Contrasting decay rates of freshwater bivalves’ shells: Aquatic versus terrestrial habitats

Abstract

a b s t r a c tFreshwater flow regimes are particularly vulnerable to global climate change with changes to the volume and regime of water contributing to global declines in freshwater biodiversity. Droughts or floods can cause massive mortalities of freshwater bivalves, facilitating the accumulation of shells in the aquatic but also in adjacent terrestrial habitats. In order to fully understand the long term impact of these massive mortality events, it is important to assess how bivalve shells persist in the environment. Given that, the present study aimed at studying the shell decays of four different bivalve species (Anodonta anatina, Corbicula fluminea, Potomida littoralis and Unio delphinus) in aquatic (i.e. river) versus terrestrial (i.e. sand soil) habitats. Shell decay rates were significantly different among species and habitats. In the aquatic habitat the shell decay rates varied among species, with the native species A. anatina, which have the largest and thinnest shell, showing the highest decay rate. Alternatively, in the terrestrial habitat the shell decay rates were more even among species and not related to a particular shell feature or morphology, with the native U. delphinus showing the fastest decay. The shell decay rates were 6 to 12 times higher in aquatic than in the terrestrial habitat. These results suggest that bivalve shells can persist for long periods of time on both habitats (but mainly in terrestrial), which may perhaps trigger significant changes on the ecosystem structure and functioning.

Palatability of the Asian clam Corbicula fluminea (Müller 1774) in an invaded system

“…The unique exception were some C. fluminea juveniles (whole individuals) found in the gut contents of a few Salmo truta fario specimens (Ilarri et al, 2014). Beyond the fact that C. fluminea present the shells as a physical defence, it is important to state also that their shells are harder when compared to other bivalve species present in Minho River with the exception of Potomida littoralis (Ilarri et al, 2015). This situation may be the main reason for the avoidance of this species as a prey.…”

Assessing the effects of temperature and salinity oscillations on a key mesopredator fish from European coastal systems

“…However, it is important to consider that the subsequent effects of climatic extremes may have opposite trends and negative feedback processes (IPCC, 2014). For instance, a massive die-off of bivalves after droughts (Ilarri et al, 2011) and floods (Sousa et al, 2012), may lead to a significant increase on the quantity of empty shells in the river bottom that might be used for P. microps reproduction in the next breeding season, which may led to an increase in the population density after one or more generations due to the persistence of these shells in the system for years (Ilarri et al, 2015b). Actually, the reproduction of common gobies seems to be limited by the presence of nest substrates (Nyman, 1953;Magnhagen, 1998) and their abundance and availability can directly influence the number of breeding males (Breitburg, 1987;Lindström, 1988).…”

Live, dead, and fossil mollusks in Florida freshwater springs and spring-fed rivers: Taphonomic pathways and the formation of multisourced, time-averaged death assemblages

“…The modern, live community is the single source for less-degraded shells, whereas reworked fossils and fluvial processes both contribute to higher TT scores in death assemblages. Freshwater bivalves likely undergo similar reworking, though this may be complicated by their range of life modes, poor preservation of shell material (particularly of taphonomically nonrobust mussels), and other biological/ecological differences (Cummins 1994;Newell et al 2007;Wolverton et al 2010;Ilarri et al 2015Ilarri et al , 2019Martello et al 2018).…”