Algae
Algae are a complex and diverse group of mostly aquatic organisms that obtain their energy from sunlight through the process of photosynthesis. Algae can be found in macroscopic forms that are easily visible to the naked eye, as well as in microscopic forms that live free-floating in the water column and on rocks, wood, sand, and aquatic plants. Algae that float in the water column are called phytoplankton. Algae that live on rocks, logs, and sand are called periphyton. Algae that grow on aquatic plants and mosses are called epiphytes.
The Biological Monitoring Program collects algal species from the following groups:
Algae are an important component of the ecosystem in rivers, streams, and wetlands, making them a valuable indicator of water quality. Algae serve as a food source for invertebrates and small fish and play an essential role in nutrient and energy cycling. Algae strongly influence oxygen levels in the water column through photosynthesis and respiration. They are highly sensitive to a range of environmental stressors, including nutrient enrichment, changes in pH, and increased concentrations of some dissolved chemicals and contaminants. Some species of algae are more sensitive to changes in water quality than macroinvertebrates or fish. Since algae have rapid growth rates and respond quickly to changes in their habitat, they often provide an early warning of changing environmental conditions which may not be detected by other methods.
Algae can also tell biologists about the historical condition of waterbodies. A group of algae called diatoms creates cell walls that consist of silica, a glass-like material which persists in sediments over long periods of time. These cell walls can be collected from the sediment even after the organism inside them is gone, and can give scientists information about how an algae community has changed over time in response to changing pressure from environmental stressors.
