Massive mortality of the giant freshwater mussel Anodontites trapesialis (Lamarck, 1819) (Bivalvia: Mycetopodidae) during a severe drought in a Neotropical reservoir

Abstract

In 2012, a severe drought struck the southeastern of Brazil compromising the Paraná River Basin reservoirs. Here, we described how this climatic event promoted a massive mortality of the giant freshwater mussel Anodontites trapesialis in Furnas reservoir and reported the consequences of this phenomenon. In November 2012, three quarters of 100 m 2 were sampled in this reservoir, where 812 dead shells of A. trapesialis were analyzed and measured (33 ˫ 133 mm). The species showed an aggregated distribution with high density (X _ : 1.0-5.5 ind/m 2). Despite the massive mortality detected in fi eld, it was possible to fi nd living specimens in a small channel in the studied area, allowing the species to survive the water level fl uctuations. Large adult individuals (100 ˫ 124 mm) were more affected by drought than juveniles, accounting for about 90% of the dead mussels analyzed. Two years after the massive mortality event, water level was not reestablished and a terrestrial succession (with elevations in the concentration of organic matter and calcium in sediment) was observed in the studied area. We verifi ed that the damming associated with extreme climatic events affect negatively the populations of A. trapesialis and should be faced as a conservationist problem.

The role of anthropogenic habitats in freshwater mussel conservation

“…This can lead to the death of large numbers of V. ambiguus and A. pertexta . In extreme cases, such as during the 2012 drought in Brazil when the water level decreased by up to 17 m in the Furnas HPS reservoir, water levels were still not re‐established several years after the drought (Paschoal et al, 2020). This extreme situation acted as an ecological trap for the freshwater mussel Anodontites trapesialis , resulting in massive mortalities.…”

“…This extreme situation acted as an ecological trap for the freshwater mussel Anodontites trapesialis , resulting in massive mortalities. Surveys conducted 3 years later showed a terrestrial succession with increases in organic matter and calcium in the soil caused by the decomposition of mussels (Paschoal et al, 2020; Figure 3). Very similar results were reported in reservoirs during extreme droughts in Portugal and Australia resulting in high mortalities of M. margaritifera (Sousa, Ferreira, et al, 2018) and A. pertexta and V. ambiguus (M. W. Klunzinger, personal observation, January, 2010 and 2017), respectively.…”

Thermal sensitivity modulates temporal patterns of ecosystem functioning by freshwater mussels

“…Freshwater mussels are already experiencing dramatic declines throughout their range primarily due to anthropogenic alterations to freshwater habitats and extended drought, specifically when flows cease, which can result in high mussel mortality (Garrido Nogueira et al, 2021; Golladay et al, 2004; Paschoal et al, 2020; Strayer et al, 2004; Vaughn & Hoellein, 2018). Further changes to freshwater ecosystems due to changes in climate and human demand for freshwater are likely to exacerbate this decline.…”

“…In the face of rapid climate change, freshwater animal distributions could shift to more favourable habitats (Poff et al, 2012). However, the fragmented nature of river habitats (e.g., dams, increased length and duration of dry reaches) is a particular challenge to dispersal by mussels as they are dependent on mobile fish hosts (Garrido Nogueira et al, 2021; Lopes‐Lima et al, 2018; Paschoal et al, 2020). As we look for management solutions that reduce stress and mussel species extirpation, we need a better understanding of how mussels respond to temperature challenges within currently occupied habitats and how this might favour species with particular life history strategies and phylogenetic constraints.…”

“…In the face of rapid climate change, freshwater animal distributions could shift to more favourable habitats (Poff et al, 2012). However, the fragmented nature of river habitats (e.g., dams, increased length and duration of dry reaches) is a particular challenge to dispersal by mussels as they are dependent on mobile fish hosts (Garrido Nogueira et al, 2021;Lopes-Lima et al, 2018;Paschoal et al, 2020). As we look for management solutions that reduce stress and mussel spe-…”