The main antagonist along the Florida coast, both this year and previously, is Karenia brevis, a dinoflagellate, that, it turns out, doesn’t have the main photosynthetic pigment found in most dinoflagellates and thus doesn’t show the characteristic red color that 'red tides' were named for. (It has some orange in and usually shows more brown-green).
What causes these blooms? A change in water temperature, light, absence of algae eaters, and nutrients. This last is the reason we have managed to kill the 400 tons of fish, manatees and much more along the Florida coast (and expect many more deaths to come including, I’m sure, a few pets and that one unlucky tourist that really wanted to go down to the coast and maybe takes a swim). Run off from agriculture to the north and south of Lake Okeechobee, dumps excess nutrients, mostly phosphorus, into the lake. Blooms then occur in the lake. Then…it rains. The Army Corp of Engineers releases water from the lake into canals that run into the ocean and more blooms, this time of our not-friend Karenia brevis.
The neurotoxin from Karenia brevis can become airborne and thus has become and eye and lung irritant for people exposed. Inside the body this toxin binds to voltage- gated sodium channels disrupting the. If you’re not aware, sodium channels essentially run our nerve cells, and thus are nervous system. Neurons, the main functional cells of the nervous system, send signals to and from all areas of the body, including things like muscles, by altering the electric nature of the cell. Our nervous system is electrical.
Nerve cells rely on several types of channels that allow, when open, the passage of changed atoms (ions) in to or out of the cell. Since these atoms are charged their movement change the positive/ negative difference between the inside and outside of the cell. This is called the electric potential. One of the major channels are sodium channels, when open sadism ions, Na +, rush into the cell changing the inside from negative to more positive, this in turns causes the next set of channels to open( voltage gated means they respond to a change in voltage = electric potential ) and the domino effect runs down the long extension of the neuron, called the axon, eventually passing the signal to the next neuron, or to the muscles cell, or other target. I shouldn’t have used the term eventually above because this happens in thousandths of the second. If sodium channels can not open, due to the presence of a neurotoxin, then the signal does not get through. That next neuron, or muscle, or organ, does not receive a signal and doesn’t react. Animals that get a dose, including humans, first have digestive and neurological problems, and if the dose is large enough and too many neurons are disrupted, they die. Many things can cause death but just to illustrate the point, Your heart is run these same sodium channels.
Among organisms that cause harmful algal blooms neurotoxins are the prime toxins. Along the New England coast the the major harmful algae are species of the genus Alexandrium. They house a powerful neurotoxin that causes paralytic shellfish poisoning. If you eat a clam or mussel that has been filtering the water that contains high concentrations of Alexandrium you can get sick and even die as a result.
Lets pick on Florida a bit more.
In Florida, governor Rick Scott issued an executive order to “combat” the red tide. His order does not address anything about the nutrient pollution, in short it’s an executive order to appease people without actually doing anything. Well, that’s not exactly true, it is suppose to provide some $ to help shovel off the dead fish from the beaches. The agriculture lobby must have some sway.
AND we can help a little bit. HEY YOU, stop putting crap on your lawn. It’s a drop in the bucket compared to industrial agriculture but any little bit helps.
Short answers:
Where are the worst algal blooms?
The California coast (see the recent Smith et al. paper below) seems to be a hot spot but they occur all over the world.
Do algal blooms occur naturally? yes.
Are humans causing them to occur more often and more intensely? yes.
Is Florida fucked? For this and other reasons, yes. But there is still hope for the rest of us.
Readings:
Hallegraeff, G.M. 1993 A review of harmful algal blooms and their apparent global increase. Phycologia 32: 79 - 99.
Smith, J. P. Connell, R. H. Evans, A. G. Gellene, M. D.A. Howard, B. H. Jones, S. Kaveggia, L. Palmer, A. Schnetzer, B. N. Seegers, E. L. Seubert, A. O. Tatters, D. A. Caron. A decade and a half of Pseudo-nitzschia spp. and domoic acid along the coast of southern California. Harmful Algae, DOI: 10.1016/j.hal.2018.07.007.