Nutrient Pollution and Algal Bloom Control

Nutrient pollution is a primary cause of algal blooms. The two key nutrients of concern are;

  • Phosphorous (P), as ortho-phosphate (PO4 3- ) and,
  • Nitrogen (N), as nitrates (NO3 – )

    These nutrients enter our water ways from point source emissions, overland flow and groundwater discharge commonly associated with;

    • Excessive fertilizer use
    • Sewage Treatment Plants (STP’s)
    • Urban Stormwater

    Algal blooms impact on infrastructure and damage or destroy local ecosystems by consuming available oxygen reserves and blocking out light. Some forms of algae, most commonly cyanobacteria (or blue-green algae), can also have adverse affects on human and animal health and its presence can severely limit water use.

    The Role of Bottom Sediments

    In freshwater systems, excess phosphorous is the main concern, as this is the key limiting nutrient in algal growth. Phosphorous can occur as soluble compounds in the water column and as a variety of solid compounds (eg. ferric phosphate) stored in the sediments at the base of rivers and lakes.

    Recent research has demonstrated that some algal blooms are related to the seasonal release of stored phosphorous from lake or river sediments. Algal bloom prevention and control measures will therefore require;

    • Blocking or limiting the seasonal release of P from bottom sediments,
    • Lowering soluble phosphorous concentrations in the water, and
    • Management and control of P inputs into water bodies.

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