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Fisheries Management Water Quality Analysis Dissolved Oxygen
Fisheries Management Water Quality Analysis Dissolved Oxygen
Key Parameters - Dissolved OxygenDissolved oxygen (DO) is one of the most important parameters, and is simply oxygen that is dissolved in water. It gets there by diffusion from the surrounding air; aeration of water can be accelerated by tumbling over falls and rapids. It is also a bi-product of photosynthesis in aquatic plants.Oxygen measurement is often presented in two forms, as a percentage saturation figure (% sat.) or as an amount of oxygen per (milligram) per unit of water (litre) this is often shown as mg/l or p.p.m. The amount of oxygen that is dissolved in water is critical, different species of fish require a great deal more than others, salmonids such as the Atlantic salmon (Salmo salar) and the Brown trout (Salmo trutta) require much more than cyprinid fish such as the carp (Cyprinus carpio) and the tench (Tinca tinca). The amount of oxygen that is in solution as dissolved gas can vary significantly for numerous reasons. The weather in the form of low pressure can lead to de-oxygenation especially in times of thunder storms. Oxygen can be depleted by organic pollution and by the die back of algae following a bloom. The amount of oxygen that is taken from water by organic pollution is often shown as its biochemical oxygen demand (BOD). Plants are both a source of oxygen usage and oxygen productivity in aquatic system, they produce oxygen during the day and use it during the hours of darkness and this diel rhythm can often be responsible for low dissolved oxygen levels before dawn during the warmer summer months. Although dissolved oxygen is considered one of the most important water quality parameters, levels fluctuate greatly and different species require different levels. This makes it hard to accurately assess dissolved oxygen needs but it is considered levels should stay above 5mg/l in a healthy fisheries. |
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| Last Updated ( Sunday, 02 March 2008 10:47 ) |
