The meek shall inherit the Earth – at least the wet parts of it. The lowly jiggly jellyfish, those simple critters that are mostly water and stomach, may be the big winners in the high-stakes gamble we’re playing in the oceans on a global scale.
Beautiful and bizarre, jellyfish are on the rise in many places. These otherworldly gelatinous floaters are appearing in greater numbers and causing an increasing array of problems in coastal waters favored by people for swimming, fishing, and working.
They can be physically harmful, stinging and sometimes killing swimmers unfortunate enough to get close. They clog up fisherman’s nets (or it that there’s nothing else left to catch?), and the intake pipes of power plants. They jam up harbors, and slaughter penned salmon by the thousands. Their stinging tentacles can ruin a catch by tainting or killing the fish caught up with them in nets.
Some of the biggest threats to overall marine biodiversity benefit these creatures. Warmer waters seem to favor some species, enabling them to expand their ranges, appear earlier in the year and increase overall numbers. Nutrient pollution – the runoff of enormous amounts of fertilizer from fields and lawns into ocean waters – stimulates phytoplankton blooms that in turn feed huge swarms of jellyfish. Overfishing removes many of their predators, and they compete with the fish we like to eat for prey, often preying on fish larvae as well.
What is a jellyfish? Of course, they’re not fish in any sense of the word. The stinging jellies, also known as medusa, are free-swimming members of the phylum Cnidaria (pronounced without the “c”). This phylum also includes corals and sea anenomes, all of which capture prey with stinging cells called nematocysts. Comb jellies are members of the phylum Ctenophore. These non-stinging creatures use rows of tiny hairs called cilia to move about. Both types of jellies are on the rise.
Jellies are found everywhere – from the tropics to the poles and the surface to the deepest reaches of the sea. More than fifty new species of jellies were discovered by the Census of Marine Life in the cold salty depths of the Arctic sea.
They’re coming to take over a coastline near you! Or are they? Not all researchers agree with the dire scenarios of “Jellies Gone Wild!” Steven Haddock who studies gelatinous phytoplankton at the Monterey Bay Research Institute (MBARI) jellies capture people’s imaginations – and fear – because of their resemblance to the stuff of B-movies. (This is the second post in a row where I’ve managed to invoke B-movies!) However, as creatures that need to eat, and which are themselves eaten, jellies are a natural part of the ecosystem. But the same can be said for many invasives, no?
Part of the problem is that there are few reliable estimates of jellies before the 1990s. That’s when people started taking notice of large blooms near where they live, fish, and swim. “Undoubtedly there are localized areas where blooms have increased. … On a global scale, we don’t know enough about jellyfish populations, their biology, their distribution, to make a judgment,” says Rob Condon, one of the lead investigators for the National Center for Ecological Analysis and Synthesis jellyfish working group.
This past summer saw a jellyfish invasion in Spain. In Japan’s waters, blooms of jellies the size of refrigerators, weighing up to 450 pounds are now an annual occurrence. Last year, a netful of jellies capsized a ten-ton trawler off the coast when fisherman tried to pull the nets up. In 2007, 100,000 penned salmon were killed by a bloom of jellies off Ireland. Off the coast of Sweden, American comb jellies and the stinging larvae of sea anemones have become late summer pests. Local officials have placed nets around some Queensland beaches to fend off common box jellyfish and the deadly irukandji. One of the few studies to look at long-term trends confirmed an increase in size and density of blooms of the mauve stinger, Pelagia noctiluca, in the Northeast Atlantic and Mediterranean over the past fifty years.
Misunderstood marvel or toxic threat? Ever been stung by a jelly? Swam in a swarm? Stumbled upon a beached Portuguese man-o-war? (Don’t touch! The stinging cells remain dangerous and can be fired even after the creature is dead). Leave your comments below!
For more interesting info about jellies, check out this interview with ‘renowned Jellyologist’ Monty Graham of the Dauphin Island Sea Lab in Alabama.
Also the National Science Foundation has a wonderful multi-media special report on jellies: “Jellyfish Gone Wild!” (I didn’t make that up!) Definitely worth a peek.
P. Licandro, D. V. P. Conway, M. N. Daly Yahia, M. L. Fernandez de Puelles, S. Gasparini, J. H. Hecq, P. Tranter, R. R. Kirby. A blooming jellyfish in the northeast Atlantic and Mediterranean. Biology Letters, 2010; 6 (5): 688 DOI: 10.1098/rsbl.2010.0150
Jellyfish Swarms: Menacing or Misunderstood? By Wynne Parry, LiveScience Senior Writer posted: 20 October 2010 08:09 am ET.
Huge Jellyfish Numbers “Signal Something Has Changed” in Oceans, by Kimberley Mok, Montreal, Canada on 06.23.08