Enhancement of coccolithophorid blooms in the Bering Sea by recent environmental changes

Abstract

[1] Since 1997, ocean color satellite images have revealed large-scale blooms of the coccolithophorid Emiliania huxleyi in the eastern Bering Sea. The blooms are often sustained over several months and have caused ecosystem changes in the Arctic Ocean, as well as in the Bering Sea. We examined continental shelf sediment profiles of alkenone, a biomarker for E. huxleyi, covering the past $70 years. The alkenone records suggest that large E. huxleyi blooms are a novel feature in the Bering Sea as they have occurred only since the late 1970s. Recent changes in alkenone content were closely related to the 1976-77 climatic regime shift in the North Pacific, implying that warming and freshening of Bering Sea waters promoted E. huxleyi blooms. The production rate of diatoms (total valves in sediment samples), the dominant primary producers in the Bering Sea, also increased during the past several decades. However, the ratio of alkenone content to total diatom valves in the sediments increased as E. huxleyi production increased, suggesting that the increase in the E. huxleyi production rate frequently exceeded the increase in the diatom production rate. Overall, our results indicate a possible subarctic region ecosystem shift driven by climate change.

Change in coccolith size and morphology due to response to temperature and salinity in coccolithophore <i>Emiliania huxleyi</i> (Haptophyta) isolated from the Bering and Chukchi seas

“…The MR strains had thin distal shield elements, categorized into Types B, B/C, and C. Concerning the ocean-geographical implications of these data, Type C and B/C strains are reported at higher latitudes in cold, sub-Antarctic oceans, while Types A and B were found around the southern Subtropical Front in a warmer-water areas (Patil et al, 2014). In the Bering Sea, the lightly calcified Type A was identified during the bloom that occurred in August 2006 (Harada et al, 2012 various oceanic areas (including in previous reports) is summarized in Table 3. Both the MR57N and MR70N E. huxleyi strains can be categorized as Type B/C, although both were isolated from cold waters: the Bering Sea and Arctic Sea, respectively.…”

“…A large-scale change in the oceanic environment was observed as a climatic regime shift in the subpolar Pacific region, such as the Bering Sea, in 1976-1977(Mantua et al, 1997. Siliceous diatoms are the dominant primary producers in that location (Tsunogai et al, 1979), but an increase in the population of the calcareous haptophyte Emiliania huxleyi is suggested by the alkenone biomarkers preserved in the oceanic sediments (Harada et al, 2012). The reduction of sea ice in the northern Chukchi Sea from 2008 to 2010 has influenced the phytoplankton distribution pattern (Fujiwara et al, 2014).…”

“…As a constituent of oceanic ecosystems, phytoplankton are important primary producers and key markers for understanding changes in the oceanic environment (e.g., Fujiwara et al, 2014;Harada et al, 2012). A large-scale change in the oceanic environment was observed as a climatic regime shift in the subpolar Pacific region, such as the Bering Sea, in 1976-1977(Mantua et al, 1997.…”

Simultaneous shifts in elemental stoichiometry and fatty acids of <i>Emiliania huxleyi</i> in response to environmental changes

“…Evidence from in situ and satellite observations indicates that E. huxleyi has been increasingly expanding its range poleward in both hemispheres over the last two decades, and contributing factors to this poleward expansion may differ between regions and hemispheres (Winter et al, 2014). For example, warming and freshening have promoted E. huxleyi blooms in the Bering Sea since the late 1970s (Harada et al, 2012), while temperature and irradiance were best able to explain variability in E. huxleyi-dominated coccolithophore community composition and abundance across the Drake Passage (Southern Ocean) (Charalampopoulou et al, 2016). Hence, empirical data on the responses of E. huxleyi to different environmental drivers would be critical for fully understanding the roles of this prominent coccolithophore species in marine ecosystems.…”

Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

“…The nutrient-rich Pacific water doesn't supply a significant proportion of the total supply of nutrient-rich water to the "deep" Arctic Ocean, that is about one-fifth that of nutrient-rich Atlantic water (Carmack and Wassmann, 2006). The high nutrient concentrations in the Pacific water that enters the Arctic Ocean via the northern Bering Sea reflect the high productivity throughout the food chain of the Bering Sea continental shelf ecosystem (Taniguchi, 1999;Grebmeier et al, 2006;Harada et al, 2012;Cooper et al, 2013) as well as the contribution of the Anadyr Current, which consists of Bering Slope Current water that has upwelled onto the Bering shelf (Kinder et al, 1975;Wang et al, 2009). Runoff from the Yukon River contributes a substantial flux of terrestrial dissolved organic carbon (DOC) derived from glaciers to the Gulf of Alaska; the DOC flux is 0.13 Tg y −1 (standard deviation 0.01 Tg y −1 ), of which 77% (~0.1 Tg) is highly labile (Hood et al, 2009).…”