Mussels partition resources from natural waters under flowing conditions

Area of Science:

• Freshwater Ecology
• Bivalve Biology
• Aquatic Resource Management

Background:

• High species richness of freshwater mussels in river ecosystems suggests niche partitioning.
• Understanding mussel feeding ecology is crucial for conservation, especially for species of differing conservation status.
• River seston characteristics (algal fluorescence, particle size, taxa) influence bivalve feeding.

Purpose of the Study:

• To examine the feeding of three freshwater mussel species (Ptychobranchus fasciolaris, Quadrula quadrula, Potamilus alatus) on river seston.
• To investigate feeding under static versus flowing conditions.
• To determine if mussels partition resources by algal taxa or particle size, and identify a novel resource partitioning mechanism.

Main Methods:

• Collected seston from the Sydenham River, Ontario.
• Analyzed seston using chlorophyll a fluorescence and flow cytometry for particle size and algal taxa identification.
• Measured mussel clearance rates (CR) under static and flow conditions for different seston characteristics.

Main Results:

• Clearance rates (CR) differed among mussel species, with Potamilus alatus showing higher CR.
• Mussels exhibited higher CR under flowing conditions and preferred larger seston particles (28-35 μm).
• Species-specific resource partitioning of algal taxa was observed, with different species preferring distinct algal groups (e.g., diatoms, Cryptomonas, Chloromonas).

Conclusions:

• A novel mechanism of hydrodynamically mediated resource partitioning explains high mussel species richness.
• Resource partitioning occurs via selective feeding on different algal taxa within flowing water, not spatial/temporal separation.
• Mussel-algal relationships are vulnerable to climate change and anthropogenic impacts like agriculture and urbanization.