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Microzooplanton play a crucial role in marine ecosystems, as they transfer matter and energy from pico- and nano-phytoplankton to mesozooplankton. In this study, we explored the seasonal variations of microzooplankton grazing derived from dilution experiments in a typical eutrophic coast of Southern China, as well as the abundance and biodiversity of its key group (ciliate), to further understand its function in the subtropical coastal food web associated with potential regulation factors. A total of 29 ciliate species belonging to 18 genera were identified, with the dominating species of Mesodinium rubrum, Strombidium globosaneum and Strombidium conicum. The spatial difference of ciliates abundance was attributed by the changes of temperature and salinity. Phytoplankton growth rate (μ) and microzooplankton grazing rate (m) ranged from 0.03 to 1.36 d−1 and 0.10 to 1.57 d−1, respectively, and both μ and m showed the highest values in summer and the lowest in winter. Moreover, microzooplankton grazing pressure on the phytoplankton standing stocks and potential primary production ranged from 10% to 79% and 58% to 471%, respectively. Our results indicated that temperature is the main environmental driving force for the seasonal changes of μ and m, and that the impacts of run-offs from the Pearl River and offshore seawater intrusion from the South China Sea are responsible for the spatial-temporal variations of phytoplankton growth and microzooplankton grazing.

In this study, the variations of the seawater carbonate system parameters and air-sea CO2 flux (FCO2) of Shen’ao Bay, a typical subtropical aquaculture bay located in China, were investigated in spring 2016 (March to May). Parameters related to the seawater carbonate system and FCO2 were measured monthly in 3 different aquaculture areas (fish, oyster and seaweed) and in a non-culture area near the bay mouth. The results showed that the seawater carbonate system was markedly influenced by the biological processes of the culture species. Total alkalinity was significantly lower in the oyster area compared with the fish and seaweed areas, mainly because of the calcification process of oysters. Dissolved inorganic carbon (DIC) and CO2 partial pressure (pCO2) were highest in the fish area, followed by the oyster and non-culture areas, and lowest in the seaweed area. Oysters and fish can have indirect influences on DIC and pCO2by releasing nutrients, which facilitate the growth of seaweed and phytoplankton and therefore promote photosynthetic CO2 fixation. For these reasons, Shen’ao Bay acts as a potential CO2 sink in spring, with an average FCO2 ranging from -1.2 to -4.8 mmol m-2 d-1. CO2 fixation in the seaweed area was the largest contributor to CO2 flux, accounting for ca. 58% of the total CO2 sink capacity of the entire bay. These results suggest that the carbonate system and FCO2 of Shen’ao Bay were significantly affected by large-scale mariculture activities. A higher CO2 sink capacity could be acquired by extending the culture area of seaweed.

The spatio-temporal variations of the significant wave height (SWH) in the Western North Pacific and South China Sea (WNP-SCS) region, as well as their driving mechanisms, are investigated based on the long-term (1981–2014) simulation by a coupled ocean–atmosphere model and a WAVEWATCH III model. The Empirical Orthogonal Function modes of SWH anomalies show different patterns in the cold and warm seasons. In winter, the first mode (explaining 40.63% of the variance) shows a monopole pattern with large loadings lying in SCS and the WNP to the east of the Philippine Islands, which is primarily associated with the El Nino-Southern Oscillation (ENSO) on inter-annual time scales. The second mode (explaining 19.62% of the variance) shows a dipole pattern with negative loadings in the northeastern SCS and positive loadings to the east of Japan, which is prominently connected with the intensity variation and longitudinal shift of Aleutian Low on decadal time scales. In summer, the first leading mode (explaining 73.47% of the variance) presents large loadings located mainly in the WNP region between 10° N and 30° N and secondarily in the central SCS, which is associated with the ENSO-affected tropical cyclone activities and South China Sea summer monsoon, respectively.

The abundance and community structure of nirS-encoding and nirK-encoding denitrifiers inhabiting the sediment of the Pearl River Estuary was examined with quantitative PCR and high-throughput MiSeq sequencing. The results indicated that the low-oxygen condition (around 4 mg/L) of the Pearl River Estuary was the suitable environment for the denitrifying bacterial growth, and the abundances of nirS-encoding and nirK-encoding denitrifier were both highest in station P3, while the diversity and evenness were highest in stations P2 and P4, respectively. In addition, gene abundance and diversity of nirS was higher than nirK, which indicated that the denitrifying potential of nirS-encoding denitrifiers were significantly greater than that of nirK-encoding denitrifiers (p < 0.05). The most dominant nirS-encoding denitrifiers present in the sediment samples belonged to the phylum Proteobacteria, followed by Chloroflexi. However, the dominant classes of Betaproteobacteria and Gammaproteobacteria showed obvious salinity heterogeneity along the Pearl River Estuary. Betaproteobacteria have a strong survival ability in oligohaline environments and Gammaproteobacteria were opposite. Additionally, the distribution of both Betaproteobacteria and Gammaproteobacteria positively correlated with TOC and $${\text{NO}}_{2}^{ - }.$$ For nirK-encoding denitrifiers, the distribution of cluster A and cluster C also showed salinity heterogeneity; the former favored oligohaline environments and the latter were opposite.

We report the first mitochondrial genome sequences for the three band pennant fish, Heniochus chrysostomus. The whole mitogenome of H. chrysostomus was circular in shape and 16,650 bp in length. Th...

Finfish cage culture is the most predominant form of mariculture. The rapid expansion of fish cage culture systems has raised concerns about their environmental impact, such as nutrient release. In this study, for the first time, we estimated the release of nitrogen (N) and phosphorus (P) from fish cage culture in Daya Bay, southern China, by constructing N and P budget models based on a mass balance principle. In addition, the contribution and importance of nutrients from fish culture and other nutrient sources, including submarine groundwater discharge, benthic sediments, local rivers, and atmospheric deposition were assessed. The annual amount of N and P released from fish cage culture was 205.6 metric tons (hereafter tons) of N and 39.2 tons of P, including 142.7 tons of dissolved inorganic nitrogen (DIN) and 15.1 tons of dissolved inorganic phosphorus (DIP). Among the analyzed nutrient sources, the contributions of DIN and DIP from fish culture were 7.0% and 2.7%, respectively. For cages consuming conventional trash fish, 142 kg of N and 26 kg of P were released into the environment per ton of fish products, much higher than the values (72 kg N and 17.3 kg P) for cages using formulated feed. In fish culture, the dissolved nutrients were more N rich, but the particulate nutrients were more P rich. The ratio of cage-derived N and P was 21.1, higher than the ratio of coastal seawater (27.1), indicating that cage culture may also impact the local nutrient forms around farming regions. Oyster cultivation and harvest removed 126.3 tons of N and 35.1 tons of P from of the bay. Replacing trash fish with formulated feed and co-culturing of nutrient extractive species (e.g., bivalves, macroalgae) and deposit-feeding species (e.g., sea cucumber) in fish culture zones can be efficient nutrient mitigation strategies.

Summary: The seasonal patterns of the denitrifiers (denitrifying bacteria) in the sediment of Daya Bay, southern China, were examined using quantitative PCR and high-throughput MiSeq sequencing methods in spring, summer and winter. The abundance and diversity of nirS-encoding denitrifiers were much higher than that of nirK-encoding denitrifiers, indicating that the former probably dominated the denitrification processes in sediments of Daya Bay. The average abundance and diversity of nirS-encoding denitrifiers were much higher in spring than that in summer and winter, on the other hand, the abundance of nirK-encoding denitrifiers showed the opposite pattern. The species composition of nirS-encoding denitrifiers community in spring differed significantly from that in summer and winter, whereas, no significant difference existed between summer and winter. The dominant environmental drivers for the diversity of community species were NO2−, NO3− and DO concentrations. The abundances of dominant genera of nirS- encoding denitrifiers, Accumulibacter sp. and Cuprizvidus sp., were significantly higher in summer and winter than that in spring, and were negatively correlated with NO2−, NO3−, and DO concentrations (p

Creseis acicula is a pteropod species, widely distributed in the world’s ocean. The latest report of its bloom was in the Mediterranean Sea in 1990. On June 12, 2020, an unprecedented bloom of C. acicula was observed in Daya Bay, China, that lasted for over a month and caused economic losses. The maximum abundance of C. acicula was up to 5595 ind. m-3, 1000 times the local record high, and 10 times the highest number recorded elsewhere. Higher abundance (≥ 1000 ind. m-3) was found in the warm water of ≥ 30℃ along the southwest shore of Daya Bay. The initiation of the bloom matched a sharp increase of temperature and chlorophyll a and an abrupt decrease of salinity attributed to heavy rainfall that lasted for more than 20 days. Considering rising occurrences of extreme weather due to global change, possibilities of recurrent C. acicula blooms worldwide certainly deserve attention.

With the rapid development of mariculture in China, large amounts of antibiotics are being discharged into the aquatic environment. Little information is available regarding antibiotics and corresponding antibiotic resistance genes (ARGs) associated with maricultural environments in China. Sediments from eleven typical mariculture areas along the whole coastline of China were collected, and the sediment in Meijijiao in southern China was used as a non-mariculture control. The results revealed that antibiotics and their corresponding ARGs were widely distributed in most maricultural sediments, and present at low concentrations in samples from Meijijiao. The sulfonamide-resistance genes were prevalent, and the sul1 and sul2 in Penglai were the highest detected by using quantitative PCR. Moreover, remarkable differences in ARGs among different sites were observed. Due to the limited availability of primers to detect ARGs, illumina high-throughput sequencing was also used for profiling ARGs, and the results showed that the abundance of bacA in all samples was the highest compared to other ARGs, followed by mexF and mexB. This is the first study to comprehensively investigate the antibiotic resistance profile in typical mariculture areas along the whole coast of China. This study provides insights into the impacts of mariculture on the profiles of bacterial and ARG compositions in China.

As an important nutrient source for coastal waters, submarine groundwater discharge (SGD) has long been largely ignored in Daya Bay, China. In this study, we estimate the fluxes of SGD and associated nutrients into this region using a 224Ra mass balance model and assess the contribution/importance of nutrients by SGD, benthic sediments, local rivers, and atmospheric deposition. The results of 224Ra mass balance show that the estimated SGD ranges from (2.76 ± 1.43) × 106 m3/d to (1.03 ± 0.53) × 107 m3/d with an average of (6.32 ± 2.42) × 106 m3/d, about 16 times the total discharge rate of local rivers. The nutrient loading from SGD is estimated to be (1.05–1.99) × 105 mol/d for NO3-N, (4.04–12.16) × 103 mol/d for DIP, and (3.54–11.35) × 105 mol/d for Si. Among these considered nutrient sources, we find that SGD is the primary source for Si and NO3-N, contributing 68% and 42% of all considered sources, respectively. The atmospheric NO3-N flux is comparable to that from SGD. The local rivers are the most important source for DIP, contributing 75% of all considered sources. SGD with high N:P ratio (NO3-N/DIP) of 37.0 delivers not only a large quantity of nutrients, but also changes nutrient structure in coastal water. Based on a DIP budget, primary productivity is evaluated to be 54–73 mg C/m2 d, in which SGD accounts for approximately 30% of total production. This study indicates that SGD is a key source of nutrients to coastal waters and may cause an obvious change of primary production and nutrient structure in Daya Bay.

The abundance and composition of bacterioplankton of the Northern South China Sea (NSCS) were investigated using flow cytometry and high-throughput sequencing. The results showed that the absolute abundance of bacterioplankton retained high values in surface waters at both continental shelf and oceanic sites and Proteobacteria, Cyanobacteria, and Bacteroidetes represented the three typical dominant phyla in NSCS. The average bacterioplankton abundances at 5 m, 75 m, and 200 m were 9.55, 5.04, and 1.32 × 105 cells mL−1, respectively, and there was a significantly positive correlation between bacterioplankton abundance and Chl a content (r = 0.84, p

We examined the separate effect of Portuguese oyster Crassostrea angulata and the interactive effects of oyster and red seaweed Gracilaria lemaneiformis on seawater dissolved inorganic carbon (DIC) systems and the air-sea CO2 flux (FCO2) in Daya Bay, southern China. Respiration and calcification rates of oysters were measured and the effects of oyster aquaculture on marine DIC systems were evaluated. The interactive effects on seawater DIC and air-sea FCO2 were examined using mesocosms containing oyster and seaweed assemblages. Results showed populations of C. angulata cultured in Daya Bay sequestered ca. 258 g C m-2 yr-1 for shell formation, whereas the CO2 released due to respiration and calcification was 349 and 153 g C m-2 yr-1, respectively. This indicates that oyster cultivation in Daya Bay is a CO2 generator, favoring the escape of CO2 into the atmosphere. DIC, HCO3- and CO2 concentrations and the partial pressure of CO2 in oyster-seaweed co-cultured mesocosms were significantly lower than the oyster monoculture mesocosm. These results indicated that G. lemaneiformis effectively absorbs the CO2 released by oysters. The negative values of air-sea FCO2 in the co-culture groups represent a CO2 sink from the atmosphere to the sea. These results demonstrated that there could be an interspecies mutual benefit for both C. angulata and G. lemaneiformis in the integrated culture system. Considering that photosynthesis of seaweed is carbon limited, we suggest that the 2 species are co-cultured at a ratio of ca. 4:1 (based on fresh weight) for efficient utilization of DIC in seawater by G. lemaneiformis, and further to increase the ocean CO2 sink.

Sargassum hemiphyllum is a common species in many countries of the world. Its culture is both economically and ecologically important. Ulva prolifera is an annoying macro-epiphyte during seedling cultivation of S. hemiphyllum and becomes a bottleneck for the successful production of Sargassum seedlings. The present study aimed to develop an effective control method of U. prolifera. The performances of the two macroalgae cultivated under co-culture and mono-culture mode using NO3− or NH4+ as nitrogen resource were evaluated to test whether the U. prolifera could be inhibited through manipulation of nitrogen availability. Increasing NO3− and NH4+ concentrations accelerated the growth and tissue N accumulation in U. prolifera better than in S. hemiphyllum. However, the maximum growth rate of U. prolifera at infinite tissue N contents was about 70% higher than that of S. hemiphyllum, and the critical N content (NC) of U. prolifera was about twice that of S. hemiphyllum, indicating a higher risk of N limitation for U. prolifera than for S. hemiphyllum. In co-culture mode, when cultivated with 5 and 10 μM NO3− or 5 μM NH4+, the tissue N content of S. hemiphyllum was comparable to or higher than its NC, whereas the tissue N content of U. prolifera was much lower than its NC; the growth rate, chlorophyll a and soluble protein contents of U. prolifera were lower than its corresponding values in mono-culture mode. The inhibition effect of S. hemiphyllum on U. prolifera was highest in the cultivation medium with 5 μM NO3−. This suggested that the competitive advantage of epiphytic U. prolifera can to some extent be mitigated by manipulating nitrogen availability in cultivation medium. We recommend using NO3− as the N resource, and set the N concentration at approximately 5–10 μM in cultivation medium.

Suspended mariculture has significantly influences on the benthic sediment. However, our understanding on how bacterial communities respond to mariculture induced changes in redox profiles is limited. In present study, sediments from two maricultures and reference areas were collected and incubated for 28 day. The results indicated that the dominant pathway of organic matter mineralization in the sediment varied from groups, in the reference, it was the iron reduction, but in the two mariculture groups it was the SO42− reduction. Remarkable changes of bacteria community were recorded in the aerobic zone, where the abundances of 14 OTUs belonging to Gammaproteobacteria and Alphaproteobacteria were significantly higher than that in oxidation and anaerobic zones. However, 4 keystone OTUs were strictly anaerobic and belonging to Desulfobacteraceae (n = 3) and Marinilabiaceae (n = 1). The main environmental drivers determining sediment bacterial distribution were the particle organic carbon, dissolve oxygen, NO3−, and moisture content.

The oyster Crassostrea angulata is a major species for shellfish aquaculture in southern China. In this study, the in situ biodeposition method was used to estimate the clearance rate (CR) of C. angulata cultivated in Dapeng Cove, southern China, from January 2012 to January 2013. Relationships between CR and the dry tissue weight (DW) of the oyster were estimated for each experimental period. Results indicated that the CR of C. angulata related to DW by allometric relationships (CR = a × DWb) (the a values, representing CR of an oyster with 1 g DW) varied with time. The maximum value (7.678) was observed in November 2012, and the minimum value (0.655) in August 2012, when the oysters were in their reproductive period. The exponent value of b was low when oysters were large, and the minimum (0.215) occurred in August 2012; the b values were all > 0.9 during November and December 2012 when oysters were small. The relationship between the standardized CR (1 g DW; outside the reproductive period) and water temperature (T) can be described by non-linear regression: CRstd = − 0.098 T2 + 4.885 T − 53.476 (n = 6, R2 = 0.949, p = 0.012), and the CRstd increased with T until a theoretical maximum (7.400 L g− 1 h− 1) was reached at 24.92 °C. No statistically significant relationship was observed between CRstd and other environmental parameters (all p > 0.05). These results may facilitate oyster aquaculture management in southern China.

For the purpose of indoor mass culture of seedlings of Sargassum hemiphyllum during spring and summer, a series of experiments were designed to evaluate nitrogen (N) uptake, growth performance, and N accumulation of seedlings. Transient uptake rates by N-limited seedlings for nitrate (NO3 −), ammonium (NH4 +), and urea were more rapid than uptake rates by N-replete seedlings. NO3 − uptake revealed a rate-saturating uptake kinetic for both N-limited and N-replete seedlings. Uptake rates of NH4 + and urea for N-limited seedlings were linear, whereas the N-replete seedlings displayed Michaelis-Menten curves. The slope of the linear models or equivalently affinity calculated from Michaelis-Menten curves was highest for NH4 + and lowest for urea, indicating that seedlings were more efficient at taking up NH4 +. Tissue N content in seedling increased with increasing N concentrations, with the highest values with all three N sources at 150 μM. The N requirement to support maximum growth varied 2.2-fold from 0.39 ± 0.15% dry weight (DW) in NH4 + to 0.84 ± 0.09% DW in NO3 −, and hence, seedlings became more easily N limited at low NO3 − availability. The results showed that seedlings cultured in NO3 − enrichment (50–100 μM) may be better able to meet their maximum growth than at high NH4 + availability, although seedlings have higher NH4 + uptake capacities.

Planktonic ciliate composition, abundance and its response to environmental change were investigated during four seasons (winter of 2013, spring, summer and autumn of 2014) in Daya Bay, the South China Sea. A total of 41 species belonging to eight orders were identified, 14 of which were dominant. Planktonic ciliate communities showed a distinct seasonal pattern in ciliate abundance and a clear seasonal shift in the taxonomic composition. The largest number of ciliate species occurred in summer, whereas the highest abundance peaked in spring, mainly due to oligotrichids. In terms of spatial distribution, ciliate species were abundant in the area of artificial reefs, and ciliate abundance was higher in the Dapeng Cove aquaculture area and lower at the Daya Bay Nuclear Power Station. Clustering analysis demonstrated that the seasonal variations of the ciliate community structure were more obvious than spatial variations. Multivariate and univariate analyses illustrated that ciliate abundance was significantly correlated with the water nutrient level and chlorophyll-a concentration, temperature, salinity and dissolved oxygen. Moreover, the dominant abiotic environmental factors affecting the spatial pattern of ciliate communities varied between seasons.

The effects of dietary protein level on nutrient digestibility and utilization of protein and energy of juvenile Chinese soft-shelled turtle, Pelodiscus sinensis, were investigated. Seven isoenergetic diets containing graded levels of protein (25, 27, 29, 31, 33, 35, and 43%) were fed to turtles initially averaging 4.8 ± 0.7 g for 8 wk at 30 ± 0.5 C. The apparent digestibilities of dry matter, protein, and energy were generally increased with dietary protein level. Proportions of nitrogen intake (CN) allocated to excretory nitrogen (UN) were higher in 25 and 43% protein diets than the other diets. UN proportion was lowest in the 33% protein diet, whereas retained (growth) nitrogen (RN) followed an inverse pattern with UN. Percentages of gross energy intake (IE) used for excretory energy (UE) generally increased when dietary protein levels increased. Turtles fed 25–29% protein diets showed a markedly higher proportion of metabolizable energy (ME) than those fed 31–43% protein diets. Analysis by second-order polynomial regression using RN as the indicator indicated that the estimated optimal dietary protein level was 34.6%. The lowest and highest percentages of retained (growth) energy (RE) were observed in the 25 and 33% protein groups. Nitrogen and energy budget equations of turtles fed 33% protein diet were 100 CN = 8.22 FN + 37.48 UN + 54.30 RN and 100 IE = 10.88 FE + 2.82 UE + 65.60 ME + 20.69 RE, respectively. Diets with excessive protein resulted in high proportions of protein and energy used for excretion.

Phytoplankton pigment concentrations in the sur-face sediments of a fish and oyster farm in Dapeng Cove, South China Sea, were measured monthly to investigate the effects of mariculture on the envi-ronment from December 2011 to December 2012. The highest contents of the identified phytopig-ments, sulphides and total organic carbon in the surface sediments were all found at the fish farm, followed by the oyster farm; the lowest contents were detected at the control site. Fucoxanthin in the surface sediments was the most abundant car-otenoid and was significantly correlated with chlorophyll a (Chl a; r = 0.922, P < 0.01). This finding suggested that the deposited diatoms could be the main source of the Chl a concentration. Besides a differential sedimentation of phytoplank-ton (i. e. higher downflux at fish and oyster site than that at control site), we assume that the extent of pigment diminution from the fish site to control site was also controlled by the chemical conditions of the surface sediments. The fish farm provided the most optimum preservation condi-tions for the phytopigments and was a good sink for phytodetritus among the three sites because of its anoxic and reductive characteristics. Phyto-plankton pigments could be useful biomarkers to evaluate the influence of mariculture on sediment environment.

Ciliates are very important components in most marine ecosystem. They are trophic link between the microbial food web and grazing food chain. In this study, ciliates were collected from 11 sites in the southern South China Sea (SCS) during August 25 to September 28, 2011. Their composition and distribution at the surface and 75 m deep depth of the ocean were studied. A total of 30 species belonging to 22 genera were identified, and 22 species of 15 genera were Tintinnids. Eutintinnus fraknoii and E. stramentus were the most common species. The other dominants were strombidiids ciliates including Strombidium conicum and S. globosaneum, which were followed by the tide form, Mesodinium pulex. Ciliates abundance ranged from 46 ind L-1 to 368 ind L-1 in the open sites, 46–368 ind L-1 at surface and 73–198 ind L-1 at 75 m deep layer. In the Yongshu reef, ciliates abundance ranged from 167 ind L-1 to 365 ind L-1 in the water column, similar to that in Sanya coral reef waters. Ciliates composition showed obvious difference between surface and 75 m deep layer at station S2 (P < 0.05), while no similar result was observed at other sites. At 75 m deep layer, salinity was negatively related to mixed layer depth (P < 0.05), but positively to chlorophyll a concentration (P < 0.05), indicating that the change of vertical mixing in water column influenced vertical distribution of ciliates in the southern SCS.

Wave glider is a new class of ocean mobile observation vehicle. It is a new applied research direction that using wave glider for wave observation. Currently, wave observation is usually performed at fixed points by using wave buoys, the research on using wave glider for navigational observations is still rare, and the characteristics of wave observation using wave glider is not yet mastered. The article Research on the characteristics of wave observation of wave glider, Based on the experimental results, analyze the differences and the correlations between wave glider and wave buoy in wave height, wave period, wave number and wave direction. Analyze the existence mechanism of the difference and propose the theoretical basis for eliminating the difference or correcting the observation data of wave glider. Based on experimental data and theoretical analysis, it is proved that the wave glider is feasible to observe wave. The average correlation coefficient between the observation data of wave glider and the observation data of wave buoy is above 0.9, the results prove that there is a strong correlation between wave glider and wave buoy.

The physiological responses of aquaculture organisms (e.g., oyster and seaweed) have the potential to affect seawater carbon fluxes and subsequently are affected by these seawater changes. In this study, a laboratory experiment and a field mesocosm experiment were carried out in Daya Bay, southern China. In the laboratory experiment, Portuguese oyster Magallana angulata and the brown seaweed Sargassum hemiphyllum were mono-cultured in 20-L transparent glass bottles for 24 h. Water sample were collected at four incubation time points (i.e. 0 h, 4 h, 12 h and 24 h) to examine their physiological responses across the incubation period. The results showed that the oyster calcification rate was not significantly changed among 4 h, 12 h and 24 h. On the other hand, during the 24 h incubation time, the oyster respiration rate, seawater pH, dissolved oxygen (DO), and CO32– concentration were significantly declined, but the seawater CO2 concentration was increased. For the seaweed, from 0 h to 12 h, seawater CO2 and HCO3– concentrations were significantly declined. However, the seawater pH and DO concentration were increased. In the field experiment, oyster and seaweed were cultured in mesocosm bags. The effects of different culture models of M. angulata and S. hemiphyllum (i.e. oyster monoculture, seaweed monoculture and oyster-seaweed co-culture) on seawater CO2‑carbonate system and air-sea CO2 flux (FCO2) were investigated after 24 h incubation. The results showed that DIC, HCO3– and CO2 concentrations and the partial pressure of CO2 in co-culture bags were significantly lower than the control bags (without any culture organisms) and oyster bags, indicated that S. hemiphyllum can effectively absorb the CO2 released by the oysters. The negative values of air-sea FCO2 in the co-culture bags represent a CO2 sink from the atmosphere to the sea. These results demonstrated that aquaculture organism monoculture could result in a stress for itself, and there could be an interspecies mutual benefit for both M. angulata and S. hemiphyllum in the co-culture system. The negative environmental impacts of mono-trophic oyster aquaculture in this view could be mediated with the multi-trophic inclusion of seaweed.

Ascidians are globally important members of marine fouling communities. We meas- ured in situ biodeposition rates of Ciona intestinalis and Styela clava, common biofoulers of aqua- culture infrastructure, in Sanggou Bay, northern China, during September. Ascidian numbers were recorded within a scallop Chlamys farreri farming zone to assess biodeposit loading. Both ascidians were most abundant on lantern nets and scallop shells in August and September. The average densities of C. intestinalis and S. clava in the farming zone in September were approxi- mately 329 and 22 ind. m −2 , respectively, and their biodeposition rates were 32.1 and 121.2 mg dry material ind. �1 d �1 , respectively. Total daily biodeposit production by ascidians in September within the scallop farming zone may amount to 13.24 g m �2 , with daily organic matter, C, N, and P biodeposition rates of 1.88, 0.94, 0.11, and 0.98 × 10 �2 g m �2 , respectively. The predicted daily biodeposit production by C. intestinalis and S. clava within the scallop farming zone in the bay during September was 105.9 t dry material, 7.52 t C, 0.86 t N, and 0.078 t P. By comparison, drop- off to the sea floor was approximately 143.0 t of dry matter for an entire growing season, which would be a relatively small input if averaged on a daily basis. However, some of the drop-off is expected to occur as a short-duration pulse of material (e.g. during cleaning), which may be rela- tively important in terms of benthic effects. The results suggest that the biodeposition processes and drop-off of C. intestinalis and S. clava may play an important role in coupling material fluxes from the water column to the seabed.

article i nfo A feeding trial was conducted to determine the optimal protein requirement of juvenile Chinese soft-shelled tur- tle (Pelodiscus sinensis).Seven isoenergetic dietscontaininggradedlevelsof protein(25%,27%,29%,31%,33%,35%, and 43%) were fed to turtles initially averaging 4.8 ± 0.7 g for 8 weeks. The specific growth rate (SGR) of turtles increased significantly with dietary protein from 25% to 33% without any further significant increases in SGR at 35% or 43% protein. Feed intake was highest in turtles fed with the diet containing 25% protein, followed by the 27-31% protein groups, and was lowestin turtles fed with the33-43%proteindiets. Feed efficiency(FE) of turtles followed an inverse pattern with feed intake. Protein efficiency ratio (PER) in turtles initially increased with die- tary protein levels, with the highest value observed in the 33% protein group, followed by decreases with further increases in dietary protein content. Protein productive value (PPV) of turtles followed the same pattern as PER. Body lipid content decreased with increasing dietary protein level. Analysis of SGR by broken-line regression in- dicated that the estimated optimal dietary level of protein for juvenile Chinese soft-shelled turtles was 32.8%. © 2014 Elsevier B.V. All rights reserved.

In recent years, the GPS wave buoy has been developed for in situ wave monitoring based on satellite GPS signals. Many research works have been completed on the GPS-based wave measurement technology and great progress has been achieved. The basic principle of the GPS wave buoy is to calculate the movement velocity of the buoy using the Doppler frequency shift of satellite GPS signals, and then to calculate the wave parameters from the movement velocity according to ocean wave theory. The shortage of the GPS wave buoy is the occasional occurrence of some unusual values in the movement velocity. This is mainly due to the fact that the GPS antenna is occasionally covered by sea water and cannot normally receive high-quality satellite GPS signals. The traditional solution is to remove these unusual movement velocity values from the records, which requires furthering extend the acquisition time of satellite GPS signals to ensure there is a large enough quantity of effective movement velocity values. Based on the traditional GPS wave measurement technology, this paper presents the algorithmic flow and proposes two improvement measures. On the one hand, the neural network algorithm is used to correct the unusual movement velocity data so that extending the acquisition time of satellite GPS signals is not necessary and battery power is saved. On the other hand, the Gaussian low-pass filter is used to correct the raw directional wave spectrum, which can further eliminate the influence of noise spectrum energy and improve the measurement accuracy. The on-site sea test of the SBF7-1A GPS wave buoy, developed by the National Ocean Technology Center in China, and the gravity-acceleration-type DWR-MKIII Waverider buoy are highlighted in this article. The wave data acquired by the two buoys are analyzed and processed. It can be seen from the processed results that the ocean wave parameters from the two kinds of wave buoys, such as wave height, wave period, wave direction, wave frequency spectrum, and directional wave spectrum, are in good consistency, indicating that the SBF7-1A GPS wave buoy is comparable to the traditional gravity-acceleration-type wave buoy in terms of its accuracy. Therefore, the feasibility and validity of the two improvement measures proposed in this paper are confirmed.

The temporal variation and spatial distribution of plankton ciliate communities were investigated in Shen’ao Bay, South China Sea. In all, 35 species belonging to 17 genera and 7 orders were identified. The number of ciliate species was lower in spring than in summer, whereas ciliate abundance was higher in spring than in summer. Spatially, the number of ciliate species and ciliate abundance were higher in the oyster–algae mixed culture area and non-aquaculture area, and lower in the caged fish culture area. Multivariate and univariate analyses demonstrated that ciliate communities were associated with environmental factors (e.g. temperature, chlorophyll (Chl)-a, nutrient levels). In addition, two dominant species, namely Mesodinium rubrum and Tintinnopsis beroidea, were significantly positively correlated with Chl-a. Three dominant species, namely Strombidium globosaneum, Tintinnopsis minuta and Strombidium conicum, showed more sensitivity to dissolved oxygen, pH and chemical oxygen demand, whereas Tintinnopsis parvula and Tintinnopsis chinglanensis were significantly related to NO2–. Ciliate species diversity, species evenness and species richness were higher in the oyster–algae mixed culture area and non-aquaculture area and lower in the caged fish culture area. Therefore, the results of this study suggest that the ciliate community is significantly correlated with its aquatic habitat and the dominant species can be considered a favourable bioindicator of the marine water environment.

For marine environment observation, especially for open-sea wave-measuring application, a low cost and small size Wave Drifter is introduced as a preferred wave observing instrument. The Wave Drifter is developed based on Global Positioning System (GPS) receivers and deployed in open sea. Based on a single low-cost GPS receiver, the Wave Drifter can provide the standard wave parameters. A Wave Drifter Prototype was launched in the West Pacific area. Wave conditions were recorded especially during Typhoon KROSA (201329). In order to verify the effective of GPS Wave Drifter, comparison between the derived wave parameters and wave model forecast data is carried out. The results show good agreement and discover the underlying applications such as data assimilation into wave forecast models, validation of wave forecast models, calibration of satellite wave sensors and investigation of ocean wave climate and variability.

Along with the construction and development of Global Navigation Satellite System (GNSS) technology, GNSS has been widely and increasingly used in the ocean field, such as offshore wind retrieval, sea ice observation, sea state monitoring et al. Researchers from National Ocean Technology Center take advantage of GNSS satellites signal Doppler shift to measure the buoy state, then inverse the wave spectrum, and calculate the wave characteristic values; Furthermore, GNSS receiver and GNSS Ground-based Augmentation System (GBAS) is used to measure the real-time height of the buoy, then the tide data is extracted through a low-pass filter and a tide revised. Presently, both of the inversion algorithms have passed the laboratory and field test, the results are summarized as follows: the measured wave data is in good consistency with the reference instruments and the tide accuracy of measurement can arrive at centimeter-level. Recently, researchers are concentrating on further improvement of simultaneous inversion algorithm.

Four marine bacterial strains P1, P5, N5 and N21 were isolated from the surface water and sediment of Mirs Bay in southern Chinese coast using the liquid infection method with 48-well plates. These bacteria were all shown to have algicidal activities against Skeletonema costatum. Based on morphological observations, biochemical tests and homology comparisons by 16S rDNA sequences, the isolated strains P1, P5, N5 and N21 were identified as Halobacillus sp., Muricauda sp., Kangiella sp. and Roseivirga sp., respectively. Our results showed that bacterial strain P1 killed S. costatum by release of heat labile algicide, while strains P5, N5 and N21 killed them directly. The algicidal processes of four bacterial strains were different. Strains P1, N5 and N21 disrupted the chain structure and S. costatum appeared as single cells, in which the cellular components were aggregated and the individual cells were inflated and finally lysed, while strain P5 decomposed the algal chains directly. We also showed that the algicidal activities of the bacterial strains were concentration-dependent. More specifically, 10 % (v/v) of bacteria in algae showed the strongest algicidal activities, as all S. costatum cells were killed by strains N5 and N21 within 72 h and by strains P1 and P5 within 96 h. 5 % of bacteria in algae also showed significant algicidal activities, as all S. costatum were killed by strains N5, P5 and N21 within 72, 96 and 120 h, respectively, whereas at this concentration, only 73.4 % of S. costatum cells exposed to strain P1 were killed within 120 h. At the concentration of 1 % bacteria in algae, the number of S. costatum cells continued to increase and the growth rate of algae upon exposure to strain N5 was significantly inhibited.

The rapid development of human activities has caused serious eutrophication of coastal waters in China in the recent decades. The study of the biofiltration capacity of Laminaria japonica under laboratory conditions showed a significant nutrient uptake. After 36 h of incubation, around 42%, 46%, 44% of N and 45%, 42%, 35% of P were removed from three gradients of medium concentrations, respectively. In the conditions of different ratios of N/P and NO 3 –N/NH 4 –N, the optimum N/P ratio for nutrient uptake was 7.4 and L. japonica prefered NO 3 –N rather than NH 4 –N as nitrogen source. Temperature and irradiance affected uptake rates significantly. The maximal N uptake rate appeared at 10 °C and 18 μmol photons m −2 s −1 and the maximal P uptake rate was found at 15 °C and 144 μmol photons m −2 s −1 . Moreover, further studies were needed to investigate the bioremediation potential of L. japonica in the open sea.

The suitability of two algae species, Gracilaria lemaneiformis and Sargassum pallidum, for use as food sources for the abalone Haliotis discus hannai Ino was evaluated. Abalones were fed one of five experimental diets: 1) kelp Laminari japonica: 2) G. lemaneiformis: 3) S. pallidum; 4) a mixed diet of L. japonica and G. lemaneiformis (1:1); and 5) a mixed diet of L. japonica and S. pallidum (1:1) for a period of 4 months. The survival, growth (shell length and body weight), condition index (body weight/shell length), and feed utilization were measured. Survival was excellent (100%) in all groups. Growth rate (body weight) was highest in the abalone fed kelp exclusively, followed by the mixed diet of kelp and G. lemaneiformis. The abalone fed S. pallidum had the lowest increase in body weight and the lowest feed intake. The mixed diet of kelp and G. lemaneiformis yielded the biggest increase in shell length. There were no significant differences in the condition index among all the treatment groups. The mean daily feed intake of L japonica was highest, followed by the mixed diets of kelp and G. lemaneiformis, and was lowest for S. pallidum. Abalone exhibited a preference for L japonica. The feed conversion efficiency was highest for G. lemaneiformis. Results suggest that G. lemaneiformis can be used as a partial substitute for kelp in the diet of cultured abalone. (C) 2010 Elsevier B.V. All rights reserved.