Picophytoplankton distribution along Khatanga Bay-shelf-continental slope environment gradients in the western Laptev Sea

Mikhail V. Flint,Аndrey B. Demidov,Tatiana A. Belevich,Sergei A. Shchuka,Peter N. Makkaveev

doi:10.1016/j.heliyon.2021.e06224

Abstract

The spatial variations of photosynthetic picoplankton abundance and biomass and the picoplankton's contribution to chlorophyll a concentration along the transect from Khatanga Bay to the continental slope in the western part of the Laptev Sea were studied in September 2017. Picoeukaryotes dominated in the picophytoplankton communities. Picophytoplankton in Khatanga Bay showed more variability than those over the Laptev shelf and continental slope: abundance and biomass were the highest in the southern part of the bay and markedly decreased with increasing salinity in its northern part. Picocyanobacteria were found over the shelf and slope at temperatures of +2.4 to -1.6°С and salinity from 22 to 34. Picophytoplankton contribution to total chlorophyll a on the shelf was higher than in Khatanga Bay. The study of picophytoplankton of Khatanga Bay and in the western Laptev Sea can serve as a baseline for future assessment of the Laptev Sea ecosystem response to interannual and climate changes.

Highlights

Picophytoplankton comprises two major groups, eukaryotic algae and cyanobacteria, and ranges in the size from 0.2 to 2.0 μm (Sieburth et al, 1978; Vaulot et al, 2008; Massana, 2011)
The depth of the euphotic zone exceeded the upper mixed layer and was found at depths of 7–10 m in Khatanga Bay, 16–21 m on the shelf, and to 26 m over the continental slope (Table 1)
Whereas we found that picophytoplankton contribution to the total chlorophyll a (Chl a) on the western part of the Laptev Sea shelf (51%) and on the eastern part (62%) (Heiskanen and Keck, 1996) was close

Summary

Introduction

Picophytoplankton comprises two major groups, eukaryotic algae and cyanobacteria, and ranges in the size from 0.2 to 2.0 μm (or 3.0 μm) (Sieburth et al, 1978; Vaulot et al, 2008; Massana, 2011). Picoeukaryotes (PEs) are well adapted to harsh environment polar seas and in some areas numerically dominate arctic phytoplankton communities for most of the year (Sherr et al, 2003; Kilias et al, 2014). Picocyanobacteria (PC) are poorly represented in the Arctic seas in general (Murphy and Haugen 1985; Booth and Horner 1997; Mostajir et al, 2001; Sherr et al, 2003). Studies in the Arctic indicated the total absence of Prochlorococcus, and very limited presence of Synechococcus while the latter dominants in small size phytoplankton in most areas of the World Ocean (Li et al, 2009). Factors that affected the spatial heterogeneity of picophytoplankton abundance at the mesoscale and submesoscale have not yet been sufficiently determined (Slapeta et al, 2006)

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