Trophic niche and potential carbon source of three reef-associated fishes of Zhongjieshan Islands.

To clarify the trophic relationship of important rock fishes, we analyzed trophic niche of three typical rockfish species (Oplegnathus fasciatus, Sebastiscus marmoratus and Conger myriaster) in the Zhongjieshan Islands in summer 2020, based on the carbon and nitrogen stable isotope techniques. We calculated the contributions of major carbon sources [macroalgae, phytoplankton, suspended particulate organic matter (POM) and substrate organic matter (SOM)]. The results showed that: 1) the δ13C values of the three species ranged from -21.44‰ to -15.21‰, with an average value of (-16.85±1.12)‰, while the δ15N values ranged from 8.32‰ to 10.96‰, with an average value of (9.69±0.66)‰. There were significant differences in carbon and nitrogen stable isotopes among the three species. 2) There was small niche overlap between O. fasciatus and S. marmoratus, indicating that the interspecific competition was not intense. There was no overlap between C. myriaster and the first two, indicating feeding differentiation. 3) The total ecotone area, corrected core ecotone area, and food source diversity of C. myriaster were the highest, indicating that it had a more generalized diet and richer food sources. 4) With Mytilus coruscus as a baseline organism, the trophic level of C. myriaster was the highest (3.38), followed by S. marmoratus (3.09), and the trophic level of O. fasciatus was the smallest (3.00). 5) Results of the stable isotope mixture model (SIAR) showed that POM was the main carbon source of the three species, contributing 57.4%, 57.9%, and 92.0% of the total, respectively. In addition, the contribution rate of SOM was also high for O. fasciatus and S. marmoratus, which was 21.5% and 33.9%, respectively. This study could provide basic information and reference for understanding trophic structure and marine food web in Zhongjiashan Islands.

The impact of ocean acidification on the eye, cuttlebone and behaviors of juvenile cuttlefish (Sepiella inermis).

The cuttlefish (Sepiella inermis) is an economically important species in the coastal seas of China. The impacts of ocean acidification on the ability of juvenile cuttlefish to select a suitable habitat, its hunting and swimming behavior, remains unknown. We examined behavior-related responses and the eye and cuttlebone structure of juvenile cuttlefish following short-term exposure to CO2-enriched seawater. The predation success rate decreased with the elevation in CO2 concentration. In the CO2 treatment groups, cuttlefish spent more time in the dark zone and the average swimming speed and total swimming distance significantly decreased. The structure of the retina and cuttlebone was affected by seawater acidification. Moreover, apoptotic cells were significantly increased in the eyes. In the wild, the impairment of the eye and cuttlebone may decrease the predation ability of juvenile cuttlefish and negatively affect their ability to select a suitable habitat, which would be detrimental to its population.

Carbazole and polyhalogenated carbazoles in the marine environment around the Zhoushan Archipelago: Distribution characteristics, environmental behavior, and sources.

The distribution characteristics and drivers of carbazole (CZ) and polyhalogenated carbazoles are still poorly understood. In this study, 96 samples were collected around the Zhoushan Archipelago, and their distribution characteristics were assessed. The results showed that CZ, 36-CCZ, and 36-BCZ were the top three abundant congeners in most collected samples. The bioaccumulation analysis revealed that marine plants prefer to accumulate CZ and bromocarbazoles rather than chlorocarbazoles. Both the mean concentrations of total carbazole and its derivants (ΣCZDs), as well as individual congeners, are the highest in sediments around the berthing areas of cargo ships and oil tankers. Meanwhile, ΣCZDs of these sediments are significantly influenced by the geo-weighted displacement of ships (r = 0.61; p < 0.05), indicating the ballast water from these ships as potential contributor for marine CZDs. Moreover, the accumulation of CZ in plankton, planktonic origin of sedimentary organic matter, and relationship between CZ and C/N ratio (p < 0.05) in sediments support the scenario that plankton absorbs and takes CZ into the sediments. These findings will promote the understanding of the sources, environmental behaviors, and fates of marine CZDs.

[Growth heterogeneity of Larimichthys polyactis in spring and autumn along the coast of Zhejiang, China]. / 浙江沿岸春秋季小黄鱼生长异质性.

In order to understand the growth dynamics of Larimichthys polyactis in spring and autumn along the coast of Zhejiang Province, we used the survey data of bottom trawlers in spring (April) and autumn (November) from 2014 to 2019 along the coast of Zhejiang Province to examine the heterogeneity of L. polyactis growth by constructing a generalized linear model (GLM) and nine linear mixed effect models (LMEM). The results showed that body length of L. polyactis ranged from 15 mm to 210 mm, with an average of 124.12 mm. The dominant body length group ranged from 110 mm to 140 mm. The body weight ranged from 0.04 g to 156.2 g, with an average of 33.28 g. The dominant body weight group ranged from 30 to 50 g. According to the AIC minimum criterion, the LMEM model with the random effects of seasons and water zones on growth parameters a and b was the best. The results of cross validation also showed that the prediction of this model was the best. In the optimal model, the fixed value of growth parameter a was 0.61×10-4, which ranged in (0.32-1.91)×10-4 after adding season and water random effect. The fixed value of parameter b was 2.73, and ranged from 2.49 to 2.86 after adding the random effects of season and water area, indicating that small yellow croaker was under negative allometric growth. Season and water zone had significant effects on the relationship between body length and body weight of small yellow croaker. From a seasonal perspective, the growth rate of small yellow croaker in spring was higher than that in autumn. From water zone perspective, the closer the offshore distance, the faster the growth rate of small yellow croaker.

[Population structure and resource change of Larimichthys polyactis in spring in Zhoushan fishery spawning ground protection area, China]. / 舟山渔场产卵场保护区春季小黄鱼群体结构及资源动态.

We investigated population structure, resource density changes of Larimichthys polyactis and its relationship with environmental factors in spring, based on the survey data of bottom trawl in adjacent sea areas of Zhoushan fishery spawning ground protection area from 2014 to 2019. The results showed that the relationship between body length and body weight of Larimichthys polyactis was W=0.44×10-4×L2.78, and parameter b was less than 3, which indicated that L. polyactis had negative allometric growth in recent years. There was a negative correlation between fullness and body length, with body becoming slender. From 2014 to 2019, body length and weight of L. polyactis were the highest in 2014 and the lowest in 2019. Since 2014, population size of L. polyactis in Zhoushan fishery spawning ground protection area and adjacent sea area had gradually decreased, indicating that the miniaturization of L. polyactis had not altered in recent years. From the perspective of the annual change of resource density, resource density of L. polyactis was higher than that before the establishment of the reserve, indicating that the management and protection of the reserve area played a protective role in the recovery of L. polyactis resources. The fitting results of GAM model showed that water depth and bottom water temperature were the environmental factors closely related to the density distribution of L. polyactis resources. With increasing water depth, the resources showed a fluctuating upward trend and were the highest near the water depth of 60 m. In the range of 12-16 ℃ water temperature, the resources increased with the increases of bottom water temperature. When water temperature was above 16 ℃, resources decreased with the increases of bottom water temperature.

[Feeding ecology of Engraulis japonicus based on stomach contents and stable isotope]. / åŸºäºŽèƒƒå«ç‰©åˆ†æžå’Œç¨³å®šåŒä½ç´ æŠ€æœ¯ç ”ç©¶é³€çš„æ‘„é£Ÿç”Ÿæ€.

Engraulis japonicus, an important fishery resource, is a key species in ecosystem trophodynamics studies. In this study, we examined stomach content of E. japonicusby stable isotope analyses, with samples collected from the East China Sea in 2008-2009 and 2020. The aim of this study was to demonstrate their diet composition, diel and ontogenetic changes in feeding habits and trophic level. Results of the stomach content analysis showed that E. japonicus mainly fed on planktonic crustaceans and small fish. The main prey species were Euphausia pacifica [index of relative importance (IRI)=87.6%; frequency(F)=57.6%], Paracalanus parvus (IRI=3.2%, F=15.3%), and Themisto gracilipes (IRI=2.1%, F=13.1%). Results of the stable isotope analysis showed that Copepoda were the main food source of E. japonicus, followed by Euphausiacea, and the contribution rate of Amphipoda was the least, which was less than 1%. There was significant diel change in diet composition. Feeding intensity was higher in the daytime than at night, with the highest in the dusk and the lowest at midnight. Ontogenetic change in feeding habit occurred when fork length reached 90 mm, over which the fish fed both zooplankton and small fishes. The δ13C of E. japonicus was between -21.66‰ and -18.14‰, with an average of (-19.92±0.86)‰. The δ15N of E. japonicus ranged from 4.07‰ to 10.78‰, with an average of (8.14±2.48)‰. Both δ13C and δ15N values were positively correlated with fork length. Trophic level of the fish was 3.4 with stomach content analysis and 2.7 with stable isotope analysis. The results would provide important reference for understanding nutritional status of pelagic small fish, and offer some basic data to establish ecopath model.

[Characteristics of crustaceans community structure and its relationship with environmental factors in Dachenyang Spawning Ground Reserve, China.] / å¤§é™ˆæ´‹äº§åµåœºä¿æŠ¤åŒºç”²å£³ç±»ç¾¤è½ç»“æž„ç‰¹å¾åŠå ¶ä¸ŽçŽ¯å¢ƒå› å­çš„å ³ç³».

To elucidate the characteristics of fishery resources structure in the Dachenyang Spaw-ning Ground Reserve, the index of relative importance (IRI), biodiversity index and canonical correspondence analysis (CCA) were used to explore the relationship between crustaceans community and marine environment based on the bottom trawl survey data collected from April and November in 2018. A total of 38 crustaceans species were recorded, belonged to 25 genera in 14 families. The dominant species were Oratosquilla oratoria, Portunus trituberculatus, Charybdis bimaculata, and Parapenaeopsis hardwickii. The resource density of crustaceans was generally high in depths below 50 m in spring and in depths above 50 m in autumn. The density in the southern area was higher than nouthern area. The Margalef species richness index (D), Shannon diversity index (H) and Pielou evenness index (J) of crustaceans in spring was higher than that in autumn. The H of crustaceans in depths above 50 m was the highest. Based on cluster analysis and non-matrix multidimentional scaling analysis, the crustaceans could be classified into three groups in spring and four groups in autumn. The differences in crustacean community structure in spring were more significant than in autumn. The results of canonical correspondence analysis (CCA) showed that water depth, bottom temperature, salinity and dissolved oxygen were the main environmental factors affecting species composition and spatial structure of crustaceans in the surveyed area.

[Spatial niches of dominant zooplankton species in Yueqing Bay, Zhejiang Province]. / æµ™æ±Ÿä¹æ¸ æ¹¾æµ®æ¸¸åŠ¨ç‰©ç©ºé—´ç”Ÿæ€ä½.

The index of dominance (S), average crowding (X*), niche breadth (Bi), and niche overlap (Qik ) of dominant zooplankton species were calculated using data collected from four zooplankton surveys from May 2016 to February 2017 in Yueqing Bay, Zhejiang Province. The results showed that there were 17 dominant zooplankton species (with S＞0.02). The niche breadth values of those dominant species differed greatly and were positively correlated with S. The niche overlaps of zooplanktons were extremely low. The total amount of species pairs with niche overlap higher than 0.6 (Qik＞0.6) were 25 in Yueqing Bay, which represented 18.4% of the total pairs. Results from the redundancy analysis showed that the distribution of dominant zooplankton species was mainly affected by temperature and salinity, which caused ecological differentiation of zooplankton species.

[Spatial niche of major fish species in spring in the coastal waters of central and southern Zhejiang Province, China]. / 浙江中南部近岸海域春季主要鱼类空间生态位.

The relative importance index (IRI), mean crowding, niche breadth, and niche overlap (Qik) of major fish species were calculated based on two fishery resource surveys from April to May 2016 (spring) in the coastal waters of central and southern Zhejiang Province. The results showed that there were 24 major fish species (IRI:100), the niche breadth values of which differed greatly and were positively correlated with IRI. The niche overlaps of fishes were extremely low in spring. The total amount of species pairs with niche overlap 0.6 (Qik :0.6) were six in April and five in May, which represented 3.9% and 4.8% of the total pairs, respectively. Results from the redundancy analysis showed that the distribution of major fish species were mainly affected by temperature, salinity, water depth, and dissolved oxygen, which caused ecological differentiation of fish species.

Are bacterial communities associated with microplastics influenced by marine habitats?

This study investigates the influence of marine habitats (i.e., the intertidal zone, supralittoral zone, and seawater), and polymer types (i.e., polyethylene, PE; polyethylene terephthalate, PET) on the diversity and structure of bacterial communities in marine microplastics. A three-month exposure experiment was conducted in Zhairuoshan Island, Zhoushan, China, a typical caldera volcanic island with minor anthropogenic disturbances. At the end of the exposure period, the transition for peaks corresponding to oxidized groups was observed using micro-Fourier transform infrared spectroscopy. Damages, including pits and cracks, and microorganisms were observed on the surfaces of the PE and PET pellets using scanning electron microscopy. Next-generation amplicon sequencing of the bacterial communities that had colonized the microplastics revealed that bacterial composition significantly varied depending on marine habitats and exposure times, rather than polymer type. Plastic debris in the intertidal zone exhibited the highest bacterial richness and diversity, and Bacillus was considered a potential degrader of plastic debris. The findings demonstrate that bacterial communities that colonize on microplastics are more potentially shaped by marine habitat and exposure time, and this would deepen our understanding of the ecological niche of microplastics surface.

[Spatial niche and differentiation of major nekton species in Yueqing Bay, Zhejiang, China]. / ä¹æ¸ æ¹¾ä¸»è¦æ¸¸æ³³åŠ¨ç‰©ç©ºé—´ç”Ÿæ€ä½åŠå ¶åˆ†åŒ–.

The index of relative importance (IRI), niche breadth, and niche overlap (Qik) of nekton species were calculated using data collected from four fishery resource surveys from May 2016 to February 2017 in Yueqing Bay, Zhejiang Province. The results showed that there were 27 major nekton species (IRI＞100) with higher turnover rates across different seasons, while their niche breadth values differed greatly and showed significant positive correlation with IRI. The niche overlaps of nekton were generally low, with the highest overlap value in autumn and the lowest in spring. The total amount of species pairs with niche overlap over 0.6 (Qik＞0.6) were 14 in the autumn and five in the spring, which represented 15.4% and 7.6% of the total pairs, respectively. Results from the redundancy analysis suggested that the distribution of main nekton species were mainly affected by temperature, salinity and turbidity, which cause ecological differentiation of nekton species.

Feifantangia zhejiangensis gen. nov., sp. nov., a marine bacterium isolated from seawater of the East China Sea.

A marine bacterium, NMD7(T), was isolated from seawater of the East China Sea. The cells were found to be aerobic, Gram-stain negative, non-motile rods. Growth of strain NMD7(T) could be observed in the medium without Na(+). Flexirubin-type pigments were observed to be produced. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NMD7(T) is an authentic member of the Cytophaga-Flavobacterium-Bacteroides phylum, forming a monophyletic clade as retrieved in neighbor-joining, maximum-likelihood and maximum-parsimony phylogenetic trees, and is closely related to Formosa spongicola A2(T) (96.0 %). The predominant respiratory quinone was determined to be MK-6. Major cellular fatty acids were identified as iso-C15:0, iso-C15:1 G and iso-C17:0 3-OH. The main polar lipids were found to consist of phosphatidylethanolamine, one aminophospholipid, three aminolipids and five unidentified lipids. Based on phenotypic, chemotaxonomic and phylogenetic characteristics, it is proposed that strain NMD7(T) be classified as representing a new genus, Feifantangia gen. nov. and a new species, Feifantangia zhejiangensis sp. nov. The type strain is NMD7(T) (=KCTC 42445T =MCCC 1K00458T).

[Feeding habits of Trachurus japonicus in the East China Sea].

A total of 453 Trachurus japonicus specimens with a fork length (FL) of 46-250 mm were sampled in the seasonal light seine net surveys in the East China Sea in May, August, and November, 2008 and in February, 2009. The stomach contents of the specimens were analyzed, and the seasonal and ontogenetic variations in the feeding habits of the T. japonicus were examined by the Kruskal-Wallis test, chi-squared test, and cluster analysis. There were 124 prey species (including not identified) ingested by the T. japonicus, among which, planktonic crustaceans and small-scale marine fish made up the dominant prey groups. According to the percentage index of relative importance (IRI%), Bregmaceros macclellandi was the most dominant prey, accounting for 39.2%, followed by Macrura mysis larva (18.4%), brachyura zoea larva (7.6%), and Euphausia pacifica (6.6%). The feeding intensity of the T. japonicus varied significantly with its FL and season, being the highest for the T. japonicus with a FL of 140-159 mm, higher for the T. japonicus juveniles with a FL of 45-99 mm, while lower for the T. japonicus of other size classes, and the highest in spring and the lowest in winter. Cluster analysis revealed there was an abrupt change in the diet composition for the T. japonicus with a FL of about 100 mm FL. The average trophic level of the T. japonicus in four seasons was 3.51, indicating that the T. japonicus in the East China Sea was of low-level carnivores feeding on plankton and nekton.