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The development of effective nonlethal biomonitoring techniques is imperative for the preservation of imperiled freshwater mussel populations. Changes in hemolymph chemistry profiles and tissue glycogen are potential biomarkers for nonlethally monitoring stress in mussels. We sampled three species in the Flint River Basin over 2 years to evaluate how these hemolymph and tissue biomarkers responded to environmental changes. We used hierarchical linear models to evaluate the relationships between variation in the biomarkers and environmental factors and found that the responses of the hemolymph and tissue parameters were strongly related to stream discharge. Shifts in alanine aminotransferase and glycogen showed the largest relations with discharge at the time of sampling, while magnesium levels were most explained by the discharge for 5 days prior to sampling. Aspartate aminotransferase, bicarbonate, and calcium showed the strongest relations with mean discharge for 15 days prior to sampling. The modeling results indicated that biomarker responses varied substantially among individuals of different size, sex, and species and illustrated the value of hierarchical modeling techniques to account for the inherent complexity of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Freshwater mussel populations are highly susceptible to environmental alterations because of their diminished numbers and primarily sessile behaviors; nonlethal biomonitoring programs are needed to evaluate the health of populations prior to mass mortality events. Our objectives were to determine ( i) which biochemical parameters in freshwater mussel hemolymph could be consistently quantified, ( ii) how hemolymph parameters and tissue glycogen respond to a thermal stress gradient (25, 30, and 35 °C), and ( iii) the effects of tissue and hemolymph extraction on long-term growth and survival of smaller- and larger-bodied mussel species. Glucose exhibited elevated expression in both species with increasing water temperature. Two transaminase enzymes had elevated expression in the 30 °C treatment. The effects of hemolymph extraction and tissue biopsies were evaluated with a large-bodied species, Elliptio crassidens, and a smaller species, Villosa vibex. Individuals were monitored for 820 to 945 days after one of four treatments: hemolymph extraction, tissue biopsy, tissue and hemolymph extraction, and control. Hemolymph extraction and tissue biopsy adversely affected survival of V. vibex, suggesting that these extraction methods may add some risk of reduced survival to smaller-bodied species. Survival of E. crassidens was not impaired by any of the treatments, supporting the use of these techniques in nonlethal biomonitoring programs for larger-bodied mussel species. [ABSTRACT FROM AUTHOR]