Why do nitrates affect algae growth

Scientists must monitor these conditions to make sure that the ecosystem is in balance and the water is healthy. Strong or foul odors can indicate high levels of decomposition—the breakdown of dead organisms, such as fish, invertebrates and algae.

These processes can lower the dissolved oxygen DO and harm aquatic organisms that require oxygen to live. Increases in flow rate and erosion can bring extra nutrients and soil into the water.

This can decrease water clarity and the amount of light available to algae. This affects water temperature and DO dissolved oxygen. Flow rate is the amount of fluid passing over a surface in a given amount of time. Water flow affects the amount of oxygen, nutrients, and pollutants in the water body. Erosion is the transport of solids soil, rock in the environment.

Erosion is caused by wind and water. Human activities that involve clearing land of vegetation and changing the flow of water by building dams can also lead to erosion. Turn on your LabQuest. Plug in the light sensor to any channel at the top of the LabQuest. Make sure the light sensor is vertically pointed with the lens towards the sky. W hile being very still, click the green arrow collect button and the LabQuest will automatically collect data for 10 seconds.

On the graph screen, click "Analyze", then "Statistics", then "Illumination. Be sure to note other factors that may affect the light intensity reading at your site. For example, trees and aquatic plants may block incoming light.

Clouds, overcast conditions and seasonal changes also affect the amount of light able to reach the surface of the water. Follow the directions at the Nitrate Station. Record your answer in the "Nitrates" blank on the data entry page. Range: ppm. Nitrate Levels above 0. Use the CHEMets phosphate kit to measure the level of phosphate in your water. Follow the directions at the Phosphate Station.

Record your answer in the "Phosphates" blank on the data entry page. Phosphate levels above 0. Plug in the DO sensor to any channel at the top of the LabQuest. Gently place the DO sensor in the water and slowly stir it in a circle. Do NOT touch or scrape the sensor along the bottom. Click the green arrow collect button and collect data for 30 seconds.

On the graph screen, click "Analyze", then "Statistics", then "DO. Look at the results and determine the average or mean of your data and record your findings in the "Dissolved Oxygen" data entry blank. This process of nutrient loading is known as eutrophication. Algal blooms can disrupt normal functioning of marine ecosystems, causing a variety of problems such as depletion of the oxygen in the water that fish and shellfish need to survive.

Certain species of marine algae produce harmful blooms, known as red or brown tides, which can be toxic to both marine animals and humans. In Part A of this investigation, you will grow your own algal bloom and test the effects various nutrients and other water qualities have on the occurrence and intensity of algal blooms. Your Account. Goodwin observed in this reservoir a negative relationship between the abundance of M.

The author did not find, however, any relationship with ammonium concentration. Uptake and assimilation rates for ammonium are normally higher than for nitrate, because no enzymatic reduction is required for ammonium assimilation McCarthy et al. This also means lower energetic costs because of the consumption of 8 ferrodoxins by the cyanobacteria to reduce nitrate to ammonium Syrett , Lara et al. Therefore, the growth of a phytoplankton population could be slower with nitrate than with ammonium.

Phytoplankton accumulates intracellular nitrogen in the form of a variety of compounds, such as nitrate, ammonium, amino-acids, proteins, RNA and pigments. These compounds serve as a long-term nitrogen storage reservoir Dortch et al.

Dortch et al. Protein loss is generally a result of nitrogen starvation. Ammonium concentration in the growth medium, however, did not seem to be limiting, because it was not completely harvested at the end of the experiment, opposite to nitrate, that was entirely consumed.

It is possible that the cyanobacteria take advantage over other phytoplanktonic species through their ability to uptake ammonium. Their maximal cell density, however, can be achieved under higher nitrate conditions. Smit et al. Chlorophyll a is one of the most important nitrogen pool in algae: the pigment may reduce nitrogen limitation. It is also possible that Cyanobacteria contribute to maintain undectable nitrate levels in the upper layers of water column by the uptake of most nitrate, that has been produced by the oxidation of ammonium present at very high concentration in the reservoir.

Several studies indicated that nitrate uptake suffers inhibition by the presence of ammonium McCarthy et al. When ammonium and nitrate are both present, ammonium is generally preferred, although the complete suppression of the nitrate uptake is rare Syrett This confirm our hypothesis that M. In summary, we observed that Microcystis viridis was able to attain similar cell densities growing on both ammonium and nitrate.

Nevertheless when it was growing on ammonium, high biomass values as cell number were reached more rapidly, presumably because of the higher growth rate, thus driving to the conclusion that ammonium may lead or induce a population bloom.

However, under nitrate conditions M. Therefore cyanobacteria may compete with eukaryotes for nitrate and also have better skills to the rapid use of ammonium when nitrate is no longer available in the environment, thus allowing them to suddenly increase their population and develop into a bloom. Abrir menu Brasil. Brazilian Journal of Botany.

Abrir menu. Material and methods The cyanobacterium Microcystis viridis Lemmermann figure 1 , for details see Giani et al. Growth of Oscillatoria agardhii in chemost culture - 1. Nitrogen and phosphorus requeriments. Oikos Ammonium - nitrogen: A key of non-nitrogen- fixing cyanobacteria in aquatic systems. Modified reagents for the determination of urea and amonia. Clinical Chemistry Species differences in accumulation of nitrogen pools in phytoplankton.

Marine Biology Biochemical indicators for N utilization by phytoplankton during upwelling off the Washington coast. Limnology and Oceanography Phytoplankton Nitrogen interactions. Hickey, eds. Elsevier Science Publihers, Amsterdam, p. The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: current conditions and projected changes.

Biogeochemistry Seasonal variation of the diversity and species richness of phytoplankton in a tropical reservoir. Hydrobiologia Limnology in Pampulha Reservoir: some general observations with emphasis on the phytoplankton community. In Ecology and human impact on lakes and reservoirs in Minas Gerais R. Pinto-Coelho, A. Segrac, Belo Horizonte, p. Growth dynamics and competitive ability of green Oocystis lacustris and a blue-green alga Synechocystis sp.

Verhein der Internationalen Vereinigung von Limnologie Henry, ed. Methods for physical and chemical analyses of freshwaters. IBP Handbook 8.