Please keep your eye out for late summer/early fall algae blooms!

Please keep your eyes out for late summer/early fall algae blooms!  Algae observations can be reported through Algae Watch BC, a citizen science data program to help people recognize and identify algae blooms in B.C. lakes. Read more about what affects algae growth below from an excerpt from our 2022 LakeKeepers Manual!

In late summer, shallow lakes can sometimes warm up to the point of mixing to the bottom as shown in the figure below, allowing nutrients to mix into the water column causing algae blooms. Warm temperatures can also cause late summer blooms in larger, deeper lakes.

Algal density and chlorophyll a concentrations are both dependent on the availability of sunlight and nutrients, and to a lesser degree on temperature and wind. In direct relation to algal density, chlorophyll a concentration can be expected to follow predictable seasonal fluctuations. Chlorophyll typically shows an initial peak in spring when spring overturn brings phosphorus and nitrogen into the upper photic zone. Depending on the trophic nature of the lake, chlorophyll may be sustained at moderate concentrations through the summer with a second peak following fall overturn (in oligotrophic lakes) or may reach very high peaks during late summer and fall (in eutrophic lakes). In coastal lakes, it is not unusual to have early winter algal blooms as the input of nutrients to a lake accompanies fall rainfall and the major inflow of water to coastal lakes.

Wind can also affect chlorophyll. During periods of overturn, wind drives water circulation and with it the delivery of phosphorus into surface waters where light is sufficient to encourage algal growth. In the case of cyanobacteria (blue-green algae), wind can also drive these floating bacteria (with their chlorophyll) across the water surface, causing unsightly blooms on windward bays and beaches. On eutrophic lakes, there is potential for  blue-green algal blooms to be toxic and these can be responsible for the fatal poisoning of livestock, pets, and wildlife.