Salpa thompsoni in the Indian Sector of the Southern Ocean: Environmental drivers and life history parameters

Size‐specific grazing and competitive interactions between large salps and protistan grazers

“…E. superba thrives in diatom‐dominated regions (Haberman et al 2003), and may supplement its diet via substantial carnivory on copepods and other taxa when microplankton are not abundant (Nordhausen et al 1992; Cripps and Atkinson 2000). In contrast, S. thompsoni can feed on small phytoplankton and often excels in mesotrophic conditions (Zeldis et al 1995; Pakhomov and Hunt 2017; Kelly et al 2020). Indeed, our study shows that small S. thompsoni blastozooids can feed efficiently on cells as small as 1.2 μ m, while even large (125 mm) oozooids could feed efficiently on cells > 4.7 μ m. Both groups derived over half of their (phytoplankton‐based) nutrition from < 10 μ m cells that are largely unavailable to E. superba (although we note that S. thompsoni was likely deriving some nutrition from cells greater than our 30 μ m cutoff, as well as cyanobacterial cells not assessed in this study).…”

Southern Ocean Food Web Modelling: Progress, Prognoses, and Future Priorities for Research and Policy Makers

“…Salps have long been considered to be an alternative dominant herbivore to Antarctic krill (Murphy et al, 2012), possibly even competing but more likely occurring in different water masses (Johnston et al, in this research). The role of salps in the food web is less known but becoming increasingly recognised as an alternative energy pathway to krill and copepods in some areas (Kelly et al, 2020). Further comparative analysis of the structure and pathways of energy in food webs at South Georgia and the west Antarctic Peninsula was undertaken by Murphy et al (2016, Supplementary Information).…”

“…Such studies would also need to quantify the seasonal and interannual variation, food web subsidies (input of external energy: allochthonous production) and inter-food web connectivity (Murphy et al, 2007(Murphy et al, , 2013(Murphy et al, , 2016Treasure et al, 2019). Understanding of the lifehistories of many of the less-studied key mid-trophic level species is improving (e.g., Moteki et al, 2017;Queirós et al, 2018;Groeneveld et al, 2020;Kelly et al, 2020;Lin et al, 2020;Saunders et al, 2020;Zhu et al, 2020), however, for most species, quantitative understanding of lifecycles and population dynamics is still very limited (Constable et al, 2014(Constable et al, , 2017. Models of distribution and population processes of these species are required to provide inputs into food web models.…”

Population demographics and growth rate of Salpa thompsoni on the Kerguelen Plateau

“…Swarms of S. thompsoni populations form because of synchronized reproductive efforts, usually after the summer bloom of phytoplankton, with highest abundances occurring from summer to autumn (Foxton, 1966;Atkinson et al, 2017). There are relatively few studies on S. thompsoni in the Indian sector of the Southern Ocean (20 • E -170 • E) compared to the Pacific and Atlantic sectors, especially during autumn (March-May) (Kelly et al, 2020). This lack of sampling is evident in KRILLBASE, the most comprehensive database of S. thompsoni abundance that spans 90 years.…”

“…Duhamel et al, 2000;Carlotti et al, 2008;Béhagle et al, 2017) and one including the salp, S. thompsoni (Hunt et al, 2011). However, to date there is only one study that explored the population structure of the S. thompsoni population south of the Kerguelen Plateau (Kelly et al, 2020). This is despite the Kerguelen Plateau region being a suitable habitat (chlorophyll rich with surface waters warmer than 3 • C) for the development of large S. thompsoni swarms.…”