Chlorophyll is the pigment that allows plants (including algae) to convert sunlight into organic compounds (photosynthesis). Of the several kinds of chlorophyll, chlorophyll a is the predominant type in algae.
Measuring chlorophyll concentrations in water is a surrogate for an actual measurement of algae biomass, which is far more expensive and time consuming.
Excessive amounts of chlorophyll indicate the presence of blooms. Blooms usually consist of a single species of algae, typically one that is not desirable for consumption by fish and other predators. Unconsumed algae sink to the bottom and decay, depleting deeper water of oxygen.
On the other hand, too little chlorophyll a would mean that not enough “fish food” is available to fuel the food web.
The criteria, which are being refined, will identify seasonal chlorophyll a concentrations for different shallow water and open water areas of the Bay (and areas with varying degrees of salinity) which represent high-quality algae communities that supply adequate food without causing blooms.