Living the high turbidity life: The effects of total suspended solids, flow, and gill morphology on mussel feeding

Abstract

Unionid mussels from clear‐water rivers are often found in turbid waters in which their feeding and reproductive efficiency should be impaired. We examined the feeding response of Lampsilis siliquoidea from a clear and turbid river in response to increased concentrations of total suspended solids (TSS) and water velocity in a funnel chamber and a recirculating flow chamber. Four TSS concentrations (0, 5, 20, and 100 mg L−1) and four velocities (0, 0.05, 0.15, and 0.25 m s−1) were used to create 16 experimental conditions corresponding to nine TSS flux (concentration × velocity) levels. TSS flux significantly affected clearance rates (CR); however, the relationship was complex. Increased TSS led to lower CR in mussels from clear and turbid river at all velocities; however, increases in velocity reduced the magnitude of the decline with respect to TSS. Overall, the turbid river mussels were less affected by increased TSS than those from the clear‐water rivers. The mussels from the turbid river also differed anatomically (i.e., greater palp:gill ratio; number of cilia per cirri; number of cirri cm−1; and thickness of palp cilia, and less cilia per unit area of palp) from the clear river animals. It is likely that these anatomical differences allow the mussels to feed more efficiently in turbid water, which explains the observed differences in CR response to TSS. These results demonstrate the importance of multistressor approaches in evaluating aquatic organisms, as well as providing a potential mechanism to explain how mussels thrive in turbid rivers.

The Effects of River Algae and Pore Water Flow on the Feeding of Juvenile Mussels

“…Scenedesmus was avoided at higher flux in the present study likely because of its large size, shape, and spines (Beck & Neves, ). Algal flux combines the effects of algal concentration and its delivery (Mistry & Ackerman, ), especially when neither of the factors dominates CR (Tuttle‐Raycraft & Ackerman, ); single factors, such as velocity, may only affect feeding under certain conditions (e.g., low algal concentration in scallops, Argopecten irradians ; Cahalan et al, ). Algal flux affected the CR and feeding electivity of juvenile L. siliquoidea , especially their selection of diatoms, which has been observed in other freshwater bivalves (e.g., Diplodon enno , Hyriidae; Alves et al, ).…”

Evidence of phenotypic plasticity in the response of unionid mussels to turbidity

“…≤5 mg/L total suspended solids [TSS]) and turbid rivers (i.e. 64 ± 12 mg/L [mean ± SE ] TSS; Tuttle‐Raycraft & Ackerman, 2019), even though turbid conditions are associated with decreased feeding and reduced reproduction (i.e. Gascho Landis & Stoeckel, 2016; Tuttle‐Raycraft, Morris, & Ackerman, 2017).…”

“…Lei, Payne, & Wang, 1996; Tokumon, Cataldo, & Boltovskoy, 2015), and unionid mussels (e.g. Gascho Landis, Haag, & Stoeckel, 2013; Tuttle‐Raycraft & Ackerman, 2019; Tuttle‐Raycraft et al, 2017). As TSS concentrations increase, the handling time of the particles increases, and mussels spend more time cleaning their gills and producing pseudofaeces (rejected material expelled from the inhalant opening; Foster‐Smith, 1975) than feeding.…”

“…Although these declines in CR may be modulated by the nutritional quality of the TSS (Tuttle‐Raycraft & Ackerman, 2018), and increasing water flow (e.g. Tuttle‐Raycraft & Ackerman, 2019), the resultant algal CR remain lower compared to no‐TSS controls. Despite the negative impacts of TSS, large and diverse mussel populations can be found in turbid rivers (e.g.…”

“…Recently, Tuttle‐Raycraft and Ackerman (2019) demonstrated a positive interaction of velocity that mitigated the negative effects of elevated TSS on mussel CR. Interestingly, L. siliquoidea from a turbid river were less affected by TSS flux (TSS flux = velocity ×TSS) than their conspecifics from a clear river (Tuttle‐Raycraft & Ackerman, 2019). The mussels from the turbid river also had denser gill surfaces (i.e.…”