Xiumei Zhang

Assessment of the benthic macrofauna in an artificial shell reef zone in Shuangdao Bay, Yellow Sea

The effects of artificial shell reef (ASR) on the benthic macroinvertebrates were studied in Shuangdao Bay, Yellow Sea, China. Results showed that the biomass of macroinvertebrates in the ASR increased with the age of the ASR. Based on self-organizing map (SOM), the macroinvertebrate community of short-term artificial reef (SAR), medium-term artificial reef (MAR) and long-term artificial reef (LAR) emerged as a cluster, which may indicate that the benthic community in the ASR formed after three years. The age of the ASR was the main factor affecting the benthic community. The macroinvertebrates belonged to six phyla, Platyhelminthes, Nemertea, Annelida, Mollusca, Arthropoda and Echinodermata, among which the latter four were the ones that contributed the most for abundance. The biomass of Mollusca increased dramatically with age. The dissimilarity of the species composition of Mollusca was mainly caused by Meretrix meretrix and Protothaca jedoensis. The two species accounted for 15.61%, 28.05% and 75.11% of the macroinvertebrate biomass found in SAR, MAR and LAR, respectively. The ASR might be served as a bivalve stock enhancement tool. We conclude that ASR could assemble macrobenthos effectively and increase the environmental quality of the adjacent area, being a valid option for marine habitat restoration purposes.

Seasonal variation in species composition and abundance of demersal fish and invertebrates in a Seagrass Natural Reserve on the eastern coast of the Shandong Peninsula, China

Seagrass habitats are structurally complex ecosystems, which support high productivity and biodiversity. In temperate systems the density of seagrass may change seasonally, and this may influence the associated fish and invertebrate community. Little is known about the role of seagrass beds as possible nursery areas for fish and invertebrates in China. To study the functioning of a seagrass habitat in northern China, demersal fish and invertebrates were collected monthly using traps, from February 2009 to January 2010. The density, leaf length and biomass of the dominant seagrass Zostera marina and water temperature were also measured. The study was conducted in a Seagrass Natural Reserve (SNR) on the eastern coast of the Shandong Peninsula, China. A total of 22 fish species and five invertebrate species were recorded over the year. The dominant fish species were Synechogobius ommaturus, Sebastes schlegelii, Pholis fangi, Pagrus major and Hexagrammos otakii and these species accounted for 87% of the total number of fish. The dominant invertebrate species were Charybdis japonica and Octopus variabilis and these accounted for 98% of the total abundance of invertebrates. There was high temporal variation in species composition and abundance. The peak number of fish species occurred in August–October 2009, while the number of individual fish and biomass was highest during November 2009. Invertebrate numbers and biomass was highest in March, April, July and September 2009. Temporal changes in species abundance of fishes and invertebrates corresponded with changes in the shoot density and leaf length of the seagrass, Zostera marina.

Assessing the ecological quality status of transplanted mangrove wetland in the Oujiang estuary, China

Although numerous studies have performed ecological quality status (EcoQS) assessments in aquatic ecosystems, knowledge regarding the assessment of the EcoQS of mangrove transplant wetlands is still lacking. Therefore, we investigated the influence of mangrove transplants on the EcoQS by comparing the sediment quality status and benthic quality status in mangroves with those of reference sites (Spartina alterniflora stand and mudflat). The findings confirm that the benthic quality status of mangroves was superior to those of the reference sites. Subsequently, we tested the performances of various indices (AMBI, BENTIX, H, EX, Δ+, and Ʌ+). BENTIX, H, EX and Ʌ+ seemed be more suitable than AMBI and Δ+ for assessing the benthic quality status. The results also confirm that mangrove transplants may not facilitate or restrain the accumulation of heavy metals (except Cu and Hg) in sediments. Moreover, mangrove transplants posed a low ecological risk.

Experimental evaluation of fluorescent (alizarin red S and calcein) and clip-tag markers for stock assessment of ark shell, Anadara broughtonii

Release programs to enhance stocks of ark shell (Anadara broughtonii) have been undertaken in a number of Asian countries, but their effectiveness has rarely been investigated owing to a lack of marking methods. The quality and longevity of fluorescent markers, alizarin red S (ARS) and calcein (CAL) (200 and 300 mg/L), as well as clip tags, were tested on juvenile A. broughtonii. No significant differences in survival or shell growth were observed in juveniles stained with either of the two fluorochromes after a 160-day culture period, but the retention rate was 100% after 1 year. Fluorescent marks (≥grade 3) were observable microscopically in juveniles stained with the two fluorochromes, and some fluorescent marks (≥grade 4) were visible with the naked eye after 1 year. ARS-marked shells were brighter than those marked with CAL, and shells marked with 300 mg/L of the fluorochromes were easier to detect than those marked with 200 mg/L. Clip tags were incorporated into the shell as the bivalve grew, and the retention rate was 64.25% after 160 days. Significant differences in survival (at 30 days), shell length (at 60, 90, 120, and 160 days), and wet weight (at 90, 120, and 160 days) were observed between the clip-tagged and control groups (all P< 0.05), indicating that the tags may have passive effects on the ark shell. The results suggest that both ARS and CAL are suitable to mark A. broughtonii for large-scale restocking programs, and that optimal marking quality was achieved with 300 mg/L ARS. Lighter and smaller clip tags need to be developed to reduce injury and increase survival rate of clams.

Evaluation of four seagrass species as early warning indicators for nitrogen overloading: Implications for eutrophic evaluation and ecosystem management

Seagrasses are major coastal primary producers and are widely distributed on coasts worldwide. Seagrasses show sensitivity to environmental stress due to their high phenotypic plasticity, and therefore, we evaluated the use of constituent elements in four dominant seagrass species as early warning indicators for nitrogen eutrophication of coastal regions. A meta-analysis was conducted with published data to develop a global benchmark for the selected indicator, which was used to evaluate nitrogen loading at a global scale. A case study at three bays was subsequently conducted to test for local-scale differences in leaf C/N ratios in four seagrasses. Additionally, morphological and physiological metrics of seagrasses were measured from the three locations under varied nitrogen levels to develop further assessment indexes. The benchmark and local study showed that leaf C/N ratios of Zostera marina were sensitive to nitrogen discharge, which could be a highly valuable early warning indicator on a global scale. Moreover, the threshold value of seagrass leaf C/N was determined according to the benchmark to differentiate eutrophic and low nitrogen levels at a local scale. Of the eight phenotypic metrics measured, leaf width, total chlorophyll (au202f+u202fb), chlorophyll ratio (a/b), and starch in the rhizome were the most effective at discriminating between the three locations and could also be promising indicators for monitoring eutrophication.

Comparative study on the surface ultrastructures of fertilized eggs of three Sebastes species

ABSTRACT Fertilized eggs of Sebastes schlegelii, Sebastes pachycephalus and Sebastes hubbsi are morphologically similar under stereomicroscope. However, under the scanning electron microscope, significant differences in the ultrastructures of the egg surface among the three species were observed, and herein, a taxonomic key was proposed for future applications. A clustering analysis based on the ultrastructures of the egg surface and the diameter of the oil globule suggested that among the three species, S. hubbsi and S. pachycephalus were more genetically similar, while S. schlegelii had diverged earlier. The results agree with the conclusions drawn from morphological and molecular analyses on adult samples of the same species.

Effect of water motion and microhabitat preferences on spatio-temporal variation of epiphytic communities: a case study in an artificial rocky reef system, Laoshan Bay, China

Epiphytic fauna community structure is mainly determined by macro-scale environmental characteristics (e.g., water motion), whereas the influences of, and interaction with, micro-scale habitat-forming species are not well known. In order to explore the effects of water motion and functional macroalgal group on the community structure of epiphytic faunas, macroalgae and epiphytic faunas from four isolated artificial rocky reefs with different levels of hydrodynamic conditions were investigated in Laoshan Bay of China. A total of 32 macroalgal species and 22 faunal species were recorded on the surveys. The biomass and abundance of macroalgae and epiphytic faunas showed significant variations among stations and months. The biomass and abundance of epiphytic faunas were highest at outer Huangshankou station (H1) with medium hydrodynamic force. The lowest biomass of epiphytic faunas occurred at inner Huangshankou station (H3) with highest level of water motion, while the lowest abundance of epiphytic faunas occurred at Liepo station (L) with lowest level of water motion. Results showed that medium water motion level contributed to increasing biodiversity of epiphytic faunas. Epiphytic communities generally presented higher biomass and abundance in summer than in spring or autumn, which indicated temperature could be the ecological driver for temporal variation of epiphytic communities. The epiphytic faunas showed distinct preferences to structural morphology of macroalgae which forms suitable habitat for these organisms. This study suggests that artificial rocky reefs are of great significance to restore and maintain coastal biodiversity, and appropriate physical disturbance promote community reestablishment.

Comparison of intestinal microbiota and activities of digestive and immune-related enzymes of sea cucumber Apostichopus japonicus in two habitats

Sea cucumber Apostichopus japonicus stock enhancement by releasing hatchery-produced seeds is a management tool used to recover its population under natural environmental conditions. To assess the suitability of releasing sites, we examined the microbiota of the gut contents of A. japonicus from two populations (one in sandy-muddy seagrass beds and one in rocky intertidal reefs) and the microbiota in their surrounding sediments. The activities of digestive and immune-related enzymes in the A. japonicus were also examined. The results indicated that higher bacterial richness and Shannon diversity index were observed in all the seagrass-bed samples. There were significant differences in intestinal and sediment microorganisms between the two habitats, with a 2.87 times higher abundance of Firmicutes in the seagrass bed sediments than that in the reefs. Meanwhile, Bacteroidetes and Actinobacteria were significantly higher abundant in the gut content of A. japonicus from seagrass bed than those from the reefs. In addition, the seagrass-bed samples exhibited a relatively higher abundance of potential probiotics. Principal coordinates analysis and heatmap showed the bacterial communities were classified into two groups corresponding to the two habitat types. Moreover, compared to A. japonicus obtained from rocky intertidal habitat, those obtained from the seagrass bed showed higher lysozyme, superoxide dismutase and protease activities. Our results suggest that bacterial communities present in seagrass beds might enhance the digestive function and immunity of A. japonicus. Therefore, compared with the rocky intertidal reef, seagrass bed seems to be more beneficial for the survival of A. japonicus.

Heavy metal concentrations and chemical fractions in sediment from Swan Lagoon, China: Their relation to the physiochemical properties of sediment

This study was performed to determine the distribution and chemical fractions of five heavy metals (Cd, Cr, Cu, Pb, and Zn) in sediment from three sampling areas in Swan Lagoon, and their relation to the physiochemical properties of sediment were explored. The results revealed that Cd in sediment from the sand part (SP), muddy sand part (MSP) and sand muddy part (SMP) were potentially highly susceptible and bioavailable since the exchangeable fractions were 21.0%, 27.4%, and 32.1%, respectively, of the total concentrations. A portion of Pb and Zn were observed as reducible fractions owing to their affinity to Fe-Mn; they were able to complex with Fe-Mn oxides and oxyhydroxides in the sediment. A large amount of Cu in the oxidizable fraction may be due to the fact that Cu can easily form stable complexes with organic matter. Cr was overwhelmingly found in the residual fraction, suggesting that Cr was strongly bound in mineral lattices. Enrichment factors (EF) indicated that Cd in three sampling areas suffered severe enrichment, whereas other metals were present in only minor amounts. In addition, Cd may pose a medium to high risk in the MSP and SMP based on risk assessment codes. According to the mean probable effects level quotient, the samples from the MSP and SMP had a 21% probability of toxicity. The multivariate statistical analysis suggested that sediment texture (d0.5, sand and silt), Fe-Mn, and the total organic carbon (TOC) influenced the distribution of the studied metals and their chemical fractions.

Zostera marina seed burial can be enhanced by Manila clam Ruditapes philippinarum: A microcosm study

Seagrass seed bank plays a key role in the regeneration of new vegetation when seagrasses are removed by the natural or man-made disaster. Various factors may affect the development of sediment seed bank. We conducted a microcosm experiment to test the effects of burrowing and feeding activities of Manila clam, Ruditapes philippinarum on the burial of Zostera marina seeds in sediments. The effects of lasting time (3-hour, 1-day, 3-day, 7-day, 14-day and 28-day), clam density (0, 2, 4 and 8 clams with shell length of 3 cm in each microcosm) and clam size (shell length of 2, 3 and 4 cm at 4-clam density) on seed burial were examined in plastic microcosm cores (30 cm high × 10 in inner diameter) in a 28-day period. Results showed that the seed burial depth significantly increased with time, the density and the size of clams. No seeds were buried in the sediment in the cores without clams during the whole experiment period. For the 3-cm clams, about 91.61% of the seeds were buried in the sediment at the end of the experiment in the high-density treatment (8 clams at each core); while in the medium and low-density treatments (4 and 2 clams in each core, respectively), about 76.93% and 60.61% of the seeds were buried in the sediment, respectively. For the size treatments, large (4 cm) clams buried 89.56% of the seeds at the end of the experiment, much more than those of medium (3 cm, 76.93%) and small (2 cm, 61.50%) size clams. During the whole experiment period, nearly all of the buried seeds were at a depth of from 0 cm to 5 cm. These results suggested that Manila clam Ruditapes philippinarum may play an important positive role in seagrass seed bank dynamics in the field.