Factors Affecting Georgian Bay Coastal Wetlands

Coastal wetlands of Georgian Bay have been virtually ignored by ecologists until recently, when these ecosystems were found to have exceptionally high biodiversity compared to other Gr,~at Lakes wetlands. To address this deficiency, we conducted a baseline survey (2002 to 2007) to determine the biotic and abiotic characteristics of 92 wetlands in 18 quatemary watersheds, using a suite of published ecological indices developed specifically for coastal wetlands (Water Quality Index (WQI); adjusted Wetland Macrophyte Index (WMiadj), and the Wetland Fish IndexBasinPAex (WFIBasinPAex)). Although a majority of the watersheds are located in remote eastern and northern parts of the Bay and therefore receive minimal human disturbance, one watershed, Sturgeon River, located in southern Georgian Bay receives relatively high urban, recreational and agricultural disturbance. Mean scores of WQI and WMiadj varied significantly across the watersheds, ranging from 0.48 to 2.15, and from 2.29 to 3.77, respectively. Mean WFIBasinPAex scores, however, were less variable and only ranged from 3.53 to 3.86. Of the 88 macrophyte species identified, the most common were hardstem bulrush. (Schoenoplectus acutus), water celery (Vallisneria americana), richardson's pondweed (Potamogeton richardsonii), slender waternymph (Najasjlexilis) and Canadian waterweed (Elodea canadensis). Six non-native macrophytes, Purple loosestrife (Lythrum wlicaria), narrow-leaf cattail (Typha angustifolia), hybrid cattail (Typha x glauca), Eurasian milfoil (Myriophyllum spicatum), curly pondweed (Potamogeton crispw) and frogbit (Hydrocharus morsus-ranae) were also recorded, the most common ofwhieh was Eurasian milfoil. Sago pondweed (Stuckenia pectinata), a native species that can be invasive, and is tolerant of poor water-quality, was present in about half of the watersheds. Ofthe 51 fish species, pumpkinseed (Lepomis gibbosus) bluntnose minnow (Pfmephales notatus), brown bullhead (Ameiurus nebulosus), rock bass (Ambloplites rupestris), and yellow perch (Percajlavescens) were the most widespread and abundant. Three non-native species, common carp (Cyprinus carpio), alewife (Alosa pesudoharengus), and round goby (Neogobius melanostomus) were present but not dominant. WMI scores were highly correlated with WQI scores, and as expected, wetlands in the most disturbed southern watershed were associated with the lowest WQI and WM[ scores, and had the greatest number of exotic species. However, WMI scores of wetlands in a few exposed sites located at the tip of the Bruce Peninsula were similarly low, even though these sites are not yet impacted by human activities. There was no significant relationship between WFIBasinPAand WQI scores, although the WFIBasin PA did not seem to be affected by exposure. We recommend that the WQI and WMiadj be used in long-term monitoring programs of Georgian Bay to track negative impacts of human disturbance on these valuable ecosystems.

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