Summer of Slime (Freshwater Algae)

Observation: Low water, warm temperatures and our seasonal waterfowl population are factors we think are contributing to the unprecedented algae and weed growth in the lake at the the Alaska Native Health Campus. We wonder if some of the aquatic plants maybe introduced. We have been monitoring the low water level all summer and so the algae is not really a surprise. But the lake is not as attractive or (perhaps) as healthy a system as in the past. We wonder about the health of waterfowl and aquatic life in the lake, and at what point remedial actions are needed.

Cooperative Extension Services Consult: , Gino Graziano, Invasive Plant Instructor writes, "We have observed and received reports of excessive algae growth on lakes in the Anchorage area. There are two major types of algae filamentous green algae and blue-green algae which are actually a cyanobacteria. To tell the difference between these try picking up a mat of the material. If you can pick up the algae masses then it is a type of filamentous green algae. If you cannot pick up the algae than it is a type of blue-green algae. Large blooms of either of these algae are usually a sign of high nutrient levels, and I bet the warm weather and low water levels are helping. I have been to several non-urban lakes this summer, and not observed these algal blooms, so I suspect it is a combination of extra nitrogen from waterfowl, dogs, and other runoff sources that are causing the blooms in some urban water bodies. When these algae decay they can deplete oxygen or cause undesirable odors. If they are cyanobacteria, some species can produce toxins in the water. I do not immediately see any non-indigenous or invasive species such as Elodea in the pictures, but since Elodea is a submerged aquatic it may be right underneath some algae. In a conversation with the Anchorage Waterways Council they seemed interested in determining if people feeding waterfowl is a contributing factor to excess nitrogen in water bodies. They may be another group to talk to about this." Source: University of Alaska Fairbanks