Micro plastics in sandy sediments collected from the intertidal zone of the offshore area of Qinhuangdao were floated by saturated NaCl solution and filtrated with membrane filter. Micro plastic particles were observed using microscope and infrared spectroscopy to discuss the origin and morphology. The surface morphology of micro plastics particles was characterized by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) to analyze surface morphology and elements. The geo accumulation indexes (I_geo) and enrichment factors (EF) were used to study the pollution level and enrichment of heavy metals (Hg, Cd and Pb) in sandy sediments. Total organic carbon (TOC), total nitrogen (TN) and loss on ignition (LOI) and stable isotopes of carbon and nitrogen (δ¹³C and δ¹⁵N) in sandy sediments were determined in order to analyze the source characteristics. The results indicated that there were three types of micro plastics: fiber, foam and film. Fiber was in the majority of micro plastics. Micro plastic particles were enriched with Si, Al, Mg, Fe and Ca in the surface. Hg and Cd were seriously enriched, and Pb was not enriched in the sandy sediments. The concentrations of TOC and TN were low; TOC/TN ratio and stable isotopic composition of C and N (δ¹³C and δ¹⁵N) indicated that TOC originated from marine plankton algae.

Based on the survey data from the bottom-trawl surveys in Shandong coastal waters in autumn (October 2016), winter (January 2017), spring (May 2017) and summer (August 2017), the seasonal variations of population structure and spatial distribution of Cleisthenes herzensteini were studied. The results showed that the average length of C. herzensteini was larger in autumn and winter, while the average mass was larger in summer and autumn. When the length is more than 15 cm, the seasonal variation of mass is larger, and the growth rate of mass is the biggest in summer. The ages of C. herzensteini ranged from 1 to 5 years old, in which individuals of 1 and 2 years old accounted for 45.15% and 40.23% of the population, respectively. The parameters of the von Bertalanffy growth equation, L_∞, K and t₀, were 37.85 cm, 0.28 and −0.57, respectively. The Pauly empirical formula evaluated the natural mortality to be 0.54. The total mortality, the fishing mortality, the exploitation ratio, the age of first capture and the length of first capture were 1.69, 1.15, 68.05%, 1.48 years old and 12.68 cm, respectively. In each season, only the ratio of male to female in summer was significantly different from that in 1:1 (p<0.05), and the number of females was significantly higher than that of males. 50% of the length of sexual maturity is 22.35 cm. The highest ratio of sexual maturity and the highest average coefficient of sexual maturity occur in summer. C. herzensteini mainly distributes in areas with bottom water temperature of 6.45−19.06℃, bottom salinity of 31.82−33.10 and depth of more than 50 m. Its average catch in autumn is much more than that in other seasons, which declines sharply in winter and then rises slowly. The C. herzensteini in Shandong coastal waters showed some phenomena, such as narrow length distribution, deterioration of food supply, delayed spawning period and over-exploited stock. The resources changed dramatically before and after the forbidden fishing period.

Some so-called circumglobal and/or circumpolar marine species are proved to be complexes of cryptic species with restricted distributions by molecular analyses. These phenomena imply that marine species diversity has been underestimated. In this study we use shell morphological characteristics together with mitochondrial COI and 16S rRNA gene sequences in order to study the taxonomy and to identify species of genera Cavolinia and Diacavolinia in family Cavoliniidae from the Indian Ocean and Northwest Pacific Ocean. Our results showed that the species delimitation of Diacavolinia is not supported by molecular analyses, those morphospecies (D. grayi, D. vanutrechti, D. pacifica, D. elegans, D. angulosa, etc.) with distinct morphology from northwestern Pacific are a single species, namely D. longirostris. The subdivision of subspecies and/or forms for C. uncinata could not be confirmed by DNA evidence. Phylogenetic analysis of COI revealed two independent geographical lineages for C. uncinata, C. globulosa and D. longirostris respectively, suggesting that these morphspecies may harbour cryptic diversity. Nuclear mitochondrial pseudogene sequences of COI were detected from most individuals of D. longirostris, which can affect the analysis of DNA barcoding.

The extracellular enzyme activity of seawater can indicate the distribution characteristics of organic and the nutritional status of microorganisms. Activities of eight extracellular enzymes, including alkaline phosphatase, lipase, leucine aminopeptidase, chitinase, cellulose, xylosidase, α-D-glucosidase and β-D-galactosidase, were measured in the surface seawaters collected from 44 stations of the Yellow Sea and the East China Sea from March 25 to April 15, 2017 and from 10 stations of the Jiaozhou Bay nearby waters from April 28 to 29, 2018. In the spring of 2017, the high-value areas of alkaline phosphatase and lipase appeared in the northern coast of Jiangsu and the middle of the Yellow Sea, alkaline phosphatase activity and phosphate concentration were positively correlated. High activity areas of the other six enzymes (leucine aminopeptidase, chitinase, cellulose, xylosidase, α-D-glucosidase and β-D-galactosidase) appeared in the open sea outside the east of the Changjiang River Estuary. The average activities of β-D-galactosidase and xylosidase were significantly higher in the East China Sea than in the Yellow Sea. The decreasing order of average enzyme activities of the eight enzymes was as follows: alkaline phosphatase, lipase, leucine aminopeptidase, chitinase, α-D-glucosidase, β-D-galactosidase, cellulose, xylosidase, the values of α-D-glucosidase and β-D-galactosidase are proximate. The activities of alkaline phosphates, lipase and xylosidase in the Jiaozhou Bay nearby waters in spring 2018 decreased from nearshore to far shore. The decreasing order of the average enzyme activity of the eight enzymes was as follows: alkaline phosphatase, lipase, leucine aminopeptidase, xylosidase, α-D-glucosidase, β-D-galactosidase, cellulose, chitinase, the values of cellulose and chitinase are proximate. The alkaline phosphatase and lipase activities in the Yellow Sea were significantly higher than those in the East China Sea and Jiaozhou Bay. The average enzymatic activities of polysaccharide hydrolases (chitinase, cellulose, α-D-glucosidase, β-D-galactosidase and xylosidase) were the lowest in the Yellow Sea compared with those in the East China Sea and Jiaozhou Bay nearby waters. Our results are beneficial to understand the degradation of organic carbon by plankton and heterotrophic bacteria and the distribution of marine organic carbon in the coastal water of China.

Sexual reproduction of hermatypic corals for coral reef restoration has become a hot topic in recent years. In May 2018, the samples of Favia favus and Platygyra carnosus were collected from the water of Weizhou Island, Guangxi. All of them were cultured in laboratory and the fertilized eggs were collected. The early development process of embryos and larvae was observed and recorded. The results showed that F.favus and P.carnosus were both hermaphrodites, in vitro fertilization, and began to spawn on the fifth to eighth day after the full moon; the early development of embryos and larvae experienced the cleavage stage, blastula stage, gastrula stage and planula stage; the oocytes of two corals did not have zooxanthella as they were ejected. This study records the sexual reproduction behavior of reef-building corals in Weizhou Island, and provides a theory when using sexual reproduction for coral ecological restoration in the future.

Research on the structure and complexity of food webs helps to analyze the function, nutrient dynamics and energy conversion of food webs. Based on the survey data of fishery resources and the analysis of gastric contents in five voyages in Haizhou Bay and its adjacent waters from March to December 2011, this study constructed a Haizhou Bay topology network based on 11 topological network indices. To study the structure and complexity of the Haizhou Bay food network. The results showed that the number of species in the Haizhou Bay food network (S) was 93, the number of connections (L) was 1 021, the number of interactions per species (L/S) was 10.98, the number of connections (L/S²) was 0.12; the proportions of top species, intermediate species, foundation species were 29%, 69% and 2%, respectively; the omnivorous index of food web was 87%; the connection complexity index SC was 22.2; the characteristic path length ChPath was 2.11, and the clustering coefficient CC was 0.23. Studies on the number of interactions and the number of connections in each species showed that the values of L/S and L/S² were within the normal range, so the complexity of the Haizhou Bay food web remained high. Through the analysis of the structure of the food web by species ratio, omnivorous index, connection complexity index, characteristic path length and clustering coefficient, it was found that the food network structure of Haizhou Bay was in a stable state, and the proportion of basic species was low because the phytoplankton and seaweed groups were not classified. Through the study of the structure and complexity of Haizhou Bay food network, it provides an important basis for the in-depth study of the function of Haizhou Bay food network and the scientific management of Haizhou Bay fishery resources.

Neon flying squid Ommastrephes bartramii is a short-lived cephalopod species whose abundance is highly susceptible to marine environmental changes and has large interannual fluctuations. Based on the statistical data from the squid fishery in the Northwest Pacific from 1995 to 2017, catch per unit effort (CPUE) was derived as an abundance index and the grey catastrophic prediction method was used to establish the GM（1, 1）model for the upper and lower catastrophic years and to forecast the future catastrophic years. The results show that the average relative error of the lower limit catastrophic prediction model established based on GLM-model-standardized CPUE is 15.32%, the average relative error of the upper catastrophic prediction model is 8.19%, and the accuracy tests for both models attain the level I accuracy. The study forecasts that the next upper catastrophic year may occur in 2021 (CPUE≥2.39 t/(ship·a)), and the lower catastrophe year occurred in 2027 (CPUE≤2.13 t/(ship·a)). The study also suggests that the Pacific Decadal Oscillation and El Niño-La Nina events are important factors driving large fluctuations in the squid abundance. The forecast can provide a reference for squid fishing enterprises and managing departments in the Northwest Pacific.

In order to assess the health status of ecosystem on the Changjiang River Estuary waters, the ichthyoplankton is used to be indicators. Selecting 10 evaluation indices, which are the total number of ichthyoplankton species, number of benthic species, number of column species, number of intolerant species, proportion of tolerant species, proportion of omnivores, proportion of insectivorous, proportion of carnivores, number of individuals in each sample, proportion of hybrid. This study calculates the estuarine biotic integrity index (EBI) value of the 1986, 1999, 2007 and 2016 by using 1, 3, and 5 approximation of value assignment, and assesses the change trend of the ecosystem health in the Changjiang River Estuary water in recent 30 years. The results show that in 1986, 1999, 2007 and 2016, the EBI values were 52, 40, 36 and 34, respectively, and the corresponding EBI levels were “good”, “fair”, “fair-poor” and “poor”, respectively. By analyzing the results of EBI annual changes, it was found that the health status of ecosystem in the Changjiang River Estuary in recent 30 years showed a trend of declining first and then maintaining at a low level, indicating that the ecosystem of the Changjiang River Estuary waters is urgent to carry out timely protection and restoration.

In this study, we first used the spectral vegetation indices such as normalized difference vegetation index (NDVI), normalized difference water index (NDWI), atmospheric impedance vegetation index (ARPI) and visible spectrum slope ratio of coastal zone imager (CVSSR) to reconstruct the HY-1C coastal zone imager (CZI) image data of the Shankou mangrove national ecosystem nature reserve in Guangxi. And then, the minimum noise fraction rotation (MNF) was used to enhance the spectral difference between mangroves and general terrestrial vegetation on the reconstructed multi-band data set. We established a decision tree based on the MNF components to achieve automatic extracting mangrove information. The results show that the spectral indices reconstruction data and its MNF transformation can effectively enhance the difference between the mangroves and the general terrestrial vegetation on CZI images, the mangrove information can be effectively extracted by our decision tree. Compared with the experts’ interpretation results, the extracted accuracy of area of our method is over 90%. The overall detection accuracy is 88% after verification by random sample points.

In this study, the activity range and distribution patterns of radium and radon isotopes in the coast sea of the Hongyanhe Nuclear Power Plant were investigated in autumn, 2017. The water ages were calculated by "Apparent Radium Age Model", which distribution was then used to assess the major direction of water transport in the study area. We also discussed the relationship between jellyfish abundance distribution and water transport direction. The results indicate that: (1) the activity ranges of ²²⁴Ra, ²²⁶Ra and ²²²Rn were 2.9−62.4 dpm/(100 L), 11.9−57.4 dpm/(100 L), and 0.1−1.3 dpm/L in the study area in autumn, respectively. (2) Based on the “Apparent Radium Age Model”, the so-calculated water ages were ranged from 0 to 16 d, with an average of (10.9±3.6) d. The major water transport direction was towards northeast with the velocity of 7.2 cm/s. (3) There was clear correlation between the distribution of jellyfish abundance and the major water transport direction. The higher jellyfish abundance was found in main water transport direction with older water ages.