Abstract
The seasonal biological drawdown of the partial pressure of CO2 (pCO2) in the surface waters of the Oyashio region of the western subarctic Pacific is one of the greatest among the worldโs oceans. This is attributable to spring diatom blooms. Transparent exopolymer particles (TEPs) are known to affect efficiency of the biological carbon pump, and higher TEP levels are frequently associated with massive diatom blooms.However, TEP dynamics in the Oyashio region remain unclear. This study investigates the TEP distribution from three cruises during the spring diatom bloom periods in 2010 and 2011. TEP concentrations varied from -1 above 300 m and generally declined with depth. Vertical TEP concentrations were significantly related not only to chlorophyll a concentrations but also to bacterial abundance. Average TEP concentrations within the mixed layer were significantly higher during the bloom (155 ยฑ 12 ยตg Xanthan gum equiv. L-1) than in the post-bloom phase (90 ยฑ 32 ยตg Xanthan gum equiv. L-1). In contrast, bacteria abundance within the mixed layer changed little during the bloom to post-bloom phases. These results suggest that the abundance of phytoplankton greatly contributed to dynamics of the TEP distribution. To evaluate the ability of the phytoplankton to produce TEP, an axenic strain of the diatom Thalassiosira nordenskioeldii, which is a representative species of Oyashio blooms, was examined within a batch culture system. Cell abundance-normalized TEP and dissolved organic carbon (DOC) production rates changed simultaneously with growth of the strain. Although these production rates were significantly higher in the stationary phase than in the exponential growth period, values of the TEP/DOC ratio changed little throughout incubation. These findings suggest that TEP production in the Oyashio region may be enhanced by an increase in DOC production from spring diatoms.
Highlights
Transparent exopolymer particles (TEPs) are defined as > 0.4ฮผm transparent particles that consist of acidic polysaccharides, and are stainable with the dye Alcian blue (Alldredge et al, 1993)
This study revealed TEP dynamics and dissolved organic carbon (DOC) productivity in the Oyashio region of the Northwest Pacific during spring diatom blooms
Our results showed that TEP levels within the mixed layer were correlated with diatom-derived Chl a biomass, suggesting that diatoms were the main TEP producers
Summary
Transparent exopolymer particles (TEPs) are defined as > 0.4ฮผm transparent particles that consist of acidic polysaccharides, and are stainable with the dye Alcian blue (Alldredge et al, 1993). These particles are very sticky, so that they can facilitate the aggregation of particles in seawater (e.g., Passow, 2002a; Wurl et al, 2011; Mari et al, 2017). It is known that many marine organisms, including phytoplankton and bacteria, can generate extracellular polysaccharides such as TEPs (Passow, 2002a). The relationship between the physiology of diatoms and TEP production remains poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
