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This study uses the local knowledge of artisanal fishers to assess ecosystem structure, functioning, and fishing impacts within a coastal lagoon in Uruguay. To this end, we used an Ecopath with Ecosim modelling approach based on fishers' knowledge and scientific data. The model considered 23 functional groups, while three fleets represented fishing activities targeting different species. The model output shows a foodweb which spans four trophic levels, including fish species as top predators, such as the flatfish Paralichthys orbignyanus and the tararira Hoplias malabaricus. Furthermore, according to fishers' knowledge, gastropods, polychaetes, and bivalves constitute primary consumers, while detritus and phytoplankton represent the primary food sources. The trophic impact analysis shows that the fish Mugil spp. and Odontesthes spp. generate important positive and negative impacts on most other ecosystem components, while fishing impacts occur at moderate exploitation levels on the targeted fish species. The indicators of the ecosystem effects of fishing including The Trophic Level of the Catch ranging from 2.4 to 2.6, the Primary Production Required showing relative low values of 2.3% and low probability of an ecosystem being sustainably fished alert us to the risk of ecosystem-level overfishing. The vast potential of fishers' knowledge in research can allow the co-creation of new insights into ecosystem structure and function. By including fishers in research, local communities can be empowered and benefit from management decisions through their trust in science. [ABSTRACT FROM AUTHOR]

We model and compare for the first time the ecosystem structure and trophic networks of two sandy beaches with contrasting morphodynamics (i.e. dissipative and reflective). To this end, an Ecopath model was implemented to represent the macroscopic food web on each sandy beach ecosystem. The dissipative beach model comprised 20 compartments and the reflective nine, including detritus, phytoplankton, zooplankton, benthic invertebrates, fishes and seabirds. Input data mainly came from direct surveys, whereas additional information was gathered from published and unpublished sources. Results revealed a major number of top predators and higher trophic levels (TLs) in the dissipative beach (seabirds, fishes, gastropods and the polychaete Hemipodus olivieri) than in the reflective one (fishes and Hemipodus olivieri). Detritivorous and filter feeding benthic invertebrates constituted intermediate trophic levels on both beaches. Exportation of most primary production and detritus was a common feature, with a detritivory:herbivory ratio of 0.42 in the dissipative beach and 0.51 in the reflective, indicating a higher utilization of the primary production in the former. The aggregation analysis showed five TLs in the dissipative beach and four in the reflective. Lower transfer efficiencies in the reflective beach could be attributed to a lower diversity of predators when compared to the dissipative system. Comparison of global ecosystem properties showed that the dissipative system had higher values for total system throughput, total biomass, net production, Ascendency and total number of pathways. We concluded that the greater diversity and biomass in the dissipative beach are reflected in a higher dimension and ecosystem organization than in the reflective beach, thus providing new evidences at the ecosystem level about well-established differences in biological descriptors between beach types. Finally, we stressed the need for acquiring experimentally-based information on benthic invertebrate's consumption rates and the inclusion of the surf zone microbial loop and the interstitial compartment to test for differences in structure and functioning of these coastal ecosystems. [Copyright &y& Elsevier]