Recovery trends of Scrobicularia plana populations after restoration measures, affected by extreme climate events

Abstract

The Mondego estuary (Portugal) went through different ecological scenarios over the last decades. An eutrophication process led to a decline in the ecosystem quality. The ensuing restoration plan resulted into a gradual ecological recovery, which was impaired by the occurrence of successive extreme climate events that affected dynamics and productivity of key species. In this study we assess the response of the bivalve Scrobicularia plana to the impacts of these events in a recovery scenario, by comparing populations in two different intertidal habitats: a seagrass bed and a sandflat area. As a general tendency, S. plana, which was negatively affected by eutrophication, responded positively to restoration. However, the occurrence of extreme climate events seemed to affect recruitment success, biomass and production, impairing the recovery process. In the seagrass bed, S. plana maintained a stable and structured population, while in the sandflat area recovery clearly reverted into a decline, mainly concerning biomass and production values. This sequence of multiple stressors might have reduced S. plana resilience to further impacts and therefore, understanding the behavior of biological populations following restoration initiatives requires acknowledgement that some changes may not be easily reversible.