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

Natasha Henschke,Iain M Suthers,Jason D Everett

doi:10.1186/s41200-016-0023-8

Natasha Henschke, Iain M Suthers + Show 1 more

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https://doi.org/10.1186/s41200-016-0023-8

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Abstract

Large oceanic salps are rarely encountered. The highest recorded biomasses of the salps Thetys vagina (852 g WW m−3) and Cyclosalpa affinis (1149 g WW m−3) were observed in the Tasman Sea during January 2009. Due to their fast sinking rates the carcasses and faecal pellets of these and other large salps play a significant role in carbon transport to the seafloor. We calculated that faecal pellets from these swarms could have contributed up to 67 % of the mean organic daily carbon flux in the area. This suggests that the flux of carbon from salp swarms are not accurately captured in current estimates. This study contributes information on salp abundance and biomass to a relatively understudied field, improving estimates for biogeochemical cycles.

Highlights

When salps occur in high abundances, their fast-sinking faecal pellets (Bruland and Silver, 1981) and carcasses
Salps were sampled at the surface with a neuston net (0.75 m × 0.75 m, 500 μm mesh; n = 2) and from to 40 m using a rectangular mid-water trawl (RMT; m × 1 m, 1 mm mesh, double-oblique tows; n = 1)
This study confirms recent literature that has identified that swarms of large salps frequently occur in the Tasman Sea (Henschke et al, 2013), and this is likely the case in oceans around the world

Summary

Introduction

Salps (Phylum: Thaliacea, Order Salpidae) in particular, are significant contributors to oceanic carbon flux. They have the highest per-individual filtration rates of all marine zooplankton filter feeders (Alldredge and Madin, 1982) consuming particles across three orders of magnitude (1 μm up to 1 mm in size; Vargas and Madin, 2004; Sutherland et al, 2010). Using a fine mucous net that is continuously secreted and fed toward the oesophagus This efficient feeding mechanism and their alternating sexual and asexual life-cycle results in fast individual (up to 21 % in length h−1; Heron, 1972a) and population (up to 2.5 d−1; Heron, 1972b; Henschke et al, 2015) growth rates. Salps form large swarms that often reach abundances greater than individuals m−3 (~6 kg WW m−3; Henschke et al., 2014) and persist for up to 6 months (Smith et al 2014).

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