Does suspended sediment affect the phytoplankton community composition and diversity in an Arctic fjord? A comparative study during summer

The Arctic regions experience strong seasonality and are largely affected by increasing temperature. This is particularly evident in the Kongsfjorden, which is surrounded by glaciers and is affected by seasonal and annual changes in temperature. It is largely influenced by glacial meltwater bringing in fluvial inputs such as total suspended matter (TSM) and warm Atlantic waters, which could alter the phytoplankton community. Seven stations in the Kongsfjorden representing glacier-influenced head (KF7, KF6, KF5), mid (KF4, KF3), and open region of the fjord (KF2 and KF1) were considered to evaluate the effect of TSM on phytoplankton community structure, abundance, chlorophyll a (Chl a), diversity index, evenness, and richness during summer 2011 (June) and 2018 (August) and related with atmospheric and hydrological parameters. The annual average atmospheric temperature (AAAT) over Ny-Ålesund showed an increase in temperature by a degree from -3.52 °C in 2011 to -2.44 °C in 2018, while the summer average atmospheric temperature (SAAT) over the same period increased from 5.80 to 6.16 °C. Increased freshening of the fjord led to an increase in TSM during 2018 which coincided with a decrease in Chl a by an order of magnitude. Although sea surface temperature (SST) was warmer in 2011, TSM was higher in 2018. The number of phytoplankton groups identified decreased from 11 in 2011 to 4 in 2018. A distinct alteration in phytoplankton community structure was observed from head fjord to open fjord with higher diversity observed during 2011 compared to 2018. This work highlights the effect of TSM on the phytoplankton community in the Kongsfjorden.

Variation of phytoplankton assemblages of Kongsfjorden in early autumn 2012: a microscopic and pigment ratio-based assessment

Phytoplankton species distribution and composition were determined by using microscopy and pigment ratios in the Kongsfjorden during early autumn 2012. Variation in sea surface temperature (SST) was minimal and matched well with satellite-derived SST. Nutrients were generally limited. Surface phytoplankton abundance ranged from 0.21 × 10(3) to 10.28 × 10(3) cells L(-1). Phytoplankton abundance decreased with depth and did not show any significant correlation with chlorophyll a (chl a). Column-integrated phytoplankton cell counts (PCC) ranged from 94.3 × 10(6) cells m(-2) (Kf4) to 13.7 × 10(6) cells m(-2) (Kf5), while chl a was lowest at inner part of the fjord (6.3 mg m(-2)) and highest towards the mouth (24.83 mg m(-2)). Biomass from prymnesiophytes and raphidophytes dominated at surface and 10 m, respectively. The contribution of Bacillariophyceae to biomass was low. Generally, heterotrophic dinoflagellates were great in abundance (12.82 %) and ubiquitous in nature and were major contributors to biomass. Various chl pigments (chl b, chl c, phaeopigments (phaeo)) were measured to obtain pigment/chl a ratios to ascertain phytoplankton composition. Phaeo were observed only in inner fjord. Chl b:a ratios and microscopic observations indicated dominance of Chlorophyceae at greater depths than surface. Furthermore, microscopic observations confirmed dominance of chl c containing algae throughout the fjord. The study indicates that pigment ratios can be used as a tool for preliminary identification of major phytoplankton groups. However, under the presence of a large number of heterotrophic dinoflagellates such as Gymnodinium sp. and Gyrodinium sp., pigment signatures need to be supplemented by microscopic observations.

Assessment of Godavari estuarine mangrove ecosystem through trace metal studies

Trace metals (Fe, Mn, Cu, Co, Ni. Pb, Cd and Cr) analyses in particulate matter and sediments were carried out at 16 different stations in the Godavari mangrove ecosystem covering the three regions viz., Kakinada (KKD) bay, Goutami-Godavari estuary (GGE) and Coringa and Gaderu mangrove environments (CGME). Higher concentrations of trace metals in particulate matter and in sediments were noticed in the mangrove environment compared to the KKD bay and GGE region. The significant correlations observed between several couples of metals in different regions as well as between numbers of heavy metals (Fe, Mn, Zn) with Total Suspended Matter (TSM) in particulate organic matter could be an indication of the role of the complexation with organic matter in the distribution pattern of these metals. Further significant correlations between organic carbon (OC) and Cr, Co, Pb, Cu and Mn in sediments of all the three regions indicate that organic matter acts as a metal carrier. The values of Pollution Load Index (PLI) were low and varied between 0.34 and 0.68 in KKD bay, 0.47 and 0.49 in GGE and, from 0.62 to 1.03 in CGME area, which indicate that the estuarine ecosystem is not of pollution concern under the present scenario.