Mass balanced trophic models and short-term dynamical simulations for benthic ecological systems of Mejillones and Antofagasta bays (SE Pacific): Comparative network structure and assessment of human impacts

Abstract

Mass-balanced and dynamical multispecies trophic models were constructed for benthic systems of Mejillones and Antofagasta bays. We analysed data on biomass, P/B ratios, catches, food spectra, and the consumption and dynamics of commercial and non-commercial species or functional groups using the Ecopath with Ecosim framework. The biomass of the Rhodophyta group, which contributed 25.5% of the total system biomass, was the most abundant compartment in Mejillones bay, whilst the bivalve Transenella pannosa recorded the highest biomass (∼39%) in Antofagasta bay. Amongst the carnivores, the commercial gastropod Tais chocolata (∼2%) and the sea star Luidia magallanica (∼4%) were the compartment containing the highest biomass in Mejillones Bay and Antofagasta Bay, respectively. Based on the magnitudes of Pp/R, Relative Ascendency (A/C), Relative Overhead (Ov/C), Redundancy, Finn's cycling index and the system recovery time (SRT), the benthic system of Antofagasta Bay was more developed or mature and, in turn, less resistant against perturbations compared to Mejillones Bay. The outcomes of the mixed trophic impacts (MTI) indicate that the small epifauna carnivore (SEC) and the phytoplankton propagate the highest magnitudes of direct and indirect effects on the remaining compartments in the Mejillones and Antofagasta bays, respectively. According to the Ecosim short-term simulations (increasing 10, 30 and 50% the mortality by fishing and/or toxic substances) the snail Tegula spp. had the highest impact on the other compartments in Mejillones Bay, whilst the bivalve T. pannosa exhibited the highest impacts in Antofagasta Bay. Based on our results, we suggest that environmental studies should not only aim to promote and ensure the quality of physical components of nature, but should also consider the ecosystem properties and dynamics that emerge from complex networks.