Why is it so hard to determine the sources of nutrients for a Florida red tide?
It is difficult to track the nutrients which support a red tide because nutrient concentrations within and surrounding red tides are very low, often too low to be detected. Scientists have thus used a variety of different methods to try to ‘source’ the nutrients supporting a bloom, including examining nutrient concentrations in a region immediately prior to a red tide, stable nitrogen isotope signatures, and nutrient ‘budgets’ of the amount of nutrient a red tide requires compared to the amount of nutrients provided by coastal nutrient inputs. All methods indicate that coastal nutrient pollution does not cause the start of a red tide, and while it may contribute in part to maintaining a red tide in coastal waters, it cannot solely account for an entire larger tide. Scientists have thus concluded that many different nutrient sources contribute to a red tide, including nutrients from bottom sediments, from other microalgae able to fix N2 gas and excrete it into seawater as dissolved orga
