ALVA – Can scientists find a way to prevent harmful algae blooms (HABs)?
“We’re looking for a kink in the armor,” Dr. Barry Rosen, of the U.S. Geological Survey, explained Monday as researchers set up an experiment on the Caloosahatchee River.
“Once you have an algae bloom, it’s almost too late,” he said. By then, there are tens of millions of organisms in the water. If scientists can identify all of the factors that trigger a bloom, they might find something in the sequence that can be disrupted in order to prevent a HAB, Dr. Rosen explained.
Researchers from the U.S. Geological Survey, Florida Gulf Coast University and Nova Southeastern University are conducting an experiment this week at the Franklin Lock on the Caloosahatchee River. On Monday, July 8, they filled a dozen large fiberglass tubes (5 feet tall and about 30 inches in diameter) with water from the river. The tubes are arranged on metal frames in groups of four and secured in place. Floats will keep them at the same level in the river. In each group one tube acts at the experiment control; one will have phosphorus added; one will have nitrate added; and, one will have ammonium added. Samples will be taken daily for a week. The samples will be filtered and the filters containing cyanobacteria, algae and other organisms will be flash frozen for transport to the lab.
The tubes, which are sealed at the bottom and open at the top, provide a mescosom – an outdoor experimental system that examines the natural environment under controlled conditions. Mesocosm studies provide a link between field surveys and highly controlled laboratory experiments.
Dr. Rosen said for this phase of the experiment they will double the concentrations of nitrates, ammonium and phosphorus found in the river water to see if that quick increase of nutrients triggers an algal bloom. Submersing the tubes in the river means they will be the same temperature as the river water, and because they are opaque, the water samples in the tubes will receive the same amount of sunlight as algae in the river. If it rains, rain will fall both in the river and in the tubes.
The samples will be shipped to a lab for DNA testing of the organisms in the sample such as algae, cyanobacteria and other bacteria. There are about 6,000 different organisms in the water, said Dr. Rosen. They hope to identify the pathways that allow some cyanobacteria to bloom.
Thanks to recent rainfall, most of the water currently in the Calooshatchee River is from local basin runoff. Water is only released from the lake if the local basin runoff is not sufficient to provide the minimum flow of 450 cubic feet per second (cfs) needed at the Franklin Lock to prevent saltwater intrusion in the river. The average flow for the past seven days at Moore Haven was 162 cfs. On Sunday, there was no flow from the lake at Moore Haven. Flow at the Franklin Lock averaged 1,808 cubic feet per second – all from local basin runoff. On Monday, there was no flow at Moore Haven. Flow at the Franklin Lock – all from local basin runoff – was 1,971 cfs.
The river has sufficient nutrients and cyanobacteria in it without any additional input from the lake, said Dr. Rosen.
Dr. Rosen said 28 different species of cyanobacteria have been documented in the Okeechobee Waterway, which includes the Caloosahatchee River, Lake Okeechobee, the St. Lucie Canal and the St. Lucie River. He said about 25% of the species of cyanobacteria are capable of producing toxins, but cyanobacteria capable of producing toxins do not always do so. In future experiments, researchers will try to discover what causes the cyanobacteria to produce toxins.
Every algal bloom is different, Dr. Rosen said. Each bloom also contains algae in different stages within the bloom, More than one species may be producing toxins with a bloom. Some bacteria may be producing nitrogen and feeding the bloom.
Dr. Jose Lopez of Nova Southeastern University said he will study the DNA of the cyanobacteria and other organisms in the water samples.
He said most microbes are beneficial, but when they are out of balance, they grow out of control. He said the mesocosm will help them understand what is going on within an algal bloom. “Many of the bacteria can’t be cultured in the lab,” he explained.
“We can understand this bacteria through their genomes. If we can look at the genetics at the DNA and RNA level, we can get a better handle on it,” said Dr. Lopez.
The main goal of the series of experiments is to understand what is in the water, he said. “We know there is cyanobacteria present in the water all the time. What is that causes it to bloom?”
This research was not done before because there was not funding for it. A proposal to the Environmental Protection Agency (EPA) for a similar study was not funded, he said. This study is funded by the U.S. Army Corps of Engineers, with money included in the 2018 Water Resources Development Act (WRDA).
“If we can get to the point that we can predict these blooms, maybe we can prevent the blooms,” he said. “The overall goal is to make our waters healthier.”
This week’s experiment is the second in series. The third phase of the experiment on the river will be conducted in September. In addition, they have been taking monthly samples from 17 sites in Lake Okeechobee, plus one at the Moore Haven Lock, one at the Port Mayaca Lock, one at the St. Lucie Lock and one at the Franklin Lock since March. That testing will continue for a full year.
Researchers hope to continue the lake sampling for three years.