A Tragedy of Errors: the fate of lionfish, moon jellies, and groupers are intertwined

What do lionfish and moon jellies have in common? In Florida, it's the goliath grouper. And what links these three sea creatures together is our ability to meddle with the balance of nature.

I have written about lionfish, moon jellies, and groupers in the past (Click here for lionfish, here for jellies, and here for groupers). The lionfish is a beautiful and graceful addition to any South Pacific reef where it exists as a predator that keeps reef fish communities in balance. As an invasive species to Florida and the Caribbean (possibly inadvertently introduced in the early 90's), the lionfish is a voracious predator with an enormous appetite and their numbers have exploded in recent years, posing a significant threat from Florida throughout the Bahamas to reef ecosystems unprepared for such a hungry eating machine.

Sea jellies, or jellyfish, are also beautiful and graceful, but the yin to their yang is the powerful sting in the tentacles of many species, an ability that is used for hunting and feeding rather than as some sort of offensive or defensive weapon. In recent years, scientists have been seeing a greater number of sea jelly "blooms" - huge congregations that some believe are the result of warming temperatures due to climate change or, possibly, a lack of common predators like turtles, tuna, and sharks. For scientists, the jury is still out as to a definitive cause but the anecdotal observation is that sea jelly blooms are being reported with greater frequency.

The goliath grouper, capable of reaching up to a massive 800 pounds, is one of Florida's apex predators, right up there with sharks, billfish, and the other denizens of the deep that nature has entrusted to maintain equilibrium between predators and prey. Unfortunately, the goliath grouper was also a prized catch for sportfishermen and commercial operators and so their numbers declined rapidly over the past few decades. Listed as critically endangered in Florida waters by the International Union for the Conservation of Nature (IUCN), in 1990 Florida imposed restrictions on the taking of any goliath grouper. However, like sharks and other apex predators, the grouper's slow reproductive rate has meant a slow recovery and a typical large grouper is currently in the 200-pound range if you're lucky to see one.

So what is the common thread between the three? Well, the goliath grouper would be an ideal candidate to serve as an exterminator of lionfish, if there were only sufficient number. The loss of the grouper to overfishing, combined with the invasion of lionfish due to, well, our thoughtlessness has left the reef communities of Florida and the Caribbean with a real threat on their hands and without a natural defender. This makes the loss of even one grouper a critical one to the marine ecosystem. Then, what about the loss of up to 75 groupers? Seventy-five groupers gone due to moon jellies. Moon jellies, you say?

That's just what happened this past August in the surrounding waters at the St. Lucie nuclear power plant near Ft. Pierce in southeast Florida. A swarm of moon jellies inundated the seawater intake to the plant, causing a shutdown that lasted two days. With thousands of moon jellies plastered up against intake grates, the jellies' delicate tentacles broke off and traveled through the plant's seawater pipes to be expelled back out to sea where they apparently came in contact with a school of groupers, stinging and inflaming their gills. Biologists, who happened to be at the plant overseeing the facility's turtle protection program, were only able to save ten of the groupers before having to leave the water themselves due to multiple stings from the floating fragments of tentacles.

The end result was the loss of several tons of goliath groupers - predators desperately needed to combat the growing army of lionfish. This is often the result when natural resources are abused: not one problem, but a series of overlapping causes and effects. And the common thread was mankind. The cascading effects of our actions when we choose to consume rather than conserve could be our lasting legacy to this planet unless we act now.

Here's a brief video of moon jellies which shut down a nuclear power plant in Israel.

Source: Huffington Post.

Moon Jellies: mass stranding near San Francisco

Just this past September I reported on a sea jelly invasion in Monterey, California. For a good portion of the late summer, the popular central California ocean community was beset with west coast sea nettles - beautiful to look at but potentially painful, given the numbers that were accumulating from the bay right up to the shoreline.

Another high concentration of sea jellies recently occurred at Ocean Beach, located near San Francisco. This time it was thousands upon thousands of moon jellies that had washed up on the beach overnight this past weekend. But in this instance, it was not so much an invasion as it was a freak occurrence linked to a cyclical event.

Moon jellies are one of the more prolific of all jellies. A popular attraction at many aquariums, they are relatively easier to breed, compared to other species, and do not pose a threat to humans. In the fall, they can have large spikes in their populations along the eastern Pacific coast. These sea jelly "blooms" can go unnoticed for the most part, unless the right tidal and wave conditions push the floating moon jellies ashore. Which is apparently what happened this past weekend.

Gary Williams, a researcher of invertebrates at the California Academy of Sciences described it as a "regular event," “Jellyfish cluster in massive blooms well offshore that we rarely see. But sometimes, with just the right combination of wind and currents, those blooms wash ashore.”

As relatively common as the moon jelly is, there is surprisingly little we know about them. The when, where, and how of their reproduction habits is still predominantly a mystery. Because of that, it makes it difficult for scientists to attribute any apparent rise in population to outside factors such as climate change.

However, further south from San Francisco in San Diego, California, a rare black sea nettle has been making more frequent appearances along that Southern California coast. Actually deep purple in color, the black sea nettle is much larger than the west coast sea nettle, reaching 3 feet across and with up to 30 feet of trailing tentacles.

Though not yet seen in invasion-size numbers, the black sea nettle, according to some oceanographers, could be increasing in numbers due to warming temperatures or a consistent increase in the primary food source, plankton - which also "blooms" with warmer water temperatures.

Beautiful, fascinating, and in many ways a mystery, sea jellies are basic predatory invertebrates (and, technically, by definition not a fish - as in "jellyfish"), simple in structure with no brain or heart but exhibiting behaviors that have yet to be fully explained.

Read about San Francisco's moon jelly stranding.
Read about San Diego's black sea nettle.