Rethinking the Role of Salps in the Ocean

Henschke, Natasha; Everett, Jason D.; Richardson, Anthony J.; Suthers, Iain M.

doi:10.1016/j.tree.2016.06.007

Cited by 177 publications

(189 citation statements)

References 88 publications

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“…They can grow up to 20 m in length and are found in the epipelagic and mesopelagic layers of warm oceans between 50°N and 50°S (van Soest, ). Although they can form dense aggregations (e.g., Andersen & Sardou, ; Brodeur et al, ; Drits et al, ), the trophic function and ecology of pyrosomes are not well known and they are the least studied of all pelagic tunicates (Henschke et al, ; Madin & Deibel, ).…”

Section: Introductionmentioning

confidence: 99%

Large Vertical Migrations ofPyrosoma atlanticumPlay an Important Role in Active Carbon Transport

et al. 2019

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Pyrosomes are efficient grazers that can form dense aggregations. Their clearance rates are among the highest of any zooplankton grazer, and they can rapidly repackage what they consume into thousands of fecal pellets per hour. In recent years, pyrosome swarms have been found outside of their natural geographical range; however, environmental drivers that promote these swarms are still unknown. During the austral spring of 2017 a Pyrosoma atlanticum swarm was sampled in the Tasman Sea. Depth‐stratified sampling during the day and night was used to examine the spatial and vertical distribution of P. atlanticum across three eddies. Respiration rate experiments were performed onboard to determine minimum feeding requirements for the pyrosome population. P. atlanticum was 2 orders of magnitude more abundant in the cold core eddy (CCE) compared to both warm core eddies, with maximum biomass of 360 mg WW·m−3, most likely driven by high chlorophyll a concentrations. P. atlanticum exhibited diel vertical migration and migrated to a maximum depth strata of 800–1,000 m. Active carbon transport in the CCE was 4 orders of magnitude higher than the warm core eddies. Fecal pellet production contributed to the majority (91%) of transport, and total downward carbon flux below the mixed layer was estimated at 11 mg C·m−2·d−1. When abundant, P. atlanticum swarms have the potential to play a major role in active carbon transport, comparable to fluxes for zooplankton and micronekton communities.

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Section: Introductionmentioning

confidence: 99%

Large Vertical Migrations ofPyrosoma atlanticumPlay an Important Role in Active Carbon Transport

et al. 2019

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“…Unlike S. thompsoni having few known predators (Pakhomov et al ; Henschke et al ), E. superba are a keystone species in the Southern Ocean because they are an important prey for higher trophic levels such as fish, squid, whales, and seabirds (Everson ). Generally there is little interaction between these species as S. thompsoni and E. superba are spatially segregated, with S. thompsoni preferring warmer waters of the Antarctic Polar Front (APF) (Foxton ; Pakhomov et al ; Loeb and Santora ) whereas E. superba dominate the cooler high latitude waters closer to the Antarctic continent (Loeb et al ).…”

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confidence: 99%

Latitudinal variations in Salpa thompsoni reproductive fitness

Henschke

Pakhomov

2018

Limnology & Oceanography

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Salpa thompsoni is a major grazer that plays a significant and disproportionate role in the Southern Ocean biogeochemical cycle. It occurs in higher numbers in the warmer mid‐latitude waters of the Southern Ocean. In recent decades, salp populations shifted significantly southward intruding into areas generally dominated by Antarctic krill. It is unclear whether salps can survive in high latitude waters because of their hypothesized negative reproductive response to low temperatures and scarcity of food. To explore how environmental conditions impact S. thompsoni reproductive fitness, we examined a long‐term (1993–2013), cross‐latitudinal dataset of S. thompsoni population demographics in the Atlantic sector of the Southern Ocean. Observations cover over 25° of latitude, from just south of the Subtropical Convergence to the Antarctic continent. S. thompsoni populations were strongly driven by temperature with higher abundances observed at temperatures between 3°C and 5°C. Occasionally, dense and mature populations of S. thompsoni occurred at high latitudes during summer, declining in density by autumn, which was accompanied by significant increases in the appearance of failed embryos. The proportion of failed embryos was significantly correlated with decreasing temperature and Chl a, indicating the importance of these parameters in autumn and high latitude population collapses. The successful development and release of an embryo is a critical factor determining the persistence of S. thompsoni populations. Blastozooid bud release occurred continuously from spring to autumn, and may be a way S. thompsoni populations mitigate against the sensitivity of the blastozooid's reproductive fitness to high‐Antarctic conditions.

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“…Species that build lipid deposits to survive winter or are efficient at exploiting other pelagic carbon sources, such as T. macrura, D. antarctica and S. thompsoni , may gain a relative competitive advantage. Their lower trophic sea ice dependency in combination with a higher adaptability regarding environmental changes might result in a replacement of krill by salps in numbers as frequently suggested in the past (Constable et al, ; Ducklow et al, ; Henschke, Everett, Richardson, & Suthers, ; Montes‐Hugo et al, ; Słomska, Panasiuk‐Chodnicka, Żmijewska, & Mańko, ; Smetacek & Nicol, ). Ongoing climatic changes might also benefit growth and survival of T. macrura , as a consequence of increasing pelagic primary productivity (Steinberg et al, ) and increasing water temperatures (Driscoll, Reiss, & Hentschel, ).…”

Section: Discussionmentioning

confidence: 74%

“…Even small changes in low abundance species can contribute to profound consequences for the future Southern Ocean ecosystem and carbon fluxes (Henschke et al, ; McBride et al, ; Perissinotto & Pakhomov, ; van Franeker, Bathmann, & Mathot, ). These changes affect recruitment, species abundances and distribution patterns of intermediate trophic levels, which in turn can affect predator reproductive success and survival.…”

Section: Discussionmentioning

confidence: 99%

Dependency of Antarctic zooplankton species on ice algae‐produced carbon suggests a sea ice‐driven pelagic ecosystem during winter

Kohlbach

Graeve

Lange

et al. 2018

Global Change Biology

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How the abundant pelagic life of the Southern Ocean survives winter darkness, when the sea is covered by pack ice and phytoplankton production is nearly zero, is poorly understood. Ice-associated ("sympagic") microalgae could serve as a high-quality carbon source during winter, but their significance in the food web is so far unquantified. To better understand the importance of ice algae-produced carbon for the overwintering of Antarctic organisms, we investigated fatty acid (FA) and stable isotope compositions of 10 zooplankton species, and their potential sympagic and pelagic carbon sources. FA-specific carbon stable isotope compositions were used in stable isotope mixing models to quantify the contribution of ice algae-produced carbon (α ) to the body carbon of each species. Mean α estimates ranged from 4% to 67%, with large variations between species and depending on the FA used for the modelling. Integrating the α estimates from all models, the sympagic amphipod Eusirus laticarpus was the most dependent on ice algal carbon (α : 54%-67%), and the salp Salpa thompsoni showed the least dependency on ice algal carbon (α : 8%-40%). Differences in α estimates between FAs associated with short-term vs. long-term lipid pools suggested an increasing importance of ice algal carbon for many species as the winter season progressed. In the abundant winter-active copepod Calanus propinquus, mean α reached more than 50% in late winter. The trophic carbon flux from ice algae into this copepod was between 3 and 5 mg C m day . This indicates that copepods and other ice-dependent zooplankton species transfer significant amounts of carbon from ice algae into the pelagic system, where it fuels the food web, the biological carbon pump and elemental cycling. Understanding the role of ice algae-produced carbon in these processes will be the key to predictions of the impact of future sea ice decline on Antarctic ecosystem functioning.

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Rethinking the Role of Salps in the Ocean

Cited by 177 publications

References 88 publications

Large Vertical Migrations ofPyrosoma atlanticumPlay an Important Role in Active Carbon Transport

Large Vertical Migrations ofPyrosoma atlanticumPlay an Important Role in Active Carbon Transport

Latitudinal variations in Salpa thompsoni reproductive fitness

Dependency of Antarctic zooplankton species on ice algae‐produced carbon suggests a sea ice‐driven pelagic ecosystem during winter

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