Stream monitoring: Algae
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A number of states assess the water quality of streams and rivers by using algal IBIs [Index of Biotic Integrity], including Montana and Oklahoma. Montana recommends using only natural substrates. They have metrics for both soft-bodied algae and diatoms. The metrics for soft-bodied algae consist of the following: Dominant phylum, Indicator taxa, and Number of genera. The metrics for diatoms consist of the following: Diversity index, Pollution index, Siltation index and Similarity index.
Photo of algaeOklahoma focuses more on using diatoms on artificial substrates as their algal assessment tool. Diatoms are useful for several reasons, including their hard shells and their response in community structure to changes in nutrients, pH, and other chemical changes.
MPCA believes artificial substrates have value when studying the impacts of a point source or a tributary on a receiving stream. In that case, it is important to minimize variability not related to the parameter of interest. However, artificial substrates do not provide a sense of the actual stream potential for algal community development and preferentially select some types of algae over others. Thus they are not good for developing algal IBIs, which is MPCA’s goal.
The Agency has begun the process of relating nutrient concentrations to algal populations. There are strong and predictable relationships among total phosphorus [TP], algal concentrations [represented by chlorophyll a, or CHL], and biochemical oxygen demand [BOD] in streams (Heiskary & Markus, 2001). Ecoregion differences must be accounted for and very turbid watersheds, like the Red River basin, affect the predictive strength of the relationships. Preliminary assessments suggests that ratios such as diatoms:blue-green algae and TP:BOD may be useful for assessing water quality. These relationships must be further defined and appropriate algal metrics must be created and tested to complete the development of an algal IBI.
Reports
Establishing Relationships Among Nutrient Concentrations, Phytoplankton Abundance, and Biochemical Oxygen Demand in Minnesota, USA, Rivers- Establishing Relationships Among In-stream Nutrient Concentrations, Phytoplankton and Periphyton Abundance and Composition, Fish and Macroinvertebrate Indices and Biochemical Oxygen Demand in Minnesota USA Rivers. 2003
Relation of Nutrient Concentrations and Biological Responses in Minnesota Streams: Applications for River Nutrient Criteria Development. March 2008
