Aquatic biomonitoring
Aquatic biomonitoring is the science of inferring the ecological condition of rivers, lakes, streams, and wetlands by examining the organisms (fish, invertebrates, insects, plants, and algae) that live there. While aquatic biomonitoring is the most common form of biomonitoring, any ecosystem can be studied in this manner. Purpose. Aquatic biomonitoring is an important tool for assessing aquatic life forms and their ecosystems. Monitoring aquatic life can also be beneficial in understanding land ecosystems. Aquatic biomonitoring can reveal the overall health and status of the environment, can detect environmental trends and how different stressors will affect those trends, and  can be used to evaluate the effects that various environmental activities may have on the overall health of the environment. Water pollution and general stresses to aquatic life have a major impact on the environment. The main sources of pollution to oceans, rivers, and lakes are human caused events or activities, such as sewage, oil spills, surface runoff, littering, ocean mining, and nuclear waste. Rapid changes to an environment, like, pollution, can alter ecosystems and community assemblages, and endanger species that live in or close to water. Many aquatic species also serve as food sources for terrestrial species. Thus, aquatic  ecosystems are interconnected with their adjacent terrestrial ecosystem. Indicator organisms. Aquatic invertebrates, most popularly the larva of the caddis fly sp., are responsive to climate change, low levels of pollution and temperature change. As a result, they have the longest history of use in biomonitoring programs. Additionally, macroscopic species: frogs, fish, and some plant species, as well as, many forms of microscopic life, like bacteria and protozoa are used as indicator organisms in a variety of applications, storm water run-off among them. Many species of Macroalgae are used in biomonitoring for both aquatic and marine environments. Common methods. A  biomonitoring assessment typically requires two or more sets of data . First, a baseline dataset that, ideally, defines the environment in its natural state, or default state. This is used to compare with any datasets that follow. Variables considered. Water quality. Water quality is graded both on appearance—for example: clear, cloudy, full of algae—and chemistry. Determining the specific levels of enzymes, bacteria, metals, and minerals found in water is extremely important. Some contaminants, such as metals and certain organic wastes, can be lethal to individual creatures and could thereby ultimately lead to extinction of certain species. This could affect  both aquatic and land ecosystems and cause disruption in other biomes and ecosystems. Water temperature. Water body temperature is one of the most ubiquitous variables collected in aquatic biomonitoring. Temperatures at the water surface, in the water column, and at the water bodies bottom can all provide insight into different aspects of an aquatic ecosystem. Water temperature is directly effected by climate change and can have negative affects on many aquatic species, such as salmon. Community make-up. Species community assemblages and changes there in can help researchers to infer changes in the health of an ecosystem. In typical unpolluted  temperate streams of Europe and North America, certain insect taxa predominate. Mayflies (Ephemeroptera), caddisflies (Trichoptera), and stoneflies (Plecoptera) are the most common insects in these undisturbed streams. In contrast, in rivers disturbed by urbanization, agriculture, forestry, and other perturbations, flies (Diptera), and especially midges (family Chironomidae) predominate. Local geology. Local geology can effect sub-surface influences on surface water, for example, metal contamination.