Jelly-falls

Jelly-falls are primarily made up of the decaying bodies of Cnidaria and Thaliacea (Pyrosomida, Doliolida, and Salpida). In general, however, jelly-falls are linked to jelly-blooms and primary production, with over 75% of the jelly falls in subpolar and temperate regions occurring after spring blooms, and over 25% of the jelly-falls in the tropics occurring after upwelling events. As the climate changes and ocean waters warm, jelly blooms become more prolific and the transport of jelly-carbon to the lower ocean increases. With a possible slowing of the classic biological pump, the transport of carbon and nutrients to the deep sea through jelly-falls may become more and more important to deep ocean. == Anthropogenic links ==

Due to human activity there has been an increase in the frequency and intensity of jellyfish blooms. This in turn has been speculated to enhance the occurrence of jelly-falls. Overfishing small pelagic fishes and other zooplanktivores can reduce competition for planktonic resources and removes the key predators that feed on gelatinous zooplankton which allows jellyfish populations to increase. Coastal eutrophication from agricultural and urban runoff also creates hypoxic zones that are avoided by most fish and crustaceans species, but many cnidarians and thaliaceans can tolerate which further benefits jellyfish populations. Jelly derived carbon on the seafloor is expected to increase substantially due to these reasons along with the rise of sea surface temperatures primarily in coastal and shelf regions. ==Decomposition==

The decomposition process starts after death and can proceed in the water column as the gelatinous organisms are sinking. Lone gelatinous organisms may spend less time on the sea floor as one study found that jellies could be decomposed by scavengers in the Norwegian deep sea in under two and a half hours. Decomposition of jelly-falls is largely aided by these kinds of scavengers. In general, echinoderms, such as sea stars, have emerged as the primary consumer of jelly-falls, followed by crustaceans and fish. The dynamics of scavenging varies greatly across Norwegian fjords. Shallow jelly-falls have been consumed by demersal fish and large crustacean species, while the deeper falls are dominated by smaller, slower moving scavengers such as ophiuroids and gastropods which results in longer carcasses persistence. With increased populations and blooms becoming more common, with favorable conditions and a lack of other filter feeders in the area to consume plankton, environments with jellies present will have carbon pumps be more primarily supplied with jelly-falls. This could lead to issues of habitats with established biological pumps succumbing to nonequilibrium as the presence of jellies would change the food web as well as changes to the amount of carbon deposited into the sediment. Finally, decomposition is aided by the microbial community. In a case study on the Black Sea, the number of bacteria increased in the presence of jelly-falls, and the bacteria were shown to preferentially use nitrogen released from decaying jelly carcasses while mostly leaving carbon. In a study conducted by Andrew Sweetman in 2016, it was discovered using core samples of the sediment in Norwegian fjords, the presence of jelly-falls significantly impacted the biochemical process of these benthic communities. Bacteria consume jelly carcasses rapidly, removing opportunities of acquiring sustenance for bottoming feeding macrofauna, which has impacts traveling up the trophic levels. In addition, with the exclusion of scavengers, jelly-falls develop a white layer of bacteria over the decaying carcasses and emit a black residue over the surrounding area, which is from sulfide. This high level of microbial activity requires a lot of oxygen, which can lead zones around jelly-falls to become hypoxic and inhospitable to larger scavengers. == Global scale and biogeochemical fingerprint ==

Gelatinous zooplankton has substantial global biomass. Estimates are derived from net tows and optical surveys that indicate jellyfish, salps, and other gelatinous organisms contribute significantly to the total zooplankton carbon from all ocean basins. The geographic variation of biomass is primarily controlled by temperature and water column stability. Highest concentrations of biomass are observed in coastal upwelling zones, polar regions, and areas that have high seasonal productivity. The small fluctuations of gelatinous zooplankton on a daily basis could produce a flux of particulate organic carbon comparable to that of non-gelatinous detritus like phytoplankton blooms. ==Research challenges==

Researching jelly-falls relies on direct observational data such as video, photography, or benthic trawls. A complication with trawling for jelly-falls is the gelatinous carcass easily falls apart and as a result, opportunistic photography, videography, and chemical analysis have been primary methods of monitoring. This means that jelly-falls are not always observed in the time period in which they exist. Because jelly-falls can be fully processed and degraded within a number of hours by scavengers and the fact that some jelly-falls will not sink below 500 m in tropical and subtropical waters, the importance and prevalence of jelly-falls may be underestimated. ==See also==