Salp-falls in the Tasman Sea: a major food input to deep-sea benthos

Abstract

Large, fast-sinking carcasses (food-falls) are an important source of nutrition to deepsea benthic communities. In 2007 and 2009, mass depositions of the salp Thetys vagina were observed on the Tasman Sea floor between 200 and 2500 m depth, where benthic crustaceans were observed feeding on them. Analysis of a long-term (1981 to 2011) trawl survey database determined that salp biomass (wet weight, WW) in the eastern Tasman Sea regularly exceeds 100 t km −3 yr −1 , with biomasses as high as 734 t km −3 recorded in a single trawl. With fast sinking rates, salp fluxes to the seafloor occur year-round. Salps, like jellyfish, have been considered to be of low nutritional value; however, biochemical analyses revealed that T. vagina has a carbon (31% dry weight, DW) and energy (11.00 kJ g −1 DW) content more similar to that of phytoplankton blooms, copepods and fish than to that of jellyfish, with which they are often grouped. The deposition of the mean yearly biomass (4.81 t km −2 WW) of salps recorded from the trawl database in the Tasman Sea represents a 330% increase to the carbon input normally estimated for this region. Given their abundance, rapid export to the seabed and high nutritional value, salp carcasses are likely to be a significant input of carbon to benthic food webs, which, until now, has been largely overlooked.

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling

“…It reduces the loss of energy and makes the exchange between the surface layer and the bottom more efficient (Gili et al, 2006;Pfannkuche and Lochte, 1993;Schnack-Schiel and Isla, 2005). It has been estimated that salp carcasses deposit 16 t km À 2 yr À 1 of carbon in the Tasman Sea (Henschke et al, 2013).…”

Jellyfish fisheries in the Americas: origin, state of the art, and perspectives on new fishing grounds

“…Recent investigations are also revealing the importance of jellyfish as prey for more than one hundred species of fish (Arai 1988;Ates 1988;Mianzan et al 2001;Purcell and Arai 2001;Arai 2005;Pauly et al 2009;Cardona et al 2012). In addition, large blooms of jellyfish that die and sink to the ocean floor (known as 'jelly-falls') have mainly been investigated for their role in the biological pump (Lebrato et al 2012(Lebrato et al , 2013; however, it is becoming apparent that they may also be an important nutritional input for benthic animals (e.g., Henschke et al 2013;Sweetman et al 2014).…”

An observation of two oceanic salp swarms in the Tasman Sea: Thetys vagina and Cyclosalpa affinis

“…Although these smaller salps contribute significantly to biogeochemical cycling with fast growth rates (Heron, 1972a) and faecal pellets, carcasses of these smaller salps rarely sink as they are neutrally buoyant (Tsukamoto et al, 2009). The carcasses of larger salps however, sink rapidly and have the potential to reach the sea floor in less than 2 days (Henschke et al, 2013;Lebrato et al, 2013). Due to the combined input from both faecal pellets and carcasses, swarms of larger salps are thought to play a greater role in carbon export (Smith et al 2014).…”

“…The role of gelatinous zooplankton, such as salps, pyrosomes and cnidarians, in ocean food webs and biogeochemical cycling has garnered increased attention in recent years (Lebrato et al, 2011;Henschke et al, 2013;Lebrato et al, 2013;Smith et al 2014). Salps (Phylum: Thaliacea, Order Salpidae) in particular, are significant contributors to oceanic carbon flux.…”

“…When salps occur in high abundances, their fast-sinking faecal pellets (Bruland and Silver, 1981) and carcasses (Henschke et al, 2013) can increase the carbon flux in an area up to ten-fold the daily average (Fischer et al, 1988) for a sustained period of time (Smith et al 2014). …”