Crisis in the Caloosahatchee: Algal blooms in local waters
Toxic algal blooms are turning the Caloosahatchee into a smelly green mess east of the Franklin Lock. West of the lock, the river is streaked by a brown dinoflagellate bloom. The Olga Water Treatment Plant (east of Franklin Lock) was shut down on May 5 because of algae and high salinities.
On Monday, June 6, a large algal bloom in a canal on Sanibel’s east end was sampled by SCCF Marine Lab scientists. Preliminary identification is Gymnodinium, a dinoflagellate. A sample has been sent out for positive identification.
For the past several weeks, blue-green algae has been affecting the river. Also known as cyanobacteria, bluegreen algae releases toxins that can affect the liver, the nervous system, and the skin; the toxins can also be respiratory and gastrointestinal irritants.
The toxic blue-green algae identified by SCCF Marine Lab scientists is predominantly Anabaena circinalis, with Aphanizomenon sp. among other species. The dinoflagellate in the river,identified as Ceratium hircus, is non-toxic.
Where does algae come from?
Algal blooms are caused by unhealthy levels of phosphorus and nitrogen that enter the water column from fertilizer, pastures, septic and stormwater runoff. These blooms thrive in stagnant waters with sunlight and high nutrient levels.
Policy decisions by the South Florida Water Management District (SFWMD) have cut off water supply from Lake Okeechobee to the river for the past 13 weeks, causing the river to stagnate east of Franklin Lock. The lack of freshwater flow and algae are responsible for the closure of the Olga Water Treatment Plant.
Toxic algae
Bluegreen algae cause concern because they produce neurotoxins. The degree of toxicity of an alga can vary by genus, species, strain and environmental conditions.
Cyanotoxins (the toxins in blue-green algae) can be classified into four broad categories:
• Hepatotoxins – affect the liver
• Neurotoxins – affect the nervous system
• Dermatoxins – affect the skin and and they are a respiratory irritant
• Endotoxins – gastrointestinal irritants
Impacts to wildlife
Wildlife is also affected by algae. In addition to toxic effects, algae also cause oxygen depletion in the water that negatively impacts fish and macroinvertebrates. Algae shield out light which is needed for photosynthesis by submerged plants. When algae die and decay, they cause oxygen depletion, which affects fish and other organisms.
In addition, water quality problems are suspected of impacting bird nesting on rookery islands in the Refuge at the mouth of the river.
Source: SCCF