large longline. Importantly, benthic-pelagic coupling is affected by direct and indirect impacts among groups of species, fleets and fleets-species through the whole trophic spectrum of the food web. Moreover, functional groups able to move on large spatial scales or life history of which is spent between shelf and slope domains play a key role in linking subsystems together and mediate interactions in the Mediterranean mixed fisheries.

Ecosystem functioning of two marine food webs in the North‐Western Ionian Sea (Central Mediterranean Sea)

“…However, due to their ecological and commercial importance, several species were ungrouped and defined as a single FG: the blackmouth catshark ( Galeus melastomus ), the hake ( Merluccius merluccius ), the red mullet ( Mullus barbatus ), the anglers ( Lophius piscatorius and L. budegassa ), the bluntsnout grenadier ( Nezumia sclerorhynchus ), the red giant shrimp and blue and red shrimp ( Aristaeomorpha foliacea and Aristeus antennatus , respectively), the deep‐water rose shrimp ( Parapaeneus longirostris ), and the golden shrimp ( Plesionika martia ). Moreover, other components of the NWIS ecosystem, such as the plankton community, the benthic invertebrates, the benthic producers, the top predators, mammals, seabirds, the sea turtles, and three non‐living groups namely bottom detritus, dead discards, and suspended organic matter (Detritus, Discard and Marine snow, respectively; see also Agnetta et al, ) were described in 19 additional FGs (Table ).…”

“…The EwE approach has been developed over the last 30 years, and it is now widely used for building and analyzing mass balance food-web models of aquatic and terrestrial ecosystems worldwide (Christensen & Walters, 2004;Colléter et al, 2015). EwE allows the static (e.g., Agnetta et al, 2019), time dynamic (e.g., Celić et al, 2018), and spatio-temporal dynamic (e.g., Coll, Steenbeek, Sole, Palomera, & Christensen, 2016;Walters, 2000) approaches to be implemented through the Ecopath, Ecosim, and Ecospace modules, respectively. Food webs are described by means of Functional Groups (FGs), each representing a species, a life stage of a species, or a group of species with similar trophic, ecological, and physiological features.…”

“…Mediterranean areas, such as the Central Adriatic Sea, the Aegean Sea, the Gulf of Lions and the Strait of Sicily (Agnetta et al, 2019;Banaru et al, 2013;Coll et al, 2007;Tsagarakis et al, 2010), indicating the occurrence of a benthic-pelagic coupling. In general, benthic-pelagic coupling is mainly regulated by a direct link between plankton and benthic invertebrates, with many aquatic organisms that contribute to the energy transfer processes between several compartments (sensu Griffiths et al, 2017).…”

The living marine resources in the Mediterranean Sea Large Marine Ecosystem

“…In the Mediterranean Sea LME, the major driving forces behind species dynamics/changes include primary production, temperature and fishing pressure ( Macias et al, 2015 ; Piroddi et al, 2017 ; Agnetta et al, 2019 ; Moullec et al, 2019 ). Recent studies ( Piroddi et al, 2015 , 2017 ), which coupled a food web model with an hydrodynamic-biogeochemical model, have highlighted the important role and impact of the environment and anthropogenic pressures (e.g., fishing pressure) in shaping the dynamics of the Mediterranean marine resources.…”

Rewiring and indirect effects underpin modularity reshuffling in a marine food web under environmental shifts

“…Results presented herein could be representative for processes occurring in other complex ecological systems under perturbation: The effects are detected using synthetic metrics and descriptors (see Link et al, ) but often processes behind are difficult to disentangle for the long delays of higher trophic levels population dynamics, which can be also largely impacted by indirect effects (e.g., Agnetta et al, ). Our work calls for further efforts in increasing the resolution when investigating the bottom and the middle of pelagic food webs, that is, where plankton stand.…”