On the phytoplankton bloom in coastal waters of southern King George Island (Antarctica) in January 2010: An exceptional feature?

Abstract

Since the early 1990s, phytoplankton has been studied and monitored in Potter Cove (PC) and Admiralty Bay (AB), King George/25 de Mayo Island (KGI), South Shetlands. Phytoplankton biomass is typically low compared to other Antarctic shelf environments, with average spring-summer values below 1 mg chlorophyll a (Chl a) m 23 . The physical conditions in the area (reduced irradiance induced by particles originated from the land, intense winds) limit the coastal productivity at KGI, as a result of shallow Sverdrup's critical depths (Z c ) and large turbulent mixing depths (Z t ). In January 2010 a large phytoplankton bloom with a maximum of around 20 mg Chl a m 23 , and monthly averages of 4 (PC) and 6 (AB) mg Chl a m 23 , was observed in the area, making it by far the largest recorded bloom over the last 20 yr. Dominant phytoplankton species were the typical bloom-forming diatoms that are usually found in the western Antarctic Peninsula area. Anomalously cold air temperature and dominant winds from the eastern sector seem to explain adequate light : mixing environment. Local physical conditions were analyzed by means of the relationship between Z c and Z t , and conditions were found adequate for allowing phytoplankton development. However, a multiyear analysis indicates that these conditions may be necessary but not sufficient to guarantee phytoplankton accumulation. The relation between maximum Chl a values and air temperature suggests that bottom-up control would render such large blooms even less frequent in KGI under the warmer climate expected in the area during the second half of the present century.

Composition, density and size-structure of the autotrophic plankton community in a shallow coastal zone at King George Island, West Antarctic Peninsula (WAP), during early summer 2010

“…This observation is in line with the raising summer water temperatures observed for KGI coastal waters during the last two decades (Schloss et al, 2012;Lange et al, 2014;Schloss et al, 2014). In a long-term study, Boyce et al (2010) reported that phytoplankton biomass in the global ocean, including Arctic and Antarctic regions, declined by 1%, which strongly correlates with the increase in sea surface temperatures over the past century.…”

Fluorescence-Based Approach to Estimate the Chlorophyll-A Concentration of a Phytoplankton Bloom in Ardley Cove (Antarctica)

“…The spatial pattern of IPAR (Figure 5b), which showed good agreement with chlorophyll-a concentration (Figure 1c), clearly illustrated the influence of light limitation on phytoplankton growth. This physical condition prevents optimal light for phytoplankton growth and this along with intense wind and terrigenous particles, typically leads to low primary productivity KGI [25]. From the perspective of this study, low light conditions ensured the reliability of the fluorescence approach and the nFLH algorithm.…”

“…The phytoplankton bloom reported in 2010 was dominated by micro-algae (e.g., Porosira glacialis, Thalassiosira antarctica, and T. ritscheri [25]). Phytoplankton tends to adapt their cellular physiology to optimize light harvesting and photoreception [44].…”

“…Historical records in KGI have shown that no phytoplankton blooms [6] occurred in these waters until 2010, during which maximum chlorophyll-a reached 20 mg/m 3 . Research has assumed that the increasing phytoplankton growth was exacerbated by global warming [25]. This manuscript documented another phytoplankton bloom in 2016 and attempted to determine its potential cause from optics and satellite history records.…”

“…An obvious phytoplankton bloom was reported until 2010, during which maximum chlorophyll-a reached 20 mg/m 3 . In situ records show an increasing trend of phytoplankton biomass in this area, likely caused by increasing SST (sea surface temperature) related to global warming [25]. The aim of this study was to document an algal bloom in Ardley Cove through the validation and regionalization of the MODIS nFLH algorithm.…”