Removal of seston by Crassostrea rhizophorae (Guilding, 1828) in the Vitória bay estuarine system, Brazil

Abstract

ABSTRACT The clearance of organic suspended particles by bivalve mollusks in estuarine ecosystems has been considered a critical regulating service. In Neotropical estuaries and associated mangrove ecosystems, the mangrove oyster, Crassostrea rhizophorae, is a key species in such process. To evaluate C. rhizophorae clearance rates (CRbd), biodeposit experiments were carried out at dry (2015) and wet (2016) seasons, in three sites of the Vitoria Bay Estuarine System (VBES), southeastern Brazil. The average CRbd was 0.67 L.g−1.h−1, which can be regarded as low CR. Although organic fraction predominates in the particulate matter (>60%), high estuarine salinity caused by low river discharge during prolonged regional drought, impaired oyster feeder rates. When the CRbd take into account the estimate entire mangrove oyster biomass at the VBES (3.77 × 105 kg.km−2) it yields a rate of 6.51 × 106 m3.kg−1.day−1, corresponding to a mean daily capacity of organic seston removal of 26% of the total estuarine volume. Even conservative, this result highlights the importance of mangrove oyster for the estuarine regulation, emphasizing its ecological importance and the need to sustain the critical ecosystem services of regulating estuarine environmental quality.