Inter- and intra-specific differences in filtering activities between two unionids, Anodonta woodiana and Unio douglasiae, in ambient eutrophic lake waters

Abstract

Inter-specific and intra-specific differences in the filtering activities of two unionid bivalves. Unto douglasiae and Anodonta woodiana, which thrive in small agricultural canals, were compared using a flow-through chamber system of ambient eutrophic lake water. The mean filtration rates (FRs) of these two species, size-matched for similar shell length, were not significantly different (t-test, t = 0.024, P= 0.981), whereas there were significant differences in the FRs between mussels of different ages (t-test, t= 5.137, P= 0.001), different densities (t-test, t = 8.297, P< 0.0001), and different currents (t-test, t = 3.898, P= 0.005). The FRs of A. woodiana increased significantly more with higher temperatures in younger mussels (P< 0.01, maximum FR= 0.352 +/- 0.157 L/h at 13.5-20.4 degrees C) than in adults. However, the mortality of the mussels was comparatively higher in younger mussels due to a low tolerance to ammonia. Correlation coefficients and PCA results collectively indicate that the two dominant unionid mussels in the canal had a strong relationship with the seston level in the lake (turbidity, suspended solids and chlorophyll-a), resulting in a higher FR, pseudo-faeces production, and ammonia tolerance and a lower mortality. In addition, the validation of the biomanipulation used in the mussel-controlled system is discussed in an effort to improve the water quality of eutrophic lakes and streams and the conservation of the benthic mussel community. (C) 2011 Elsevier B.V. All rights reserved.