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Oil spill accidents contaminate the oceanic environment and cause economic distress, and they continue to occur. Many methods have been developed to restore waters contaminated with spilled oil. However, still most commercially available methods are not environmentally or economically sustainable solutions. Therefore, there is a need for the development of sustainable materials with running water treatment capabilities. In recent years, a polyurethane (PU) sponge-based adsorbent has been reported as an oil–water separation and reusable adsorbent. This is because the porous 3D structure of the PU sponge provides a large surface area. However, as the PU sponge has a carboxyl group and an amino group, it exhibits hydrophilicity, so surface modification is essential for oil–water separation. Therefore, to modify the surface of PU to have hydrophobic/oleophilic properties, a hydrophobic/oleophilic adsorbent (HOA) was prepared using graphite and polydimethylsiloxane. On the basis of this, a PU sponge, a porous material, was used to manufacture an adsorbent that can be used in a sustainable and environmentally friendly way. The prepared HOA can selectively adsorb water or oil and can be reused. Furthermore, continuous oil–water separation is possible through a simple flow of fluid. Therefore, it is confirmed that the studied HOA can have great potential for ocean restoration in the future as an adsorbent that mitigates the disadvantages of the currently commercialized method.

Nanocomposite (NC) hydrogels based on N,N′-dimethyl acrylamide (DMAAm) using Laponite were prepared. The mechanical properties, adhesive properties to concrete material, and bio-fouling behavior of microalgae Nitzschia sp. were investigated. The elongation and fracture strength of the NC hydrogels were greatly increased and the elastic modulus was decreased in comparison with those of typical hydrogels prepared by using the organic cross-linking agent N,N′-methylenebis(acrylamide) (MBAA). In case of NC hydrogels, they had excellent adhesion properties to the concrete material. The adherence of microalgae on the NC hydrogel surface was also much higher. As the concentration of Laponite in the nanocomposite hydrogels increased, the elastic modulus and fracture strength increased, and the elongation at break, peeling force, and peeling energy were found to be at a maximum at certain concentrations.

When mixtures of aggregates and water dredged from the seabed are discharged at the surface into the adjacent water from a barge, coarse sediments sink immediately and fine sediments are suspended forming a plume. Recently, elongated plumes of fine sediment were observed by satellites near a dredging location on the continental shelf. Such plume streaks were longer in certain conditions with seasonality than expected or reported previously. Therefore, the present work studied the appearance of sediment plume with field measurements and numerical simulations and explains the seasonally varying restoring force and thicknesses of the surface mixed layer resulting from the vertical density distribution near the surface, along with mixing by hydrodynamic process. The resulting mixtures, after vertical restoring and mixing with the surroundings, determine the horizontal transport of suspended sediments. A numerical model successfully reproduced and explained the results from field measurements and satellite images along with the seasonal variations.

Simultaneous satellite and ship-borne surveys have been conducted to investigate the dispersion patterns of dredging plumes off the south coast of Korea in two contrasting seasons (spring and autumn). The distribution of total suspended solid (TSS) derived from sequential satellite imagery showed that the dredging plumes in spring developed over longer distances along the surface current than those in autumn. In spring, the deep and strong stratified condition in the water column contributed to the increase in radius of plume dispersion along the water surface. In autumn, the shallow and vertically well-mixed (or un-stratified) condition in the water column enhanced sinking of suspended dredged materials. This difference is due to the Brunt-Vaisala frequency being higher in spring (0.0183 s − 1 ) than in autumn (0.0123 s − 1 ). Although the sediment-laden overflow significantly increased TSS near the surface during the dredging period, the TSS contribution to water column stratification was only 2.3−5.6% of the thermohaline contribution. Therefore, the seasonal variation of thermohaline density is the main factor determining the dispersion patterns of dredging plumes in the study area.

오늘날 해양생물로부터 얻어진 미생물유래의 이차대사물질은 구조적, 생물학적으로 새로운 화합물의 주요한 자원이다. 그 중에서 해면동물과 미생물 관계는 생리활성 물질을 탐색하는데 가장 흥미있는 자원 중 하나로서 주목받아 왔다. 본 연구에서는 서해안 조간대에서 채집된 주황해변해면(Hymeniacidon sinapium)으로부터 분리된 세균 균주(Microbulbifer sp., 127CP-12)를 검토하였다. 배양된 세균은 자주색 색소를 생산하였으며, 색소생산의 최적 배양조건을 조사하였다. 최대 색소생산을 위한 미생물 배양조건은 25℃, pH 6.0, 3% NaCl임을 알 수 있었다. 추출용매는 에탄올과 메탄올에 비해 아세톤이 더 적절한 것으로 나타났다. 추출된 색소의 주요성분은 HLPC, NMR, MS, 그리고 UV 스펙트럼의 구조 분석을 통해 유용한 생리활성물질인 비올라세인으로 밝혀졌다. 본 연구는 해양미생물이 관여한 대사물질로부터 생리활성물질을 조사하는 연구기법을 서술함과 동시에 오늘날 변화하는 해양환경에서 해면동물과 미생물 관계의 생태학적 의의를 제시하고 있다.

The effects of the 2011 mega-earthquake and massive tsunami on the recruitment process of juvenile abalone Haliotis discus hannai inhabiting the rocky shore ecosystem were investigated at Oshika Peninsula, northeastern Japan. Before the earthquake and tsunami, H. discus hannai of 2007–2010 yr classes were shown to undergo habitat shifts with growth from the crustose coralline algal area (CCA) to kelp beds (KB) via algal turfs (AT). These habitat shifts of abalone appear to occur because of its migration, associated with the ontogenetic changes in feeding behavior. Densities of 0-yr-old juvenile abalone (2010 yr class) and the sea urchin Mesocentrotus nudus inhabiting the CCA largely decreased just after the earthquake and tsunami, mainly affected by the catastrophic disturbance by this event. After that, previously unrecorded recruitments of juvenile macroalgae were observed in the CCA after the event probably because of the large-scale removal of the primary herbivore, the sea urchin M. nudus. Subsequently, the KB and AT expanded into the previous CCA area. After the tsunami, the major factors causing the continuously low densities of the 0-yr-old juvenile abalone (2011–2013 yr classes) are inferred to be the limited nursery CCA habitat because of mud and silt sedimentation, the expansion of the KB and AT, and/or the decreased densities of reproductive adult abalone due to the direct disturbance of the tsunami. The results of this study imply that maintaining diverse algal communities which enable the habitat shifts of juvenile abalone H. discus hannai is one of the crucial factors to their successful recruitment.

To overcome the difficulties of discharge measurements during flood season, MWSCM(micowave water surface current meter) which measures river surface velocities without contacting water has been applied in field work since its development. The existing version of MWSCM is for floods so that its applicability is low due to the short periods of floods. Therefore the renovative redesign of MWSCM to increase the applicability was conducted so that it can be applied to the discharge measurements during normal flows as well as flood ones by extending the measurable range of velocity. A newly developed high-performance MWSCM for general use can measure the velocity range of 0.03-20.0 m/s from flood flows to normal flows, whereas MWSCM for floods can measure the velocity range of 0.5-10.0 m/s. The improvement of antenna isolation between transmitter and receiver to block the inflow of transmitted singals to receiver and the improvement of phase noise of oscillator are necessary for detecting low velocity with MWSCM technology. Separate type antenna of transmitting and receiving signals is developed for isolation enhancement and phase locked loop synthesizer as an oscillator is applied to high-performance MWSCM for general use. Microwave frequency of 24 GHz is applied to the new MWSCM rather than 10 GHz to make the new MWSCM small and light for convenient use of it at fields. Improvement requests on MWSCM for floods-stable velocity measurement, self test, low power consumtion, and waterproof and dampproof-from the users of it has been reflected on the development of the new version of MWSCM.

Periodicities in siphon extension behavior, which is considered an index of feeding behavior, of the Manila clam Ruditapes philippinarum were investigated by sequential visual observations in water tanks under laboratory conditions. Most clams actively extended their siphons in the dark period and closed their shells in the light period under the 12L:12D condition, and this diel cycle of the siphon extension behavior was maintained even under constant light and dark conditions, indicating that Manila clams had an endogenous rhythm with a 24-h cycle. Although the Manila clam has been considered to have a circatidal rhythm in previous studies, a 24.8-h circatidal cycle of the siphon extension behavior was not observed in any of the experimental trials in this study. Although the diel cycle of the siphon extension behavior was temporally collapsed by supplying food after starvation for 10 days, the diel cycle recovered thereafter. This phenomenon indicates that the endogenous rhythm remains even if the cycle of the behavior is lost due to changes in physiological conditions like starvation or in external environments such as food availability.

The coastal ecosystems are considered as one of the most dynamic and vulnerable environments under various anthropogenic developments and the effects of climate change. Variations in the composition and diversity of microbial communities may be a good indicator for determining whether the marine ecosystems are affected by complex forcing stressors. DNA sequence-based metagenomics has recently emerged as a promising tool for analyzing the structure and diversity of microbial communities based on environmental DNA (eDNA). However, few studies have so far been performed using this approach to assess the impacts of human activities on the microbial communities in marine systems. In this study, using metagenomic DNA sequencing (16S ribosomal RNA gene), we analyzed and compared seawater and sediment communities between sand mining and control (natural) sites in southern coastal waters of Korea to assess whether anthropogenic activities have significantly affected the microbial communities. The sand mining sites harbored considerably lower levels of microbial diversities in the surface seawater community during spring compared with control sites. Moreover, the sand mining areas had distinct microbial taxonomic group compositions, particularly during spring season. The microbial groups detected solely in the sediment load/dredging areas (e.g., Marinobacter, Alcanivorax, Novosphingobium) are known to be involved in degradation of toxic chemicals such as hydrocarbon, oil, and aromatic compounds, and they also contain potential pathogens. This study highlights the versatility of metagenomics in monitoring and diagnosing the impacts of human disturbance on the environmental health of marine ecosystems from eDNA.

The effects of intensity and timing of disturbances on recovery of marine benthic organisms were investigated on a rocky intertidal shore in Gwangyang Bay, Korea. We hypothesized that the recovery pattern of the benthic community structure would be affected by disturbance intensity and season. Twenty-eight permanent plots were set up, with disturbance intensity (cleared plots and sterile plots) and seasonal disturbance (fall 1999 and spring 2000) incorporated into the experimental design. To monitor natural seasonal variation in benthic community abundances, we established seven permanent unmanipulated plots. Turf-forming algae were observed in the unmanipulated plots throughout the experimental period, whereas green algae and invertebrate presence varied with season. In the disturbance-intensity experiment, turf-forming and green algae were dominant in cleared plots. The highest coverage of sessile organisms was observed in sterile plots, which exhibited the highest species richness because of their relatively low macroalgal coverage. Seasonal effects of disturbance were an important factor in the recovery pattern of benthic organisms under high disturbance intensity. Coverage of green algae was higher in sterile spring plots than in sterile fall plots; this result was attributed to low spatial competition, as the disturbances occurred just before green algal blooms. On the other hand, the abundances of barnacles and bivalves were highest on sterile fall plots, as these organisms were suppressed by green algal blooms in other periods. These results indicate that the effects of disturbance intensity on benthic community recovery patterns can be influenced by season of disturbance.

We tested the hypothesis that the community structure and biochemical composition of macroalgae reflect the degree of nutrient concentrations in the water column. Benthic community structure and tissue nitrogen (N) content of macroalgae on intertidal rocky shores at three sites were investigated in relation to sewage effluents on Mireuk Island, Tongyeong city, on the southern coast of Korea. Ulva australis clearly dominated at site 1, which was close to a sewage treatment plant, where higher dissolved inorganic N and dissolved inorganic phosphate concentrations were observed. U. australis-dominated communities also appeared at site 2 (intermediate levels of nutrient enrichment). The macroalgal assemblage at site 3 (unimpacted site) was significantly different from those at sites 1 and 2. Five species (U. australis, Sargassum fusiforme, Grateloupia elliptica, Gelidium amansii, and Sargassum horneri) were dominant at site 3, representing 87 % of the total coverage throughout the study period. Species richness (d), evenness (J'), and diversity index (H') were highest at site 3, intermediate at site 2, and lowest at site 1, showing a negative relationship with nutrient levels. These results indicate that macroalgal community structure can be used as a bioindicator in water quality assessment. The tissue N content of green and red algae was responsive to nutrient availability, while the tissue N content of brown algae was relatively unchanged among the sites. This suggests that tissue N content as a bioindicator for detecting the influence of sewage effluent should be considered to reflect the N storage capacity of macroalgae.

The abundance, species composition, and stable isotope ratios of benthic organisms were investigated to determine the trophic structures in abalone (Haliotis discus hannai) habitats, which are characterized by contrasting vegetation of crustose coralline algae (CCA) and kelp beds. A size–frequency analysis revealed that juvenile abalones with shell lengths (SLs) smaller than ~30 mm primarily inhabited CCA beds, whereas adults were abundant in kelp beds. Stable isotope analyses indicated that CCA beds were composed of a single food chain, whereas kelp beds supported multiple food chains. The abalone were divided into three size groups to estimate potential species interactions during their ontogeny. A small gastropod, Homalopoma sangarense, was the most abundant species, but is suspected to be less competitive with abalone, especially in CCA beds. An abundant starfish Asterina pectinifera appeared to function as a potential predator of juvenile abalones in both CCA and kelp beds. We concluded that CCA beds are essential for immediate post-settlement processes of abalones, whereas kelp beds are more important for providing refuge and food sources for adult abalones. The present study highlights that ontogenetic niche shifting can be a successful life-history strategy to sustain the abalone population in a subtidal rocky shore ecosystem.

On 11 March 2011, a massive tsunami generated by amega-earthquake with a moment magnitude of 9.0 hita wide area of Pacific coast of northeast Japan. Weobserved and analyzed the effects of the earthquakeand tsunami event on populations of the abaloneHaliotis discus hannai and sea urchin Strongylocentrotusnudus at Tomarihama in Miyagi, where we have car-ried out regular surveys since January 2008. Before theevent, algal forests dominated by the brown macroalgaEisenia bicyclis had developed in the survey area shal-lower than 5 m in depth, where adult abalone>50 mm in shell length (SL) inhabited. Juvenileabalone 50 mm SL, mainly inhabiting the algal forests, wasreduced by more than half. The impact of the tsunamiwas more profound in the CCA area than in themacroalgal forest. Juvenile abalone and urchins largelydecreased to 14 and 5% of the densities just before theevent, respectively. The distribution pattern of juve-nile abalone and urchins could be a cause of themarked decrease, because most of these animalsinhabited the CCA area where the disturbance by themassive water movement was not reduced by theeffects of the macroalgal forest.Key words: benthic community, marine invertebrates,mortality, physical disturbanceINTRODUCTIONOn 11 March 2011, the Great East Japan Earthquakeoccurred off the Pacific coast of northeastern part ofHonshu Island Japan with a moment magnitude of 9.0at a depth of 24 km. The massive tsunami generatedby this earthquake severely impacted the coast ofnortheastern Honshu Island and resulted in the loss ofnearly 19 000 people and devastated many towns inthe coastal areas of this region. Fisheries are one of themost important industries in the coastal area impactedby the tsunami, and the population depends on thehigh production of marine resources and the sustain-able condition of marine ecosystems. Rapid assess-ments are needed to evaluate effects of the earthquakeand tsunami on coastal ecosystems and populations offishery resource organisms for the future fishery andstock management in the area.Tsunamis are rare disturbance events for marineecosystems but they possess a high intensity and⁄orenergy, which have great potential to affect coastalbenthic communities (e.g., Lomovasky et al., 2011).Previous studies have described effects of tsunamis onmarine ecosystems, especially after the event of 26December 2004 that struck the coastline of tropicaland subtropical zone around the Islands of Sumatraand the Indochina Peninsula. In these studies, effectsof the tsunami on seagrass beds (Whanpetch et al.,2010), coral reefs (Chavanich et al., 2005; Kumarag-uru et al., 2005; Goffredo et al., 2007) and mangroves(Danielsen et al., 2005; Vermaat and Thampanya,2006) were described and analyzed. However, scien-tific evaluation has not been conducted on the effectsof such a massive tsunami on populations of importantfishery resources in temperate areas.On coastal rocky shore reefs in temperate areasaround the world, abalone and sea urchins are eco-logically and economically important species. Both

Distinct seasonal characteristics of monsoon climate significantly affect river streamflow in South Korea. The roles of direct runoff and baseflow on streamflow have become more important to ecosystems and human communities in various watersheds of South Korea. Understanding river characteristics, including direct runoff and baseflow, is the first step of river management and can make a significant contribution to maintaining a sustainable and effective river environment. In this regard, this study involves twin objectives: (1) developing the web-based BFlow system to gain advantages in the time and effort required relative to the DOS (Disk Operation System)-based BFlow program; and (2) assessing the contributions of baseflow and direct runoff to streamflow for river management at the national level. For this, we investigated all streamflow gauge stations in South Korea and, then, used the BFlow program to separate baseflow from the available streamflow data. The results showed that baseflow index for 254 streamflow gauge stations ranged from 0.28 to 0.89. Gauge stations with a baseflow index greater than 0.5 accounted for 64% of total stations. The web-based system developed in this study is a more MS (Microsoft) user-friendly version of BFlow. Furthermore, this study illustrated that high baseflow indexes were generally found at gauge stations with a low coefficient of variation of streamflow. The web-based BFlow system will provide understanding to strategically control rivers and improve the efficiency and safety of river management at the national level.

Climate variability influences fishery production in a variety of ecological processes. There are increasing concerns with ecosystem level impacts of climate variability on fisheries. To understand climate effects on abalone fishery, two climate indices, Arctic Oscillation Index (AOI) and Aleutian Low Pressure Index (ALPI), were compared to abalone catch fluctuations in Hokkaido and Miyagi regions in Japan, affected by the Tsushima Warm Current (TWC) and the Kuroshio and Oyashio Currents (KOC), respectively. The species compositions and trophic structures of benthic communities in natural habitats of abalone Haliotis discus hannai were investigated at Iwanai (Hokkaido) and Tomarihama (Miyagi) coasts. The long-term catch fluctuations were closely related with AOI and ALPI for Hokkaido and Miyagi, respectively. Species replacement from a competitor gastropod Homalopoma amussitatum to a congener H. sangarense was detected in Tomarihama, showing that the latter is non-competitive with juvenile abalone. Species interactions appeared different, possibly affecting recruitment success: favourable [weak competition and weak predation] at Tomarihama and unfavourable [strong competition and strong predation] at Iwanai, setting up a hypothesis for the recent notable catch increase in the KOC region. This study highlights that climate variability could influence benthic fisheries by changing species interactions in a benthic ecosystem.

Studies on the feeding habits of postlarval abalone in their natural habitats have never been carried out primarily because of the lack of an investigating tool. In this study, carbon and nitrogen stable isotope ratios (δ13C and δ15N) were tested to detect nutritional sources during the early life stages of the abalone Haliotis discus hannai in laboratory experiments to evaluate stable isotope analyses as an appropriate investigative tool for field studies. Fertilized eggs, larvae, and the parent spawner muscle were analyzed to detect a nutritional source during the nonfeeding period. The δ13C of fertilized eggs showed slight depletion, about 2‰, compared with that of the parent muscle, and was not detectable after lipid extraction of fertilized eggs. As for the larvae, the isotopic values in postlarvae after settlement and metamorphosis were 2‰ more enriched, become similar to that of the spawner muscle. These results imply that the lipid portion of the eggs is the primary nutritional source dur...

The ontogenetic changes in the feeding habits of the abalone Haliotis discus hannai were elucidated for the first time in natural habitats using stable isotope analyses. Abalone individuals were grouped into three developmental stages: small juveniles (50 mm SL). The inferences of natural diets indicated that benthic diatoms, small red macroalgae and (or) juvenile brown macroalgae, and adult brown macroalgae were the primary food sources for small juveniles (6.5 ± 1.0 mm SL), large juveniles (23.7 ± 6.1 mm SL), and adults (81.8 ± 14.3 mm SL), respectively. The changes of δ13C in abalone were similar among three sampling stations and were explained by ontogenetic changes in feeding habits. The decrease of δ13C in abalone (≤20 mm SL) indicated a transition from diatom feeding to juvenile brown macroalgae and (or) small red macroalgae feeding, whereas the subsequent increase of δ13C (>20 mm SL) represented a feeding transition to adult brown macroalgae. These results prove the hypothesis of the ontogenetic changes in the feeding habits of the abalone H. discus hannai.

We investigated the distribution of δ13C and δ15N of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The δ13C values of benthic animals ranged from −27 to −15‰ in the upper estuary, −21 to −15‰ in the lower estuary, −20 to −16‰ in the shallow coast (5–10 m depths), −18 to −16‰ in the deep coast (30–60 m depths) and −19 to −15‰ in offshore (100–150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river–estuary–marine system.

Controlled feeding experiments with juvenile abalone Haliotis discus hannai were performed to evaluate the suitability of stable isotope analyses for diet inference. Juvenile abalone were divided into five size groups with distinct isotopic ranges caused by different dietary regimes before the experiments. Three different foods were provided for 42 days: a benthic diatom Cylindrotheca closterium (BD), a macroalga Laminaria japonica (MA), and a formulated pellet (FP). For the FP diet, the smallest juvenile group (8.3 mm in mean initial shell length (SL)) showed significant changes in carbon and nitrogen stable isotope ratios from the natural diet within approximately 1 wk. Using final tissue-diet isotopic differences in the two largest juvenile groups for the FP diet, the fractionation values were estimated as 1.6& and 2.2& for d 13 C and d 15 N, respectively. An exponential decay function of the change in d 13 C with time indicated that the shortest period to complete equilibrium fractionation was >120 days. Given the estimated fractionation values, the major diets of juvenile abalone (1.9-6.9 mm in SL) in the field were inferred to be benthic microalgae and several red macroalgae.

The community and trophic structures of the subtidal habitat of the abalone Haliotis diversicolor were examined in Nagai, Sagami Bay, Japan. Conventional community indices showed no significant differences among three sampling stations. The overall continuum of stable isotope ratios was structured into three different trophic linkages: (i) brown algae-dependent benthic food chain; (ii) red algae-dependent benthic food chain; and (iii) planktonic food chain. Brown algae and red algae likely play different roles with respect to carbon sources in the habitat. Conventional fractionation values indicated that the abalone H. diversicolor (δ13C = 12.4 ± 1.0‰, δ15N = 9.3 ± 0.5‰) feeds on the lamina of Undaria pinnatifida during juvenile and adult stages (8.0–65.6 mm shell length). Stable isotope signatures suggested that the juveniles of other abalone species as well as some amphipods and a sea cucumber Holothuria decorata are competitors of H. diversicolor, whereas some Muricidae gastropods such as Thais bronni and Ergalatax contractus are predators. The isotopic differences among macroalgal species and the subsequent transfer to consumers indicate that stable isotopic analysis is an effective means of studying food webs in an open rocky shore community with little influence from external primary production such as terrestrial vegetation.