Rapid scavenging of jellyfish carcasses reveals the importance of gelatinous material to deep-sea food webs

Abstract

Jellyfish blooms are common in many oceans, and anthropogenic changes appear to have increased their magnitude in some regions. Although mass falls of jellyfish carcasses have been observed recently at the deep seafloor, the dense necrophage aggregations and rapid consumption rates typical for vertebrate carrion have not been documented. This has led to a paradigm of limited energy transfer to higher trophic levels at jelly falls relative to vertebrate organic falls. We show from baited camera deployments in the Norwegian deep sea that dense aggregations of deep-sea scavengers (more than 1000 animals at peak densities) can rapidly form at jellyfish baits and consume entire jellyfish carcasses in 2.5 h. We also show that scavenging rates on jellyfish are not significantly different from fish carrion of similar mass, and reveal that scavenging communities typical for the NE Atlantic bathyal zone, including the Atlantic hagfish, galatheid crabs, decapod shrimp and lyssianasid amphipods, consume both types of carcasses. These rapid jellyfish carrion consumption rates suggest that the contribution of gelatinous material to organic fluxes may be seriously underestimated in some regions, because jelly falls may disappear much more rapidly than previously thought. Our results also demonstrate that the energy contained in gelatinous carrion can be efficiently incorporated into large numbers of deep-sea scavengers and food webs, lessening the expected impacts (e.g. smothering of the seafloor) of enhanced jellyfish production on deep-sea ecosystems and pelagic-benthic coupling.

Decomposition of jellyfish carrion in situ: Short-term impacts on infauna, benthic nutrient fluxes and sediment redox conditions

“…Jellyfish carrion that reaches the benthos can be rapidly scavenged by a diverse range of taxa, including echinoderms, crustaceans and fish (see Lebrato et al, 2012;Sweetman et al, 2014). However, the biomass of carcasses that accumulates on the benthos after a bloom collapses can be so large that it exceeds the amount that can be scavenged.…”

Benthic scavengers and predators of jellyfish, material for a review

“…Yamamoto et al (2008) implicated one sea anemone, two decapod, one gastropod and one ophiurid species to be scavengers of Nemopilema nomurai carcasses in deep water of the Sea of Japan. In their experiments in a deep Norwegian fiord Sweetman et al (2014) found evidence of scavenging by hagfish and some species of small crustaceans in high numbers consuming jellyfish carcasses in a matter of hours. If a high number of dead jellyfish fall down in a very short time scavengers may be too few to deal with their remains, as has been documented by Billett et al (2006) and Lebrato et al (2012).…”

“…Nevertheless, jellyfish continue to be depicted occasionally (see Arai 2005 for examples) as dead ends in the food chains of the sea and/or as a rare source of food for predators (e.g. Condon et al 2011), despite an increasing number of species of fishes (Redeke 1911, Luttenberger 1981, Gorelova & Grudtsev 1986, Kelley 1987, Ates 1988, Arai 1988, Zann 1988: 208, Cerqueira & Haimovici 1990, Hall 1992, Harbison 1993, Massuti et al 1998, Purcell & Arai 2001, Bonaldo et al 2004, Arai 2005, Orsi Relini et al 2010a, Orsi Relini et al 2010b, Chaves et al 2010, Thaler 2012, Cardona et al 2012, Milisenda et al 2014, Battaglia et al 2014, Sweetman et al 2014, Dias & Almeida 2015, birds, reptiles and mammals (Dathe 1989, Ates 1991, Gronert 1992, Shiomi & Ogi 1992, Bell 1996, Zonfrillo 1997, Peglow 1998, Corsi 2000, Arai 2005, Suazo 2008, Cardona et al 2012, Jarman et al 2013, Melville 2013, Jones & Seminoff 2013, other cnidarians and ctenophores …”

The secret lives of jellyfish

“…In November 2010, Sweetman began to periodically lower a camera rig 400 metres to the bottom of Lurefjorden in southwestern Norway to track the fate of this fjord's dense population of jellyfish 6 . Previous observations from elsewhere had suggested that dead jellies pile up and rot, lowering oxygen levels and creating toxic conditions.…”