Featured Image Credit: Hubbs-SeaWorld Research Institute
By Jessica Kittel
The dolphins living in the Saint Johns River aren’t doing so well. Over the last few years, these dolphins have been increasingly plagued by health problems. They are underweight, covered in skin lesions, and are found dying in areas of the river with low salinity. Until recently, no one really knew what was ailing these poor dolphins. However, research at the University of North Florida is suggesting that the issue may come down to a little something called cyanobacteria.
Image Credit: UNF
If you’ve never heard of cyanobacteria maybe you’ve heard of its other names: have you ever heard anyone talking about blue-green algae? What about harmful algal blooms? It’s all the same!
Although it’s known as algae, cyanobacteria or blue-green algae is the name for a group of very simple bacterial organisms. The confusion comes from the fact that these bacteria get their energy via photosynthesis, therefore, back in the day, scientists assumed they were algae. Nowadays we know better but that doesn’t stop them from looking suspiciously similar to green algae.
These organisms have actually been around for a really, really long time, roughly 3.5 billion years. During those 3.5 billion years they’ve managed to spread all over the globe and can be found anywhere from the Arctic to the tropics and from the desert to the ocean! They’re even found in Saint Johns River and herein lays the problem.
If a body of water has an excessive amount of nutrients (from either agricultural run off or from nearby developed areas) the cyanobacteria will start reproducing like crazy and will turn into an algal bloom, virtually taking over the area. When the individual bacterial organisms are alive there’s usually no toxins. However, once they die and their cells rupture they release toxins into the water called cyanotoxins.
Microcystin is one of the most widespread cyanotoxins and can bioaccumulate in aquatic residents such as zooplankton, mussels, and fish. Thanks to that bioaccumulation, it can also cause anything (such as, say, dolphins) that eats the zooplankton, mussels, or fish to get very sick. Microcystin is known to mainly affect the liver, kidney, and even the reproductive system.
Turns out microcystin might be the culprit when it comes to the dolphin deaths in Saint Johns River. Several other cyanotoxins have also been discovered in the river that affects the skin and the nervous system.
Since 2010, there have been more and more harmful algal blooms occurring in the area and with the blooms come unusual mortality events. Dolphins aren’t the only ones that should be worried about the effects these blooms can have on their health. Dolphins are known as sentinel organisms (think, a canary in a coal mine) due to the fact that they share our ecosystem. We have the same water and food and could, therefore, both be affected by toxic buildup.
While these blooms are naturally occurring, it is concerning that the frequency and size of the blooms have been exponentially increasing in recent years. More research about these cyanobacterial blooms will not only benefit these sick dolphin populations but also could potentially save human lives as well.