Tatiana Vitchenko1, Olga Tyukina2, Andrey Dolgov3
1Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia
2Murmansk State Technical University, Murmansk, Russia
3Knipovich Polar Research Institute of Marine Fisheries and Oceanography, Murmansk, Russia
Abstract
The research was done in the south-western and central Kara Sea during 91-st cruise of R/V
“Fridtjof Nansen” (Polar Research Institute of Fisheries and Oceanography, PINRO) in late October 2013. Phytoplankton taxonomic composition and distribution, abundance and biomass, ratio and role of autotrophic and heterotrophic species in the community were studied. Phytoplankton community was represented mainly by marine neritic arcto-boreal species with a small part of cosmopolitan forms and fresh-water microalgae. Totally 68 species of phytoplankton were found.
Diatoms predominated in the species composition. Phytoplankton abundance ranged from 352 to 3857 Х 103cell/m3, biomass varied from 1,77 to 20.05 mg/m3. Bacillariophyceae, Dinophyceae and Prasinophyceae had great contribution to the phytoplankton abundance, with small size autotrophic diatoms prevailing. Biomass was mainly formed by Prasinophyceae and Dinophyceae.
Phytoplankton was at the autumn stage of succession with typical seasonal transformation to the resting stage: taxonomic restructuring and a significant decrease in abundance and biomass.
Keywords: Kara Sea, phytoplankton , species composition, abundance, biomass Introduction
In recent decades, interest in the Kara Sea study has increased significantly due to the high economic activity in the continental shelf waters. The Kara Sea has an important role in the river runoff transformation of the Arctic basin, as it brings more than 40% of the total river flow to the Arctic region. Over the last years there has been an ice area shrinking in summer and ice-free waters area extension as well as increase an open water period duration, affecting the marine ecosystem functioning.
The study of the structural and physiological characteristics of marine ecosystems in the Russian Arctic is becoming one of the priority areas of the environmental research, in connection with increasing anthropogenic effect on the region and the climate change. Phytoplankton communities of the arctic seas are the most important component of marine ecosystem and the basis of the biological productivity. This paper presents data on species composition, abundance and biomass of phytoplankton in the South-West and Central part of the Kara Sea in October 2013. Regular collecting of biological data provides an opportunity to development of conservation, preservation and rehabilitation methods of the Arctic marine environment.
Material and methods
The research was done in the south-western and central Kara Sea during 91-st cruise of R/V
“Fridtjof Nansen” (Polar Research Institute of Fisheries and Oceanography) in late October 2013 (Figure 1).
Figure 1. R/V “Fridtjof Nansen” (Polar Research Institute of Fisheries and Oceanography).
The material was collected at stations located to the East of the Novaya Zemlya archipelago to 65°
E, between 70° N and 76° N (Figure 2).
Figure 2. Map-scheme of phytoplankton sampling in the Kara Sea, the cruise R / V “Fridtjof Nansen” in October 2013.
Phytoplankton taxonomic composition and distribution, abundance and biomass, ratio and role of autotrophic and heterotrophic species in the community were studied.
Totally 31 integral samples for microphytoplankton (cell sizes 15 - 200 μm) taxonomic composition and quantitative parameters analysis were collected. The phytoplankton samples were concentrated by the standard method of reverse filtration and then preserved with 40% neutral formalin to a final concentration of 2% on the shipboard. Phytoplankton taxonomic analysis, microphotography and quantification was done in the PINRO laboratory with light biological microscopes MBS-9 and XS-402 (magnification X40-800) The obtained data on abundance and biomass were recalculated by volume 1 m3 (Figure 3).
Figure 3. Representatives of the Kara Sea phytoplankton community in the samples of October 2013: A – Ceratium longipes; Б – Chaetoceros danicus; В – Ceratium arcticum; Г – Dictyocha speculum; Д – Pterosperma polygonum; Е – Pterosperma marginatum (micrography and taxonomic analysis by O. S. Tyukina).
Results
Phytoplankton community was represented mainly by marine neritic arcto-boreal species with a small part of cosmopolitan forms and fresh-water microalgae. Totally 68 species of phytoplankton were found. Diatoms predominated in the species composition (Figure 4).
Figure 4. The ratio of the species number in different taxonomical groups of the Kara Sea phytoplankton community in October 2013.
Phytoplankton abundance ranged from 352 to 3857 Х103 cell/m3 (average 1006 Х103 cell/m3) (Figure 5).
Figure 5. Distribution of phytoplankton abundance (N, 103 cell/m3) in the Kara Sea in October 2013.
Bacillariophyceae, Dinophyceae and Prasinophyceae had great contribution to the phytoplankton abundance, with small size autotrophic diatoms prevailing. The maximum abundance values were observed in the Barents Sea water masses, the lowest in the mixing zone of the Barents Sea and the Arctic surface waters.
Biomass varied from 1,77 to 20.05 mg/m3 (average - 6.52 mg/m3). Biomass was mainly formed by Prasinophyceae and Dinophyceae (Figure 6).
Figure 6. Distribution of phytoplankton biomass (mg/m3) in the Kara Sea in October 2013.
Conclusions
Phytoplankton was at the autumn stage of succession with typical seasonal transformation to the resting stage: taxonomic restructuring and a significant decrease in abundance and biomass. The obtained data is well correlated with seasonal phytoplankton characteristics in this area. In October 2013 the phytoplankton community of the Kara Sea was predominated by diatoms, which is typical for the arctic seas and the Kara Sea in particular. Phytoplankton consisted mainly of neritic marine arcto-boreal algae complex with a small proportion of cosmopolitan forms. The percentage of freshwater species in the phytoplankton community was insignificant even in the coastal stations, probably due to standoff distance of sampling stations from the shore and minimal river flow at this season. Phytoplankton activity depends on the seasonal insolation and the water column cooling, which leads to disintegration of the community species structure and decrease of abundance and biomass. In biomass, the phytoplankton was predominated by a small size fraction of autotrophic diatoms, flagellates, Chaetoceros and Ceratium genera and Dinophyta algae, mainly Protoperidinium and Dinophysis. The change of the main dominants in the community took place in accordance with the season and was expressed in the progressive replacement of autotrophic forms with heterotrophic and mixo-heterotrophic. The study area included the southernmost shallow part of the basin, the central and deep western part of the sea. A significant impact on the Kara Sea ecosystem is provided by continental runoff, due to which the Kara Sea is characterized by a pronounced zoning in the distribution of marine ecosystem biotic components, including phytoplankton. The southern and central regions of the sea are influenced by the Ob’ and the Yenisei river flow. In the western part of the sea convective mixing of waters extends approximately to a depth of 50 m. The particular feature of phytoplankton biomass distribution in this area is circumferential concentration in the coastal areas. The maximum biomass was recorded at the eastern coast of the Novaya Zemlya archipelago. The relatively high local biomass values were observed at stations with depths of more than 150 m. Spatial differences in the abundance and biomass distribution have been associated with the hydro physical and hydro chemical parameters of the environment, particularly the Barents Sea waters penetration and the influence of the coastal currents along the Yamal Peninsula. The Kara Sea phytoplankton status in autumn 2013 substantially similar to the seasonal stage of development representative of arctic microalgae communities.
Acknowledges
This work was supported by the Russian Science Foundation Project “Structure and functioning of plankton and fish communities in the Kara Sea in recent warming period” (Grant No. № 14-14-00808).