Carbon Uptake Rates Of Phytoplankton Research Articles

Impact of Freshwater Discharge on the Carbon Uptake Rate of Phytoplankton During Summer (January–February 2019) in Marian Cove, King George Island, Antarctica

Rapidly changing conditions in high-latitude coastal systems can significantly impact biogeochemical cycles because these systems are strongly influenced by freshwater discharged from melting glaciers and streams on land. Generally, Antarctic coastal areas are considered high-productivity areas in which phytoplankton growth prevails under various environmental conditions (e.g., oceanographic and meteorological conditions). This study provides carbon uptake rates of phytoplankton in Marian Cove during summer (January-February 2019). Daily depth-integrated carbon uptake varied greatly and averaged 0.8 g C m–2 day–1, with a maximum of 4.52 mg g C m–2 day–1 recorded on 14 January. Similarly, the observed biomass standing stocks were very high (up to 19.5 mg m–3 chlorophyll a) and were dominated by microphytoplankton (20–200 μm), representing 84% of total chlorophyll a (chl-a). The depth-integrated chl-a and carbon uptake decreased from outer to inner areas (close to the glacial front) in the cove. As the austral summer progressed, the freshening of the surface waters coincided with high water stability and suspended material and with low productivity when nanophytoplankton were present (2–20 μm; >60%). These findings suggest that both photosynthetically active radiation penetrating the water column and enhanced turbidity control light availability for phytoplankton, as well as their community compositions.

Transparent Exopolymer Particle (TEPs) Dynamics and Contribution to Particulate Organic Carbon (POC) in Jaran Bay, Korea

Transparent exopolymer particles (TEPs) are defined as acidic polysaccharide particles and they are influenced by various biotic and abiotic processes that play significant roles in marine biogeochemical cycles. However, little information on their monthly variation, relationship and contribution to particulate organic carbon (POC) is currently available particularly in coastal regions. In this study, the water samples were collected monthly to determine TEP concentrations and POC concentrations in a southern coastal region of Korea, Jaran Bay from April 2016 to March 2017. The TEP concentrations varied from 26.5 to 1695.4 μg Xeq L−1 (mean ± standard deviation (S.D.) = 215.9 ± 172.2 μg Xeq L−1) and POC concentrations ranged from 109.9 to 1201.9 μg L−1 (mean ± S.D. = 399.1 ± 186.5 μg L−1) during our observation period. Based on the 13C stable isotope tracer technique, monthly carbon uptake rates of phytoplankton ranged from 3.0 to 274.1 mg C m−2 h−1 (mean ± S.D. = 34.5 ± 45.2 mg C m−2 h−1). The cross-correlation analysis showed a lag-time of 2 months between chlorophyll a and TEP concentrations (r = 0.86, p < 0.01; Pearson’s correlation coefficient). In addition, we observed a 2 month lag-phased correlation between TEP concentrations and primary production (r = 0.73, p < 0.05; Pearson’s correlation coefficient). In Jaran Bay, the TEP contribution was as high as 78.0% of the POC when the TEP-C content was high and declined to 2.4% of the POC when it was low. These results showed that TEP-C could be a significant contributor to the POC pool in Jaran Bay.

Seasonal carbon uptake rates of phytoplankton in the northern East/Japan Sea

Korea-Russia joint expeditions have been conducted mainly in the less studied Russian sector of the East/Japan Sea to understand the physical and ecological structures. In this study, the carbon uptake rates of phytoplankton measured in 2012 (middle-late October) and 2015 (middle April-early May) were analyzed to understand seasonal and spatial distributions of phytoplankton production, using a 13C-15N dual isotope tracer technique. The water columns in the euphotic layers were well mixed during our cruise periods in both years. The water column-integrated chl-a concentrations (mean ± S.D. = 2.28 ± 1.47mgm−3) in 2015 was significantly higher (t-test, p < 0.01) than in 2012 (mean ± S.D. = 0.49 ± 0.29mgm−3) because of different sampling seasons. Small phytoplankton (< 2 μm) were relatively dominant in 2012, whereas different sizes of phytoplankton were evenly distributed in 2015 although a spatial distribution of large phytoplankton (> 20 μm) was observed near the Russian coast. The daily carbon uptake rates in this study were 180.5 and 441.6mgC m−2 d−1 in 2012 and 2015, respectively which are significantly (t-test, p < 0.01) lower than the averaged values previously reported in the East/Japan Sea (863 ± 679.6mgC m−2 d−1). The potential reasons for the lower rate in this study are discussed. The small phytoplankton contribution (47.4%) averaged from the two different cruises in this study is consistent with the result (47%) reported in temperate regions. Moreover, a significantly (t-test, p < 0.01) lower contribution of small phytoplankton in total primary production than total phytoplankton biomass in this study is consistent with the results from other regions. Lower total primary production might be expected due to increasing contribution of small phytoplankton under warmer conditions.

Latitudinal carbon productivity in the Bering and Chukchi Seas during the summer in 2007

The Bering and Chukchi Seas are well known to be one of the most productive regions in the world. However, these regions have many climate induced-environmental changes over the last decades. Whether these changes enhance or reduce the overall primary production is important in major ecosystems of the Bering and Chukchi Seas. During the Oshoro Maru cruise in 2007 as an IPY (International Polar Year) event of Hokkaido University, nitrogen and carbon uptake rates of phytoplankton were measured at 15 productivity stations in the Bering and Chukchi Seas, using a 13C–15N dual isotope tracer technique. The 2007 mean daily carbon uptake rates of phytoplankton were 0.20 and 0.16gCm−2d−1, respectively in the southern and northern Bering Sea. These rates are lower than those reported previously in the regions mainly because of the well-known strong seasonal variation of the carbon uptake rate between May (bloom period) and July (post-bloom period; this cruise). In the Chukchi Sea, the mean uptake rates from this study were 1.63 and 0.18gCm−2d−1, respectively in the central and northern regions which are noticeably lower than those reported previously in decades ago. Based on the enhancement experiments, light is an important controlling factor for the phytoplankton productivity rates in the Bering and Chukchi Seas during the cruise period as indicated by higher carbon uptake rates with increased light conditions. Accordingly, nutrients might not be the controlling factor, given there were only minimal increases of primary productivity rates with higher nitrate concentrations.

Recent phytoplankton productivity of the northern Bering Sea during early summer in 2007

Although the northern Bering Sea is one of the most productive regions in the northern North Pacific Ocean and currently considered a declining productivity region, no recent primary productivity measurements have been collected in this region. Phytoplankton productivity was measured in the northern Bering Sea in 2007 using a dual 13C–15N isotope tracer technique to quantify present rates of primary productivity and to assess changes under recent environmental conditions in this area. We found that large diatoms (mostly Fragilaria sp.) dominated the phytoplankton during the initial part of the cruise, whereas unidentified nano + pico phytoplankton largely dominated at the surface about 2 weeks later (at “revisited stations”). At the 1% light depth, diatoms and Phaeocystis sp. were the dominant species, whereas diatoms and unidentified nano + pico cells were dominant at the revisited sites. Based on nitrate and ammonium uptake rates, the estimated f-ratios (the ratio of nitrate uptake rate/nitrate + ammonium uptake rates of phytoplankton) were high (0.65–0.74), indicating that nitrate was an important nitrogen source supporting primary production in the northern Bering Sea during the cruise in 2007. Compared with previous studies performed several decades ago, we found significantly lower chlorophyll-a concentrations and carbon uptake rates of phytoplankton in the northern Bering Sea in 2007. This is consistent with recent studies that have shown lower rates of production in the Chukchi Sea and declines in benthic biomass and sediment oxygen uptake in the northern Bering Sea.

Uptake and resource allocation of inorganic carbon by the temperate seagrasses Posidonia and Amphibolis

Productivity measurements from carbon uptake have been suggested as good indicators of the physiological health of seagrasses. As seagrasses acquire carbon from the surrounding water, the rate of uptake often provide a good measure of the efficiency at which seagrasses meet their resource demands for growth. This rate is often used to assess the photosynthetic efficiency of the plants, a proxy for the physiological status of seagrass. This has special relevance to the Adelaide region as over 5000 ha of seagrasses have been lost from Adelaide coastal waters over the last 70 years, with much of this loss attributed to nutrient inputs from wastewater, industrial and stormwater discharges. This study used an in-situ inorganic carbon isotope-labelling and spike approach to obtain ecologically relevant estimates of seasonal variability in carbon uptake and its allocation in two species of temperate seagrass common to this coast ( Amphibolis antarctica and Posidonia angustifolia). Uptake of carbon by the seagrass complex (leaves, roots, phytoplankton and epiphytes) was affected by both season and species. Carbon uptake rates of phytoplankton were generally higher than other components of the system. Uptake rates ranged from 0.01 mg C g − 1 DW h − 1 (summer) to 0.61 mg C g − 1 DW h − 1 (spring) in Posidonia and 0.02 mg C g − 1 DW h − 1 (summer) to 0.93 mg C g − 1 DW h − 1 (winter) in Amphibolis. Carbon uptake by the Amphibolis complex was higher than in the Posidonia complex. The Amphibolis complex had higher uptake rates in summer whereas the Posidonia complex was higher in spring. Fine sediments probably from a nearby dredging operation, are likely to have resulted in lower carbon uptake and a reduction in the above-ground and below-ground biomass in summer.