Composition and Distribution of Plankton Communities in the Atlantic Sector of the Southern Ocean

Abstract

In recent decades, the waters off the Antarctic Peninsula and surrounding region have undergone a significant transformation due to global climate change affecting the structure and distribution of pelagic fauna. Here, we present the results of our study on the taxonomic composition and quantitative distribution of plankton communities in Bransfield Strait, Antarctic Sound, the Powell Basin of the Weddell Sea, and the waters off the Antarctic Peninsula and South Orkney Islands during the austral summer of 2022. A slight warming of the Transitional Zonal Water with Weddell Sea influence (TWW) and an increase in its distribution area was detected. Among the pelagic communities, three groups were found to be the most abundant: copepods Calanoides acutus, Metridia gerlachei, and Oithona spp., salpa Salpa thompsoni, and Antarctic krill Euphausia superba. Euphausiids were found in cases of low abundance, species diversity, and biomass. In the studied region, an increase in the amount of the salpa S. thompsoni and the euphausiid Thysanoessa macrura and the expansion of their distribution area were observed. Significant structural shifts in phytoplankton communities manifested themselves in changes in the structure of the Antarctic krill forage base. The composition and distribution of pelagic fauna is affected by a combination of environmental abiotic factors, of which water temperature is the main one. The obtained results have allowed us to assume that a further increase in ocean temperature may lead to a reduction in the number and size of the Antarctic krill population and its successive replacement by salps and other euphausiids that are more resistant to temperature fluctuations and water desalination.

Comparative Analysis of the Fatty Acid Profiles of Antarctic Krill (Euphausia superba Dana, 1850) in the Atlantic Sector of the Southern Ocean: Certain Fatty Acids Reflect the Oceanographic and Trophic Conditions of the Habitat

“…It is worth noting that the main multidisciplinary concept of the cruise was presented by our scientific group in [23]; the main aim of the cruise and research was the assessment of the current state of natural complexes of the Atlantic sector of the Southern Ocean and their multiperiod variability (ecosystems, bioproductivity, hydrophysics, and hydro-and geochemistry). There have already been several papers published based on the obtained results of composition and distribution of plankton communities in the Antarctic sector of the Southern Ocean [24]. In the present research, certain findings from this paper are used to refer to the forage base (biotic factor) of Antarctic krill in the studied area, and the next biological papers associated with the study are about studying the distribution and demography of Antarctic krill and salpas in the same season and study area [25].…”

“…Research areas included the Bransfield Strait (BS), Station 7299 (62 • 30.9 S; 58 02.8 W). Krill samples were obtained using pelagic double square micronekton nets (DSN) (505 µm mesh, 1.0 m 2 inlet area) equipped with a pterygoid deepener weighing 24 kg (Hydrobios, Altenholz, Germany) [24]. Oblique tows were performed at 0-300 m (BS), 0-490 m (AS), and 0-210 m (AP) at an average speed of 1.5 knots.…”

“…Only at Station 7331, the samples were obtained using the Isaak-Kidd mid-water trawl modified by Samyshev-Aseev (IKMT-SA), at a depth of 0-440 m. The biological analysis of the sampled krill was described in [25]. The oceanographic measurements in the studied areas were performed recently [23,24]. The General Oceanics GO1018 water sampler system equipped with an Idronaut Ocean Seven 320 plus CTD probe and 18 sampling Niskin bottles from 5 to 10 L capacity was used for measurements of thermohaline properties of the environment.…”

Seasonal acoustic presence of marine mammals at the South Orkney Islands, Scotia Sea

“…The AP and Scotia Sea region has been recognized as an important feeding area for several species of marine mammals [19][20][21][22], a probable result of high prey abundance [4]. The South Orkney Islands, located in the Scotia Sea, have high seasonal phytoplankton productivity and krill density, probably related to the seasonal sea ice cover, nutrients, bathymetric features and inflow from the Weddell Sea [1,23,24]. As a result, the South Orkney Islands have developed to become the most important commercial krill fishing ground in the SO and support both residential and migratory predators [1,19].…”

Influencia glaciar en la composición y diversidad de la comunidad del fitoplancton marino en la Bahía Almirantazgo, Isla Rey Jorge, Antártida

“…Esta región ha experimentado un aumento notable de la temperatura media anual del aire de 1-2 °C durante los últimos 50 años (Ducklow et al 2007) y un aumento de 0.56 °C por década (Turner et al 2014), lo que ha generado importantes efectos sobre el hielo marino, las plataformas de hielo y los sistemas glaciares (Steig et al 2009, Pan et al 2019. En consecuencia, el retroceso de los glaciares y la desintegración de la capa de hielo están generando cambios en las condiciones hidrofísicas, la duración del periodo de producción y la estructura y distribución de las comunidades de plancton en la región antártica (Kasyan et al 2022).…”