Stream Bioassessment Methods

A Stream Bioassessment includes biomonitoring tools to assess the aquatic biological communities and characterize the community structure for a stream.

These assessment methods provide a direct measure of designated use attainment, where the goal is propagation and maintenance of a healthy, well balanced aquatic community.

•  Stream Condition Index (SCI) Report  - Fore, L. et al. 2007. Development and Testing of Biomonitoring Tools for Macroinvertebrates in Florida Streams. The statistical basis for SCI and Biorecon calculation SOPs. 

•  Sampling and Use of the Stream Condition Index (SCI) for Assessing Flowing Waters: A Primer  - DEP 2011. Provides information on the sampling process and decision making involved with SCI.

•  Development of Aquatic Life Use Support Attainment Thresholds for Florida’s SCI and LVI  - DEP 2011. Describes factors necessary to consider when developing a quantitative measure of biological health with focus on establishing the biological thresholds for the SCI and LVI.

•  SCI Stressor Identification Process  - DEP 2020. Describes natural and human-induced factors known to influence the SCI, and the process by which DEP evaluates which stressors are most likely to cause SCI failures.

The Qualitative Periphyton Sampling was a method for the collection of algal community composition information from natural substrates. A total of 10 sample aliquots are apportioned across available habitats (snags, roots, leaf packs, vegetation and rock, excluding sediments) in a 100 m stream reach. To perform the method, a seasoned substrate is chosen, and algae is removed from a 9 cm diameter area and placed into a wide-mouth jar filled with 100 mL of site water.

Final analysis of the method did not show any significant relationships with other metrics, and has weak signals related to human disturbances on stream systems.

In a process similar to the SCI and LVI, DEP attempted to develop a periphyton assessment tool, the Stream Diatom Index (SDI), using a combination of the Human Disturbance Gradient (HDG) and Biological Condition Gradient (BCG) approaches.

Final analysis of the method revealed that the diatoms appear to be very strongly influenced by pH (as well as conductivity and color), which confounds the periphyton community response to human disturbance, including nutrient enrichment effects. The SDI does not appear to clearly or predictably respond to objective measures of human disturbance, currently making it an unreliable tool for assessing adverse human effects on stream systems. (Final SDI Report, see  Report Search  page)

Several program areas use these bioassessment tools. There have also been smaller projects that have used bioassessment methods.

• Impaired Waters Determination – Currently used for streams or rivers, to determine whether or not a waterbody is meeting water quality standards for a particular pollutant or pollutants under the Impaired Waters Rule (IWR), Chapter 62-303, F.A.C. A stream or river with multiple failing SCI or BioRecon scores may be put on the  303(d) list   if a causative pollutant is identified.

• Basin Wide Assessments – Used to evaluate watershed health.

• Forestry Non-Source Program – Bioassessment tools were used to evaluate the effectiveness of forestry best management practices (BMPs).

• Fifth-Year Inspections - Currently used to evaluate the discharge of domestic and industrial wastewater treatment plants.

• Mitigation Assessments - Currently used to evaluate the success of created or restored aquatic ecosystems.

• Site-Specific Alternative Criteria - Bioassessment data can be used to show that a waterbody is biologically healthy under water quality conditions that may be different from the generally applicable criteria.

• NNC evaluations – Currently used for assessment of the statewide Numeric Nutrient Criteria standards in Rule 62.302.531, F.A.C., for Streams. Please see  FDEP's website on Numeric Nutrient Criteria  for more information.

• Waterbody Reclassification – Currently used as part of the Use Attainability Analysis (UAA), a biological assessment, used in conjunction with other physical and water quality data. This can provide justification for reclassifying waters.

Bioassessments are also used as an educational tool in public/volunteer monitoring programs to provide basic information about watershed health.

Training is provided by AEQAS to other regulatory staff.

Please visit the  Training Resources webpage  and the  Bioassessment Training webpage  for more information.

Check out our  EcoSummary Reports Interactive Web Map  for reports that summarize the biological health and water quality conditions for single freshwater streams.