Essay On Harmful Algal Blooms

Aquaculture farms are also responsible for the development of harmful algal blooms as they contribute to nutrient loading. (Sellner et al, 2003) The farmed fish and shellfish produce high quantities of excretory products rich in nitrogen and phosphorous. The excretory products and uneaten food falls to the sea bed and remineralises to become soluble nitrogen and phosphorous. If the surrounding water of the farms are not regularly flushed, the nutrient will accumulate and potentially trigger a bloom (Rensel & Whyte, 2003). Thus, coastal and cultural eutrophication due to human activities can extend and increase the intensity of blooms.

Another cause of harmful algal blooms can be due to unusual environmental conditions caused by changing climatological conditions.

Ships act as vectors. While most of the plankton species carried in the ballast water are harmless to a non-indigenous area and may even die off, the process poses a risk to vulnerable ecosystems as a toxic species may potentially be transported. Diatoms and dinoflagellates in their planktonic stages pose a low risk since they show limited survival ability during transportation in the dark ballast tanks. The resting spore (cysts) of these species, however pose a greater risk as they are well adapted to be able to survive the unfavourable conditions of the ballast tanks. One ballast tanks can contain an estimated 300 million of these toxic cysts which can germinate and set off an algal bloom (refer to figure 4) (Hallegraef & Bolch, 1991). The transportation of shellfish to different parts of the world is another way algae, in the form of cysts, or dispersed. Algal species such as Alexandrium can be found in the faecal matter and in the digestive tracts of shellfish in abundance (Bricelj et al,