Algae and Cyanobacteria: Tiny members of the aquatic community

Algae in snowfed creek on Bennet Mountain, Idaho. (Thayne Tuason)

By Vicki Browne
Iron County Lakes & Streams Partnership
Summer has arrived! The calendar indicates that it is still spring, but we had 17 days in a row with temperatures over 80ºF from the end of May through the beginning of June. Dogs, kids and even adults are jumping into lakes and enjoying the water.
Swimming in a lake means sharing the water with fish, waterfowl, beavers, otters and minks. Rooted and floating plants are also soaking up the sunshine. Less obvious are the tiniest members of the aquatic realm, algae and cyanobacteria. 
There are thousands of species of algae that live in a wide range of habitats. Algae are found below polar ice sheets, but also in backyard bird baths. They produce their own food through photosynthesis. Along with cyanobacteria, algae produces about half the world’s oxygen.
Cyanobacteria have been around for billions of years and are credited with creating the first whiffs of oxygen on the planet. There are over a thousand species and most live in filaments (threads) or colonies (clusters).
Cyanobacteria are often called blue-green algae because of the color seen when some species ‘bloom’. Cyanobacteria are not scientifically considered algae. Cyanobacteria are also different from most bacteria because they use chlorophyll-A for photosynthesis, which other bacteria do not have. 
Both algae and cyanobacteria are found in all lakes. Both are considered phytoplankton — simple, rootless, mostly single-celled, aquatic organisms. Both are essential for the aquatic ecosystem but go unnoticed until conditions are right for them to grow rapidly into a ‘bloom’ and become cause for concern.
When algae bloom into bright green blobs, fish can die because their gills get clogged. Algal blooms can also change the pH of the water and decrease the amount of dissolved oxygen. 
Many algal blooms on local lakes are filamentous algae. When you use a stick or net to remove it from the lake, the strands resemble wet wool. 
An algal bloom is often just a nuisance for humans, unlike a cyanobacterial bloom which can be hazardous.
When cyanobacteria cause a bloom, the water becomes green, opaque, or murky. The surface scum looks like foam or spilled paint and may be bluegreen, green, red or tan. When you run a stick through it, the bloom separates into small chunks, unlike filamentous algae which clings together. Some cyanobacterial blooms coat the stick like paint.
Never approach a potential cyanobacterial bloom without protective gear. Cyanobacterial blooms can produce toxins that cause intestinal distress and skin rashes. They can be fatal for dogs, babies and those with weakened immune systems. Microcystis is one of the cyanobacterial species that is a major concern for public health.
Two other surface water accumulations that are neither algae or cyanobacteria are pollen and duckweed. Pollen might look similar to algae, but pollen is yellow-green and dust-like, and it floats mainly on the surface. Over time, pollen becomes waterlogged and sinks from sight. Duckweed is the smallest known flowering plant. From afar a mat of duckweed can resemble a bloom.
The California Water Quality Board offered this distinction: “Algae and aquatic plants are usually neutral or leafy in scent, but when dying or dead smell musty/rotting. Cyanobacteria blooms can have a distinctive smell, sometimes described as gasoline, septic or fishy.”
If you suspect a cyanobacterial bloom, contact the Michigan Department of Environment, Great Lakes, and Energy by calling the Environmental Assistance Center at 800-662-9278 or e-mail AlgaeBloom@Michigan.gov.
A harmful bloom can persist for several weeks. Preventing blooms is preferable to waiting for the water to be safe. Because a major factor leading to algal and cyanobacterial blooms is excess phosphorus and nitrogen in a lake that is warming to temperatures above 75ºF, all strategies for reducing runoff and erosion are helpful. Natural shorelines with deep-rooted native plants, well-maintained septic systems, and careful strategies that keep fertilizers and animal waste from entering the lake are important prevention strategies.