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The bioaccumulation potential (“B”) of compounds is one of the major considerations in assessing chemical hazards. A variety of metrics, including hydrophobicity (KOW), bioconcentration factor (BCF), bioaccumulation factor (BAF), and to an increasing degree biomagnification factor (BMF) and trophic magnification factor (TMF), are widely used to characterize “B”. In the present study, the variation and hydrophobicity-dependence of each of these metrics for recalcitrant hydrophobic organochlorine compounds (HOCs) was determined from four food webs collected in two different seasons at two different sites of the Han River, Korea. Measured environmental parameters and stable isotopic ratios exhibited distinct seasonal and spatial shifts in the ecological condition of the river. The observed values of individual metrics were positively and linearly related with their log KOW values, but linearized slopes differed significantly among the four food webs, with the largest variation being exhibited by TMF and log fugacity ratio (log F) followed by log BMF > log BAF. When based on field-derived mean linear equations, different log KOW values were obtained for a critical point for the identification of biomagnification of HOCs. Consequently, the biomagnification potential of HOCs and its relationship with KOW can vary, being seriously affected by not only on the metrics used for its assessment but also on spatial and temporal variations in ecological conditions. Our results indicate that TMF for “B” might be more robust than the other metrics but the development of new methodologies to reduce uncertainty and to enhance the accuracy of TMFs by correcting for ecological variation, together with addition efforts to harmonize individual metrics for “B”.

The bay scallop Argopecten irradians, a warm-water and hermaphroditic bivalve species, is native of the Atlantic coast of North America and was introduced for aquaculture to the Chinese coast in 1982 and, in turn, to the Korean coast in 1996. The present study analyzed the gross biochemical composition and stable isotope ratios of separated organs (i.e., the adductor muscle, digestive gland, gonad, mantle, and gill tissues) of the scallop over a culturing cycle (September 2015 to May 2016), to understand its energy-storage allocation strategy in association with reproductive success for survival in the new habitat. The condition index (CI) of the bay scallop increased slowly but steadily from the beginning of deployment in the grow-out area in September and peaked in the following month of March. The gonadosomatic index (GSI) increased rapidly in April and peaked in May, when the CI decreased drastically. The seasonal somatic growth, as defined by dry tissue weight, of whole tissues and individual organ tissues differed from each other. Most of the energy reserves were stored in the adductor muscle in the summer–fall period. The subsequent sudden decreases in proteins and carbohydrates in the adductor muscle suggested that these reserves were used as catabolic substrates during winter maintenance in the December–January period, and during spring spawning in the April–May period. The δ13C values of all the lipid-free organ tissues displayed seasonal fluctuations in parallel with those of phytoplankton. Seasonal fluctuations in gross weights of biochemical constituents as well as δ13C and δ15N values of individual organ tissues confirmed a mobilization of proteins from the digestive gland to the gonad, suggesting that gonadal growth is catabolized by recently assimilated food (i.e., phytoplankton). Overall, our results clearly indicate that, although the bay scallop in a newly introduced coast of Korea possessed slightly different energy-gain-allocation processes vs the native US populations, they might adapt to new environments and keep an intrinsic trait of fast growth and reproductive success through a slight modification of adaptive strategy for survival.

Coastal vegetated habitats such as mangroves, salt marshes, and seagrasses, referred to as blue carbon ecosystems, play an important role in climate change mitigation by an effective CO

We examined microbial food webs in Seomjin River and Gwangyang Bay in South Korea, using 18S rRNA amplicon sequencing of environmental DNA (eDNA) with a weighted gene correlation network analysis (WGCNA) – Cytoscape analysis, considering various environmental variables. WGCNA with weight >0.5 revealed two taxon-specific trophic interactions. One was composed of Chlorophyceae and Cryptophyceae-based primary producers and ciliates-based primary consumers. In another one, Bacillariophyceae was a main primary producer while rotifer and ciliates were primary consumers. The Bray-Curtis dissimilarity and correlation matrix of gene abundance with gene significance related to environmental variables showed that the Chlorophyceae and Cryptophyceae-based microbial food web was a function of dissolved inorganic nitrogen in the Seomjin River, whereas the Bacillariophyceae-based microbial food web was a function of dissolved inorganic phosphate in the Gwangyang Bay. Our study provides new insight into microbial food webs while considering the nutrient status of estuarine ecosystems.

We determined the dietary composition and trophic position (TP) of walleye pollock in the western East Sea (Japan Sea), based on the δ13C and δ15N values of this species, sympatric dominant fish and invertebrates, and their putative food sources in winter. A broad range of the consumer δ13C′ (lipid-corrected) values reflected clear distinctions between benthic and pelagic feeders, differentiating benthic vs. pelagic trophic pathways. The intermediate δ13C′ and δ15N values of pollock fell between those of benthic and pelagic feeders, indicating their trophic links through both pathways. Increases of their isotopic values with increasing body length suggest an ontogenetic change in dominant diets from pelagic to benthic prey as confirmed by stomach content analysis. Their ontogenetic pattern in resource utilization might be associated with deeper migration range with size, increasing TP during ontogeny.

Brucella abortus, one of the most important members of the genus Brucella responsible for human disease, is an intracellular pathogen capable of avoiding or interfering components of the host immune responses that are critical for its virulence. GPR84, on the other hand, is a seven-transmembrane GPCR involved in the inflammatory response and its induced expression was associated with B. abortus infection of RAW264.7 cells. Here we examined the effects of the reported GPR84 surrogate and endogenous agonists, namely 6-n-octylaminouracil (6-OAU) and lauric acid (LU), respectively in the progression of B. abortus infection in a cell and mouse models. The in vitro studies revealed the LU had bactericidal effect against Brucella starting at 24 h post-incubation. Adhesion of Brucella to RAW264.7 cells was attenuated in both 6-OAU and LU treatments. Brucella uptake was observed to be inhibited in a dose and time-dependent manner in 6-OAU but only at the highest non-cytotoxic concentration in LU-treated cells. However, survival of Brucella within the cells was reduced only in LU-treated cells. We also investigated the possible inhibitory effects of the agonist in other Gram-negative bacterium, Salmonella Typhimurium and we found that both adhesion and uptake were inhibited in 6-OAU treatment and only the intracellular survival for LU treatment. Furthermore, 6-OAU treatment reduced ERK phosphorylation and MCP-1 secretion during Brucella infection as well as reduced MALT1 protein expression and ROS production in cells without infection. LU treatment attenuated ERK and JNK phosphorylation, MCP-1 secretion and NO accumulation but increased ROS production during infection, and similar pattern with MALT1 protein expression. The in vivo studies showed that both treatments via oral route augmented resistance to Brucella infection but more pronounced with 6-AOU as observed with reduced bacterial proliferation in spleens and livers. At 7 d post-treatment and 14 d post-infection, 6-OAU-treated mice displayed reduced IFN-γ serum level. At 7 d post-infection, high serum level of MCP-1 was observed in both treatments with the addition of TNF-α in LU group. IL-6 was increased in both treatments at 14 d post-infection with higher TNF-α, MCP-1 and IL-10 in LU group. Taken together, 6-OAU and LU are potential candidates representing pharmaceutical strategy against brucellosis and possibly other intracellular pathogens or inflammatory diseases.

A major highlight of restoration efforts is to improve the ecological structure and function of the natural ecosystem in the restored habitat. Assessment of restoration success is a crucial component of an optimal ecological management strategy. In studies to determine the restoration success of a transplanted seagrass habitat by assessing trophic recovery, we examined carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic assemblages in a transplanted eelgrass Zostera marina bed. The eelgrass bed was restored about 2 years after transplantation in a southern coastal bay of Korea, and consequently, the food web structure in the bed was compared with that in a natural reference site. Our results revealed no significant differences in isotopic values of both macrobenthic consumers and their putative food sources between the transplanted and natural seagrass beds. These isotopic similarities in florae and faunae in the two beds suggest a uniformity in food web structure formed by the diversity and availability of resources, and thereby suggest similarities in the resource–consumer relationship. Isotopic niche indices and high dietary overlaps of feeding guilds in the transplanted and natural beds further suggest the transplanted habitat provides similar ecological functions and ecosystem services to its natural counterpart. Collectively, our results suggest the eelgrass transplantation led to successful restoration of a common seagrass bed, with recovery of the functional properties of the food web structure. Finally, our findings support the idea that stable isotope measures can provide a better understanding of the functioning of restored ecosystems, and improve post-transplantation monitoring efforts for the future planning and managing of successful habitat restoration.

The East/Japan Sea (EJS) is well ventilated to deep water via brine rejection from ice formations and thermohaline convection, resulting in a short overturning period in several decades. Due to these characteristics, the dissolved oxygen concentration in the EJS deep water is much higher (190–200 μg L −1 at 3000 m water depth) than that found at the same depths of the Northwestern Pacific (30 μg L −1 ) or anywhere in the Pacific Ocean. The total mercury (THg) and methylmercury (MeHg) distributions, and MeHg mass budgets were investigated to identify how the EJS's distinct circulation pattern affects Hg speciation. Whereas the THg concentration in the surface seawater (ranging from 0.20 to 1.2 pM, mean 0.59 ± 0.24 pM) showed no site variation between the Japan Basin and the Ulleung Basin, the MeHg concentration in the surface seawater was significantly higher (p −2 yr −1 ) than in the Ulleung Basin (1.9 nmol m −2 yr −1 ) due to the shallow thermocline depths in the Japan Basin. In contrast, the MeHg concentration in deep seawater (1000–3000 m) was similar between the Japan Basin (530 ± 87 fM) and the Ulleung Basin (610 ± 99 fM) and significantly (p

The Ulleung Basin in the southwestern East/Japan Sea (hereafter East Sea) is known as a biologically productive “hot spot” but climate-associated changes in the physicochemical oceanographic conditions and some biological changes have been reported. In this study, our main objective was to determine the contribution of small phytoplankton to the total primary production, which is valuable information for detecting marine ecosystem changes in the Ulleung Basin. The small phytoplankton productivity contributions determined by Moderate-Resolution Imaging Spectroradiometer (MODIS)-derived monthly productivities using a phytoplankton community-based productivity algorithm was significantly consistent with the field-measured productivity contributions of small phytoplankton in this study. The daily primary productivity of small phytoplankton ranged from 42.7 to 418.7 mg C m −2 d −1 with an average of 172.9 mg C m −2 d −1 (S.D. = ±61.4 mg C m −2 d −1 , n = 120), and the annual contribution of small phytoplankton ranged from 19.6% to 28.4% with an average of 23.6% (S.D. = ±8.1%) in the Ulleung Basin from 2003 to 2012. Overall, large phytoplankton were a major contributor to the total primary production in the Ulleung Basin (76.4 ± 8.2%) from 2003 to 2012, which indicates that the Ulleung Basin is a highly productive region. A significantly negative relationship (p

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 ± 1.47 mg m−3) in 2015 was significantly higher (t-test, p 20 μm) was observed near the Russian coast. The daily carbon uptake rates in this study were 180.5 and 441.6 mg C 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 ± 679.6 mg C 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.

Step changes to seawater temperature (SWT) in the East Asian marginal seas (EAMS) are associated with three recent climate regime shifts (CRS) occurring in the mid-1970s, late 1980s, and late 1990s, but the responses of the ocean conditions and marine ecosystems had regional differences. A step change in SWT in the East China Sea (ECS) was detected after the CRS of the 1970s as were step changes in the North Pacific Index (NPI), Pacific Decadal Oscillation Index (PDOI), and East Asian Winter Monsoon Index (EAWMI). SWT in the ECS decreased with decreasing warm water volume transport into the EAMS and a strong monsoon, but step changes in SWT in other regions were not detected as clearly. After the CRS of the 1980s, SWT in all EAMS increased rapidly with step changes detected in all five climate indices examined. These changes were associated with a weak winter monsoon, increasing surface air temperature (SAT), and increasing warm water volume transport into the EAMS. However, after the CRS of the 1990s, a decrease in SWT around the EAMS was detected in the northern part of East China Sea (NECS), and the ECS with step changes also in the EAWMI and the Arctic Oscillation Index (AOI). In contrast, SWT in the East Sea/Sea of Japan (EJS) and the Yellow Sea (YS) continuously increased during this time. Long-term changes in zooplankton biomass were affected by regional differences in the responses of atmospheric and oceanic variability to CRSs. Specifically, long-term changes in the timing of peaks in zooplankton abundances exhibited differences. During warm periods (e.g. after the 1980s CRS) in the EJS, the amount of zooplankton biomass in October increased, while in February it decreased. On the contrary, in the YS and the NECS, the peaks of October and June in zooplankton biomass occurred during cold periods (after the 1970s and 1990s CRS). Major fisheries resources also responded to the three CRSs, although warm and cold water species responded differently to changes in oceanographic conditions in regional spawning grounds.

Three cruises were undertaken along a meridional transect in the East/Japan Sea (EJS) in spring (May 2007), summer (July 2009), and fall (October 2012) to determine the geographic variations in phytoplankton biomass and community composition. This study revealed a gradient of surface temperature and a fluctuation of hydrographic conditions along the transect. Although a subpolar front (SPF) formed between the warm- and cold-water masses (37–40°N), no significant differences in phytoplankton biomass and community composition were detected between the southern and northern parts of the EJS. These results disprove our initial hypothesis that different water masses may contain differently structured phytoplankton communities. In the present study, isothermal layers (≤ 12 °C) fluctuated over a depth of 50 m in both warm- and cold-water masses, depending on the SPF. In contrast, the nitracline (i.e. 2.5 μM nitrate isopleth) depth was recorded within a limited range of 20–40 m in spring, 30–50 m in summer, and 40–60 m in fall. The chlorophyll a concentrations at the subsurface chlorophyll maxima (SCM) were significantly higher in spring and summer (356 ± 233 and 270 ± 182 ng L –1 , respectively) than in fall (117 ± 89 ng L –1 ). The relative contributions of individual phytoplankton groups to the depth-integrated chlorophyll a concentration conformed to the composition of the phytoplankton community in the SCM layer, showing a dominance of diatoms (58 ± 19% in spring, 48 ± 11% in summer, and 30 ± 20% in fall). Canonical correspondence analysis revealed that the geographic structures of phytoplankton communities were strongly associated with the vertical structures of water temperature and nutrient concentration in the water column rather than with horizontal gradients of hydrographic conditions. Finally, our findings suggest that water column stability and light–nutrient availability in the euphotic zone play a key role in determining geographical consistency of the biomass and the community structure of phytoplankton in the EJS.

The minke whale ( Balaenoptera acutorostrata ) is the most common baleen whale among several marine mammal species observed in Korea. Since a high concentrated condition of prey to whales can be obtained by physical structures, the foraging whale distribution can be an indicator of biological hotspot. Our main objective is verifying the coastal upwelling-southwestern East Sea as a productive biological hotspot based on the geographical distribution of minke whales. Among the cetacean research surveys of the National Institute of Fisheries Science since 1999, 9 years data for the minke whales available in the East Sea were used for this study. The regional primary productivity derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) was used for a proxy of biological productivity. Minke whales observed during the sighting surveys were mostly concentrated in May and found mostly (approximately 70%) in the southwestern coastal areas ( −2 y −1 ) estimated in the southwestern coastal region of the East Sea belongs to the highly productive coastal upwelling regions in the world. A change in the main spatial distribution of minke whales was found in recent years, which indicate that the major habitats of mink whales have been shifted into the north of the common coastal upwelling regions. This is consistent with the recently reported unprecedented coastal upwelling in the mid-eastern coast of Korea. Based on high phytoplankton productivity and high distribution of minke whales, the southwestern coastal regions can be considered as one of biological hotspots in the East Sea. These regions are important for ecosystem dynamics and the population biology of top marine predators, especially migratory whales and needed to be carefully managed from a resource management perspective.

We investigated bacterial production (BP) and respiration (BR), as well as the physico-chemical properties of the water column, to elucidate the effect of upwelling on heterotrophic bacterial metabolic activities and growth efficiency (BGE) in July 2012 and May 2013 in the Ulleung Basin (UB), East/Japan Sea. The upwelled conditions were characterized by higher chlorophyll-a (Chl-a) concentrations resulting from the upward shift of the nitracline compared to that of the non-upwelled condition. Analyses of the size fractions of Chl-a and pigment composition revealed that large size phytoplankton (> 20 µm), mainly consisting of diatoms, appeared to be the major phytoplankton component. BP and BR were significantly correlated with Chl-a (P 0.05). These results suggest that bacterial metabolic activities are stimulated by the availability of organic resources enhanced by upwelling in the UB. Further statistical analysis showed that the difference in BP and BGE with variations in upwelling intensity were significant (P = 0.018 for BP, P = 0.035 for BGE), but the difference in BR was not significant (P = 0.321). These results suggest that metabolic energy is partitioned more for BP under a strong upwelling condition, i.e. high nutrient and Chl-a conditions. In contrast, the energy generated via respiration was partitioned more for maintaining metabolism rather than for biomass production under weakly or non-upwelled conditions, i.e. stratified and low Chl-a conditions. Overall, our results suggest that any changes in upwelling intensity would significantly affect the carbon cycle associated with the fate of primary production, and the role of the microbial loop in the UB where changes in the intensity and frequency of upwelling associated with climatic changes are in progress.

Seasonal variability of sinking fluxes of total mass (TMF), particulate organic carbon and nitrogen (POC and PON) was examined using sinking particles collected from sediment traps during July 2011 to December 2011, and December 2012 to June 2013 at an offshore channel site; and from November 2013 to August 2014 at a nearshore slope site of the Ulleung Basin in the East/Japan Sea. δ13C and δ15N values of sinking particles were measured to elucidate the major export processes of POC and PON. Annual TMF (112–638 g m−2 yr−1) and fluxes of POC and PON (9.6–32.1 g C m–2 yr–1 and 1.2–4.5 g N m−2 yr−1, respectively) in the Ulleung Basin corresponded to the upper limit of values reported for other open seas and oceans in the world. No great seasonal variability in both quantitative (TMF, and fluxes and contents of POC and PON) and qualitative (C/N ratios, and δ13C and δ15N values) estimates of vertical fluxes was observed, reflecting a steady standing stock of chlorophyll a in the upper part of water column. Furthermore, high contents of POC and PON and nearly constant δ13C and δ15N values in sinking particles collected in the sediment traps, indicate that primary production in the euphotic zone may be a good predictor of TMF and export flux of organic matter. In this regard, our pilot study points out the importance of high annual primary production and low water temperature (

The East/Japan Sea (EJS) where is surrounded by the Korean peninsula, the Japanese islands, and the Russian coast has been experiencing a large change in physicochemical properties. Based on biochemical composition analysis (carbohydrates, proteins, and lipids), the current qualitative status of phytoplankton was identified in the northern EJS from two different sampling seasons (fall and spring in 2012 and 2015, respectively). The average chlorophyll-a (chl-a) concentration integrated from the euphotic depths was significantly higher in 2015 (99.3 ± 69.2 mg m−2) than 2012 (21.5 ± 6.7 mg m−2). Large phytoplankton (> 2 µm) were predominant in 2015 accounting for 64.5 ± 19.7% whereas small-size phytoplankton (0.7–2 µm) were dominant (49.1 ± 17.5%) in 2012. The biochemical compositions of phytoplankton were predominated by lipids (42.6 ± 7.8%) in 2012 whereas carbohydrate composition largely contributed (53.2 ± 11.7%) to the total biochemical composition in 2015, which is mainly due to different nutrient availabilities and growth stages. Interestingly, the averaged FM concentrations and calorific values for phytoplankton based on the biochemical compositions had similar values between the two years, although the integrated chl-a concentrations were substantially different between 2012 and 2015. In terms of different cell sizes of phytoplankton, we found that small phytoplankton assimilate more FM and calorific energy per unit of chl-a concentration than total phytoplankton. Our results are meaningful for the understanding of future marine ecosystems where small phytoplankton will become dominant at a scenario of ongoing warmer oceans.

This study investigates the biological pump system in the East Sea (Japan Sea) by conducting an analysis of the total particle flux, biogenic material composition, and carbon isotope ratios of sinking particles. The samples were collected for one year starting from March 2011 using time-series sediment traps deployed at depths of 1040 m and 2280 m on bottom-tethered mooring at Station EC1 (37.33°N, 131.45°E; 2300 m water depth) in the Ulleung Basin (UB), southwestern part of the East Sea. The temporal variation in the particulate organic carbon (POC) flux at 1000 m shows a good relationship with the primary production in the corresponding surface water. The ratio of POC flux at 1000 m to satellite-based primary production in the corresponding region in the UB was ~ 3%, which is comparable to the values of 2 to 5% estimated from previous studies of other part of the East Sea. The lithogenic material accounted for > 17% of the sinking particles at 1000 m and for a larger fraction of 40 to 60% at 2280 m. The radiocarbon contents of the sinking POC at both trap depths imply the additional supply of aged POC, with a much greater contribution at 2280 m. Overall, the particle flux in the deep interior of the East Sea appears to be controlled by the supply of complex sources, including aeolian input, the lateral supply of resuspended sediments, and biological production in the surface water.

The southern coast of Korea comprises many small bays where the Pacific oyster, Crassostrea gigas, has been cultivated intensively employing a long-line hanging culture system. Naturally harvested oyster spats used in the long-line culture system are hardened in mid-intertidal area and transplanted to the center of the bay for grow-out usually in May. The May transferred oyster produced considerably smaller quantity of eggs during spawning in September. To enhance the reproductive effort and growth during grow-out, we transferred the hardened oyster juveniles to grow-out sites in January rather than May to allow them to accumulate energy reserves at the time of spring phytoplankton bloom that normally occurs during April and early May. The January transferred oyster juvenile (JTO) showed fast somatic and shell growth during grow-out, reaching a marketable size in August, while the juvenile oyster transplanted in May (MTO) did not reach a market size until November. JTO spawned from June to September, with a single spawning pulse in July, while most of the MTO spawned in September. Quantity of eggs produced by the JTO was 5.7 times higher than MTO, indicating that early grow-out enhanced egg production. The meat weight and levels of tissue carbohydrate and protein of JTO harvested in November were significantly higher than MTO harvested at the same time, suggesting that the meat quality of JTO is superior to the MTO. Overall, our results suggest that transplanted hardened juveniles to grow-out in January increase natural oyster seed harvest in the bay as well as improve quality of the oyster for marketing. Statement of relevance Oyster farming is one of the leading aquaculture industries in the world, producing over 4 million tons of oysters annually world-wide. In the oyster industry, Crassostrea gigas, the Pacific oyster, has been cultured extensively in Asia, and recently in Europe using different modes of culture. In Asia, the Pacific oysters are raised using subtidal hanging long-line system, while they are cultured in intertidal areas using net bags and rack system in Europe. In Korea and Japan, the oyster seeds are supplied mostly from wild, by harvesting oyster larvae during post-spawning season. The newly harvested oyster spats are stunted in intertidal before they are transplanted to the subtidal hanging long-lines, to maximize survival of the seed oysters. This stunting process is called hardening and the hardening of oyster has been practiced for several decades in Korea and Japan. In Korea, the hardening seed oysters are transplanted in May, and the May transplanted oysters are harvested in December as they grow up to 8 cm in shell length. The May transplanted oysters produce relatively smaller quantity of eggs during their first spawning, although the small reproductive effort may increase their survival during post-spawning season. The natural oyster spats harvested in late summer or early fall for the oyster culture in Korea are mostly originated from the May transplanted oysters. Currently, the natural oyster spat harvest in Korea suffers from insufficient quantity. In part, this insufficiency is associated to the poor reproductive activity of the May transplanted oyster. Low reproductive effort of May transplanted oysters during their first spawning is, in part, associated to too late transplantation to the bay, and earlier transplantation of the stunted oysters from the hardening ground to the grow-out ground in the bay may enhance the reproductive effort, resulting in subsequent successful larval recruitment and settlement of the larvae. Accordingly, we experimentally transplanted the hardened oysters 4 months earlier to the traditional transplanting period (January) and monitored their reproduction and growth. Although the hardening process has been practiced over 50 years, no studies have compared growth and reproduction of differentially transplanted oysters in Korea. As the data demonstrated, January transplanted oyster demonstrated earlier gonad maturation and produced 5 × more eggs during spawning, compared to May transplanted oysters. No severe mortality was observed from the early transplanted oysters during the course of study, although reproductive activity of January transplanted oysters was relatively intensive, compared to May transplanted oysters. The present study first attempted to evaluate effectiveness of transplantation timing of the hardened oysters, in terms of growth and reproduction. Also, quantity of the eggs produced from differentially transplanted female oysters was first measured and compared in this study using ELISA. As the data indicated, January transplanted oyster produced 5 × more eggs, which may enhance the natural oyster spat harvest in the bay, as well as to evaluate the transplantation period and management of oyster farming on the south coast of Korea.

The effects of blooms of opportunistic green macroalgae, Ulva prolifera, on the trophic structure of the macrobenthic food web in a temperate intertidal zone on the western coast of Korea were evaluated using carbon and nitrogen stable isotopes. Biomasses of Ulva and microphytobenthos (MPB) increased significantly at the macroalgae-bloom and the non-bloom sites, respectively, from March to September 2011. The δ(13)C values of most the consumers were arrayed between those of MPB and Ulva at both sites, and differed according to feeding strategies at the macroalgae-bloom site. Seasonally increasing magnitudes in δ(13)C and δ(15)N values of consumers were much steeper at the macroalgae-bloom site than at the non-bloom site. Our findings provide evidence that blooming green macroalgae play a significant role as a basal resource supporting the intertidal macrobenthic food web and their significance varies with feeding strategies of consumers as well as the resource availability.

Two years after the Hebei Spirit oil spill occurred off the west coast of Korea, we determined sub-lethal effects of the spilled oil on hemocyte parameters of Ruditapes philippinarum in the damaged areas. Clams in the spilled sites displayed unusually high proportion of granulocytes, which may result in higher phagocytosis capacity and reactive oxygen species production. Hemocytes in clams from the polluted sites also displayed less DNA damage and mortality than in the control site, possibly due to a faster phagocytosis of the impaired cells. Glycogen, the major energetic reserve, was depleted in clams from the spilled sites, potentially due to energetic consumption for maintenance of a large pool of granulocytes, detoxification processes and oxidative stress. Modified hemocyte parameters in clams in the spilled area, may reflect sub-lethal physiological stresses caused by the residual oils in the sediment, in conjunction with environmental modifications such as food availability and pathogens pattern.

The spatial and seasonal variations in resource use of the lacustrine shrimp Palaemon paucidens were investigated in three different Korean lagoon systems in June and October 2018 by measuring their carbon and nitrogen stable isotope ratios. P. paucidens had much higher δ13C values at the permanently open lagoon (PL) as compared to the intermittently open lagoons (ILs), revealing a disparity in resource utilization. Isotopic niches of the shrimp were relatively wider at the PL than at the ILs, suggesting a greater diversity of carbon pathways in the PL system. These results indicate that the degree of water exchange with the sea, associated with lagoon geomorphology, may be a major factor influencing resource availability for P. paucidens. Our findings suggest that the duration and degree of inlet opening may affect dietary variation at the population level, and may be one of the key components of sustainable management for coastal lagoon ecosystems.

Harmful algal blooms involving the dinoflagellate Cochlodinium polykrikoides occur every summer off the Korean peninsula's central southern coast. To determine whether Cochlodinium bloom-derived organic carbon is incorporated into the subtidal macrobenthic food web, we compared the δ13C and δ15N values of suspended particulate organic matter (SPOM) and sedimentary organic matter, and macrobenthic consumers between bloom and non-bloom seasons. Chemotaxonomic analysis revealed the presence of Cochlodinium blooms in summer and a predominance of diatoms in autumn. Both the δ13C and δ15N values of SPOM were higher in the bloom than in the non-bloom seasons. Such temporal shifts in the δ13C and δ15N values were also observed for most macrobenthic consumers collected in both seasons. Consistent temporal isotopic shifts in SPOM and macrobenthos revealed that the Cochlodinium bloom-derived carbon was incorporated into the coastal benthic food web, resulting from its increasing availability during blooms.

The broad temperature range on the temperate coast of Korea has led fishermen to develop a unique and specialized procedure for the longline culture of ascidians. In Korea, warming of the coastal sea in winter has accelerated over the past few decades. After warmer winters, the rising temperatures of earlier springs have precluded the rearing of the ascidian spat in the culturing area and have imposed spring spat cultivation in colder-water nursery grounds. To examine the seasonal dynamics of energy reserves and the physiological strategies to optimize energy balance for the growth in the cultured sea squirt Halocynthia roretzi, its gross biochemical composition and physiological energetics were investigated monthly over two culturing periods from July 2005 to January 2006 and July 2013 to January 2014 in Geoje-Hansan Bay on the south coast of Korea. No indicators of the growth performance of sea squirts showed differences between the two culture practices (2005–2006 and 2013–2014) carried out using spat reared in different localities, i.e., the grow-out area and the colder nursery grounds. The seasonal patterns in accumulation and utilization of biochemical constituents in the sea squirt tissues were similar between the two periods. During the culturing period in the grow-out area, sea squirts retained physiological functions across the temperature range. Food energy acquisition and metabolic cost were positively related to water temperatures in the field conditions, probably due to the low and narrow range of suspended particulate matter (SPM) concentrations. A less-clear seasonal variability in food consumption rates yielded a seasonal discrepancy in scope for growth (SFG; i.e., negative during summer vs positive during autumn–winter). Consequently, the tissue weight and protein reserves of sea squirts varied concomitantly with the seasonal changes in SFG, supporting a fast growth during autumn–winter. Our results suggest that the spat reared in colder nursery grounds are suitable for cultivating sea squirts in the traditional grow-out area and support their sustainable culturing performance as an adaptation strategy to the winter–spring warming conditions that are unique to coastal seas.

The Hebei Spirit oil spill in December 2007 at Taean off the west coast of Korea was the largest oil tanker accident in Korea. However, the impact of the spill on physiology of benthic animals remains largely unknown. Two-years after the accident, we compared reproductive effort and annual gametogenesis of the wild Pacific oyster Crassostrea gigas , residing at oil spill site with a control oyster population in Incheon Bay, North-West coast of Korea. Results showed that the oyster sampled from the oil spill site showed a significantly higher (279.0 mg standard animal − 1 , P − 1 , P −1 , P −1 , P − 1 , P − 1 , P

To estimate detailed contributions of particulate organic carbon (POC) as a potential food source in various environments of the Arctic sea ice floes, intensive investigations were executed at two different types of sea ice stations (ST 1 and ST 2) in the northern Chukchi Sea during the summer period in 2011. The average uptake rates of carbon and nitrogen in melt ponds from this study were within the range measured previously. The surface ice of melt ponds at ST 1 had the highest POC concentration with a mean of 148.0 mg C m −3 (S.D.=±86.0 mg C m −3 ), followed by sea ice cores at ST 2 (mean±S.D.=125.7±128.2 mg C m −3 ). The POC concentrations in melt ponds ranged between 90.0 mg C m −3 (S.D.=±12.7 mg C m −3 ) and 103.9 mg C m −3 (S.D.=±47.7 mg C m −3 ) at ST 1 and ST 2, respectively. Major POC contributors to melt ponds were diatoms with a mean biovolume contribution of 48.7% (S.D.=±39.1%) which was strongly related to in situ salinity. Although the total POC concentration of entire sea ice floes ranged from 2.8% to 5.3% of the POC concentration within the euphotic water column at the study locations, the carbon contribution of sea ice floes could be important to higher trophic levels because of the concentrated POC within sea ice floes.

Data on persistent organochlorines (OCs) in sharks are scarce. Concentrations of OCs such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in the muscle tissue of 13 shark species (n=105) collected from offshore (Indian and Pacific Oceans) and coastal waters of Korea, to investigate species-specific accumulation of OCs and to assess the potential health risks associated with consumption of shark meat Overall OC concentrations were highly variable not only among species but also within the same species of shark. The concentrations of PCBs, DDTs, chlordanes, hexachlorobenzene, and heptachlor in all shark species ranged from < LOQ (limit of quantification) to 184 (mean: 35.0), < LOQ to 1135 (58.2), < LOQ to 56.2 (4.31), < LOQ to 18.8 (1.64) and < LOQ to 77.5 (1.37) ng/g lipid weight, respectively. The determined concentrations of PCBs and DDTs in shark in our study were relatively lower than those reported in other studies. Aggressive shark species and species inhabiting the Indian Ocean had the highest levels of OCs. Inter-species differences in the concentrations and accumulation profiles of OCs among shark species could be explained by differences in feeding habit and sampling locations. Several confounding factors such as growth velocity, trophic position, and regional contamination status may affect the bioaccumulation of OCs in sharks. Hazard ratios of non-cancer risk for all the OCs were below one, whereas the hazard ratios of lifetime cancer risks of PCBs and DDTs exceeded one, implying potential carcinogenic effects in the general population in Korea. This is the first report to document the occurrence of OCs in sharks from Korea. (C) 2015 Elsevier Inc. All rights reserved.

We examined trophic relationships in a newly established community 1.5 years after the Hebei Spirit oil spill on the west coast of Korea. Carbon and nitrogen stable isotope ratios in consumers and their potential food sources were compared between the oil-spill site and reference site, located 13.5 km from the oil-spill spot. The isotopic mixing model and a novel circular statistics rejected the influx of petrogenic carbon into the community and identified spatial consistencies such as the high contributions of microphytobenthos, food-chain length, and the isotopic niche of each feeding guild between sites. We suggested that high level of trophic plasticity and the prevalence of omnivory of consumers may promote the robustness of food web against the oil contamination. Furthermore, we highlighted the need of holistic approaches including different functional groups to quantify changes in the food web structure and assess the influence of different perturbations including oil spill.

An assessment of the patterns of thermal acclimation of physiological processes of the stalked sea squirt Styela clava is needed to further understand growth patterns associated with large seasonal fluctuations in ambient temperature. The effects of different exposure temperatures on physiological processes of S. clava were measured at 5, 10, 15, 20, and 25 °C. The impact of temperature on energy balance at a whole organism level was then assessed by scope for growth (SFG) and net growth efficiency (K 2 ) measures. Physiological rates of S. clava were well correlated with its dry tissue weight (DW). Positive allometry with DW indicated that all physiological rates investigated were generally higher in the larger individuals regardless of temperature. Some allometric equations ( e.g. , feces production rate vs. DW and respiration rate vs. DW) exhibited identical estimates of exponents, enabling accurate comparisons of the rates across temperatures. In contrast, disparities across temperatures of the values for the weight exponent were detected in other allometric equations, revealing that thermal effects on these rates have different degrees for large and small individuals. The SFG value in S. clava of different sizes was similar at lower temperatures (5–10 °C), peaking at 15 °C. The SFG was positive with a relatively constant K 2 in this temperature range. This positive energy balance reflects the reduction in metabolic costs at lower temperatures. In contrast, increased metabolic costs at higher temperatures (20–25 °C) resulted in lowered SFG and K 2 values, indicating that the feeding rate did not increase as greatly in compensation for the increased metabolic costs at higher temperatures. The lowered absorption at 25 °C (compared with 20 °C) resulted in negative SFG and K 2 values. Finally, our results confirm that the absence of compensatory adjustment to warmer conditions leads to energetic disruption at a whole organism level at such temperatures.

As in all other oviparous animals, lipoprotein receptors play a critical role in lipid metabolism and reproduction in decapod crustaceans. Four full-length cDNAs encoding lipoprotein receptors (Paj-VgR, Paj-LpR1, Paj-LpR2A, and Paj-LpR2B) were identified from Pandalopsis japonica through a combination of EST screening and PCR-based cloning. Paj-LpR1 appears to be the first crustacean ortholog of insect lipophorin receptors, and its two paralogs, Paj-LpR2A and Paj-LpR2B, exhibited similar structural characteristics. Several transcriptional isoforms were also identified for all three Paj-LpRs. Each expression pattern was unique, suggesting different physiological roles for these proteins. Paj-VgR is an ortholog of vitellogenin (Vg) receptors from other decapod crustaceans. A phylogenetic analysis of lipoproteins and their receptors suggested that the nomenclature of Vgs from decapod crustaceans may need to be changed. A PCR-based transcriptional analysis showed that Paj-VgR and Paj-LpR2B are expressed almost exclusively in the ovary, whereas Paj-LpR1 and Paj-LpR2A are expressed in multiple tissues. The various transcriptional isoforms of the three Paj-LpRs exhibited unique tissue distribution profiles. A transcriptional analysis of each receptor using tissues with different GSI values showed that the change in transcription of Paj-VgRs, Paj-LpR2A and Paj-LpR1 was not as significant as that of Vgs during maturation. However, the transcriptional levels of Paj-LpR2B decreased in ovary at maturation, suggesting that their transcriptional regulation is involved in reproduction.

The relationship between the spring bloom along the Primorye coast and the sea ice of the Tatarskiy Strait in the northern region of the East/Japan Sea, a semi-enclosed marginal sea in the North Pacific, was investigated using the ten-year SeaWiFS chlorophyll- a concentration data and DMSP/SSMI sea ice concentration data from 1998 to 2007. Year-to-year variations in the chlorophyll- a concentrations in the spring were positively correlated with those of the sea ice concentrations in the Tatarskiy Strait in the previous winter with a correlation coefficient of 0.77. Abrupt increases in nutrients, essential for the spring bloom in the upper ocean during spring, were supplied from sea ice-melted waters. Time series of vertical distributions of the nutrients indicated that phosphate concentrations were extremely elevated in the upper ocean (less than 100 m) without any connection to high concentrations in the deep waters below. The water mass from sea ice provided preferable conditions for the spring bloom through changes in the vertical stratification structure of the water columns. Along-coast ratios of stability parameters between two neighboring months clearly showed the rapid progression of the generation of a shallow pycnocline due to fresh water originating from sea ice. This study addressed the importance of the physical environment for biogeochemical processes in semi-enclosed marginal seas affected by local sea ice.

To examine the influence of habitat alteration by tideflat reclamation on the physiological ecology of Ruditapes philippinarum, seasonal variations in its condition, gross biochemical composition, and reproductive cycle were compared for a yearly cycle between a reclaimed flat (Gomsohang, GS) and a natural flat (Hajun, HJ) in Gomso Bay, Korea. Concentrations of chlorophyll a and seston (as well as its energy value as food available to the clam) were consistently higher at HJ than at GS. Condition, dry tissue weight, and energy reserves (proteins and carbohydrates) of the clams were much higher at HJ than at GS during spring-summer, when fast growth and gametogenic development occur. Furthermore, their spring gametogenic development and spawning were advanced at HJ compared with GS. Our results suggest that the Manila clam encounters nutritionally stressful environmental conditions in altered habitats after tideflat reclamation that lead to lowered nutrient accumulation and a changing reproductive cycle.

The primary productivity of the East/Japan Sea (EJS) displays strong spatio-temporal variability, largely driven by the oceanographic forcings that vary across the different regions of the sea. Consequently, the ecosystem responses to climate variability could be region-dependent. A model-based analysis from this study synthesized the complex biological-physical interactions across the EJS, and suggested an intricate role of water column stability in driving the observed seasonal and basin-scale variability. Compared to the northern EJS (e.g., the Japan Basin), the southern EJS (e.g., the Ulleung and Yamato Basins) has a more favorable mixing regime for higher productivity in both winter and summer, balancing the need for phytoplankton growth in terms of nutrient and light availability. The wintertime water column in the southern EJS is relatively stable compared with the northern EJS due to the influx of warm Tsushima Warm Current (TWC) water and also weaker surface atmospheric cooling, leading to decreased light limitation for primary production in the south than in the north. During the stratified summer season, the surface stirring and mixing, due to the energy dissipation of strong TWC inflow, promote a relatively less stable surface mixed layer in the south than that in the north, and thus alleviate the nutrient limitation at the surface. In addition, the current- and wind-induced upwelling along the east coast of Korea further enhances the productivity in the southwestern EJS. The general south-north ‘see-saw’ pattern of mixing regime, combined with upwelling-downwelling switching, could be the key driver for the observed production patterns in the EJS.

We investigated the involvement of chemokine receptor type 4 (CXCR4) signaling on the outcome of Brucella (B.) abortus 544 infection in murine macrophages and in a mouse model. CXCR4 manipulation were first evaluated for Brucella invasion and intracellular survival efficiency, mitogen-activated protein kinases (ERK1/2, JNK, p38α) activation and generation of nitric oxide (NO), and then in the splenic bacterial proliferation and cytokine production in BALB/c mice. CXCR4 blockade is involved in the successful control of Brucella invasion, reduction of ERK1/2 phosphorylation and inhibition of nitric oxide release from macrophages. Furthermore, using a reported CXCR4-specific antagonist AMD3100 resulted in splenomegaly but attenuated Brucella proliferation in these organs with elevated serum levels of MCP-1, TNF and IL-12. These findings provide insights on the contribution of CXCR4 signaling in the phagocytic pathway and immune modulation during B. abortus infection.

It is hypothesized that the proportion of small phytoplankton increases if the water temperature increases. However, limited information on the biochemical compositions of small phytoplankton and their ecological contributions is currently available for estuary and coastal environments. In the present study, our goal is to determine the roles of small phytoplankton under different environmental conditions, which influence higher trophic consumers. Water samples were obtained in the Gwangyang Bay, Korea from 2012 to 2014. The contribution of small phytoplankton to the total chlorophyll-a (chl-a) concentration increased from the first period (October 2012–April 2013) to the following period (August 2013–April 2014), which was mainly due to lower nutrient inputs available to phytoplankton because of decreasing river input. Based on biochemical compositions (carbohydrates, proteins, and lipids), the overall contributions of small phytoplankton to the total food material (FM) and caloric content were significantly higher than the chl-a contribution of small phytoplankton. This result indicates that the small phytoplankton assimilated more FM and energy per unit of chl-a concentration compared to those of the large phytoplankton. These findings reveal that the potential impacts of river inputs on phytoplankton cell size and the photosynthetic biochemical composition of this primary food source should be considered in coastal management plans for anthropogenic influences, such as dam constructions.

Given a projection of thriving small phytoplankton in the Arctic Ocean under climate-induced environmental changes, it is important to estimate the contribution of small phytoplankton (0.7–5 μm) to the total primary production in the Chukchi Sea, which is an important conduit of organic matter from the North Pacific to the Arctic Ocean. Based on a 13 C– 15 N dual isotope tracer technique, small phytoplankton productivity measurements were taken during two consecutive cruises in the Chukchi Sea in 2004. The total phytoplankton carbon uptake rates ranged from 0 to 25.38 mg C m −3 h −1 , whereas the uptake rates of small phytoplankton ranged from 0 to 2.87 mg C m −3 h −1 . In comparison with the carbon uptake rates, total phytoplankton nitrate uptake rates ranged from 0 to 4.40 mg N m −3 h −1 while small phytoplankton nitrate uptake rates ranged from 0 to 0.39 mg N m −3 h −1 . Ammonium uptake rates ranged from 0 to 8.34 mg N m −3 h −1 and from 0.01 to 2.18 mg N m −3 h −1 , for total and small phytoplankton, respectively. Small phytoplankton contributed 24.80% (S.D.=±23.0%) to the total chlorophyll- a concentration, and 59.41% (S.D.=±52.12%) to the total carbon biomass due to its higher particulate organic carbon per chlorophyll- a unit during the two cruises in 2004. In the Chukchi Sea, the average contributions of small phytoplankton to carbon and total nitrogen (nitrate+ammonium) uptake rates were 31.72% (S.D.=±23.59%) and 37.31% (S.D.=±26.06%), respectively.

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 13 C– 15 N dual isotope tracer technique. The 2007 mean daily carbon uptake rates of phytoplankton were 0.20 and 0.16 g C m −2 d −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 0.18 g C m −2 d −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.

A multivalent approach to discover a novel antibiotic substance against methicillin-resistant Staphylococcus aureus (MRSA), a marine bacterium, UJ-6, exhibiting an antibacterial activity against MRSA was isolated from seawater. The isolated strain was identified to be Pseudomonas sp. by the morphology, biochemical, and genetical analyses. The ethyl acetate extract of Pseudomonas sp. UJ-6 culture showed significant ant-MRSA activity. Bioassay-guided isolation of the extract using a growth inhibitory assay led to the isolation and identification of an active compound exhibiting anti-MRSA activity. Based on the analyses of the physicochemical and spectroscopic data including nuclear magnetic resonance and mass, the compound was identified to be 1-acetyl-beta-carboline. The minimum inhibitory concentration (MIC) of the compound was determined to be in a range of 32–128 μg/ml against MRSA strains. The MIC values against MRSA were superior or equal to those of other natural compounds such as catechins, suggesting that 1-acetyl-beta-carboline would be a good candidate in applications of the treatment of MRSA infection.

We investigated the reproductive effort of the Manila clam Ruditapes philippinarum during different gametogenic stages with combining histology and immune assay techniques. To determine the level of gonad maturation, 1- to 2-mm-thick slices of the dorso-ventral section were cut from the middle of clams for histology. The quantity of eggs in each clam was determined from the remaining tissue using rabbit anti-clam egg protein IgG in an indirect enzyme-linked immunosorbent assay (ELISA). At the Begmiri tidal flat in Incheon Bay off the west coast of Korea, clams commenced gametogenesis in February and the first spawning female was observed in July. Clams continued to spawn into October (18.5 °C). The monthly mean gonad-somatic index (GSI), the ratio of egg mass to body weight, ranged from 4.27 (April) to 20.63 (July). The GSI increased rapidly from April (4.3) to May (16.8), peaked in July (20.6), then dropped dramatically from August (14.0) to September (5.5), indicating that clams at the Begmiri tidal flat have a major spawning pulse during August and September. The histology–ELISA combined technique enabled us to assess gametogenic stepwise reproductive efforts of clams because we could simultaneously determine the reproductive stage and quantity of eggs. The GSI of mature females ranged from 20.9 (May) to 26.6 (July), while that of partially spawned clams ranged from 12.8 (June) to 7.2 (September), suggesting that clams discharge as much as 50% of their eggs during the major spawning pulse. Histology revealed that residual eggs in spent clams were resorbed, and that clams may restore approximately 4.6% of their body weight by this energy-recycling process. The histology–ELISA combined technique provided both quantitative and qualitative information about clam reproduction, which is crucial for clam fisheries and aquaculture.

Crustins are among the most important antimicrobial peptides (AMPs) found in decapod crustaceans. They are small cationic AMPs (5-7 kDa) characterized by a proline-rich amino-terminal domain and a cysteine-rich carboxyl-terminal domain. Here, the first 3 crustin-like cDNAs (Pj-crus Ia, Ib, and II) were identified from the morotoge shrimp, Pandalopsis japonica. The full-length cDNAs of Pj-crus Ia, Ib, and II consisted of 1135, 580, and 700 nucleotides and encoded putative proteins containing 109, 119, and 186 amino acids residues, respectively. All 3 identified Pj-crus sequences exhibited the conserved domain organization for crustins, including a signal sequence, a cysteine-containing region, a glycine-rich region, and a whey-acidic protein (WAP) domain. Amino acid sequence comparisons and phylogenetic analysis revealed that the Pj-crus Ia and Ib belong to type I crustins (e.g., carcinin), which have been mostly identified from Brachyura and Astacidea, whereas Pj-crus II was classified as belonging to the type II crustins, which are mainly found in Dendrobranchiata. An analysis of the organization of these 3 Pj-crus genes revealed that the splicing site within the WAP domain may be an important key for classifying types I and II crustin family members. The tissue distribution profile results showed that the Pj-crus I genes were expressed in a tissue-specific manner but that the Pj-crus II gene was expressed ubiquitously, suggesting that these crustins may play different roles in various tissues or under different physiological conditions. The bacterial challenge results suggested that the Pj-crus genes may be transcriptionally influenced by different bacterial types. This comparative study of various crustin family members will help extend the knowledge on the crustacean innate immune response, which will provide important basic information for controlling shrimp immunity against various pathogens.

Crustacean hyperglycemic hormone (CHH) peptide family members play critical roles in growth and reproduction in decapods. Three cDNAs encoding CHH family members (Pj-CHH1ES, Pj-CHH1PO, and Pj-CHH2) were isolated by a combination of bioinformatic analysis and conventional cloning strategies. Pj-CHH1ES and Pj-CHH1PO were products of the same gene that were generated by alternative mRNA splicing, whereas Pj-CHH2 was the product of a second gene. The Pj-CHH1 and Pj-CHH2 genes had four exons and three introns, suggesting the two genes arose from gene duplication. The three cDNAs were classified in the type I CHH subfamily, as the deduced amino acid sequences had a CHH precursor-related peptide sequence positioned between the N-terminal signal sequence and C-terminal mature peptide sequence. The Pj-CHH1ES isoform was expressed at a higher level in the eyestalk X-organ/sinus gland (XO/SG) complex and at a lower level in the gill. The Pj-CHH1PO isoform was expressed at higher levels in the XO/SG complex, brain, abdominal ganglion, and thoracic ganglion and at a lower level in the epidermis. Pj-CHH2 was expressed at a higher level in the thoracic ganglion and at a lower level in the gill. Real-time polymerase chain reaction was used to quantify the effects of eyestalk ablation on the mRNA levels of the three Pj-CHHs in the brain, thoracic ganglion, and gill. Eyestalk ablation reduced expression of Pj-CHH1ES in the brain and Pj-CHH1PO and Pj-CHH2 in the thoracic ganglion. Sequence alignment of the Pj-CHHs with CHHs from other species indicated that Pj-CHH2 had an additional alanine at position #9 of the mature peptide. Molecular modeling showed that the Pj-CHH2 mature peptide had a short alpha helix (α1) in the N-terminal region, which is characteristic of type II CHHs. This suggests that Pj-CHH2 differs in function from other type I CHHs.

A local shortage of wild seed has led to a recent reduction in the annual production of the ark shell, Scapharca subcrenata , cultured in natural subtidal habitats on the Korean coast. To determine the best time for seed collection from natural habitats, the annual cycles in the condition, gametogenic activity, and gross biochemical composition of the bottom-cultured ark shell were investigated in a southern coastal bay of Korea over a 16 month period. Samples were collected at regular intervals between August 2009 and November 2010. The condition and dry tissue weight of a standard animal (shell length = 31.4 mm) peaked in April−May and reached minima during late summer−fall. Histological analysis of the gonadal tissues showed a unimodal gametogenesis cycle with one spawning peak (June–August) during the year. The gametogenesis of the ark shell was initiated simultaneously with the accumulation of reserve materials (i.e., glycogen, proteins, and lipids) from winter to late spring, indicating that recently ingested food energy is used to fuel gamete production. The stored energy reserves were then rapidly exhausted during and after spawning. The high chlorophyll a concentrations in the water column and surface sediments throughout the year suggest that high local phytoplankton production and the presence of resuspended microphytobenthos may produce high food availability at the study site. The results obtained during the study period show that the gametogenic development of the ark shell has accelerated and spawning has advanced by at least a month in the past decade. These changes probably reflect the elevated temperatures in winter−early spring. Finally, our results suggest that it is necessary to advance the time of seeding from late July−August to spring to ensure the successful seeding of ark shell cultures in natural habitats.

Although the Manila clam ( Ruditapes philippinarum ) culture grounds are occasionally located in Zostera japonica beds along the coasts of Korea, plant responses to the clamming activity have not been reported for this seagrass species. Intense Manila clam harvesting activity took place in the intertidal Z. japonica bed during April 2004. The Z. japonica bed at the study site has been monitored since January 2003. Thus, this study provided a unique opportunity to compare the structure of the Z. japonica population before and after the clamming activity, which was conducted for approximately 1 week in April 2004. All Z. japonica shoots were removed and buried in the sediment immediately after the clamming activity. However, a few shoots were found at the disturbed area in July 2004, 3 months after the clamming activity. By September 2004, 5 months after the disturbance, shoot density and biomass were almost recovered to the levels reported before the clamming activity. No Z. japonica seedlings were observed when the shoot density rapidly increased in August and September 2004, 4–5 months after the disturbance, because revegetation of the disturbed seagrass bed has occurred before the seed germination time which is typically winter or early spring in this area. Thus, the initial rapid revegetation of the disturbed area occurred via asexual reproduction through new shoot formation from the buried below-ground tissues. The reproductive shoot density and reproductive efforts of Z. japonica were significantly higher after the disturbance relative to the levels recorded before the disturbance, and the duration of the fertile period was approximately three times longer following the clamming activity. The belowground biomass after the disturbance was also significantly higher than that before the disturbance. These results suggest that Z. japonica allocated more energy to sexual reproduction, as well as the maintenance of belowground tissues, to persist their population under unstable environmental conditions.

The ascidian Styela clava has recently become a common species for suspended aquaculture in Korea. Because of the ecological and commercial importance of this species, it is important to understand seasonal variations in its physiological energetics and gross biochemical composition. The purpose of this study was to determine fundamental biological traits for the cultivation of S. clava . Physiological processes (food consumption, feces production, ammonia excretion and respiration), and gross biochemical composition (protein, lipids, and carbohydrates) of the ascidian were measured monthly from April 2008 to April 2009 under in situ environmental conditions in a mariculture region on the temperate coast of Jindong Bay, Korea. Changes in the physiology and somatic growth of S. clava were largely influenced by seasonal variation in water temperatures. The reduced importance of food availability in explaining their physiological adjustments seems to be due to low seston concentrations in water column of the bay. Seasonal variations in the ingestion and respiration rates of the ascidians were mismatched, resulting in an energy imbalance (i.e. an increased metabolic energy cost and lowered ingestion rate; and vice versa ). This mismatched activity resulted in negative scope for growth (SFG) values during spring–summer, followed by rapid exhaustion of energy reserves and flesh weight loss. Weight loss during this period was also related to spring spawning. During autumn–winter, the ascidians had a positive SFG as a result of decreased oxygen consumption and elevated ingestion rates, showing accumulation of nutrient reserves and weight gain. The ascidians showed positive SFG, even in cold conditions below 12 °C in the present study. In this respect, an autumn–winter culturing period is recommended to maximize ascidian production in long-line suspended culture under the natural environmental conditions occurring in the study area.

Methyl farnesoate (MF), a crustacean juvenile hormone (JH) analog, plays important roles in the regulation of a number of physiological processes such as molting, metamorphosis, and reproduction. Understanding its metabolic pathway is a key for various potential applications in crustacean aquaculture, including artificial seed production and enhancement of growth. Although the synthetic pathway of MF is well established, little is known about its degradation and recycling in crustaceans. In insects, juvenile hormone esterase (JHE), a carboxylesterase, is responsible for JH inactivation. Two cDNAs, encoding JHE-like carboxylesterases (CXEs) from the hepatopancreas and ovary of Pandalopsis japonica, were isolated by using a combination of in-silico data mining from an expressed sequence tag (EST) database and traditional PCR-based cloning. The full length Pj-CXE1 (2084bp) and Pj-CXE2 (1985bp) cDNAs encoded proteins composed of 584 and 581 amino acids, respectively. The active site sequence and domain organization of the Pj-CXEs were highly conserved, including the catalytic triad and other motifs, which suggested that both Pj-CXEs are biologically active carboxylesterases. Phylogenetic analysis of the deduced sequences of Pj-CXEs showed that both were most closely related to the JHEs from non-lepidopteran insects. End-point RT-PCR showed that Pj-CXE1 was expressed primarily in the gonad, whereas Pj-CXE2 was expressed in both the hepatopancreas and hindgut. Quantitative PCR showed that Pj-CXE1 was upregulated in the gonads by eyestalk ablation (ESA). In contrast, ESA had no significant effect on Pj-CXE2 expression in hepatopancreas or gonad. This is the first report of the cloning of two JHE-like CXE cDNAs in decapods and the upregulation of Pj-CXE1 by acute withdrawal of eyestalk neuropeptides. Further study is needed to understand the function of CXEs in MF metabolism and its regulation by eyestalk neuropeptides.

δ 13 C and δ 15 N of the Antarctic limpet Nacella concinna tissues and their potential food sources were used to determine their dietary origins and their movements between diverse habitats of intertidal and subtidal rocky shores and tide pools of Marian Cove, King George Island, Antarctica in the austral summer. δ 13 C and δ 15 N of the organic matter sources of epilithic microalgae, macroalgae and suspended particulate organic matter (SPOM) were readily distinguishable to discern their relative contribution to the limpet diets, with the most depleted values being found in SPOM and the most enriched in macroalgae. The limpets exhibited a spatial trend in distribution due to their seasonal migration, with smaller individuals in the subtidal zone compared with larger ones on the intertidal sites. The limpet isotopes had relatively broad ranges of δ 13 C and δ 15 N (−26.6 to −12.8‰ and 2.6–7.1‰, respectively), suggesting a dietary shift between habitats as well as size classes. The stable isotope ratios for each habitat seem likely to reflect the differing availabilities of the three potential food sources. Isotope mixing model results indicate a spatial shift in dietary mixture between habitats as well as limpet size classes. Epilithic microalgae and phytoplankton made great contributions to the diet of the subtidal limpets. Together with epilithic microalgae, macroalgae were significant contributors to the intertidal limpets where macroalgae were abundant. A higher contribution of macroalgae to the limpet diets was found in the tide pools. In contrast, while phytoplankton was an important food source for the limpet spat, a great dietary dependence on epilithic microalgae was found in the small-size limpets from the lower intertidal zone. Our results suggest that limpet grazing can determine microalgal and/or macroalgal abundance and coverage on the Antarctic rocky-shore ecosystem, and trophic structure of benthic food web can change along environmental gradients even at spatial scales of tens or hundreds of metres in the Antarctic.

The overall dependence of benthic secondary production on the main primary producers at three different habitats in the Nakdong River estuarine system, Korea, was estimated. Inventories of macrobenthic invertebrate biomass were combined with multiple-isotope-mixing models to evaluate the trophic base, comparing Scirpus triqueter-dominated and Phragmites australis-dominated marshes and bare intertidal flat. The feasible contributions of four main food sources, marsh macrophytes, the microphytobenthos, and riverine and marine suspended particulate organic matter (RPOM and MPOM), to the consumer biomasses were calculated using the isotopic mixing model. After weighting the feasible contributions of food sources to each taxon by the consumer biomass, the resultant values were summed for all the consumers at each habitat to quantify the trophic base of the benthic invertebrate community. Dual-isotope-mixing model calculations verified the varying dependence on those potential food sources among the functional feeding groups. In addition, the dependence on each source of the same functional group varied between bare intertidal and salt-marsh habitats, shifting from a dominance of benthic and pelagic microalgal sources on the former habitat to a mixed food source at the latter habitat. The biomasses of the species comprising each functional group differed among habitats and sampling dates, so that each functional group made a different contribution to the whole benthic community and its basal food source. Given the calculation of the overall dependence of macrozoobenthic community on each food source, our results indicate that the microphytobenthic source dominates (nearly half) the trophic base in all the intertidal habitats of different vegetational compositions. Marsh-macrophyte-derived organic matter and RPOM served as considerable subsidies only to salt-marsh food webs, reflecting the use of the mixed food source by salt-marsh-bed consumers. Conversely, the dominance of MPOM in the total food base was equal to that of the microphytobenthos in the bare intertidal ecosystem but increased during spring−summer in the salt-marsh systems. Our results also suggest that the river discharge concentrated during the summer monsoon does not lead to any shift in trophic base for estuarine secondary production.