The cycle of HAB’s in the Indian River Lagoon

The concentration of nutrients that has brought algae blooms and fish kills was a continuation of a chain of events. The chain began with the introduction of excess nutrients (over the course of years). The chain grew with blooms of macro-algae (Gracilaria) and blue green algae (Lyngbya) in early summer. It continued with the accumulation of those algae bloom rafts on the east side of the Indian River Lagoon following a period of wind from the south and west. It links to the fueling of a centralized dinoflagellate bloom that has become toxic to fish.

Dead fish only add to the nutrient load in the Indian River Lagoon. The nutrients present in the plant matter again become available to fuel blooms of Macro-algae and blue green algae and the process becomes circular. The cycle will not be broken until limits are placed on the introduction of excess nutrients into the waterbody.

This picture from late July shows a ribbon of Lyngbya majuscula algae as it drifts in the channel west of the recent fish kill. (from lower right to upper left)

Lyngbya Majuscula, Gracilaria, a macro-algae that grows in nutrient rich waters and blades of sea grass pulled free by the buoyancy of the lyngbya and the gracilaria, float in the water column and gather nitrogen as they grow.

This is a close up of the lyngbya, a blue green algae that smothers sea grass beds, causes sea grass to lose blades and then moves with currents and wind

Lyngbya usually drifts onto the shallow west bank of the Indian River Lagoon where it dries (and stinks).

Prevailing westerly winds in July and August of this year (2004) have carried the lyngbya, macro-algae and affected sea grass to the east side of the Indian River Lagoon where the lack of open beach prevents drying and allows it to rot. The rotten vegetation releases nitrogen into the localized area to fuel micro-algae blooms. Dynoflagellates like Taykayama Pulchella are able to thrive in the high temperatures present in August and September.

Water clarity is reduced to inches where the rotting mass fuels algae blooms.

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