An algal bloom indicates stress in a lake’s ecosystem. Water quality is often assessed based on laboratory and field (in situ) measurements. Algae are a critical part of a lake’s food webs and sustain primary consumers. Eutrophication, caused by excess nutrients, is a type of ecosystem stress that can lead to the formation of an overabundance of algae, which can have negative environmental or health impacts.

Without in situ measurements, aerial photographs were able to provide evidence of the growth of algae at different times of the year in Lake Indawgwi in northern Myanmar.