Monthly Variation in the Macromolecular Composition of Phytoplankton Communities at Jang Bogo Station, Terra Nova Bay, Ross Sea

Abstract

Organic carbon fixed by photosynthesis of phytoplankton during the polar growing period could be important for their survival and consumers during the long polar night. Differences in biochemical traits of phytoplankton between ice-free and polar night periods were investigated in biweekly water samples obtained at the Korean “Jang Bogo Station” located in Terra Nova Bay, Antarctica. The average concentration of total Chl-a from phytoplankton dominated by micro-sized species from the entire sampling period was 0.32 μg L–1 (SD = ± 0.88 μg L–1), with the highest concentration of 4.29 μg L–1 in February and the lowest concentration of 0.01 μg L–1 during the ice-covered polar night (April–October) in 2015. The highest protein concentration coincided with the peak Chl-a concentration in February and decreased rapidly relative to the carbohydrate and lipid concentrations in the early part of polar night. Among the different biochemical components, carbohydrates were the predominant constituent, accounting for 69% (SD = ± 14%) of the total particulate organic matter (POM) during the entire study period. The carbohydrate contributions to the total POM markedly increased from 39 ± 8% during the ice-free period to 73 ± 9% during the polar night period. In comparison, while we found a significant negative correlation (r2 = 0.92, p < 0.01) between protein contributions and carbohydrate contributions, lipid contributions did not show any particular trend with relatively small temporal variations during the entire observation period. The substantial decrease in the average weight ratio of proteins to carbohydrates from the ice-free period (mean ± SD = 1.0 ± 0.3) to the ice-covered period (mean ± SD = 0.1 ± 0.1) indicates a preferential loss of nitrogen-based proteins compared to carbohydrates during the polar night period. Overall, the average food material (FM) concentration and calorific contents of FM in this study were within the range reported previously from the Southern Ocean. The results from this study may serve as important background data for long-term monitoring of the regional and interannual variations in the physiological state and biochemical compositions of phytoplankton resulting from future climate change in Antarctica.

Seasonal Variations in the Biochemical Compositions of Phytoplankton and Transparent Exopolymer Particles (TEPs) at Jang Bogo Station (Terra Nova Bay, Ross Sea), 2017–2018

“…In spring and summer, relatively large variations in temperature and salinity were observed with the melting of sea ice, but they were nearly stable during the winter period, as expected. The ice-free period in our study was only 12 days, which is a relatively shorter period compared with a previous study in which the ice-free period lasted more than a month [23].…”

“…Previous studies on the macromolecular composition of phytoplankton in the Ross Sea have been conducted primarily during spring and summer seasons [19][20][21][22]. Only a few studies [23] on the biochemical characteristics of phytoplankton have been previously conducted throughout a single year in the Southern Ocean. The Jang Bogo Station (JBS), located on the coast of Terra Nova Bay (TNB) in the Ross Sea, is one of the overwintering science stations in Antarctica.…”

Spatial Patterns of Macromolecular Composition of Phytoplankton in the Arctic Ocean

“…Although Kim et al [29] reported the exceptionally high-calorie content in the productive polynyas of the Amundsen Sea, the calorie content from our study is in a similar range with the previous studies in the polar oceans (Table 7). According to Kim et al [32], the PRT concentration during the ice-free period in the Ross Sea of the Antarctic Ocean was 20 times increased than that during the ice-covered period, even though CHO or LIP concentrations showed a slight increase (Table 7). If it can be applied in the Arctic Ocean, the PRT concentration than other components might be largely increased under a decrease in sea ice conditions in the Arctic Ocean.…”

“…Fabiano et al [41] reported the calorie content of 1.6 kcal m −3 in the Ross Sea of the Antarctic Ocean. Recently, Kim et al [32] observed the different calorie contents of phytoplankton between the two different periods in the Ross Sea of the Antarctic Ocean, indicating 1.3 kcal m −3 during the ice-free period and 0.6 kcal m −3 during the ice-covered season. Although Kim et al [29] reported the exceptionally high-calorie content in the productive polynyas of the Amundsen Sea, the calorie content from our study is in a similar range with the previous studies in the polar oceans (Table 7).…”

“…Previously, some studies on the macromolecular composition of phytoplankton were reported to understand their physiological conditions in the Polar Oceans [23,[25][26][27][28][29][30][31][32]. The comparison of macromolecular compositions between phytoplankton and microzooplankton was conducted in the Arctic Ocean [27].…”