Jellyfish Season Coming!

Jellyfish, more particularly, the Sea Nettle (Chrysaora quinquecirra) is a sad fact of summer in the Chesapeake Bay.  Every year, just about the time the water gets warm enough to swim in comfortably, the Bay seemingly explodes with the stinging bastards. Often, they wash up in droves on the beach, where they are still capable of inflicting an annoying sting. Research into the various jelly type animals (not all of whom are technically jellyfish) has been popular in the last 15 or so years, focusing on how the jellyfish transfer from their food (phytoplankton and zooplankton) to their predators (not much, some sea turtles eat them,  but that doesn't account for much predation).  The fate of most food eaten by jellies is to end up as dead jellyfish biomass, short circuiting the food web as far as fish are concerned (hey, that's what I care about).  The Scientific American Blog has a pretty good article on them:

Excessive Jellyfish Excrement Boosts Bacteria, Stings Fish Populations

Jellyfish blooms might be more than just a nuisance to beach-goers. These explosions of stinging swarms might also be doing some major disruption to marine food webs, according to a study

Warty comb jellies (Mnemiopsis leidyi) and Atlantic stinging sea nettles (Chrysaora quinquecirrha) have been emerging by the thousands each summer in brackish Chesapeake Bay tributaries. "Jellyfish are voracious predators," researcher Robert Condon, of the Virginia Institute of Marine Science, said in a prepared statement; and they feast on some of the same plankton that fish eat. That means less food for fish and other higher-level animals, potentially shifting the distribution of predators in the food web.

These jellyfish blooms also seem to have an outsized impact on the less visible—but also important—nutrient balance in the waters. Jellyfish aren’t a popular meal for most predators, so they are generally considered a "dead end" for carbon in a food system, the authors of the new paper explained. But even if the jellyfish themselves don't become a source of nutrients, they do contribute co-called "colloidal and dissolved organic matter" (read: mucus and poo) after processing their food, transforming the available carbon from plankton to fuel that's favored by bacteria.

These excretions are apparently welcome fodder for otherwise rare local bacteria populations, which gobbled up at least half of—and sometimes all of—the gunk within eight hours of its production, the researchers found. "Our findings suggest major shifts in microbial structure and function associated with jellyfish blooms," they reported.

But the bacteria populations weren't blooming in response as much as scientists might expect. Why not? The jellyfish waste turns out to be much richer in carbon than nitrogen, and "it just doesn't provide an efficient food source for marine bacteria," Deborah Steinberg, also of the Virginia Institute of Marine Science and co-author of the new paper, said in a prepared statement. So bacteria used the jellies' fuel more for respiration than for reproduction—which means they were creating more carbon dioxide rather than more usable biomass via increased numbers.

Apparently, reported numbers of Sea Nettles have declined in our region of the Bay in recent years, in reasonably close correlation with oyster numbers.  It has been hypothesized, (by a friend of mine) that the young Sea Nettles, which grow as a sessile hydroid stage over winter, need hard substrate to live, and the decline of oysters and oyster shell has caused them to run out of hard things to winter on.