1. Great Lakes water levels will generally remain within the natural historical range of water levels with
annual means slightly below long term mean water levels. Increased precipitation, storm severity and
frequency during winter and spring months, and more drought-like conditions in the summer and early fall
have implications for short-term, seasonal, and interannual water level variability and the phenology of
organisms that rely on those seasonal and interannual water levels. Increased short-term, seasonal, and
interannual water level variability will support and maintain coastal wetland biodiversity and associated
fish and wildlife habitats.
2. Major winter and spring precipitation events will increase nutrient and sediment loadings into the Great
Lakes. Reduced ice cover on large lakes will increase surface water temperatures and evaporation, increase
productivity, initiate longer-term thermal stratification , and increases the probability for low DO events in
shallow embayments and other great lakes areas (Lake Erie dead zone). Combined with warmer surface
water temperatures, increased loadings may result in more widespread algal and cyanobacterial
3. Increased storm magnitude and frequency coupled with warmer surface water temperatures will reduce
ice cover, increase wave power, and reduce winter ice shore protection which will increase the risk for
coastal flooding and result in accelerated beach, shore, and bluff erosion.
4. During extended periods of low water levels, shallow-water areas will offer potential new habitat for
submergent aquatic vegetation and new coastal wetland communities. But exposed lakebed areas may be
vulnerable to expansion by Phragmites australis or other invasive wetland plant species.
5. Increased surface water temperatures will cause gradual ecotonal shifts in aquatic species distributions
from cold-water species to warm-water species in intermediate- to shallow-water nearshore and coastal
areas of the Great Lakes.