Watershed Conservation Plan - Destination Erie

settlement (Prepas and Charette 2003). The primary excess nutrient which contributed to the eutrophication
of Lake Erie was phosphorus (Prepas and Charette 2003; USEPA 2006b). It was the first of the Great Lakes
to exhibit major algal blooms and depletion of oxygen (USEPA 2006b), which became most pronounced in
the late 1960s and early 1970s (Prepas and Charette 2003). At this time, the phosphorus load of Lake Erie
was estimated to be four times higher than the precolonization values (Prepas and Charette 2003).
In the early 1970s, the central basin of Lake Erie was profoundly affected by eutrophication because it
was deep enough to become thermally stratified during the summer months, but contained a relatively small
volume of water in its bottom layer (hypolimnion), which became rapidly depleted of oxygen (Prepas and
Charette 2003). The eastern basin also stratified in summer, but did not experience severe oxygen depletion
due to the larger relative volume of its hypolimnion. The three basins of Lake Erie, from east to west,
exhibited progressively greater levels of eutrophication; the shallow western basin was highly eutrophic, the
central basin was considered meso- to eutrophic, and the eastern basin was judged to be mesotrophic (Prepas
and Charette 2003).
The eutrophication problem in Lake Erie was reversed in the late 1970s and 1980s, due to international
efforts to reduce phosphorus loading from detergents and municipal sewage effluents (Prepas and Charette
2003). Summer algal blooms and oxygen-depletion problems were abated, and several fish species intolerant
of water quality degradation recovered (Prepas and Charette 2003). Although Lake Erie recovered from
eutrophication because of reduction of point-source pollution, the lake is still considered enriched with
phosphorus (Prepas and Charette 2003). Most of the phosphorus entering Lake Erie currently originates from
streams and rivers that drain agricultural land (Prepas and Charette 2003). Modern efforts to manage
eutrophication in Lake Erie are focusing on phosphorus reduction from non-point sources (USEPA 2006a,b).
There remain water quality concerns in Lake Erie regarding chemical contaminants such as PCBs,
mercury, and pesticides. The United States and Canada began to work together in the 1970s to address
contaminant issues in the Great Lakes under the terms of the Great Lakes Water Quality Agreement
(GLWQA), initially signed in 1972 and subsequently renewed and amended several times (USEPA 2006c).
The GLWQA established the criteria by which the signing parties ultimately identified 43 Areas of Concern
(AOCs) throughout the Great Lakes basin where sediment contamination and water quality problems were
especially acute (USEPA 2006d), including 10 sites within the Lake Erie basin. USEPA (2006a) details the
problems being addressed and progress being made in each of the Lake Erie AOCs.
Invasive species are another major environmental concern in Lake Erie, due to its important role in
international shipping (Prepas and Charette 2003). Extensive information about invasive species problems
and management in the Great Lakes, including Lake Erie, is readily available on-line (GLIN 2006) and the
subject will not be further addressed here. The best documented case study involves the zebra mussel invasion
(Haltuch et al. 2000), which has been found to also affect contaminant cycling and bioavailability in Lake
Erie (DePinto and Narayanan 1997). The impact of invasive species on natural resources within our streams
and watershed will be evaluated in 6. Natural Resources.
5.2 The Pennsylvania Portion of Lake Erie and Presque Isle
The Pennsylvania waters of Lake Erie straddle the boundary between the lake