What are bioindicators? Bioindicators are living organisms that provide valuable insight into the quality of the natural ecosystem within the environment. These organisms (plants, plankton, animals, microbes) help determine whether or not environmental stressors are present, such as pollution, toxins, or variations from the average conditions. Each organism provides an indication regarding the health of the surrounding ecosystem. For example, tubifex worms are used as a water quality indicator because they can tolerate low oxygen conditions and presence of heavy metals, indicating oxygen-poor water or undrinkable water.
What is biomonitoring? Biomonitoring is the process of recording species diversity and abundance data of bioindicators across different locations and/or times. They are used to evaluate risks to human health or the environment. Many biomonitoring processes were created to be simple and affordable. Biomonitoring processes and bioindicators don’t explain the underlying causes behind what they are showing. They are also typically specific to a single system like a lake, stream, or forest which makes it difficult to compare across systems.
Macroinvertebrates: Macroinvertebrates are animals that are commonly used as water-quality indicators because they are sensitive to pollution and changes in their habitats, large enough to be seen with the eye, have a long life cycle, and are common in rivers and streams. Macroinvertebrates have no backbone and live on the bottom of streams, rivers, or lakes. Examples include crustaceans, chironomids, worms, and aquatic insects like beetles, stoneflies, hellgrammites, dragonfly nymphs, etc. Macroinvertebrates play an important role in the food web because they provide food to higher trophic levels. They are a key link between the producers and the secondary or tertiary consumers in the ecosystem’s food web. For more information on macroinvertebrates, check out the links below.
Applications of Lacawac Macroinvertebrates as Bioindicators: Lake Lacawac is a nonrecreational lake utilized for education and research. Alex Bros, an undergraduate student at Rochester Institute of Technology, collected aquatic macroinvertebrates to utilize in a semester long study in one of her courses. Below are two of the organisms used in the study. All organisms were freshwater aquatic invertebrates called cladocerans - these are a particular type of freshwater zooplankton and are also crustaceans. The organism on the left is Daphnia ambigua. Daphnids are commonly found in lakes and graze on algae, helping control algal populations. In recent years a competitive zooplanton, Holopedium gibberum (right), has become abundant and nearly invasive in nature in a number of North American lakes. These zooplankton also graze on algae but are omnivorous in nature and have a gel capsule along its back making it unpalatable to most predators. H. gibberum populations have boomed in Lake Lacawac most likely because of these adaptations. These zooplankton were utilized in a study assessing impacts of zinc on these zooplankton populations. Zinc was chosen as a heavy metal of interest as it persists in aquatic ecosystems and it is difficult to define its sources for pollution. A primary source of zinc pollution comes from tire treks and correlates with increased automobile traffic. D. ambigua and H. gibberum were collected as well as local populations from Rochester and exposed to zinc for an acute seven-day study and for a longer twenty-day study.
Photo of Daphnia ambigua by Alex Bros.
Photo of Holopedium gibberum by Alex Bros.
Results of the acute study at Day 4 are pictured above. The first row of bars indicates survival rate at 10 degrees Celsius while the second row of bars shows survival rate at 20 degrees Celsius. Colors indicate different zooplankton - blue is D. ambigua, green is H. gibberum, red is Daphnia pulex (a commonly used Daphnid) and orange and purple are Rochester populations of cladocerans. As you move left to right within each set of bars, the concentration of zinc increases. In this study, Rochester populations that are likely exposed to more zinc (due to increased traffic on campus and in the city) appeared to do better than Lacawac populations at most concentrations, especially higher concentrations of zinc. The figure below is set up exactly the same but shows the results at the end of the 20-day study. Most populations did worse over the prolonged period of time and differences are evident between the survival rate of all populations.
Overall, these populations showed decreases in survival rate when treated with zinc. The impacts of these populations may help scientists predict how organisms at a higher trophic level (like fish and amphibians) may be impacted due to zooplankton declines, making these zooplankton good bioindicators for zinc pollution. The differences in their survival when exposed to zinc also highlights the importance of utilizing several different populations when assessing the impact of a pollutant in an environment as some populations may be more susceptible to that particular pollutant. Knowing these differences will also help scientists predict the health of a lake or body of water and how it may react to a pollutant.