The types of animals living in lake and stream bottom sediments, Benthic Macroinvertebrates, serve as an indicator of long-term conditions and are periodically examined and enumerated to assess overall water and sediment quality conditions. Seminole County Scientists use methods established by The Florida Department of Environmental Protection (FDEP) to determine if the lakes and streams within our county support a healthy, well-balanced aquatic animal community or if human disturbance has impacted a system.
What are benthic macroinvertebrates?
Benthic (meaning "bottom-dwelling") macroinvertebrates are small aquatic animals and the aquatic larval stages of insects. They include dragonfly and stonefly larvae, snails, worms, and beetles. They lack a backbone, are visible without the aid of a microscope and are found in and around water bodies during some period of their lives. Benthic macroinvertebrates are o~en found attached to rocks, vegetation, logs and sticks or burrowed into the bottom sand and sediments.
Why is it important to evaluate benthic macroinvertebrates?
Benthic macroinvertebrates are commonly used as indicators of the biological condition of waterbodies. They are reliable indicators because they spend all or most of their lives in water, are easy to collect and differ in their tolerance to pollution. Macroinvertebrates respond to human disturbance in fairly predictable ways, are relatively easy to identify in the laboratory, often live for more than a year and, unlike fish, have limited mobility. In fact, because they cannot escape pollution, macroinvertebrates have the capacity to integrate the effects of the stressors to which they are exposed, in combination and over time. Biologists have been studying the health and composition of benthic macroinvertebrate communities for decades.
What do benthic macroinvertebrates tell us about the condition of water?
Evaluating the abundance and variety of benthic macroinvertebrates in a waterbody gives us an indication of the biological condition of that waterbody. Generally, waterbodies in healthy biological condition support a wide variety and high number of macroinvertebrate taxa, including many that are intolerant of pollution. Samples yielding only pollution-tolerant species or very little diversity or abundance may indicate a less healthy waterbody. Biological condition is the most comprehensive indicator of waterbody health. When the biology of a waterbody is healthy, the chemical and physical components of the waterbody are also typically in good condition.
What methods are used by Seminole County Scientists?
For flowing waters (rivers and streams), the following methods are used in Seminole County to determine if the macroinvertebrate communities are healthy or imbalanced:
For lakes, the following method is used in Seminole County to determine if the biological communities are healthy or imbalanced: