First report of Perkinsus olseni infections in blood cockles Tegillarca granosa on the south coast of Korea.

The protozoan parasite Perkinsus olseni has become a focus of attention since it has been responsible for mass mortalities and economic losses in a wide range of bivalve hosts globally. The P. olseni host range along the south coast of Korea may extend beyond what was previously understood, and blood cockles in the Family Arcidae are also suggested to be potential hosts of P. olseni. In the present study, we applied histology and molecular techniques to identify Perkinsus sp. infections in the blood cockles Tegillarca granosa, which have been commercially exploited on the south coast of Korea for several decades. Histology and molecular techniques, including genus-specific immunofluorescence assay, species-specific fluorescence in situ hybridization, and phylogeny based on the ribosomal DNA internal transcribed spacer region revealed that T. granosa is infected by P. olseni, although the prevalence was low (0.5%). Histology revealed massive hemocyte infiltrations in the mantle, gill, and digestive gland connective tissues, indicating that the infection exerts negative impacts on the host cockles.

Molecular and microscopic identification of Eomarteilia granula infection in Manila clam Ruditapes philippinarum off the south coast of Korea.

A report on the new species Eomarteilia (=Marteilia) granula infecting Manila clam Ruditapes philippinarum from Japan in 2014 suggests the possibility of E. granula infecting other Manila clam populations in the Northwest Pacific region, including Korea. In this study, we report the first infections by E. granula in Manila clams off the south coast of Korea. Histology revealed Marteilia-like plasmodia in the digestive tubule epithelia. Tissue imprints demonstrated that each parasite sporangium enclosed 4 spores and transmission electron microscopy (TEM) revealed ultrastructure of primary cells enclosing secondary cells, which contained spores. Mature spores consisted of 3 sporoplasms: outermost, intermediate, and innermost. The outermost sporoplasm showed a peripheral electron-dense monolayer characteristic of E. granula. The 18S rDNA amplified from the Marteilia-like parasite yielded 1784-bp PCR amplicon sequences which were 99.8% similar to that of E. granula previously reported (as M. granula) from Japan. In the molecular phylogenetic analysis, the novel Marteilia-like organism formed a well-supported clade with E. granula. Accordingly, we concluded that the novel Marteilia-like parasite that we found infecting some Korean Manila clams is Eomarteilia granula. Field surveys revealed that the infection was limited to clams of the south coast of Korea, with the prevalence ranging from 3.3 to 5.0%.

Dominance of the scleractinian coral Alveopora japonica in the barren subtidal hard bottom of high-latitude Jeju Island off the south coast of Korea assessed by high-resolution underwater images.

Coastal benthic communities in temperate regions have been influenced by climate change, including increasing sea-surface temperature. Nevertheless, scleractinian coral Alveopora japonica Eguchi, 1968, is thriving in shallow subtidal hard bottoms around Jeju Island, off the southern coast of Korea. The presence of this corals has negatively impacted subtidal kelp populations in Jeju Island. However, there is no study to document how the presence or absence of this coral relates to other benthic communities. This study investigated the benthos in three shallow subtidal sites (Shinheung (SH), Bukchon (BC), and Seongsan (SS)) in northern Jeju using underwater photography. Macro-benthic organisms appearing on a 1 × 20 m line transect installed at depths of 5, 10, and 15 m at each site were analyzed. Results showed that of the three sites investigated, A. japonica colonies were most abundant at BC, accounting for 45.9% and 72.8% of the total transect area at 10 m and 15 m, respectively. At SS, A. japonica occupied 15.3% of the total area at 15 m and less than 1% at 5 m and 10 m. The same at SH accounted for 10% of the total area at 5 m, and less than 1% at 10 m and 15 m. Dead and bleached colonies accounted for 1.2-11.5% and 1.8-5.7%, respectively, at 5, 10, and 15 m at three sites. At SS, canopy-forming brown algae Ecklonia cava and Sargassum spp. accounted for 20.2 and 24.3% of the total transect area, respectively, at 5 m depth. In contrast, the percent cover of E. cava and Sargassum spp. at SH and BC ranged from 0.1 to 1.8%, respectively. Moreover, non-geniculate coralline algae dominated the subtidal substrate at SH, ranging between 60.2 and 69% at 15 and 10 m. The low cover of A. japonica in SS (at 5 m) coincided with a high percent cover of canopy-forming brown algae. However, canopy-forming brown algae were rare at all depths at SH and BC and were dominated instead by coralline algae and the scleractinian corals. This study, by utilizing a non-destructive method, provides a baseline qualitative and quantitative information for understanding the site and depth-dependent distribution of A. japonica and algal populations, which is important to understand climate change related changes in benthic communities in Jeju and elsewhere.

The complete mitochondrial genome of the sand dollar Astriclypeus mannii (Verrill, 1867) (Echinoidea: Astriclypeidae) in the subtidal sand flat in Jeju Island off the south coast of Korea.

We sequenced the complete mitochondrial genome of sand dollar Astriclypeus mannii (Verrill 1867) (Echinoidea: Astriclypeidae) occurring in the subtidal sand flat in Jeju Island off the south coast of Korea. The mitochondrial genome was 15,744 bp in length and contained 13 protein-coding genes (PCGs), 22 transfer RNAs, two ribosomal RNAs, and 140 nucleotides representing the putative control region. We reconstructed the concatenated phylogenetic tree based on 13 PCGs of 18 echinoderms, including A. mannii. From the maximum likelihood clustering, A. mannii was grouped in the order Echinolampadacea. The complete mitochondrial sequence of A. mannii for the first time in this study provide valuable insight in understanding the evolution and phylogenetic analysis of echinoids (sea urchins).

Flow cytometric characterization of the hemocytes of sea hares from tidal pools in Jeju Island off the south coast of Korea.

The members in the family Aplysidae known as sea hares play a crucial role as a grazer in small tidal pools or shallow subtidal hard bottoms. Like other marine gastropods, hemocyte types and functions of sea hares are limitedly known. This study identified and characterized the hemocytes of common Aplysia species Aplysia kurodai, A. juliana, and A. oculifera in rocky tidal pools in Jeju Island off the south coast of Korea using flow cytometry and light microscopy. The flow cytometry identified three different hemocytes in the hemolymph of the three sea hare species: granulocytes, hyalinocytes, and blast-like cells. The granulocytes exhibited pseudopodia on the cell surface and granules in the cytoplasm. Morphology of the hyalinocyte was similar to that of the granulocytes, while they lack cytoplasmic granules. The blast-like cells were small and round, with very thin cytoplasm. The hyalinocytes were the most abundant in the hemolymph, accounting for 89.8-92.6% of the total hemocytes. Flow cytometry indicated that the granulocytes and blast-like cells were less than 5.6% and 5.4% of the total hemocyte populations. Flow cytometry also revealed that the granulocytes and hyalinocytes are engaged in cellular defensive activities such as intra-cellular lysosomal content, phagocytosis, and ROS production. The mean lysosomal contents of the granulocytes (0.4 × 105-0.2 × 105 A U.) were 2-3 times higher than that of hyalinocytes (0.2 × 105-0.6 × 105 A U.). In addition, the ROS production of the granulocytes (0.98 × 106-1.95 × 106 A U.) was about twice higher than that of the hyalinocytes (0.62 × 106-1.14 × 106 A U.). Of the three species of sea hares, the granulocytes showed comparatively higher phagocytosis capacity (70.4-92.3%) than that of the hyalinocytes (34.8-46.0%). Flow cytometry and microscopy indicated that the hemocyte types and their functions were identical, regardless of the species.

Effects of spawning stress on the immune capacity of blood cockle Tegillarca granosa occurring on the south coast of Korea.

Spawning in marine bivalves is a great energy-demanding process, and it often results in lethal and sublethal stresses during the post-spawning period, including depressed immune capacity. The blood cockle Tegillarca granosa (Linnaeus, 1758) distributes widely in silty-mud tidal flats on the south coast of Korea, and they spawn in late summer. To understand the impacts of spawning on immune parameters, we analyzed the total hemocyte count (THC), hemocyte mortality, phagocytosis capacity, and reactive oxygen species (ROS) production of T. granosa in pre-, and post-spawning condition using a flow cytometer. Histology indicated that the blood cockles occurring on the south coast of Korea ripe and ready to spawn in July, and they spawned in August and September. The THC in the blood cockle hemolymph declined from pre-spawning (1.2 × 108 cell mL-1) to post-spawning (0.9 × 108 cell mL-1), possibly due to the spawning stress and the massive infiltration of hemocytes in the gonad to phagocytose and resorb the residual gametes during the post-spawning period. The hemocyte mortality increased linearly from August (4.1%) to November (9.1%), as the histology revealed that the blood cockle completed spawning, and they resorbed the relict gametes. The granulocyte phagocytosis capacity declined dramatically from July (12.7%) to September (6.0%), when the cockles were engaged in active spawning. The flow cytometry revealed that the production of reactive oxygen species (ROS) from the granulocytes and the erythrocytes type II increased linearly from August (0.8-0.9 × 105 A U.) to December (2.1-2.8 × 105 A U.), which may cause stresses at a cellular level during this period. As the data indicated, spawning is a stressful activity inducing depressed immunological capacities in the blood cockles.

Quantification of the inflammatory responses to pro-and anti-inflammatory agents in Manila clam, Ruditapes philippinarum.

Inflammation is a form of innate immune response of living organisms to harmful stimuli. In marine bivalves, inflammation is a common defense mechanism. Several studies have investigated the morphological features of inflammation in bivalves, such as hemocyte infiltration. However, the molecular and biochemical responses associated with inflammation in marine bivalves remain unexplored. Here, we investigated changes in nitric oxide (NO) levels, cyclooxygenase 2 (COX-2) activity, and allograft inflammatory factor-1 (AIF-1) gene expression levels in hemolymph samples collected from Manila clam (Ruditapes philippinarum) exposed to pro- and anti-inflammatory substances. These included the pro-inflammatory agent lipopolysaccharide (LPS), and the nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen and diclofenac, all widely used in vertebrates. Our study showed that NO levels, COX-2 activity, and AIF-1 expression increased in response to the treatments with LPS and decreased in response to the treatments with NSAIDs in a concentration-dependent manner. These results suggest that the mechanism of inflammatory responses in bivalves is very similar to that of vertebrates, and we propose that inflammatory responses can be quantified using these techniques and used to determine the physiological status of marine bivalves exposed to biotic or abiotic stresses.

Design of an Optical Transparent Absorber and Defect Diagnostics Analysis Based on Near-Field Measurement.

To reduce the electromagnetic wave interference caused by cavity resonance or electromagnetic wave leakage, herein, an optical transparent radar absorbing structure (RAS) was designed using transparent conductive oxides (TCOs) with a high optical transmittance and electrical conductivity, and a procedure was proposed for detecting possible defects in the fabrication and operation and for assessing the influence of the defects on the electromagnetic performance. To detect locally occurring defects in planar and three-dimensional absorbing structures, a measurement system based on an open-ended near-field antenna capable of producing small beam spots at a close distance was constructed. Moreover, the reflection characteristics of the transparent RAS were derived from a simplified multiple reflection equation, and the derived results were compared with the analysis results of an equivalent circuit model to predict the surface resistance of the TCO coating layer, based on which the presence of defects could be confirmed. By using the experimental results, the predicted surface resistance results of the coating layer and the results measured using a non-contact sheet resistance meter were compared and were found to correspond, thereby confirming the effectiveness of the proposed defect detection method.

Physiological plasticity of corals to temperature stress in marginal coral communities.

Adaptation and/or acclimatization through various mechanisms have been suggested to help some tropical coral species to overcome temperature-induced bleaching that is intensifying with climate change; however, while much research has been done on the physiological responses of tropical and subtropical corals to stress, little is known about these responses in corals in marginal environments-e.g., high-latitude and non-reefal communities. In this study, we examined the thermal-tolerant physiology of the flowerpot coral, Alveopora japonica, endemic to the high-latitude Jeju Island (33.39°N), South Korea and Oulastrea crispata and Coelastrea aspera from the subtropical non-reefal coral community on the Penghu Islands (23.34°N), Taiwan. Analysis of physiological parameters; photochemical efficiency, Chlorophyll pigment, Symbiodiniaceae cell number and host soluble proteins - showed that A. japonica can survive through a wide range of temperature stresses (10-32 °C) over a period of 8 days without showing signs of bleaching. In addition, corals O. crispata and C. aspera withstood temperature stresses of up to 33 °C and repeated temperature fluctuations without bleaching. Our results indicate that, under large seasonal variations and asymmetrical daily fluctuations in temperature, corals currently living in marginal environments could have thermal plasticity, allowing them to survive in the future climate change scenarios. This study reiterates the importance of studying the eco-physiology of corals that are generally ignored because of their neutral or positive responses to stress.

Effect of Epigallocatechin Gallate on Viability of Kudoa septempunctata.

Kudoa septempunctata have been reported as a causative agent for acute transient gastrointestinal troubles after eating raw olive flounder (Paralichthys olivaceus). It raised public health concerns and quarantine control in several countries. Quantitative evaluation on viability of K. septempunctata is crucial to develop effective chemotherapeutics against it. A cytometry using fluorescent stains was employed to assess effect of three compounds on viability of K. septempunctata. Epigallocatechin gallate reduced markedly viability of K. septempunctata at 0.5 mM or more, and damaged K. septempunctata spores by producing cracks.

Flow cytometric characterization of the hemocytes of blood cockles Anadara broughtonii (Schrenck, 1867), Anadara kagoshimensis (Lischke, 1869), and Tegillarca granosa (Linnaeus, 1758) as a biomarker for coastal environmental monitoring.

Marine bivalves are often used as a sentinel species in coastal environmental monitoring since changes in the environmental quality are often well preserved in their cells and tissues. Anadara and Tegillarca species of Arcidae, the blood cockles, are considered to be good sentinel species in monitoring coastal pollution and ecosystem health because they are distributed widely in the subsurface of intertidal mudflats. Internal cellular defense of the blood cockles to physical and biological stresses is mediated by the circulating hemocytes, while their hemocyte types and functions are poorly studied. In this study, we first characterized morphology and immune-related activities of hemocytes of three common blood cockles Anadara broughtonii, A. kagoshimensis, and Tegillarca granosa using flow cytometry. Based on cell morphology and immunological functions, we described five types of hemocytes identically in the three blood cockles: erythrocytes type-I (erythrocytes-I), erythrocytes type-II (erythrocytes-II), granulocytes, hyalinocytes, and blast-like cells. Erythrocytes were round cells containing hemoglobin with numerous granules in the cytoplasm and these cells consist of two central populations. Erythrocytes-I were the most abundant cells accounting for 80-89% of the total circulating hemocytes and exhibited a certain level of lysosome and oxidative capacity. Erythrocytes-II were the largest cells and displayed high lysosome content and the most active oxidative capacity. Both erythrocytes-I and erythrocytes-II did not show phagocytosis capacity. Granulocytes were intermediated-sized hemocytes characterized by granules in the cytoplasm and long pseudopodia on the cell surface, and these cells were mainly engaged in the cellular defense exhibiting the largest lysosome content, the most active phagocytosis, and high oxidative capacity. Contrary to granulocytes, hyalinocytes were comparatively small and round cells and exhibited no granules in the cytoplasm. Hyalinocytes displayed a certain level of lysosome and phagocytosis and oxidative capacities. Blast-like cells characterized by the smallest size and small quantity of cytoplasm and exhibited an absence of phagocytosis and extremely low oxidative capacity, suggesting that this population is not directly involved in the cell-mediated immune activities. In conclusion, flow cytometry indicated that three blood cockles had five types of hemocytes, and the erythrocytes and granulocytes were mainly involved in the immunological activities.

Correction to: Scanning electron microscopic observation of the in vitro cultured protozoan, Perkinsus olseni, isolated from the Manila clam, Ruditapes philippinarum.

An amendment to this paper has been published and can be accessed via the original article.

Molecular characterization of Urosporidium tapetis sp. nov., a haplosporidian hyperparasite infecting metacercariae of Parvatrema duboisi (Dollfus 1923), a trematode parasite of Manila clam Ruditapes philippinarum on the west coast of Korea.

Recently, a putative new hyperparasitic haplosporidian in the genus Urosporidium was identified from metacercariae of the trematode Parvatrema duboisi infecting Manila clam Ruditapes philippinarum on the west coast of Korea. In this study, we applied small subunit ribosomal DNA (SSU rDNA) sequences as a marker to substantiate the phylogenetic relationship of the unidentified Urosporidium within the Order Haplosporida. In our phylogenetic analysis, the 1890 bp of SSU rDNA sequences obtained were closely related to a haplosporidian parasite forming a sister clade to Urosporidium group, although the gene sequences were only 89.22-89.70% similar to Urosporidium spp. Such molecular phylogenetic distance within the genus suggested that the unidentified Urosporidium is a new member of the genus. Accordingly, we report the unidentified haplosporidian hyperparasite as Urosporidium tapetis sp. nov.

Scanning electron microscopic observation of the in vitro cultured protozoan, Perkinsus olseni, isolated from the Manila clam, Ruditapes philippinarum.

BACKGROUND: Perkinsosis is a major disease affecting the commercially important marine mollusk Ruditapes philippinarum (Manila clam) in Asian waters. In this study, we investigated the morphological characteristics of Perkinsus olseni, the causative agent of perkinsosis, cultured under laboratory conditions at different stages of its life cycle using a scanning electron microscope (SEM). RESULTS: The prezoosporangia formed after induction with Ray's fluid thioglycollate medium (RFTM) developed into zoosporangia. During this process, a discharge tube formed a porous sponge-like structure that detached before the zoospores were released; thus, this organelle operated as a bung. Liberated zoospores gradually transformed into immature trophozoites, during which detachment of the anterior flagella occurred, but the loss of the posterior flagella was not clearly observed in the present study. Mature trophozoites underwent schizogony by cleaving the cell forming some merozoites in schizonts, which were released by the rupturing of the cellular membrane of the schizont within a few days. CONCLUSIONS: Our morphological and ultrastructural studies contribute new information on the life cycle and propagation of P. olseni.

Temporal changes in hemocyte functions of the oyster Saccostrea kegaki (Torigoe & Inaba, 1981) on Jeju Island off the south coast of Korea are closely associated with annual gametogenesis.

Hemocyte parameters have been used as a proxy to characterize the health condition of marine bivalves, as the effects of external and internal stresses are reflected well in these parameters. Marine bivalve hemocyte functions are often depressed during the post-spawning period due to physiological stress and energy depletion. In this study, we analyzed temporal changes in hemocyte parameters of the oyster Saccostrea kegaki on Jeju Island, off the south coast of Korea, using flow cytometry. Total hemocyte count (THC), hemocyte types, hemocyte mortality, and phagocytosis capacity were analyzed. S. kegaki spawned during June and August, when the sea surface temperature increased from 18 to 23 °C. Most of the oysters were in the spent and resting phases from September to January. THC dropped dramatically from September to October, when most oysters completed spawning. Histology revealed that the residual eggs or sperm were actively resorbed through phagocytosis by hemocytes during the spent stage. Hemocyte mortality also showed its annual peak in October, possibly due to increased resorbing activities. The phagocytosis capacities of the granulocytes decreased dramatically from September to February. The level of energy reserves (glycogen) in post-spawning tissues was significantly lower than that prior to spawning. The low energy level reserve during the post-spawning period likely reduced the THC and immune capacities, as oysters may have been unable to acquire sufficient food from the ambient environment.

Characteristic concentrations and isotopic composition of airborne lead at urban, rural and remote sites in western Korea.

Anthropogenic Pb emitted from East Asia, particularly China, is often long-range transported to the east by the prevailing westerlies. To characterize the geographical properties of varying atmospheric Pb concentrations by transboundary and domestic source(s)-related Pb in Korea, closely adjacent to China, the Al and Pb concentrations and the stable Pb isotopic composition were determined in the total suspended particles (TSP) collected at urban (IC), rural (TA), and remote background (JJ) sites in western Korea from August 2015 to October 2016. The annual average Pb concentrations were significantly higher in urban and rural areas (IC, 16.2 ng m-3 and TA, 11.1 ng m-3) than in remote area (JJ, 6.41 ng m-3), showing pronounced seasonal variations with relatively higher concentrations in winter and spring and lower concentrations in summer and autumn. Significantly high enrichment factors (EF) for Pb indicate that anthropogenic contributions are important for this toxic element in TSP. Coupling the Pb isotopic signatures with the air mass back trajectories identified the major potential source regions for individual samples. The results show that during winter, China was the dominant contributor, accounting for 92%, 82%, and 100% of the sampling periods at IC, TA, and JJ, respectively. The Chinese contribution decreased in summer and autumn, whereas the Korean contribution increased, according to the East Asian monsoon system. The Pb concentrations increased by 2.2 (IC), 1.2 (TA) and 1.4 (JJ) times when the Chinese contribution was dominant, compared to the Korea-dominant periods. The Pb isotopic systematics for the samples characterized by the dominant Korean contribution differed substantially between the three sites, implying that the relative importance of various domestic sources varied with geographical areas in western Korea.

A novel paramyxean parasite, Marteilia tapetis sp. nov. (Cercozoa) infecting the digestive gland of Manila clam Ruditapes philippinarum from the southeast coast of Korea.

Paramyxean parasites in the genus Marteilia deteriorate digestive tissues of the host organisms, resulting in mortality of oysters, cockles, and mussels. Most reports of infection by Marteilia spp. are from Europe, while a new species of Marteilia was identified recently in Japan. Here, we report a previously unidentified species in the genus Marteilia from digestive diverticula of Manila clam Ruditapes philippinarum from the south coast of Korea. Prevalence of the parasite was low, 0.5-3.3% in the study sites. We characterized this species using light and transmission electron microscopy (TEM), and analyzed the 18S rDNA sequence. Light microscopy revealed the sporulation process from uninucleated stage to spore in the epithelial tissues of the digestive gland. TEM revealed that the parasites produced four secondary cells containing four tri-cellular spores. An electron-dense haplosporosome-like structure and striated inclusions were evident in the spore and the primary cells, respectively, while refringent granules were rarely observed in the secondary cells. Phylogenetic analyses of the 18S rDNA sequence placed this isolate in the genus Marteilia, although it is not identical to other known species in the genus. Based on morphological and molecular characters, we describe this species as Marteilia tapetis sp. nov., the second Marteilia species reported parasitizing Manila clams in Asian waters.

Early Larval Development and Annual Gametogenesis of the Brooding Oyster Ostrea circumpicta (Pilsbry, 1904) in the Shallow Subtidal Benthic Ecosystem in Jeju Island, Off the South Coast of Korea.

The subtropical brooding oyster Ostrea (= Striostrea) circumpicta (Pilsbry, 1904) occurs at high density in the shallow, subtidal, rocky bottom in Jeju Island, off the south coast of Korea, where the sea surface temperature and salinity varies annually from 13 to 25°C and 30 to 33 ppt, respectively. In this study, the annual gametogenesis and early larval development of O. circumpicta was examined, using histology and scanning electron microscopy (SEM). Histology indicated that the females and males initiated gonial mitosis in September, shortly after sexual resting in August. In December, ripe eggs first appeared in the follicles, and most of the females exhibited fully mature oocytes in May, as the water temperature reached 17 to 18°C. Spawning females were dominant in June and July, when the trochophore and strait- hinged veliger larvae were also identified in the branchial chambers, their size ranging from 111 to 130 µm and 135-205 µm in diameter, respectively. The veliger larvae in the brooding chamber exhibited a well- developed velum and digestive tract, suggesting that the larvae are engaged in feeding in the branchial chamber. Unlike other marine bivalves in temperate coastal ecosystems, O. circumpicta has a long period of gonad maturation and a short resting phase. It has been believed that such a long period of reproductive maturation is associated with a low level of food in the environment and the comparatively large size of the oocytes, which may require a relatively longer time to accumulate necessary nutrients to produce large eggs in a food-poor environment.

Physiological processes and gross energy budget of the submerged longline-cultured Pacific oyster Crassostrea gigas in a temperate bay of Korea.

Physiological processes and gross energy budget of the longline-cultured Pacific oyster Crassostrea gigas were investigated in Geoje-Hansan Bay, Korea during two entire culturing periods. Based on physiological measurements of food consumption, feces production, ammonium excretion, and respiration from July 2008 to February 2009 and from July 2013 to February 2014, scope for growth appeared to be positive during most of the culturing period, except for one period with extremely high temperatures (up to 25°C). Estimates of physiological energy production matched well with tissue energy increment measured by gross biochemical composition during the culturing period, suggesting that the oysters might adjust their physiological performance to relatively low concentrations of suspended particulate matter in the bay to optimize energy acquisition. Such an adaptive adjustment includes an increased absorption of energy and a reduced loss of metabolic and excretory energy, resulting in positive production under high culturing density. Using physiological measurements, we further assessed the feedback effects of the longline aquaculture of oysters on the bay system. Ecological efficiency, estimated by a series of energetic efficiencies at the whole bay level, was low compared with Lindeman's law of trophic efficiency. Biodeposition and ammonia excretion rates in this study were relatively low compared with other intertidal plastic bag cultures. These results indicate that the cultured oysters might have only minor effects on benthic and pelagic environments of the bay. Overall, our results suggest that the adaptive physiological performance of oysters and consequently weak feedback effects on ambient habitats should facilitate sustainable longline aquaculture in the bay for a prolonged period without severe habitat deterioration.