. Effects of zebra mussels on chlorophyll, nitrogen, phosphorus and silica in north shore waters of Lake Erie . -100 -50 100 150 200 Figure 10. Percentage change in selected nutrient variables and ratios pre- (1984-87) and post (1990-93) zebra mussels at the Union intake sampling location. Those marked with an asterisk are statistically significant (Mann-Whitney U-test; P<). 12

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