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Effects of Porewater Flow on Interstitial Algal Composition and Juvenile Unionid Mussel Feeding

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Title: Effects of Porewater Flow on Interstitial Algal Composition and Juvenile Unionid Mussel Feeding
Author: Fung, Victor
Program: Integrative Biology
Advisor: Ackerman, Josef
Abstract: The aim of this study was to understand the habitat requirements of juvenile unionid mussels by determining the algal composition of interstitial habitats that juvenile mussels inhabit and what they consume. This aim was achieved by examining the clearance rates (CR) and selective feeding of juvenile Fatmucket mussels (Lampsilis siliquoidea) under ecologically relevant flow conditions. Flow cytometry revealed higher particle concentrations in the interstitial zone vs. surface water of the Thames River (near Innerkip, ON, Canada), and that the interstitial areas in downstream regions of boulders had the greatest particle concentrations among locations in the riverbed. Mussels were exposed to different seston flux (cells m2 s-1) in a recirculating flow chamber, and their CR were determined through changes in the concentration of chlorophyll a via fluorometry, and specific algal taxa via imaging flow cytometry. Clearance rates (volume of water cleared of particles per unit time per individual) were higher in interstitial treatments vs. surface water, but an interaction between algal taxa clearance rate and algal concentration was found, suggesting that the ability to discriminate among algal species differed (6 taxa increased, 4 decreased) with algal concentrations. Chesson’s Electivity index revealed that juvenile mussels selected diatom taxa across all ranges of velocity and algal flux examined, whereas chlorophytes were randomly selected, indicating diatoms were more important in juvenile mussel diet. Electivity of Nitzschia and centric diatom increased and decreased respectively with increasing taxon specific algal flux, suggesting juvenile mussel selective feeding behaviour is affected by algal flux. The algal composition and chemical environment at the Innerkip site were spatially and temporally dynamic. Despite greater energy availability in the interstitial zone, the chemical environment was not suitable for juvenile unionids at times (e.g., DO < 2 mg L-1, ammonia > 0.5 mg L-1). This study provides evidence on the importance of porewater flow in streambeds as a component of juvenile mussel habitats, as it influences food availability and subsequently their feeding behaviour, which will assist in reintroduction and augmentation strategies.
Date: 2019-02-14
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