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Marine Nitrogen Fixation and Phytoplankton Ecology

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Oceans and Coastal Zones".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 35780

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Special Issue Editors

Prof. Dr. Sang Heon Lee

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Guest Editor

Department of Oceanography, Pusan National University, Busan 46700, Republic of Korea
Interests: primary production; phytoplankton physiology; marine ecosystem; Arctic and Antarctic ecosystems; sea ice algae
Special Issues, Collections and Topics in MDPI journals

Dr. P.S. Bhavya

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Guest Editor

Aquatic Systems Biology, TUM School of Life Sciences Weihenstephan, Technical University of Munich
Interests: primary production; aquatic N2 fixation; freshwater mussels; aquatic pollution; climate change

Dr. Bo Kyung Kim

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Guest Editor

Division of Polar Ocean Sciences, Korea Polar Research Institute
Interests: primary production; phytoplankton ecology; particulate organic matter; biochemical compositions; polar ocean ecosystems

Special Issue Information

Dear Colleagues,

Many oceans are currently undergoing rapid changes in environmental conditions, such as warming temperature, acidic water condition, coastal hypoxia, etc. These changes could lead to dramatic changes in the biology and ecology of phytoplankton and consequently impact the entire marine ecosystems and global biogeochemical cycles. Marine phytoplankton can be an important indicator for the changes in marine environments and ecosystems, since they are major primary producers who consolidate solar energy into various organic matters transferred to marine ecosystems throughout the food-webs. Similarly, the only suppliers of biologically fixed N, the N₂ fixers (diazotrophs), are also vulnerable to changing environemtnal conditions. It has been found that polar regions can be introduced to diazotrophic activity under warming conditions and increased N availability can lead to elevated primary productivity. However, if ocean acidification arises, diazotrophic acitvity is observed to have a decresing tendency. To tackle the perplexing response of diazotrophs, a detailed assessment of diazotrophic community response toward the changing environmental conditions need to be recorded thoroughly. Considering the fundamental roles of phytoplankton in marine ecosystems and global biogeochemical cycles, it is important to understand phytoplankton ecology and N₂ fixation as a potential N source in various oceans.

The rationale of this Special Issue is to collect various articles on N₂ fixation and phytoplankton ecology, such as biodiversity, distribution, biomass, photosynthetic traits, biochemical compositions, productivity, etc. of marine phytoplankton in various oceans, including polar oceans. We are especially seeking papers that present ecological and biogeochemical interactions among various phytoplankton communities, including N₂ fixers and environments.

Prof. Dr. Sang Heon Lee
Dr. P.S. Bhavya
Dr. Bo Kyung Kim
Guest Editors

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Keywords

marine N2 fixation
diazotrophs
phytoplankton ecology
biodiversity
biogeochemical interactions
marine ecosystems
polar oceans

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Published Papers (12 papers)

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Editorial

Jump to: Research

5 pages, 217 KiB

Open AccessEditorial

Marine Nitrogen Fixation and Phytoplankton Ecology

by Sang Heon Lee, Panthalil S. Bhavya and Bo Kyung Kim

Water 2022, 14(10), 1638; https://doi.org/10.3390/w14101638 - 20 May 2022

Cited by 1 | Viewed by 1740

Abstract

Many oceans are currently undergoing rapid changes in environmental conditions such as warming temperature, acidic water condition, coastal hypoxia, etc [...] Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

Research

Jump to: Editorial

17 pages, 5886 KiB

Open AccessArticle

Contribution of Small Phytoplankton to Primary Production in the Northern Bering and Chukchi Seas

by Jung-Woo Park, Yejin Kim, Kwan-Woo Kim, Amane Fujiwara, Hisatomo Waga, Jae Joong Kang, Sang-Heon Lee, Eun-Jin Yang and Toru Hirawake

Water 2022, 14(2), 235; https://doi.org/10.3390/w14020235 - 14 Jan 2022

Cited by 4 | Viewed by 2626

Abstract

The northern Bering and Chukchi seas are biologically productive regions but, recently, unprecedented environmental changes have been reported. For investigating the dominant phytoplankton communities and relative contribution of small phytoplankton (<2 µm) to the total primary production in the regions, field measurements mainly for high-performance liquid chromatography (HPLC) and size-specific primary productivity were conducted in the northern Bering and Chukchi seas during summer 2016 (ARA07B) and 2017 (OS040). Diatoms and phaeocystis were dominant phytoplankton communities in 2016 whereas diatoms and Prasinophytes (Type 2) were dominant in 2017 and diatoms were found as major contributors for the small phytoplankton groups. For size-specific primary production, small phytoplankton contributed 38.0% (SD = ±19.9%) in 2016 whereas 25.0% (SD = ±12.8%) in 2017 to the total primary productivity. The small phytoplankton contribution observed in 2016 is comparable to those reported previously in the Chukchi Sea whereas the contribution in 2017 mainly in the northern Bering Sea is considerably lower than those in other arctic regions. Different biochemical compositions were distinct between small and large phytoplankton in this study, which is consistent with previous results. Significantly higher carbon (C) and nitrogen (N) contents per unit of chlorophyll-a, whereas lower C:N ratios were characteristics in small phytoplankton in comparison to large phytoplankton. Given these results, we could conclude that small phytoplankton synthesize nitrogen-rich particulate organic carbon which could be easily regenerated. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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15 pages, 3419 KiB

Open AccessArticle

Spatial Patterns of Macromolecular Composition of Phytoplankton in the Arctic Ocean

by Keyseok Choe, Misun Yun, Sanghoon Park, Eunjin Yang, Jinyoung Jung, Jaejoong Kang, Naeun Jo, Jaehong Kim, Jaesoon Kim and Sang Heon Lee

Water 2021, 13(18), 2495; https://doi.org/10.3390/w13182495 - 11 Sep 2021

Cited by 2 | Viewed by 2447

Abstract

The macromolecular concentrations and compositions of phytoplankton are crucial for the growth or nutritional structure of higher trophic levels through the food web in the ecosystem. To understand variations in macromolecular contents of phytoplankton, we investigated the macromolecular components of phytoplankton and analyzed their spatial pattern on the Chukchi Shelf and the Canada Basin. The carbohydrate (CHO) concentrations on the Chukchi Shelf and the Canada Basin were 50.4–480.8 μg L⁻¹ and 35.2–90.1 μg L⁻¹, whereas the lipids (LIP) concentrations were 23.7–330.5 μg L⁻¹ and 11.7–65.6 μg L⁻¹, respectively. The protein (PRT) concentrations were 25.3–258.5 μg L⁻¹ on the Chukchi Shelf and 2.4–35.1 μg L⁻¹ in the Canada Basin. CHO were the predominant macromolecules, accounting for 42.6% on the Chukchi Shelf and 60.5% in the Canada Basin. LIP and PRT contributed to 29.7% and 27.7% of total macromolecular composition on the Chukchi Shelf and 30.8% and 8.7% in the Canada Basin, respectively. Low PRT concentration and composition in the Canada Basin might be a result from the severe nutrient-deficient conditions during phytoplankton growth. The calculated food material concentrations were 307.8 and 98.9 μg L⁻¹, and the average calorie contents of phytoplankton were 1.9 and 0.6 kcal m⁻³ for the Chukchi Shelf and the Canada Basin, respectively, which indicates the phytoplankton on the Chukchi Shelf could provide the large quantity of food material and high calories to the higher trophic levels. Overall, our results highlight that the biochemical compositions of phytoplankton are considerably different in the regions of the Arctic Ocean. More studies on the changes in the biochemical compositions of phytoplankton are still required under future environmental changes. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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19 pages, 2244 KiB

Open AccessFeature PaperArticle

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

by Sanghoon Park, Jisoo Park, Kyu-Cheul Yoo, Jaeill Yoo, Kwanwoo Kim, Naeun Jo, Hyo-Keun Jang, Jaehong Kim, Jaesoon Kim, Joonmin Kim and Sang-Heon Lee

Water 2021, 13(16), 2173; https://doi.org/10.3390/w13162173 - 8 Aug 2021

Cited by 5 | Viewed by 2591

Abstract

The biochemical composition of particulate organic matter (POM) mainly originates from phytoplankton. Transparent exopolymer particles (TEPs) depend on environmental conditions and play a role in the food web and biogeochemical cycle in marine ecosystems. However, little information on their characteristics in the Southern Ocean is available, particularly in winter. To investigate the seasonal characteristics of POM and TEPSs, seawater samples were collected once every two weeks from November 2017 to October 2018 at Jang Bogo Station (JBS) located on the coast of Terra Nova Bay in the Ross Sea. The total chlorophyll-a (Chl-a) concentrations increased from spring (0.08 ± 0.06 μg L⁻¹) to summer (0.97 ± 0.95 μg L⁻¹) with a highest Chl-a value of 2.15 μg L⁻¹. After sea ice formation, Chl-a rapidly decreased in autumn (0.12 ± 0.10 μg L⁻¹) and winter (0.01 ± 0.01 μg L⁻¹). The low phytoplankton Chl-a measured in this study was related to a short ice-free period in summer. Strong seasonal variations were detected in the concentrations of proteins and lipids (one-way ANOVA test, p < 0.05), whereas no significant difference in carbohydrate concentrations was observed among different seasons (one-way ANOVA test, p > 0.05). The phytoplankton community was mostly composed of diatoms (88.8% ± 11.6%) with a large accumulation of lipids. During the summer, the POM primarily consisted of proteins. The composition being high in lipids and proteins and the high caloric content in summer indicated that the phytoplankton would make a good food source. In winter, the concentrations of proteins decreased sharply. In contrast, relatively stable concentrations of carbohydrates and lipids have been utilized for respiration and long-term energy storage in the survival of phytoplankton. The TEPS values were significantly correlated with variations in the biomass and species of the phytoplankton. Our study site was characterized by dominant diatoms and low Chl-a concentrations, which could have resulted in relatively low TEP concentrations compared to other areas. The average contributions of TEP-C to the total POC were relatively high in autumn (26.9% ± 6.1%), followed by those in summer (21.9% ± 7.1%), winter (13.0% ± 4.2%), and spring (9.8% ± 3.1%). Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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15 pages, 2616 KiB

Open AccessArticle

Picocyanobacterial Contribution to the Total Primary Production in the Northwestern Pacific Ocean

by Ho-Won Lee, Jae-Hoon Noh, Dong-Han Choi, Misun Yun, P. S. Bhavya, Jae-Joong Kang, Jae-Hyung Lee, Kwan-Woo Kim, Hyo-Keun Jang and Sang-Heon Lee

Water 2021, 13(11), 1610; https://doi.org/10.3390/w13111610 - 7 Jun 2021

Cited by 7 | Viewed by 3276

Abstract

Picocyanobacteria (Prochlorococcus and Synechococcus) play an important role in primary production and biogeochemical cycles in the subtropical and tropical Pacific Ocean, but little biological information on them is currently available in the North Pacific Ocean (NPO). The present study aimed to determine the picocyanobacterial contributions to the total primary production in the regions in the NPO using a combination of a dual stable isotope method and metabolic inhibitor. In terms of cell abundance, Prochlorococcus were mostly dominant (95.7 ± 1.4%) in the tropical Pacific region (hereafter, TP), whereas Synechococcus accounted for 50.8%–93.5% in the subtropical and temperate Pacific region (hereafter, SP). Regionally, the averages of primary production and picocyanobacterial contributions were 11.66 mg C m⁻²·h⁻¹ and 45.2% (±4.8%) in the TP and 22.83 mg C m⁻²·h⁻¹ and 70.2% in the SP, respectively. In comparison to the carbon, the average total nitrogen uptake rates and picocyanobacterial contributions were 10.11 mg N m⁻²·h⁻¹ and 90.2% (±5.3%) in the TP and 4.12 mg N m⁻²·h⁻¹ and 63.5%, respectively. These results indicate that picocyanobacteria is responsible for a large portion of the total primary production in the region, with higher contribution to nitrogen uptake rate than carbon. A long-term monitoring on the picocyanobacterial variability and contributions to primary production should be implemented under the global warming scenario with increasing ecological roles of picocyanobacteria. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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21 pages, 41953 KiB

Open AccessFeature PaperArticle

Phytoplankton Community in the Western South China Sea in Winter and Summer

by Changling Ding, Jun Sun, Dhiraj Dhondiram Narale and Haijiao Liu

Water 2021, 13(9), 1209; https://doi.org/10.3390/w13091209 - 27 Apr 2021

Cited by 8 | Viewed by 3539

Abstract

Phytoplankton are known as important harbingers of climate change in aquatic ecosystems. Here, the influence of the oceanographic settings on the phytoplankton community structure in the western South China Sea (SCS) was investigated during two seasons, i.e., the winter (December 2006) and summer (August–September, 2007). The phytoplankton community was mainly composed of diatoms (192 taxa), dinoflagellates (109 taxa), and cyanobacteria (4 taxa). The chain-forming diatoms and cyanobacteria Trichodesmium were the dominants throughout the study period. The phytoplankton community structure displayed distinct variation between two seasons, shifting from a diatom-dominated regime in winter to a cyanobacteria-dominated system in summer. The increased abundance of overall phytoplankton and cyanobacteria in the water column during the summer signifies the impact of nutrient advection due to upwelling and enriched eddy activity. That the symbiotic cyanobacteria–diatom (Rhizosolenia–Richelia) association was abundant during the winter signifies the influence of cool temperature. On the contrary, Trichodesmium dominance during the summer implies its tolerance to increased temperature. Overall, the two seasonal variations within the local phytoplankton community in the western SCS could simulate their community shift over the forthcoming climatic conditions. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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11 pages, 1862 KiB

Open AccessArticle

Physiological Changes and Elemental Ratio of Scrippsiella trochoidea and Heterosigma akashiwo in Different Growth Phase

by Xiaofang Liu, Yang Liu, Md Abu Noman, Satheeswaran Thangaraj and Jun Sun

Water 2021, 13(2), 132; https://doi.org/10.3390/w13020132 - 8 Jan 2021

Cited by 5 | Viewed by 3005

Abstract

The elemental ratios in phytoplankton are important for predicting biogeochemical cycles in the ocean. However, understanding how these elements vary among different phytoplankton taxa with physiological changes remains limited. In this paper, we determine the combined physiological–elemental ratio changes of two phytoplankton species, Scrippsiella trochoidea (Dinophyceae) and Heterosigma akashiwo (Raphidophyceae). Our results show that the cell growth period of S. trochoidea (26 days) was significantly shorter than that of H. akashiwo (32 days), with an average cell abundance of 1.21 × 10⁴ cells·mL⁻¹ in S. trochoidea and 1.53 × 10⁵ cells·mL⁻¹ in H. akashiwo. The average biovolume of S. trochoidea (9.71 × 10³ μm³) was higher than that of H. akashiwo (0.64 × 10³ μm³). The physiological states of the microalgae were assessed based on elemental ratios. The average ratios of particulate organic nitrogen (PON) to chlorophyll-a (Chl-a) and particulate organic carbon (POC) to Chl-a in S. trochoidea (57.32 and 168.16) were higher than those of H. akashiwo (9.46 and 68.86); however, the ratio of POC/PON of the two microalgae was nearly equal (6.33 and 6.17), indicating that POC/Chl-a may be lower when the cell is actively growing. The physiological variation, based on the POC/Chl-a ratio, in different phytoplankton taxa can be used to develop physiological models for phytoplankton, with implications for the marine biogeochemical cycle. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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16 pages, 3491 KiB

Open AccessArticle

Temporal and Spatial Variations of the Biochemical Composition of Phytoplankton and Potential Food Material (FM) in Jaran Bay, South Korea

by Jae Hyung Lee, Won-Chan Lee, Hyung Chul Kim, Naeun Jo, Kwanwoo Kim, Dabin Lee, Jae Joong Kang, Bo-Ram Sim, Jae-Il Kwon and Sang Heon Lee

Water 2020, 12(11), 3093; https://doi.org/10.3390/w12113093 - 4 Nov 2020

Cited by 7 | Viewed by 2373

Abstract

Food material (FM) derived from biochemical components (e.g., proteins, lipids, and carbohydrates) of phytoplankton can provide important quantitative and qualitative information of the food available to filter-feeding animals. The main objective of this study was to observe the seasonal and spatial variations of the biochemical compositions of phytoplankton and to identify the major controlling factors of FM as a primary food source in Jaran Bay, a large shellfish aquaculture site in South Korea. Based on monthly sampling conducted during 2016, significant monthly variations in the depth-integrated concentrations of major inorganic nutrients and chlorophyll a within the euphotic water column and a predominance (49.9 ± 18.7%) of micro-sized phytoplankton (>20 μm) were observed in Jaran Bay. Carbohydrates were the dominant biochemical component (51.8 ± 8.7%), followed by lipids (27.3 ± 3.8%) and proteins (20.9 ± 7.4%), during the study period. The biochemical compositions and average monthly FM levels (411.7 ± 93.0 mg m⁻³) in Jaran Bay were not consistent among different bays in the southern coastal region of South Korea, possibly due to differences in controlling factors, such as environmental and biological factors. According to the results from multiple linear regression, the variations in FM could be explained by the relatively large phytoplankton and the P* (PO₄³⁻ − 1/16 × NO₃⁻) and NH₄⁺ concentrations in Jaran Bay. The macromolecular compositions and FM, as alternatives food source materials, should be monitored in Jaran Bay due to recent changes in nutrient concentrations and phytoplankton communities. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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22 pages, 4528 KiB

Open AccessArticle

In Situ Rates of Carbon and Nitrogen Uptake by Phytoplankton and the Contribution of Picophytoplankton in Kongsfjorden, Svalbard

by Bo Kyung Kim, Hyoung Min Joo, Jinyoung Jung, Boyeon Lee and Sun-Yong Ha

Water 2020, 12(10), 2903; https://doi.org/10.3390/w12102903 - 17 Oct 2020

Cited by 9 | Viewed by 3109

Abstract

Rapid climate warming and the associated melting of glaciers in high-latitude open fjord systems can have a significant impact on biogeochemical cycles. In this study, the uptake rates of carbon and nitrogen (nitrate and ammonium) of total phytoplankton and picophytoplankton (<2 μm) were measured in Kongsfjorden in early May 2017 using the dual stable isotope technique. The daily uptake rates of total carbon and nitrogen ranged from 0.3 to 1.1 g C m⁻² day⁻¹, with a mean of 0.7 ± 0.3 g C m⁻² day⁻¹, and 0.13 to 0.17 g N m⁻² day⁻¹, with a mean of 0.16 ± 0.02 g N m⁻² day⁻¹. Microphytoplankton (20–200 μm) accounted for 68.1% of the total chlorophyll a (chl-a) concentration, while picophytoplankton (<2 μm) accounted for 19.6% of the total chl-a, with a high contribution to the carbon uptake rate (42.9%) due to its higher particulate organic carbon-to-chl-a ratio. The contributions of picophytoplankton to the total nitrogen uptake rates were 47.1 ± 10.6% for nitrate and 74.0 ± 16.7% for ammonium. Our results indicated that picophytoplankton preferred regenerated nitrogen, such as ammonium, for growth and pointed to the importance of the role played by picophytoplankton in the local carbon uptake rate during the early springtime in 2017. Although the phytoplankton community, in terms of biovolume, in all samples was dominated by diatoms and Phaeocystis sp., a higher proportion of nano- and picophytoplankton chl-a (mean ± SD = 71.3 ± 16.4%) was observed in the relatively cold and turbid surface water in the inner fjord. Phytoplankton production (carbon uptake) decreased towards the inner fjord, while nitrogen uptake increased. The contrast in carbon and nitrogen uptake is likely caused by the gradient in glacial meltwater which affects both the light regime and nutrient availability. Therefore, global warming-enhanced glacier melting might support lower primary production (carbon fixation) with higher degrees of regeneration processes in fjord systems. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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18 pages, 3805 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Variation in Phytoplankton Community Driven by Environmental Factors in the Northern East China Sea

by Yejin Kim, Seok-Hyun Youn, Hyun Ju Oh, Jae Joong Kang, Jae Hyung Lee, Dabin Lee, Kwanwoo Kim, Hyo Keun Jang, Junbeom Lee and Sang Heon Lee

Water 2020, 12(10), 2695; https://doi.org/10.3390/w12102695 - 26 Sep 2020

Cited by 14 | Viewed by 3933

Abstract

The East China Sea (ECS) is the largest marginal sea in the northern western Pacific Ocean. In comparison to various physical studies, little information on the seasonal patterns in community structure of phytoplankton is currently available. Based on high performance liquid chromatography (HPLC) pigment analysis, spatiotemporal variations in phytoplankton community compositions were investigated in the northern ECS. Water temperature and salinity generally decreased toward the western part of the study area but warmer conditions in August led to strong vertical stratification of the water column. In general, major inorganic nutrient concentrations were considerably higher in the western part with a shallow water depth, and consistent with previous results, had no discernable vertical pattern during our observation period except in August. This study also revealed PO₄-limited environmental conditions in May and August. The monthly averaged integral chlorophyll-a concentration varied seasonally, highest (35.2 ± 20.22 mg m⁻²) in May and lowest (5.2 ± 2.54 mg m⁻²) in February. No distinct vertical differences in phytoplankton community compositions were observed for all the sampling seasons except in August when cyanobacteria predominated in the nutrient-deficient surface layer and diatoms prevailed at deep layer. Canonical correlation analysis results revealed that nutrient distribution and the water temperature were the major drivers of the vertical distribution of phytoplankton communities in August. Spatially, a noticeable difference in phytoplankton community structure between the eastern and western parts was observed in November with diatom domination in the western part and cyanobacteria domination in the eastern part, which were significantly (p < 0.01) correlated with water temperature, salinity, light conditions, and nutrient concentrations. Overall, the two major phytoplankton groups were diatoms (32.0%) and cyanobacteria (20.6%) in the northern ECS and the two groups were negatively correlated, which holds a significant ecological meaning under expected warming ocean conditions. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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18 pages, 2940 KiB

Open AccessEditor’s ChoiceArticle

Characteristics of the Biochemical Composition and Bioavailability of Phytoplankton-Derived Particulate Organic Matter in the Chukchi Sea, Arctic

by Bo Kyung Kim, Jinyoung Jung, Youngju Lee, Kyoung-Ho Cho, Jong-Ku Gal, Sung-Ho Kang and Sun-Yong Ha

Water 2020, 12(9), 2355; https://doi.org/10.3390/w12092355 - 21 Aug 2020

Cited by 8 | Viewed by 2964

Abstract

Analysis of the biochemical composition (carbohydrates, CHO; proteins, PRT; lipids, LIP) of particulate organic matter (POM, mainly phytoplankton) is used to assess trophic states, and the quantity of food material is generally assessed to determine bioavailability; however, bioavailability is reduced or changed by enzymatic hydrolysis. Here, we investigated the current trophic state and bioavailability of phytoplankton in the Chukchi Sea (including the Chukchi Borderland) during the summer of 2017. Based on a cluster analysis, our 12 stations were divided into three groups: the southern, middle, and northern parts of the Chukchi Sea. A principal component analysis (PCA) revealed that relatively nutrient-rich and high-temperature waters in the southern part of the Chukchi Sea enhanced the microphytoplankton biomass, while picophytoplankton were linked to a high contribution of meltwater derived from sea ice melting in the northern part of the sea. The total PRT accounted for 41.8% (±7.5%) of the POM in the southern part of the sea, and this contribution was higher than those in the middle (26.5 ± 7.5%) and northern (26.5 ± 10.6%) parts, whereas the CHO accounted for more than half of the total POM in the northern parts. As determined by enzymatic hydrolysis, LIP were more rapidly mineralized in the southern part of the Chukchi Sea, whereas CHO were largely used as source of energy for higher trophic levels in the northern part of the Chukchi Sea. Specifically, the bioavailable fraction of POM in the northern part of the Chukchi Sea was higher than it was in the other parts. The findings indicate that increasing meltwater and a low nutrient supply lead to smaller cell sizes of phytoplankton and their taxa (flagellate and green algae) with more CHO and a negative effect on the total concentration of POM. However, in terms of bioavailability (food utilization), which determines the rate at which digested food is used by consumers, potentially available food could have positive effects on ecosystem functioning. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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14 pages, 1042 KiB

Open AccessArticle

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

by Jae Hyung Lee, Won Chan Lee, Hyung Chul Kim, Naeun Jo, Hyo Keun Jang, Jae Joong Kang, Dabin Lee, Kwanwoo Kim and Sang Heon Lee

Water 2020, 12(4), 1057; https://doi.org/10.3390/w12041057 - 8 Apr 2020

Cited by 9 | Viewed by 3058

Abstract

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. Full article

(This article belongs to the Special Issue Marine Nitrogen Fixation and Phytoplankton Ecology)

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