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Tintinnids are a major group of planktonic ciliates. To determine a desirable sampling interval for analyzing the temporal dynamics of tintinnids, intensive monitoring was conducted on the southern coast of Korea. The mean sampling interval was 1.5 days. The abundance of tintinnids were analyzed by microscopy. The high- frequency temporal pattern showed detailed changes in concentrations and a distinct seasonality in the abundance of tintinnids. An optimal monitoring interval for tintinnid abundance estimations was determined by polynomial interpolation and statistical analysis, involving three steps, namely, interpolation by increasing the number of sampling intervals, graphical analysis with interpolated data and determination of the changepoint depending on the interpolated results. The value of changepoint was 7 days, indicating the optimal monitoring interval. Therefore, data collection at weekly intervals is sufficient and desirable for tracing the temporal signals of tintinnid ecology and its long-term trends.

Acartia erythraea, a copepod species commonly found in the summer, was sampled weekly using a conical net, in Gamak Bay (southern Korea) from 19 July to 14 November 2013. Egg production rate (EPR) and hatching success rate (HS) were estimated weekly during the study period, for egg types with distinct surface morphologies, i.e. smooth or spiny. EPR ranged from 1.0 to 25.0 eggs female−1 day−1 with a mean of 12.0 eggs female−1 day−1. The weight-specific growth rate (WSGR) ranged from 0.01 to 0.19 day−1 with a mean value of 0.09 day−1. Of these, all the eggs were smooth until August, whereas spiny eggs were produced from September, and the spiny eggs contributed 88% of the total eggs in November. Both egg types hatched within 12 to 48 h, and the average HS was 80% or higher. The EPR and WSGR were significantly related to water temperature but weakly related to chlorophyll-a concentration. Contrary to previous studies, our findings suggest that it is impossible to determine whether an egg is subitaneous or diapause based on the egg surface structure. Spines on the surface of A. erythraea eggs in Gamak Bay could be an adaptation to seasonal variations and a rapidly changing coastal environment.

Characterizing ecological relationships between viruses, bacteria and phytoplankton in the ocean is critical to understanding the ecosystem; however, these relationships are infrequently investigated together. To understand the dynamics of microbial communities and environmental factors in harmful algal blooms (HABs), we examined the environmental factors and microbial communities during Akashiwo sanguinea HABs in the Jangmok coastal waters of South Korea by metagenomics. Specific bacterial species showed complex synergistic and antagonistic relationships with the A. sanguinea bloom. The endoparasitic dinoflagellate Amoebophrya sp. 1 controlled the bloom dynamics and correlated with HAB decline. Among nucleocytoplasmic large DNA viruses (NCLDVs), two Pandoraviruses and six Phycodnaviruses were strongly and positively correlated with the HABs. Operational taxonomic units of microbial communities and environmental factors associated with A. sanguinea were visualized by network analysis: A. sanguinea–Amoebophrya sp. 1 (r = .59, time lag: 2 days) and A. sanguinea–Ectocarpus siliculosus virus 1 in Phycodnaviridae (0.50, 4 days) relationships showed close associations. The relationship between A. sanguinea and dissolved inorganic phosphorus relationship also showed a very close correlation (0.74, 0 day). Microbial communities and the environment changed dynamically during the A. sanguinea bloom, and the rapid turnover of microorganisms responded to ecological interactions. A. sanguinea bloom dramatically changes the environments by exuding dissolved carbohydrates via autotrophic processes, followed by changes in microbial communities involving host‐specific viruses, bacteria and parasitoids. Thus, the microbial communities in HAB are composed of various organisms that interact in a complex manner.

In this study, we investigate the distribution of calanoid copepod eggs in the sediments of Masan Bay (South Sea, Korea), in which hypoxic conditions occur every summer. In August (2011), hypoxia was observed at all stations, while normoxia was observed in April (2012). The pH and hydrogen sulphide concentration at the sediment-water interface in the inner bay during August were 7.7 and &gt, 20 mol L−1, respectively, and there was no significant difference between the stations in April. The abundance of eggs in the sediment ranged from 0.69 to 1.49 × 106 eggs m−2 in August, and from 0.59 to 1.08 × 106 eggs m−2 in April. Notably, the proportion of abnormal eggs was high (a maximum of 77.1%) in August, and a uniform distribution of normal eggs (&gt, 80%) was observed in April. A generation of abnormal eggs hatched with deformed nauplii in Masan Bay during the summer, and a failure to hatch was likely due to the high H2S concentration and low pH caused by hypoxia. In this paper, we discuss the effects of hypoxia and seabed environments on the hatching success of calanoid copepod eggs.

To investigate the removal efficiency of the grinding device (GD) as a potential replacement for the pretreatment filtration device of ballast water, solid grinding and viability experiment were conducted according to a treatment flow rate of 5 tons (Pilot test, PT), and 200 tons (Full-scale test, FST) per h. The solid grinding effect was observed in the particle size of ≥25 μm. Under the high-turbidity conditions (&gt, 300 mg L−1), no change in pressure (0.98 kgf/cm2) or stoppage in the GD were observed. The removal efficiency of the GD for &gt, 100 μm organism was determined to be 100% in both PT and FST, whereas the removal efficiency was determined to be 93% and 87% in the PT and FST, respectively, for the &lt, 100 μm organism. There was no statistically significant change in the removal efficiency stored within 2 h after passing through the GD, while the removal efficiency was determined to be ≥99% in the sample stored for 120 h. Future study is necessary to determine the additional removal efficiency according to the storage period after passing through the GD, but the GD might be utilized as the pretreatment device for the ballast water management system.

An in situ mesocosm experiment was performed to investigate the combined effects of ocean acidification and warming on the coastal phytoplankton standing stock and species composition of a eutrophic coastal area in the temperate-subtropical region. Experimental treatments of natural seawater included three CO2 and two temperature conditions (present control: ~400 &mu, atm CO2 and ambient temperature, acidification conditions: ~900 &mu, atm CO2 and ambient temperature, and greenhouse conditions: ~900 &mu, atm CO2 and ambient temperature +3 &deg, C). We found that increased CO2 concentration benefited the growth of small autotrophic phytoplankton groups: picophytoplankton (PP), autotrophic nanoflagellates (ANF), and small chain-forming diatoms (DT). However, in the greenhouse conditions, ANF and DT abundances were lower compared with those in the acidification conditions. The proliferation of small autotrophic phytoplankton in future oceanic conditions (acidification and greenhouse) also increased the abundance of heterotrophic dinoflagellates (HDF). These responses suggest that a combination of acidification and warming will not only increase the small autotrophic phytoplankton standing stock but, also, lead to a shift in the diatom and dinoflagellate species composition, with potential biogeochemical element cycling feedback and an increased frequency and intensity of harmful algal blooms.

Background: Characterising ecological relationships between viruses, bacteria, and phytoplankton in the ocean are critical to understanding the ecosystem, yet these relationships are infrequently investigated together. To understand the dynamics of microbial communities and environmental factors in harmful algal blooms (HABs), we examined the environmental factors and microbial communities during Akashiwo sanguinea HABs in the Jangmok coastal waters of South Korea by metagenomics. Results: Specific bacterial communities showed synergistic and antagonistic relationships with A. sanguinea bloom. Endoparasitic dinoflagellate Amoebophrya sp. 1 controlled the bloom dynamics, as an increase in their abundance was correlated with HAB decline. In the nucleocytoplasmic large DNA viruses, abundance of Pandoraviridae increased following an increase in HAB. Operational taxonomic units and environmental factors associated with A. sanguinea were also visualized by network analysis: A. sanguinea-Amoebophrya sp. 1 (r=0.81, Time-lag: 2 day) and A. sanguinea-Pandoravirus dulcis (0.64, 0 day) relationships showed close association. A. sanguinea-dissolved organic carbon and -dissolved inorganic phosphorus relationships were also very closely correlated (each 0 day time-lag, respectively). Conclusions: Microbial communities and the environment dynamically and complexly changed in A. sanguinea bloom, and a rapid turnover of microorganisms could respond to ecological interactions. A. sanguinea bloom dramatically changes the environments through their exudation of dissolved carbohydrates by autotrophic processes, followed by changes in microbial communities involving host-specific viruses, bacteria, and parasitoids. Thus, microbial communities in HAB ecology are composed of various organisms and they interact in a complex way. Therefore, to interpret their ecosystem, the complex reactions among various microorganisms should be studied rather than studying a simple 1:1 reaction, such as a prey-predator interaction.

Since the ban of tributyltin in antifouling paints, many alternative biocides have been introduced to prevent settlement and growth of marine organisms on ship hulls. Zinc pyrithione (ZnPT) is one of the most frequently used alternative biocides in antifouling paints. This paper reviewed the overall chemical properties, toxicological characteristics, and environmental fates of ZnPT, as well as the analytical challenges of studying pertinent processes. ZnPT is generally toxic to a wide range of marine organisms, including algae, bivalves, sea urchins, polychaetes, crustaceans, and fish, typically at μg/L levels. ZnPT can be transchelated into other compounds in the presence of metal ions, and photodegrades when exposed to UV light. ZnPT is also reported to be biodegraded or hydrolyzed forming several metabolites of their own toxicity and stability. However, ZnPT accumulates in the water column or sediment, if it does not degrade at certain environmental conditions. To determine potential risks caused by ZnPT in the marine environment, studies have evaluated the environmental distribution of ZnPT with various chromatographic or voltammetry methods. Unfortunately, rapid transchelation and degradation of ZnPT in both the marine environment and laboratory interfered with most of the methods employed, making it difficult to evaluate its environmental distribution. More robust and sensitive analytical methods need to be developed to reliably describe the environmental release and distribution of ZnPT. To comprehensively understand the risk posed by the input of ZnPT into the marine environment, total degradation processes and its potential products also need to be adequately addressed.

Little is known regarding how harmful algal bloom species respond to different temperatures in terms of fatty acid production. This study examined the effects of temperature on the growth rates, cell volumes, and fatty acid concentrations and compositions of four harmful algal bloom species (HABs), Akashiwo sanguinea, Alexandrium tamarense, Chattonella ovata, and Prorocentrum minimum. The HABs species were cultured at 15, 20, 25, and 30°C in a nutrient-enriched medium. Three of the species maintained optimal growth rates over a wide range of temperatures, but A. tamarense did not. The cell volumes of each species showed little change over the temperature range. The total fatty acid concentrations in A. sanguinea, A. tamarense and C. ovata decreased as the temperature increased, but P. minimum showed no trend in this respect. Polyunsaturated fatty acids (PUFAs), the key biochemical components that maintain cell membrane fluidity and which are associated with toxicity, decreased in both concentration and proportion of total fatty acids as temperature increased, except in A. sanguinea, in which the proportion of PUFAs to the total fatty acids increased. These reductions in PUFA concentration and proportion could reduce cell membrane fluidity and toxicity in HABs; however, enhanced growth and/or ruptured cells, which are considered more toxic than intact cells, could compensate for the reduced per-cell toxicity. This phenomenon might impact on the marine ecosystem and aquaculture industry.

We investigated >50-µm marine planktonic organisms (mainly zooplankton) using a bongo net in Masan Bay and Jangmok Bay in order to harvest 75% of natural communities based on Phase-II approval regulations by the United States Coast Guard (USCG). The concentrated volume (in 1 ton) and abundance of zooplankton were 1.8×10 7 ind. ton -1 and 2.3×10 7 ind. ton -1 , and their survival rates were 82.6% and 80.1%, respectively. The community structure in Jangmok Bay was similar to that in Masan Bay, and dominant species were adult and immature groups (stage IV) of genus Acartia. Harvested populations were inoculated in a 500-ton test tank. Although the population abundances were 6.0×10 4 ind. ton -1 for both bay samples, the mortality rates were higher in the Masan Bay population (32%) than the Jangmok Bay population (20%). We considered the reason to be that there were 30% more immature individuals of Acartia from Masan Bay than from Jangmok Bay. The younger population may have been greatly stressed by the moving process and netting gear. After applying a Ballast Water Treatment System (BWTS) using a sample form Jangmok Bay, the mortality rates in the treatment groups were found to be 100% after 0 days and 5 days, implying that the BWTS worked well. During the winter season, the zooplankton concentration method alone did not easily satisfy the approval standards of USCG Phase II (> 10 × 10 4 ind. ton -1 in the 500 ton tank). Increasing the netting frequency and additional fishing boats may be helpful in meeting the USCG Phase II biological criteria.

In order to prevent the spread of non-indigenous aquatic species through the ballast water in commercial ships, International Maritime Organization (IMO) adopted in 2004 the International Convention for Control and Management of Ship`s Ballast Water and Sediments. The Convention mandates treatment of ballast water for most transoceanic voyages and its confirmation of treatment is made with plankton live/dead assay. Fluorescein diacetate assay (FDA), which produces bright green light for live phytoplankton, has been a de facto standard method to determine the survival of marine plankton, but its staining efficacy has been in dispute. In the present study, we examined the limitation of FDA, and compared its efficacy with Neutral red (NR) staining, another promising assay and widely used especially for zooplankton mortality. For all phytoplankton species studied in the present study, except Ditylum brightwellii, the staining efficiency was

We examined the combined impacts of future increases of CO2 and temperature on the growth of four marine diatoms (Skeletonema costatum, Chaetoceros debilis, Chaetoceros didymus, Thalassiosira nordenskioeldii). The four strains were incubated under four different conditions: present (pCO2: 400ppm, temperature: 20℃), acidification (pCO2: 1000ppm, temperature: 20℃), global warming (pCO2: 400ppm, temperature: 25℃), and greenhouse (pCO2: 1000ppm, temperature: 25℃) conditions. Under the condition of higher temperatures, growth of S. costatum was suppressed, while C. debilis showed enhanced growth. Both C. didymus and T. nodenskioldii showed similar growth rates under current and elevated temperature. None of the four species appeared affected in their cell growth by elevated CO2 concentrations. Chetoceros spp. showed increase of pH per unit fluorescence under elevated CO2 concentrations, but no difference in pH from that under current conditions was observed for either S. costatum or T. nodenskioeldii, implying that Chetoceros spp. can take up more CO2 per cell than the other two diatoms. Our results of cell growth and pH change per unit fluorescence suggest that both C. debilis and C. didymus are better adapted to future oceanic conditions of rising water temperature and CO2 than are S. costatum and T. nodenskioeldii.

Zooplankton community in the major ports of Korea, which were characterized by a specific marine environmental condition during summer, was studied. Water temperature in the ports of western areas was higher and while those in the East Sea was lower. Contradictorily, the salinity was lowest in the western areas, while being highest in the eastern area. The Chl-a concen- tration was highest in the southern areas and lowest in the eastern one. Zooplankton taxa were most diverse in the western areas and simplest in the eastern one. Copepods predominantly occurred in the western areas, but their abundance relatively decreased in the southern and eastern areas. Cluster analysis revealed that copepod communities were classified into 3 summit groups, the western, southern and eastern areas. The results indicate that zooplankton communi- ties in Korean ports may be affected by biological factors like Chl-a concentration in addition to environmental factor such as temperature and salinity.

To investigate the cause of morphological change of Scrippsiella trochoidea cysts and its ecological significance in the hypoxic zone of a eutrophied area, the effect of pH on the morphology and viability of S. trochoidea cysts was studied. In the acidification experiment, the dissolution of calcareous spines of S. trochoidea cysts was observed at less than pH 7.39, indicating that the morphological change of S. trochoidea cysts is caused by the low pH levels in acidic sediments of hypoxic zone. After being exposed to intense acidic environments, cysts of S. trochoidea without calcareous spines were able to germinate; however, they seem to be easily linked to degradation in the sediments. These results suggest that the survival of S. trochoidea cysts is being threatened by environmental conditions in the hypoxic zone of eutrophied area.

Weekly to biweekly measurements of the in situ egg production rate (EPR) of a dominant warm-temperature copepod (Paracalanus parvus) were made from August 2009 to July 2010 at a coastal station, together with analysis of environmental and food conditions. In addition, the results of a 10-year survey of P. parvus abundance and environmental parameters are presented. EPR ranged from ,1 to 24 eggs female 1 day 1 with a mean of four eggs female 1 day . The calculated female growth rate was highest in August at 0.26 day , coinciding with the highest EPR, but growth was very low in winter (,0.01 day ). The EPR and weight-specific female growth of P. parvus were both strongly related to water temperature, but weakly associated with chlorophyll-a (Chl-a) concentration. However, large variability was noticed in the summer (.208C) values of these relationships, with a negative relationship between EPR and salinity. This seemed to be related to local input, which may provide heterotrophic food from terrigenous sources. Observed high abundances during times of extremely low female growth and low EPR suggest that the populations might be sustained by supplements from offshore, where their growth condition could be better (e.g. higher water temperature). Future warming would contribute to a trend of increasing abundance of this copepod, especially of non-summer populations.

A variety of advanced electrode structures have been developed lately to address the intrinsic drawbacks of lithium sulfur batteries, such as polysulfide shuttling and low electrical conductivity of elemental sulfur. Nevertheless, it is still desired to find electrode structures that address those issues through an easy synthesis while securing large sulfur contents (i.e., > 70 wt %). Here, we report an orthogonal, "one-pot" synthetic approach to prepare a sulfur-embedded polybenzoxazine (S-BOP) with a high sulfur content of 72 wt %. This sulfur-embedded polymer was achieved via thermal ring-opening polymerization of benzoxazine in the presence of elemental sulfur, and the covalent attachment of sulfur to the polymer was rationally directed through the thiol group of benzoxazine. Also, the resulting S-B OP bears a homogeneous distribution of sulfur due to in situ formation of the polymer backbone. This unique internal structure endows S-BOP with high initial Coulombic efficiency (96.6%) and robust cyclability (92.7% retention after 1000 cycles) when tested as a sulfur cathode. Refereed/Peer-reviewed

The algicidal effects of the thiazolidinedione derivative TD49 on Heterosigma akashiwo and Chattonella marina (Raphidophyceae) were assessed, and the response of the planktonic community and environment to the algicide was evaluated in a microcosm, quantifying 12 L. The abundance of over 80 % of H. akashiwo and C. marina declined in a day significantly in microcosms to which TD49 was added (final concentration 2 μM), and this was correlated with an abrupt decline in the culture pH. The number of protists (i.e., ciliates) other than H. akashiwo and C. marina gradually increased with time in the TD49 treatments, implying that the decline in numbers of H. akashiwo and C. marina cells resulting from TD49 treatment was a major factor in the growth of the other organisms. However, TD49 may be toxic to aquatic zooplankton communities, even though it is a highly selective algicide for harmful algae bloom species. The study indicates that TD49 is an effective agent for the control for H. akashiwo and C. marina blooms in enclosed and eutrophic water bodies.

The purpose of this study is to quantitatively analyze the social welfare value given to the designated rural settlement zone by the resident-participated site unit plan that the City of Cheongju is newly attempting to draft. Firstly, the costs and benefits from the site unit planning were estimated. Secondly, through literature review especially focussed on the benefit and cost estimation, on-site questionnaire was designed, and then sample residents of the qualifying sites were asked about their willingness to pay, which could make it possible to estimate the monetary value of its benefits by the contingent valuation method (CVM). Finally, the present value of net benefits (PVNB) was estimated through the derived costs and benefits. As a result of analysis, firstly, the present value of net benefits (PVNB) was found to be 7,641 billion won, which indicated that the implementation of district-unit plan would be able to cause sufficient social welfare value for the effected residents. Secondly, in examining the result of individual average amount for willingness to pay through the CVM, the area that benefited the most was found to be the road improvement. Thirdly, as a result of sensitivity analysis, the parameter with the most effects was the discount rate, which suggested that, in carrying out public projects, excessive market interest rates would not be appropriate.

To evaluate the algicidal impact of a newly developed algicide thiazolidinedione derivative,TD49, on dinophyceae Akashiwo sanguinea in aquatic ecosystems, tentative culture experiments for thetarget species were conducted in small (SS), middle (MS), and large scale (LS) culture vessels. When TD49was introduced at the final concentration of 2 µM in SS and MS, as well as 1 µM in LS, the abundance of A.sanguinea decreased significantly in all the treatments. On the other hand, total phytoplankton abundance,except A. sanguinea in the TD49 treatments, gradually increased with culture time, which implies that a celldestruction of A. sanguinea by TD49 is a major cause of the population growth by other phytoplanktonspecies. Also, A. sanguinea was easily destroyed, which was likely to be a source of extracellularsubstances. In particular, a pH decrease was significant in the treatments than in the control, which indicatesthat the water in the treatments has been acidified, due to an increase in the heterotrophic metabolisms ofbacteria and degradation of A. sanguinea cells. Our results indicate that the TD49 substance is the potentialagents for the control of A. sanguinea in the enclosed and eutrophic water bodies.Key words :Akashiwo sanguinea, algicidal effect, thiazolidinedione, ecosystem*Corresponding author. E-mail : yokim@kordi.re.kr

Worldwide development of harmful algal blooms causes serious problem for public health and fisheries industries. To evaluate the algicidal impact on the harmful algae bloom species in aquatic ecosystems of coast, a new algicide thiazolidinedione derivative (TD49) were tentatively examined in the growth stages (i.e., lag, logarithmic and stationary phase) of rapidophyceae , and sp..Three strains could easily destroy in the lag phase due to relatively weak cell walls than those of the logarithmic and stationary phase. It is thought that inoculation of TD49 substances into initial or developmental natural blooms with a threshold concentration () can maximize the algicidal activity. Also, bio-chemical assays revealed that the algicidal substances from all culture strains were likely to be extracellular substances because those cells have easily destroyed in cell walls. On the other hand, natural zooplankton communities were influenced within the exposure experiments of , which is showed the maximum algcidal activity of tested organisms. These results indicate that although the TD49 substance is potential agents for the control of , and sp. in the enclosed eutrophic bay and coastal water, more detailed research of acute toxicity effect on high trophic organism in marine ecosystems need to be conducted.

The annual variation of mesozooplankton community in the Jangmok harbor of Jinhae Bay was studied in relation to environmental variables. Sampling was carried out weekly from January to December 2009. During the study periods, mesozooplankton community consisted of 44 taxa and the annual mean abundance was 8308 inds. m?³. The maximum abundance was observed to be 50043 inds. m?³ in August and the minimum in April with 1013 inds. m?³. Of these, Penilia avirostris, cirripedia larvae, Evadne tergestina, Acartia omorii, Oikopleura spp., Paracalanus parvus s. l., Eurytemora pacifica, Podon spp., Oithona spp., and Acartia steueri were observed as dominant species in Jangmok bay and they also contributed to 79% of total mesozooplankton. According to non-metric multidimensional scaling (nMDS) and cluster analysis based on the mesozooplankton community data from each season, the community was divided into three groups. The first group included appearence species in winter and spring season, which is mainly dominated the copepod such as A. omorii and E. pacifica. The second and third group was composed with observed species in summer and autumn, respectively. Based on the SIMPER (similarity percentages), P. avirostris in summer and cirripedia larvae in autumn were significantly dominated. Our results indicate that although the mesozooplankton abundances in Jangmok harbor fluctuated abruptly, its annual variation was strongly influenced by water temperature.

In order to assess the survival success of microphytoplankton species in ship ballast water, we examined microphytoplankton diversity from international commercial ships berthed at Ulsan and Pyeongtaek Ports, Korea, and also subjected them to laboratory studies. The ages of ballast water in each ship ranged from 1 to 365 days. Vessels originated from coastal China (Weihai, Lianyunsang and Shanghai), Chile, and from the Yellow and Pacific Oceans. The numbers of species and phytoplankton standing crops in uploaded ballast water were significantly related to the age of ballast water. The most diverse taxonomic group was diatoms. In the laboratory study, the value of in vivo fluorescence in M/V Spring Lyra gradually increased with increasing nutrients such as nitrate and phosphate. Phytoplankton in new (9 days), medium (31 days) and old (365 days) ballast water successfully survived under typical nutrient condition of port water and F/2 medium at 15oC and 20oC, whereas phytoplankton in ballast water treatment did not survive, regardless of optimal temperature. Colonization process was dominated by diatoms; Skeletonema coastatum for M/V Spring Lyra, Thalassiosira pseudonana and Thalassiosira for M/V Han Yang, Thalassiosira pacifica and Odontella aurita for M/V Modern Express, and Chaetoceros pseudocurvisetus and Pseudo-nitzschia seriata for M/V Asian Legend. The successful establishment of non-native species was also related to nutrient richness. Our laboratory design can be applied as a practical tool to assess the survivability of invasive microphytoplankton introduced into local waters of Ulsan and Pyeongtaek.

Oceanic dimethylsulfide (DMS) released to the atmosphere affects the Earth’s radiation budget through the production and growth of cloud condensation nuclei over the oceans. However, it is not yet known whether this negative climate feedback mechanism will intensify or weaken in oceans characterized by high CO2 levels and warm temperatures. To investigate the effects of two emerging environmental threats (ocean acidification and warming) on marine DMS production, we performed a perturbation experiment in a coastal environment. Two sets of CO2 and temperature conditions (a pCO2 of ∼900 ppmv at ambient temperature conditions, and a pCO2 of ∼900 ppmv at a temperature ∼3 °C warmer than ambient) significantly stimulated the grazing rate and the growth rate of heterotrophic dinoflagellates (ubiquitous marine microzooplankton). The increased grazing rate resulted in considerable DMS production. Our results indicate that increased grazing-induced DMS production may occur in high CO2 oceans in the future.

Grazing impacts of calanoid copepods on size-fractionated phytoplankton biomass [chlorophyll (Chl)-a] were measured in Jangmok Bay, Geoje Island, Korea, monthly from November 2004 to October 2005. The ingestion rate of calanoid copepods on total phytoplankton biomass ranged between 1 and 215 ng Chl-a copepod−1 day−1 during bottle incubations. Results indicated that microphytoplankton (> 20 μm) was the primary food source for calanoid copepods in grazing experiments on 3 phytoplankton size categories ( 20 μm). The ingestion rate on microphytoplankton showed a significant increase (r = 0.93, p < 0.01) with Chl-a concentration. Nanophytoplankton (3–20 μm) showed a negative ingestion rate from June 2005 to October 2005, but the reason is not completely understood. Calanoid copepods were unable to feed efficiently on picophytoplankton (< 3 μm) due to unfavorable size. Calanoid copepods removed between 0.1% and 27.7% (average, 3.6 ± 15.8%) of the phytoplankton biomass daily during grazing experiments. Grazing pressure was high in winter and early spring (January–March: 15.6–27.7%), while low in summer (June–August: −33.1–0.0%) and autumn (September–November: −1.4–5.1%). Results suggest that calanoid copepods play an important role in controlling the biomass and size structure of phytoplankton in winter and early spring.

Bacterioplankton communities in a semi-closed bay (Jangmok Bay, South Korea) were analysed using a 16S rDNA multiplex 454 pyrosequencing approach. Diversity and operational taxonomic units of bacterioplankton communities in the Jangmok Bay are highest in cold water seasons and lowest in warm water ones. During cold seasons, α-proteobacteria respond rapidly to pulses of the concentration of inorganic nutrients, while γ-proteobacteria during warm water seasons are the most active type of bacterioplankton resent in the prevailing conditions, which include high dissolved organic carbon, chemical oxygen demand and primary production. Cyanobacteria, a minor group constituting 4.58% of the total bacterioplankton, are more abundant at low temperature. Flavobacteria are more abundant in nutrient-rich conditions and the abundance of this group also demonstrated a delayed decline following summer phytoplankton blooms. The pronounced seasonal oscillations in phosphorus concentration and temperature exert strong selection pressure on bacterioplankton communities.

We examine the effects of seawater pCO2 concentration of 25, 41, and 76 kPa (250, 400, and 750 matm) on the growth rate of a natural assemblage of mixed phytoplankton obtained from a carefully controlled, 14-d mesocosm experiment. Throughout the experiment period, in all enclosures, two phytoplankton taxa (microflagellates and cryptomonads) and two diatom species (Skeletonema costatum and Nitzschia spp.) account for approximately 90% of the phytoplankton community. During the nutrient-replete period from day 9 to day 14 populations of Skeletonema costatum and Nitzschia spp. increased substantially; however, only Skeletonema costatum showed an increase in growth rate with increasing seawater pCO2. Not all diatom species in Korean coastal waters are sensitive to seawater pCO2 under nutrient-replete conditions.

Daily changes in phytoplankton abundance and species composition were monitored from July to September 2003 (n=47) to understand which factors control the abundance at a station in Jangmok Bay. During the study, the phytoplankton community was mainly composed of small cell diatoms and dinoflagellates, and the dominant genera wereChaetoceros,Nitzschia, Skeletonema andThalassionema. Phytoplankton abundance varied significantly from 6.40x104 to 1.22x107 cells/l. The initially high level of phytoplankton abundance was dominated by diatoms, but replacement by dinoflagellates started when the N/P ratio decreased to < 5.0. On the basis of the N/P and Si/N ratios, the sampling period could be divided into two: an inorganic silicate limitation period (ISLP, 14th July-12th of August) and an inorganic nitrogen limitation period (INLP, 13th of August - the end of the study). Phosphate might not limit the growth of phytoplankton assemblages in the bay during the study period. This study suggests that phytoplankton abundance and species composition might be affected by the concentrations of inorganic nutrients (N and Si), and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

We studied the phytoplankton communities in ballast water in ships that arrived at two South Korean ports. We determined the potential for phytoplankton in the ballast water to invade the South Korean marine environment, given the specific growth rates of the phytoplankton, the delay before the phytoplankton started growing, and the rate at which the phytoplankton would initially disperse in ports and bays. Most of the phytoplankton in the ballast water samples originated in countries such as China and Japan that are adjacent to South Korea, and diatoms dominated these phytoplankton communities. The abundance of phytoplankton in a sample did not appear to be related to any particular environmental parameter, including the voyage duration. However, the number of phytoplankton taxa in a sample decreased as the voyage duration increased. The survival and growth of phytoplankton communities in the South Korean marine environment were assessed, and we found that most invasions failed at the initial dispersal phase, especially when a community was introduced to pier-side seawater. However, some members of phytoplankton communities, if they were dispersed and where conditions were highly eutrophic, could grow fast enough to overcome the initial dispersal phase in South Korean ports and bays.

Oceanic dimethylsulfide (DMS) released to the atmosphere affects the Earth's radiation budget through the production and growth of cloud condensation nuclei over the oceans. However, it is not yet known whether this negative climate feedback mechanism will intensify or weaken in oceans characterized by high CO(2) levels and warm temperatures. To investigate the effects of two emerging environmental threats (ocean acidification and warming) on marine DMS production, we performed a perturbation experiment in a coastal environment. Two sets of CO(2) and temperature conditions (a pCO(2) of ∼900 ppmv at ambient temperature conditions, and a pCO(2) of ∼900 ppmv at a temperature ∼3 °C warmer than ambient) significantly stimulated the grazing rate and the growth rate of heterotrophic dinoflagellates (ubiquitous marine microzooplankton). The increased grazing rate resulted in considerable DMS production. Our results indicate that increased grazing-induced DMS production may occur in high CO(2) oceans in the future.

A 2-year survey of seawater chemistry and mesozooplankton abundance was carried out in Masan Bay, South Korea, one of the most eutrophic coastal ecosystems known. The study aimed to identify the major factors contributing to the seasonally persistent hypoxia in the bay, to characterise the Bay’s mesozooplankton community and to examine the effects of low oxygen on the distribution of mesozooplankton. Hypoxia (4000 individuals m–3) during summer. During hypoxic events, the abundance of Penilia avirostris was positively related to oxygen levels in the bottom water, suggesting that hypoxic conditions may cause mortality or have sublethal negative effects on population growth of this filter-feeding cladoceran.

Egg production, egg viability and fecal pellet production were determined for individual Acartia omorii, which were fed diets of two species of diatoms (Skeletonema costatum and Phaeodactylum tricornutum ) and three species of dinoflagellates ( Scrippsiella trochoidea, Heterocapsa triquetra and Cochlodinium polykrikoides ). Diets were analyzed for fatty acid content as an indicator of food quality. Depending on the diet, egg production of A. omorii varied over time, diminishing with some diets (S. trochoidea, C. polykrikoides, P. tricornutum ). This rate of reduction was much more rapid for a diet of C. polykrikoides, which caused egg production to decrease to ca. 2.4 eggs f 1 d 1 in only four days. As for all diets, egg viability was high at the beginning but with the C. polykrikoides and P. tricornutum diets, it rapidly decreased with time. Fecal pellet production also varied with time, depending on the diet. Egg production rate was closely correlated with fecal pellet production. There was no direct relationship between egg viability and egg production rate, but both egg production and viability were affected by the nutritional quality of food. Egg viability was also highly dependent on the composition of fatty acids in the eggs. Egg viability showed positive correlation with the ratio of ω 3:ω 6 groups among egg fatty acids, and negative correlation with the ratio of 20:5 (n3) : 22:6 (n3). While comparing several diets, egg production rate was higher on diets (H. triquetra and S. trochoidea) containing ample amounts of essential fatty acids such as 18:4 (n3) and 22:6 (n3). The results suggest that fertility of A. omorii was dependent upon the quality of the food, and dinoflagellate diets, with the exception of C. polykrikoides, were preferable to diatom diets.  2003 Elsevier Ltd. All rights reserved.

Hwang, S.-W.; Kang, H.-K.; Son, Y.-B.; Jang, M.-C., and Choi, K.-H., 2013. Collapse of the crustacean mesozooplankton in the northern East China Sea: effects of Three Gorges Dam? The damming of major rivers can have broad impacts on ecological processes in adjacent marine ecosystems. Thirty years of sampling data from the northern East China Sea show that the recent impounding of water by the Three Gorges Dam on the Changjiang River (Yangtze River) might have had dramatic impacts on the mesozooplankton community. The reduction in freshwater discharge and subsequent increases in phytoplankton biomass have resulted in a substantial increase in total mesozooplankton wet weight but sharp declines in the abundance of all of the crustacean components. The increase in mesozooplankton biomass is probably associated with an increase in small, gelatinous zooplankton. Together with an increase in sea surface temperature in the region, the reduced freshwater and sediment discharge might have led to the proli...