Florida’s Indian River Lagoon (IRL), spanning 156 miles and traversing five counties with five connecting inlets to the Atlantic Ocean, has witnessed recurring phytoplankton bloom occurrences in recent years. These events are attributed to rising seasonal temperatures and environmental influences.
Algal blooms generate various small organic molecules, some of which can pose toxicity risks to humans and animals. Microcystis aeruginosa, a freshwater cyanobacterium, is among the toxin-producing organisms found in the Southern IRL. Microcystins, toxins produced by Microcystis aeruginosa, have been detected in nasal swabs of individuals residing and working in the vicinity, though their presence in mucosal membranes may indicate the body’s natural elimination processes.
To assess potential health hazards associated with harmful algae blooms, researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute conducted a three-year study. Water samples from 20 IRL sites were collected during wet and dry seasons, extracted to concentrate organic molecules, and subjected to testing. The researchers employed a panel of human cell lines representing the liver, kidney, and brain to measure cytotoxicity and identify the presence of known or emerging toxins.
The study, detailed in the journal Toxins, revealed consistent cytotoxicity patterns induced by control toxins in human cell lines. During blooms, cytotoxicity from a specific toxin type was evident, while in non-bloom periods, cytotoxicity suggested either a mix of toxins or the presence of unidentified ones.
A noteworthy finding was that known toxins were observed only during blooms, indicating the potential existence of emergent toxins or a combination during non-bloom periods. The study suggested the presence of other toxins with potential harm to human health in the lagoon.
Geographically, the most northern IRL sites exhibited lower toxicity than their southern counterparts. Cytotoxic blooms were observed in both southern (Microcystis) and northern (Pyrodinium) regions of the lagoon. Sites in the Southern IRL and Northern IRL exhibited varying degrees of cytotoxicity during non-bloom periods.
Certain sites, such as Jensen, Fort Pierce Inlet, Harbor Branch Link Port Canal, Vero Beach Land/Ocean Biogeochemical Observatory, and Vero Beach Barber Bridge, appeared healthier with fewer samples showing significant cytotoxicity. Nevertheless, statistically significant variation was noted in these sites.
The researchers concluded that the study’s aim was to identify unrecognized toxins or signaling molecules associated with harmful algal blooms in the lagoon. The collected data suggest the presence of such substances, emphasizing the need for ongoing monitoring to better understand and mitigate potential human health impacts, particularly from emerging toxins in the ecosystem. Notably, microcystins primarily pose a threat during blooms, requiring ingestion or inhalation to impact human health.