Before–after environmental impact assessment of an artificial channel opening on a south‐western Atlantic choked lagoon system

Abstract

This study aimed to evaluate the human induced impact of a channel opening in a choked lagoon and attempted to establish the cause-effect links for the observed changes. The same lagoon system was sampled before and after the channel opening event, and the differences in fish and crustacean assemblages and environmental variables between these periods analysed. The opening of the artificial channel resulted in salinity increases, leading to a shift in species composition, favouring marine species and reducing abundance and diversity of previously dominant freshwater species. Furthermore, saltwater entrance into the choked lagoon caused an unexpected decrease in species richness and biomass, plus deterioration of ecosystem processes, reducing fishing capacity. The effects of salinity on the ecosystem vary depending on the ecosystem's composition and capacity to overcome salinity changes, thus specific monitoring projects are important strategies for developing coastal lagoon conservation management.

Climate change overtakes coastal engineering as the dominant driver of hydrologic change in a large shallow lagoon

“…The climate factor had not been considered in previous reports evaluating or predicting the consequence of the Cut-opening when it was originally designed (Lord, 1998;Manda et al, 2014;Prestrelo and Monteiro-Neto, 2016), as the focus was on the flushing benefit to reduce the accumulation of nutrients and algal biomass. The findings from this study suggest that climate change has been taking effect over the period when the Cut was implemented, and from the view point of particular metrics, it is now over-taking the effect of the Cut.…”

“…As a result, the hydrodynamics of coastal lagoons are frequently modified through the creation of artificial channels built to enhance hydrologic connectivity to the ocean, and increase nutrient export (e.g. Breardley 2005;Manda et al, 2014;Prestrelo and Monteiro-Neto, 2016), or indirectly by engineering projects associated with dredging and coastal management (e.g. Ghezzo et al, 2010;Sahu et al, 2014).…”

Climate change overtakes coastal engineering as the dominant driver of hydrological change in a large shallow lagoon

“…As a result, the hydrodynamics of coastal lagoons are frequently modified by the creation of artificial channels built to enhance hydrologic connectivity to the ocean and increase nutrient export (e.g. Breardley, 2005;Manda et al, 2014;Prestrelo and Monteiro-Neto, 2016), or they are indirectly modified by engineering projects associated with dredging and coastal management (e.g. Ghezzo et al, 2010;Sahu et al, 2014).…”

“…Among which, the opening of artificial channels in lagoon systems has been a popular measure to enhance ocean connectivity, but this activity has the effect to fundamentally alter the hydrology and aquatic communities (e.g. Lord, 1998;Manda et al, 2014;Prestrelo and Monteiro-Neto, 2016;García-Oliva et al, 2018). Changes in the connection of restricted lagoons with the ocean can exhibit a marked change in the salinity pattern or the extent of hypersaline conditions (Kjerfve, 1994;Gamito et al, 2005) and subsequently influence the ecosystem within these lagoons (Gamito, 2006;García-Oliva et al, 2018).…”

“…A series of water quality improvement plans (e.g. Environmental Protection Authority, 2008;Rogers et al, 2010) continue to be developed to promote estuary health; however, ongoing concerns about the current and future water quality and ecologic conditions of the system (Valesini et al, 2019) require knowledge of spatio-temporal changes in water retention, stratification and salinization to support adaptation efforts.…”