Modelling the risk of mortality of Corbicula fluminea (Müller, 1774) (Bivalvia: Corbiculidae) exposed to different turbidity conditions

Abstract

The provision of sediment in rivers, due to erosion processes that occur in the environment, consists of a major source of pollution and alteration of the physicochemical conditions of water resources. In addition, the increase in water turbidity may cause siltation, dramatically impacting aquatic communities. Specifically considering the bivalve Corbicula fluminea (Müller, 1774), the aim of this study was to analyse the effect of exposure to different turbidity conditions of sediments, as a risk factor for the animals. For this purpose, a docking device was designed to ensure water circulation in a closed system and to maintain the desired levels of turbidity. Although C. fluminea can generally tolerate environmental changes in aquatic systems, an intolerance to high turbidity levels was experimentally observed, expressed by the mortality rate of the animals when exposed to conditions above 150 nephelometric turbidity units (NTU). This value was similar to the one recorded at study sites in the rivers Pardo (Serrana-SP-Brazil) and Mogi Guaçu (Porto Ferreira-SP-Brazil) during the rainy season. Using a logistic regression model, the experimental results were analysed and the observed mortality rates indicate that the exposure of the animals to turbidity levels above 150 nephelometric turbidity units (NTU), for periods longer than 120 hours, may be considered a probable cause of mortality for the species.Keywords: biodiversity, bivalve, erosion, watershed, logistic regression. Modelagem do risco de mortalidade de Corbicula fluminea (Müller, 1774) (Bivalvia: Corbiculidae) exposta a diferentes condições de turbidez ResumoA disponibilização de sedimentos nos cursos d'água, em função dos processos erosivos que ocorrem no entorno, constitui-se e uma das principais fontes de poluição e alteração das condições físico-químicas dos recursos hídricos. Além disso, o aumento da turbidez da água pode causar assoreamento, impactando drasticamente as comunidades aquáticas. Especificamente para o bivalve Corbicula fluminea (MÜLLER, 1774), este estudo teve por objetivo analisar o efeito da exposição a diferentes condições de turbidez, como fator de risco para os animals. Para esta finalidade, um dispositivo de acoplamento foi concebido para assegurar a circulação da água, em um sistema fechado mantendo os níveis desejados de turbidez. Embora C. fluminea possa tolerar mudanças ambientais em sistemas aquáticos, foi observadao experimentalmente, uma intolerância a turbidez acima de 150 unidades nefelométricas de turbidez (NTU), um valor próximo ao registrado em pontos de estudo nos rios Pardo (Serrana-SP-Brasil) e Mogi Guaçu (Porto Ferreira-SP-Brasil) durante a estação chuvosa. Por intermédio da utilização de um modelo de regressão logística, os resultados experimentais foram analisados. As taxas de mortalidade observadas indicam ser a exposição dos animais a níveis de turbidez acima desse limite e por períodos mais longos do que 120 horas uma provável causa de mortalidade desta espécie.Palavras-chave: biodiversidade, bivalve...

Effects of an atypical drought on the benthic macroinvertebrate community in a tropical reservoir

“…This species has a remarkable capacity of re-colonizing and recovering its abundance after the occurrence of disturbances (Sousa et al 2008). Some studies have demonstrated that increased turbidity might increase mollusk mortality (Avelar et al 2014. Sediment type might also influence the mortality of these organisms, since very fine fractions require higher energy expenditure to keep the individuals in the sediment, and they might also clog the pallial cavity (Vianna & Avelar 2010).…”

Demographic and genetic characterization of harvestedCorbicula flumineapopulations

“…In fact, our results indicated that the density, biomass and genetic diversity of C. fluminea were correlated with the dissolved oxygen, water velocity, turbidity and water temperature. In addition, these environmental factors have been also related with survival and growth of C. fluminea (McMahon, 1979;Karatayev, Burlakova & Padilla, 2005;Müller & Baur, 2011;Avelar, Neves & Lavrador, 2014;Ferreira-Rodríguez & Pardo, 2016). For example, increase in turbidity may cause siltation potentially increasing mortality rates (Avelar, Neves & Lavrador, 2014).…”

“…In addition, these environmental factors have been also related with survival and growth of C. fluminea (McMahon, 1979;Karatayev, Burlakova & Padilla, 2005;Müller & Baur, 2011;Avelar, Neves & Lavrador, 2014;Ferreira-Rodríguez & Pardo, 2016). For example, increase in turbidity may cause siltation potentially increasing mortality rates (Avelar, Neves & Lavrador, 2014). Unusually low winter temperatures can result in massive die-offs of C. fluminea populations (Werner & Rothhaupt, 2008).…”

Peer Review #3 of "Demographic and genetic characterization of harvested Corbicula fluminea populations (v0.1)"

“…In fact, our results indicated that the density, biomass and genetic diversity of C. fluminea were correlated with the dissolved oxygen, water velocity, turbidity and water temperature. In addition, these environmental factors have been also related with survival and growth of C. fluminea (McMahon, 1979;Karatayev et al, 2005;Müller & Baur, 2011;Avelar et al, 2014;Ferreira-Rodríguez & Pardo, 2016). For example, increase in turbidity may cause siltation potentially increasing mortality rates (Avelar et al, 2014).…”