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Water Quality Wildlife 5.1 Effects Wildlife can be directly or indirectly affected by changes in organic carbon levels in aquatic systems. For example, abundance of loons are negatively correlated with TOC and DOC levels because the latter are typically highly coloured and loons require clear water to sight their prey (Alvo et al. 1988; Heglund et al. 1994). Because effects due to the optical properties of water were the focus of the recently developed water quality criteria for true and apparent colour (BC Environment 1998a), they will not be dealt with here. Possible indirect effects arise because organic carbon plays an important role in aquatic system productivity and system response to acid inputs. These effects are discussed below. Several studies have shown that the reproductive success and probability of presence of waterfowl are strongly related to pH levels (e.g., Blancher et al. 1992). Analyses of 212 lakes in central Ontario revealed a positive relationship between DOC levels and presence of insectivorous waterfowl (i.e., black duck and ring-necked duck). Several factors could explain this relationship: (i) increased DOC is generally associated with increased system productivity and thus there may be more invertebrate prey available to waterfowl in lakes with high DOC, and/or (ii) DOC acts as a buffer and thus acid-sensitive invertebrates are available as prey in lakes with high DOC levels. Andersson and Danell (1982) found that addition of organic matter to man-made water-bodies was associated with an increase in macro-invertebrate predators (e.g., Hirudinea), an important food source for diving ducks (e.g., grebes). The increase in macro-invertebrate predators, however, decreased the abundance of their prey, detritivorous invertebrates (e.g., chironomids, Asellus), an important food source for dabbling ducks. Therefore, the relationship between DOC and waterfowl abundance is likely to be complicated because waterfowl are affected by a number of other variables (e.g., lake size, food web relationships, competition with insectivorous fish, etc) that are themselves positively or negatively correlated with DOC.
No water quality criteria for the protection of wildlife were found in the literature for either total or dissolved organic carbon.
5.3.1 Total Organic Carbon The 30-day 50th percentile percentile total organic carbon concentration shall be within 20% above or below seasonally-adjusted median background levels as measured historically or at appropriate reference sites. This criterion applies to freshwater aquatic systems only. The appropriate methodology for determining total organic carbon is discussed in section 1.4 and in BC Environment (1994).
The 30-day 50th percentile dissolved organic carbon concentration shall be within 20% above or below seasonally-adjusted median background levels as measured historically or at appropriate reference sites. This criterion applies to freshwater aquatic systems only. The 30-day 50th percentile calculation should be based on a minimum of five weekly samples taken over a period of 30 days. The appropriate methodology for determining dissolved organic carbon is discussed in section 1.4 and in BC Environment (1994).
The limited
wildlife effects information indicates that changes in organic
carbon are associated with possible impacts on abundance of
waterfowl. The available information is, however, insufficient
to define numerical criteria for the protection of wildlife
that would be different from the aquatic life criteria. The
aquatic life criteria should be protective of wildlife because
the impacts of changes in organic carbon to waterfowl are likely
mediated through the aquatic food chain. Therefore, if aquatic
life are protected, wildlife should also be protected.
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