The phosphorus pollution today is different than it was in the 1970s. The invasive mussels—both zebra and quagga promote algal growth because they enhance the conditions algae need to grow: 1) increase water clarity so that the sunlight algae need to grow can penetrate deeper into the lake; 2) their waste provides nutrients for more algae growth; and 3) they provide a surface for algae to attach and grow.
Climate change is also influencing the growth of harmful algae—such as warmer water that supports more algae and extreme rain events that dump larger amounts of pollution.
Finally, wetlands which act as our lakes natural filters, are being lost to development. Without them, more nutrients can make it to our lakes and rivers. Lake Erie has lost more than 80% of its coastal wetlands since European settlement.