Evidence of temperature control on mesopelagic fish and zooplankton communities at high latitudes

Chawarski, Julek; Klevjer, Thor A.; Côté, David; Geoffroy, Maxime

doi:10.3389/fmars.2022.917985

Cited by 16 publications

(9 citation statements)

References 70 publications

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“…The strong difference between the SAZ and PFZ observed during this study, both in terms of integrated NASC, and vertical distribution of backscattering at two frequencies, was corroborated by the historical data from the IMOS database at three frequencies, that consistently showed less acoustic backscatter in the PFZ compared to the SAZ (Figure 5). This was also demonstrated in other studies that reported a general decrease in acoustic backscatter with increased latitude (Chawarski et al., 2022; Dornan et al., 2019; Escobar‐Flores et al., 2018, 2020). These changes in acoustic backscatter were not always correlated to changes in fish biomass.…”

Section: Discussionsupporting

confidence: 82%

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

et al. 2022

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Mesoscale eddies shape the foraging ecology of predators such as marine mammals and seabirds. A growing number of animal tracking studies show that predators alter their swimming, diving, and foraging behavior within mesoscale eddies. However, little is known about how Southern Ocean eddies influence the distribution of mesopelagic micronekton (fish, squid, and crustaceans), which are major prey items of megafauna. Studies in other oceanic regions have found that eddies can influence the abundance and community composition of micronekton. Here, we analyze acoustic observations from a 14‐day survey of a cyclonic mesoscale eddy, its surrounding waters, and the Polar Frontal Zone (PFZ) waters where the eddy formed. We report and interpret spatial patterns of acoustic backscatter at 18 and 75 kHz, proxies indicating combined changes in species, size, and abundance of micronekton. We find that the vertical distribution of acoustic backscatter matched the underwater light conditions characteristic of the eddy core, periphery, and surrounding waters, at scales smaller than 10 km. The median water‐column integrated acoustic backscatter values in the eddy core were only half of those measured in the Sub‐Antarctic Zone waters surrounding the eddy, but similar to those measured in the PFZ, where the eddy originated 27 days prior. These results suggest that, as for physical and chemical tracers, the eddy maintained its biological characteristics from its source waters creating a unique habitat compared to its surroundings.

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Section: Discussionsupporting

confidence: 82%

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

et al. 2022

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“…The central Nansen Basin. Backscatter declines strongly in the upper mesopelagic zone when crossing boundaries between subpolar and polar water masses 59 , and such a decline was also evident when moving from the near-slope (NB1) to the central (NB2) Nansen Basin (Figs. 2 and 4a, b).…”

Section: Discussionmentioning

confidence: 97%

Under-ice observations by trawls and multi-frequency acoustics in the Central Arctic Ocean reveals abundance and composition of pelagic fauna

Ingvaldsen

Eriksen

Gjøsæter

et al. 2023

Sci Rep

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The rapid ongoing changes in the Central Arctic Ocean call for baseline information on the pelagic fauna. However, sampling for motile organisms which easily escape vertically towed nets is challenging. Here, we report the species composition and catch weight of pelagic fishes and larger zooplankton from 12 trawl hauls conducted in ice covered waters in the Central Arctic Ocean beyond the continental slopes in late summer. Combined trawl catches with acoustics data revealed low amounts of fish and zooplankton from the advective influenced slope region in the Nansen Basin in the south to the ice-covered deep Amundsen Basin in the north. Both arctic and subarctic-boreal species, including the ones considered as Atlantic expatriate species were found all the way to 87.5o N. We found three fish species (Boreogadus saida, Benthosema glaciale and Reinhardtius hippoglossoides), but the catch was limited to only seven individuals. Euphausiids, amphipods and gelatinous zooplankton dominated the catch weight in the Nansen Basin in the mesopelagic communities. Euphausiids were almost absent in the Amundsen Basin with copepods, amphipods, chaetognaths and gelatinous zooplankton dominating. We postulate asymmetric conditions in the pelagic ecosystems of the western and eastern Eurasian Basin caused by ice and ocean circulation regimes.

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“…Changing both vertical distribution and directions may confuse predators (Christiansen et al 2022). Success in exploiting resources in the twilight zone would affect possible constraints by photoperiod imposed at high latitudes, with bearing for questions like whether or not the constancy of light regime under climate change will prevent mesopelagic fishes from invading the Arctic (Kaartvedt 2008; Proud et al 2017; Ljungström et al 2021; Chawarski et al 2022).…”

Section: Discussionmentioning

confidence: 99%

“…Mechanistic models using B. glaciale to assess climate effects on vertically migrating mesopelagic fishes at high latitudes concluded that their poleward distribution is constrained since foraging fishes would be exposed to visual predators in sunlit upper waters at night also (Ljungström et al 2021; Langbehn et al 2022). On the other hand, Proud et al (2017) suggest that mesopelagic fishes will move poleward as the oceans warm, and Chawarski et al (2022) provided evidence that low temperatures define the biogeographic boundaries of mesopelagic fishes at high latitudes.…”

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confidence: 99%

Mid‐summer fish behavior in a high‐latitude twilight zone

Kaartvedt

Christiansen

Titelman

2023

Limnology & Oceanography

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The behavior of the mesopelagic fish Benthosema glaciale was studied at 60°N in mid‐summer. We hypothesized that diel vertical migration (DVM) is constrained by short and dusk nights (surface illumination > 10−2 μmol m−2 s−1) and that individuals are active at depth during the long summer days. Submerged echosounders provided high‐resolution data throughout the water column. During the day, a part of the population ascended toward the increasing daylight. Short vertical relocations were followed by minutes of vertical inactivity. Swimming included horizontal turns and loops associated with the vertical steps. Normal DVM was initiated ~ 4 h before sunset and reflected independent individual decisions. The fish initially ascended stepwise but switched to mostly straight upwards swimming attaining 3–4 cm s−1. Their vertical speed was faster than the slow ascent of isolumes and even the deepest living fish potentially could reach upper layers shortly after sunset. However, many individuals aborted their ascent and returned to depth before the darkest time of the night, while others returned downward closer to sunrise. The daytime swimming and individual variability in diel migration behavior have implications for encounters with prey and predators in the twilight zone and the biological carbon pump. A principal conclusion is that mesopelagic fishes can modify their behavior and migration patterns to suit a wide range of changing conditions.

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Evidence of temperature control on mesopelagic fish and zooplankton communities at high latitudes

Cited by 16 publications

References 70 publications

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

Under-ice observations by trawls and multi-frequency acoustics in the Central Arctic Ocean reveals abundance and composition of pelagic fauna

Mid‐summer fish behavior in a high‐latitude twilight zone

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