Revealing the Concealed Risks of Toxic Algae Blooms: Florida's Indian River Lagoon in Crisis

The Indian River Lagoon in Florida is facing an increased incidence of phytoplankton blooms, leading to toxic conditions, according to a study conducted by Florida Atlantic University. The study identified the varying levels of toxicity present, as well as newly-discovered toxins, which underscore the necessity of monitoring these conditions to protect human health. The identification of these toxic conditions was enabled by examining algal blooms in the lagoon's waters.

Located in Florida, the Indian River Lagoon spans 156 miles and is surrounded by five counties. It has five inlets that connect it to the Atlantic Ocean. The lagoon has been through several instances of phytoplankton blooms in recent times, which are triggered by seasonal temperature changes and environmental factors.

These algal blooms generate a range of small organic molecules, some of which are toxic to both humans and animals. Notably, the bloom-producing Microcystis aeruginosa, a freshwater cyanobacterium found in the Southern part of the lagoon, can cause harm. Notably, microcystins - toxins produced by this bacterium - have been found in people living and working near the lagoon.

In their quest to understand the potential human health implications of these harmful algal blooms, researchers from the Harbor Branch Oceanographic Institute at Florida Atlantic University collected water samples from 20 different points in the lagoon. The samples were collected over three years during both wet and dry seasons. These samples were subsequently processed to concentrate the organic molecules, which were then used for further testing.

To detect both known and emerging toxins, researchers carried out tests using a panel of human cell lines associated with the liver, kidney, and brain. The cell lines were chosen due to their susceptibility to algal toxins, and would in turn show unique patterns of activity in reaction to the known toxins.

Testing was done using high concentrations of the samples to detect as many metabolites as possible. Samples that showed over 50 percent cytotoxicity were regarded as active and further tested using liquid chromatography-high resolution mass spectrometry analysis to determine the metabolites present in the samples.

The study, which was published in the journal Toxins, found patterns of cytotoxicity that were consistent in the context of each control toxin, and evident during any bloom. The presence of cytotoxicity in non-bloom conditions suggests the presence of a mix of toxins or an unidentified toxin, explained Esther Guzmán, Ph.D., the corresponding author and a research professor at FAU Harbor Branch.

Interestingly, the northernmost sites of the lagoon showed reduced toxicity compared to the southern areas, with cytotoxic blooms recorded at both ends. Findings indicate that there could be potential danger to human health from other toxins present in the lagoon, especially in the absence of blooms.

In contrast, certain other areas were found to be healthier, showing fewer samples with cytotoxicity above 50 percent. However, these sites exhibited some variation that was statistically significant.

Amy Wright, Ph.D., co-author and a research professor at FAU Harbor Branch stated, "A major question we sought to answer in this study was whether there exist unrecognized toxins or other signal molecules associated with harmful algal blooms in the lagoon. The collected data does indicate that this is the case. Hence, the use of an assay panel for assessing the presence of toxic compounds could enable better monitoring of human health impacts, especially in relation to emerging toxins within the lagoon."

The researchers note that microcystins are primarily a threat to human health in the lagoon during blooms, and because of the necessity of active transport, the toxin would need to be ingested or inhaled to present a threat to humans.

“Ingestion can be avoided by filtering water through activated charcoal,” said Guzmán. “Similarly, effects due to inhalation are effectively blocked by the mucus membrane, which traps toxins that are subsequently eliminated through coughing. However, pet and wildlife exposures can still occur.”