The role of estuarine macrofaunal patterns for the management of marine protected areas in a changing world

Abstract

The integration of biodiversity knowledge with management needs in coastal protected ecosystems is a current challenge that requires a social-ecological perspective, especially in view of the current scenario regarding climate changes. At the southeastern Brazil, estuaries inside protected areas highlight as a great source of ecosystem services connected to the biodiversity, such as the food provisioning for local communities (i.e. fishery supply). However, climate change models considering the last four decades alert to an annual rainfall increase in the region, threatening the estuarine biodiversity and its associated ecosystem services. Here, we evaluated how estuarine macrofaunal distribution could be used as ecological indicators to support the stakeholders management needs in subtropical Marine Protected Areas (MPAs). The intertidal macrofauna distribution was assessed along physical gradients in estuaries within MPAs of the southeastern Brazil, testing the effects of salinity and sediment properties on taxa richness. Then, implications of these ecological findings were discussed with the local users and managers of the MPAs, aiming to stipulate indicators and management proposals considering the rainfall increase predicted for the region. We found that macrofauna community varied between estuarine zones along the physical gradients. High values of mud and organic content in the sediment were correlated with reduced taxa richness in the upper estuarine zone, indicating high vulnerability of biodiversity to a possible estuarine mud input connected to the expected rainfall increase. Stakeholders noted that this knowledge could assist with spatial planning for an adaptive management of the biodiversity use rules on the MPAs, with focus on the ecosystem services conservation (ecosystem-based management). Stakeholders suggested using biodiversity hotspots to guide estuarine areas classification (no-take zones and sustainable use zones), maintaining the resources use rules adaptable according to the biodiversity changes. In this regard, our data revealed important bioindicators, such as the macrofaunal richness, which can be monitored as “early signals” to assess eventual ecosystem alterations related to the climate changes. These signals can include loss in taxa richness, extirpation of species exclusively found on the lower estuarine zone (sensitives to mud input) and changes in the distribution or abundance of dominant taxa. We suggest that understanding the relationships between macrofaunal indicators and ecosystems services, associated with continuous monitoring, are the key steps to implementing an adaptive ecosystem-based management of these protected estuaries in the current changing scenario, contributing to decision making at local scale that respond to global challenges, as the UN Ocean Decade.