Invertebrate distribution and abundance is influenced by many biotic and abiotic factors, and the composition of wetland invertebrate communities may reflect ecosystem health (Krieger 1992). Contaminant loading and the introduction of the zebra and quagga mussel are probably the two most tangible threats to Long Point's native aquatic invertebrates. Persistent toxins have been documented in many Lake Erie coastal wetlands, including Long Point Bay (Chapter 4). Changes in community structure of benthic invertebrates and the occurrence of morphological abnormalities have been attributed to water quality and the influence of contaminants in other wetlands (Carr and Hiltunen 1965; Krieger 1984; Barton 1988). Zebra mussels continue to pose a known and direct threat to native Unionids, and may be influencing several other species of native aquatic invertebrates. For instance, it has been determined that the concentrations of some PCBs and PAHs are elevated in zebra mussel pseudofeces compared to the algae that are the source of the pseudofeces (Reeders and Bij de Vaate 1992; Berg et al. 1996). Pseudofeces are consumed by several species of benthic invertebrates, and gammarid amphipods that feed upon PCB-contaminated zebra mussel faeces have an absorption efficiency of greater than 80% (Bruner et al. 1994). Therefore, zebra mussels may be having a direct as well as an indirect effect on native invertebrate communities at Long Point. Aquatic macroinvertebrates are also affected by the availability of aquatic plants. Since over 90% of the Inner Bay is covered with submerged aquatic plants, this is not presently a concern (Knapton and Petrie 1999). Long Point is also extensively utilized by fish, and any further introduction of exotic species that would increase the fish biomass of Long Point may in turn adversely affect invertebrate communities.
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