Year round research needed to solve algal bloom problems

OKEECHOBEE — Nutrient inflow into Lake Okeechobee, blamed in part for algal blooms, is a complicated issue.

“There are many ‘maybes’ and ‘ifs’ when it comes to algae and conditions that trigger the different species to bloom, as well as their nuisance and toxic effects,” explained H. Dail Laughinghouse V, Ph.D., Assistant Professor-Applied Phycology, Department of Agronomy, University of Florida/IFAS.
Florida Department of Environmental Regulation set 40 parts per billion as the target level for phosphorus to a healthy Lake Okeechobee ecosystem, but optimal nitrogen levels are still a mystery.

“We don’t know the magic number for nitrogen,” explained Dr. Laughinghouse. Algae in different water bodies react differently, and different species of algae are triggered to bloom at different levels of nitrogen. In addition to the phosphorus and nitrogen levels, other factors such as the pH, dissolved oxygen levels and water temperature also come into play.

Another complicating factor: If there is not enough nitrogen available in the water, some algae can use the nitrogen from the air.

According to Dee Ann Miller with the Florida Department of Environmental Protection, “some cyanobacteria and bacteria are able to convert atmospheric nitrogen N2, which is a relatively inert gas, into more readily usable forms like ammonia, nitrate and nitrite.”

Algae that can use nitrogen from the air are referred to as “nitrogen fixers.”
Dolichospermum circinale, the species of cyanobacteria that has been dominant on the northwest portion of Lake Okeechobee this year, is a nitrogen fixer, said Ms. Miller. Cylindrospermopsis raciborskii, found on the northwest side of the lake in August, is also a nitrogen fixer.

Dr. Laughinghouse noted Cylindrospermopsis raciborskii is an invasive species.

Microcystis aeruginosa, the dominant algae in the blooms found on Lake Okeechobee near Port Mayaca and near Canal Point in July and August, is not considered a nitrogen fixer, Ms. Miller explained.

While microcystis aeruginosa is not a traditional nitrogen fixer, there may be bacteria within the bloom that do fix nitrogen from the air, said Dr. Laughinghouse.

It does not have a heterocyte so it is traditionally not considered a nitrogen fixer, he continued. But nitrogen is fixed in the absence of oxygen. “In these large colonies, internat cells can lack O2 and thus fix N2.” Another factor: Bacteria which are found associated with the thick mucilage around M. aeruginosa, can fix N2 and make it available for the cyanobacterium.

Thirty years ago, FDEP set a target for phosphorus in Lake Okeechobee at 40 parts per billion (ppb) and the maximum phosphorus annual load to the lake at 140 metric tons – a goal that has not been reached. No target has been set for nitrogen.

“The target levels or Total Maximum Daily Loads, (TMDL) are for phosphorus, however, many of the projects identified in the BMAP (the Lake Okeechobee Basin Management Plan) would also be expected to reduce nitrogen,” said Ms. Miller.

An algal bloom is a huge, complex ecosystem in itself, said Dr. Laughinghouse. A bloom may be made up of different types of algae.

And the algae keeps changing and adapting to changes in the environment.

An algae species will evolve to fill a niche in the ecosystem.

Cyanobacteria have been around for 3.8 billion years, he said. Algae species have evolved and specialized to the degree that humans are more closely related to fungi than one algae species may be related to another species of algae.

Algae are a natural and important part of any marine ecosystem. Man-made changes to the environment have lead to massive algal blooms that can release toxins that may be harmful to humans. There are thousands of different toxins and/or variants that the algae produce, he explained.

This is a world-wide problem, said Dr. Laughinghouse.

Some, not all, species of algae are capable of producing toxins. Species that can produce toxins do not always do so. Also, a species of algae that does not release toxins can harbor bacteria that can be toxic.

The toxins are produced as part of the algae’s metabolism. The substances are not toxic to the algae. One theory is that the algae evolved to produce toxins as some kind of communication measure.

“We do not know the exact trigger for this,” he said. “Within a colony not all cells are producing toxins. We know it happens. We don’t know why,” he said.

To find the answers, he said, research should be done year round, not just during algal blooms. The algae are present all the time, a natural and necessary part of ecosystems of ponds, lakes, rivers and streams. Year round data are needed to better understand the many factors that trigger blooms and trigger release of toxins.

Dr. Laughinghouse is a broadly trained phycologist working with both basic and applied algal research from Tropical to Polar Regions. His background includes systematics, ecology, HABs, cyanotoxins, phycoremediation, biofuels, metagenomics and metatranscriptomics of marine, freshwater and terrestrial environments. Some of the current research in the Laughinghouse Lab focuses on diversity and toxicity of cyanobacteria, environmental influences on macroalgae and microbial photoautotrophs, novel applied uses for algae, bioremediation, and the detection and effects of bioactive compounds.

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