User:Marythemuffinlady/Aquatic biomonitoring

Indicators
Algae are relatively small, eukaryotic organisms which live in aquatic habitats. Algae as a whole are characterized by short life cycles and quick reproduction. These characteristics allow them to be classified as a main focus for short-term biomonitoring of aquatic ecosystems due to their responsiveness to environmental changes and effectiveness as bioindicators in the field. The use of algae as bioindicators is based on the species-specific responses to pollution in natural water systems. This aspect is exhibited through the changes in cell densities, species composition and richness, chlorophyll a, metabolic enzyme production, and photosynthetic capabilities of individual species due to pollutants. Toxicity of chemical pollutants, such as arsenic, has been shown to inhibit algal growth at levels as low as 0.8 mg/L with varying sensitivity among algal species at a consistent concentration. Thus highlighting the species-specific responses to pollutants by establishing that the growth order of species, i.e the growth rate of algal species studied, shifted under a variety of pollutants. Herbicide toxicity decreases the growth of algae as well as induces a change in the composition of algal communities, which is dependent on growth temperature (i.e lower observed toxicity with a higher growth temperature ). The effect of herbicides on the photosynthesis of algae, by inhibiting photosystem II , is expressed via algal density and composition shifts in the community, thus easily expresses quantifiable indicators of current pollution. Another pollutant that effects the photosynthesis of algae are microplastics. Microplastics, especially polyvinyl chloride, decrease the chlorophyll a concentration along with the fluorescent parameters in aquatic algal communities which indicates the reduction of algal growth due to the depletion of the oxygen evolving complex in photosystem II. The concentration of chlorophyll a expresses the algal density in a system which can help estimate the toxicity level based on the amount of algae present along with other factors such as species composition or average environmental parameters. Increased levels of chlorophyll a, algal biomass, and microcystin can also be used to identify harmful algal blooms caused by cyanobacteria. In regards to fecal pollution, the increasing algal density, as well as composition shifts, can indicate a higher level of pollution. One study showed a shift from the diatoms Achnanthidium minutissimus (Kützing) and Fragilaria crotonensis (Kitton) in a low-pollution area to diatoms of Gyrosigma, Navicula, and Nitzschia species in a polluted area which examines the species-specific tolerance to pollution. The diversity of algal species in an ecosystem can also help to identify the tolerance to pollution and/or water quality of a system. Heavy metals, which persist in the sediment of aquatic environments and can be reintroduced into the water system, have been shown to produce a degree of tolerance in some algal species when experienced at high concentrations over an extended period of time. One such study examined a thallium polluted stream for algal diversity, which determined a high tolerance to the heavy metal due to great diversity in euglenoids. These heavy metal pollutants can also induce species-specific responses of algae in the community. These responses were highlighted by an experiment which examined the effects of mercury, copper, cadmium, nickel, zinc, lead, chromium, dichromate, and caesium on the species Pseudokirchneriella subcapitata (Korshikov) and Gonium pectorale (Müller). The study determined that G. pectorale showed an increased sensitivity to heavy metals in decreasing order, with mercury and copper classified as the most toxic heavy metals, which demonstrates the use of data collected from species-specific responses to pollutants in biomonitoring of aquatic ecosystems. Understanding the species-specific effects of pollutants on algae allows the application of algae as indicators in natural aquatic systems. Algae can be implemented in a variety of habitats to monitor the water quality and overall health of the ecosystem. This along with the biological aspects of algal functions and morphology maintains the emphasis on use in biomonitoring applications.