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Effects of key species mud snail Bullacta exarata (Gastropoda) on oxygen and nutrient fluxes at the sediment-water interface in the Huanghe River Delta, China
Baoquan Li, Tjeerd J. Bouma, Quanchao Wang, Laura M. Soissons, Francesco Cozzoli, Guanghai Feng, Xiaojing Li, Zhengquan Zhou, Linlin Chen
doi: 10.1007/s13131-019-1430-6
Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River (Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos (MPBs; i.e., sedimentary microbes and unicellular algae) productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen (DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro- and meiofauna significantly increased the NH4-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH4-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B. exarata on the ecosystem functioning via benthic fluxes.
key words: bioturbation, mud snail Bullacta exarata, oxygen flux, nutrient flux, benthic metabolism, Huanghe River (Yellow River) Delta
Macrobenthic assemblage characteristics under stressed waters and ecological health assessment using AMBI and M-AMBI: a case study at the Xin’an River Estuary, Yantai, China
Zhengquan ZHOU, Xiaojing LI, Linlin CHEN, Baoquan LI, Tiantian LIU, Binghua AI, Lufei YANG, Bo LIU, Qiao CHEN
doi: 10.1007/s13131-018-1180-x
To understand the ecological status and macrobenthic assemblages of the Xin’an River Estuary and its adjacent waters, a survey was conducted for environmental variables and macrobenthic assemblage structure in September 2012 (Yantai, China). Several methods are adopted in the data analysis process: dominance index, diversity indices, cluster analysis, non-metric multi-dimentional scaling ordination, AMBI and M-AMBI. The dissolved inorganic nitrogen and soluble reactive phosphorus of six out of eight sampling stations were in a good condition with low concentration. The average value of DO ((2.89±0.60) mg/L) and pH (4.28±0.43) indicated that the research area faced with the risk of ocean acidification and underlying hypoxia. A total of 62 species were identified, of which the dominant species group was polychaetes. The average abundance and biomass was 577.50 ind./m2 and 6.01 g/m2, respectively. Compared with historical data, the macrobenthic assemblage structure at waters around the Xin’an River Estuary was in a relatively stable status from 2009 to 2012. Contaminant indicator species Capitella capitata appeared at Sta. Y1, indicating the animals here suffered from hypoxia and acidification. AMBI and M-AMBI results showed that most sampling stations were slightly disturbed, which were coincided with the abiotic measurement on evaluating the health conditions. Macrobenthic communities suffered pressures from ocean acidification and hypoxia at the research waters, particularly those at Stas Y1, Y2 and Y5, which displays negative results in benthic health evaluation.
key words: macrobenthos, Xin’an River Estuary, ocean acidification, hypoxia, AMBI, M-AMBI
Morphology of four Miliolinella species (Foraminifera, Protozoa) with description of a new species, Miliolinella obesa nov. spec., from the tropical West Pacific Ocean
Yanli LEI, Tiegang LI
doi: 10.1007/s13131-018-1301-6
Foraminiferal oozes were sampled from the tropical West Pacific seamount and seabed of deep sea, by a remotely operated vehicle (ROV) in December 2014 and March 2016. Using standard morphological method, four Miliolinella species, including Miliolinella obesa, M. circularis, M. suborbicularis and M. subrotunda were described. Among the four species, M. obesa is a new species. It is a large member (about 500 μm in length) of the genus. This species is characterized by having a very stout and transverse broadly circular outline, and its body width is greater than the body length. In addition, its chamber demarcations are obscure from the exterior appearance. Three chambers are unclearly visible on one side and two chambers are visible on the opposite. Finally, we provided very detailed taxonomic microphotographs and the ecological distribution information for each species.
key words: deep sea, foraminifera, Miliolinella, seamount, seabed, West Pacific Ocean
The morphological and phylogenetic characterization for the dinoflagellate Margalefidinium fulvescens (=Cochlodinium fulvescens) isolated from the Jiaozhou Bay, China
Zhangxi HU, Yunyan DENG, Yuhang LI, Ying Zhong TANG
doi: 10.1007/s13131-018-1295-0
The dinoflagellate genus Margalefidinium has been split from Cochlodinium as a new genus recently and Margalefidinium fulvescens is one of the five Margalefidinium species. Margalefidinium fulvescens is toxic and has been reported from the coastal waters of USA, Canada, Mexico, China, Japan, Indonesia, Korea, Pakistan and Spain. Here we provide the morphological and phylogenetic characterization for an isolate of it from the Jiaozhou Bay, Qingdao, China. Our results showed that the vegetative cells were subspherical to ellipsoidal, 34–60 μm in length, and 19–41 μm in width. Both single cell forms and colonies in chains of 2, 4, or 8 cells were observed in cultures, but chain forms with 2 or 4 cells were observed more often in the field samples. The cingulum was rather deep, encircling the cell approximately twice, but the sulcus was rather narrow, surrounding the cell about one turn. The nucleus was spherical and located at the central epicone. The chloroplasts were granular, brownish, and scattered peripherally. An orange pigmented body also appeared in the epicone. The apical groove appeared vase-like as previously described. Under epi-fluorescence microscopy, a pumpkin-like structure was clearly observed, in which cells were embedded. Cells were observed to exit from the structure, which led us to a hypothesis that the structure may provide cells a shelter to avoid predation or to respond to other stresses. The phylogenetic analyses based on partial LSU rDNA sequences indicated that M. fulvescens from the Jiaozhou Bay was grouped with M. fulvescens populations from other origins and closely related to the clade of M. polykrikoides. Our morphological observations and phylogenetic analyses together confirmed the presence of M. fulvescens in China and our monitoring has also observed the species dominant in the dinoflagellate community of the Jiaozhou Bay in the early autumn of 2015, which alerted us to continually monitor this bloom-forming species in the region.
key words: Margalefidinium fulvescens, morphology, phylogeny, pumpkin-like structure, Jiaozhou Bay, China
Mediomastus chinensis sp. nov., a new species of Capitellidae (Annelida: Polychaeta) from the southeast coast of China
Junhui LIN, Jianjun WANG, Fengwu ZHENG
doi: 10.1007/s13131-018-1316-z
Mediomastus is a common genus around the world, and Chinese specimens used to be identified as M. californiensis Hartman. In this study, 118 Mediomastus specimens collected from four localities along the southeast coast of China were examined. They belonged to an unknown species. We treat them as a new species, described herein. The new species is characterized as follows: (1) chaetigers 1–9 biannulate with chaetal fascicles at midsegment, thereafter multiannulate with chaetal fascicles posterior to midsegment; (2) parapodial ridges on posterior abdomen; (3) possession of bilimbate capillary chaetae on chaetigers 1–4; (4) thoracic hooks with long, straight shaft, hood length about 3–5 times width; (5) abdominal hooks shorter, with developed shoulder and distinct constriction, markedly different from those in thorax; (6) unique staining pattern with methyl green. The present study indicated that Mediomastus species inhabiting Chinese waters might be misidentified as M. californiensis, and that Mediomastus chinensis sp. nov. is widely distributed along the southeast coast of China.
key words: Mediomastus, Capitellidae, polychaeta, new species, taxonomy, China
mRNA expression of CYP4 in marine polychaete Marphysa sanguinea in response to benzo[a]pyrene
Wanjuan Li, Huan Zhao, Fuyang Ba, Shaojuan Li, Xiupeng Sun, Dazuo Yang, Yibing Zhou
doi: 10.1007/s13131-019-1362-1
Rapid amplification of cDNA ends (RACE) and real-time polymerase chain reaction (RT-PCR) were carried out to analyze the CYP4 gene expression in polychaete Marphysa sanguinea exposed to benzo[a]pyrene (BaP) in this study. The full length of MsCYP4 cDNA was 2 470 bp, and it encoded 512 amino acids. The deduced amino acid sequence showed 47% identity with CYP4F from frog Xenopus tropicalis and shared high homology with other known CYP4 sequences. To analyse the role of CYP4 in protecting M. sanguinea from BaP exposure, three BaP groups were established: 0.5, 5 and 50 μg/L. Polychaetes were sampled after 3, 7 and 12 d. At 0.5 μg/L, the effect of BaP on MsCYP4 gene expression increased with time prolonged. MsCYP4 gene expression curve showed U-shaped trend with time in 5 and 50 μg/L BaP groups. Therefore, MsCYP4 gene may play an important role in maintaining the balance of cellular metabolism and protecting M. sanguinea from BaP toxicity.
key words: Marphysa sanguinea, CYP4, benzo[a]pyrene, toxicity effect
Transcriptome assembly of Modiolus modiolus and comparative analysis with Bathymodiolus platifrons
Jie MENG, Mei YANG, Fei XU, Xinzheng LI, Li LI
doi: 10.1007/s13131-018-1232-2
The genetic basis for bivalves’ adaptation and evolution is not well understood. Even few studies have focused on the mechanism of molluscan molecular evolution between the coastal intertidal zone and deep-sea environment. In our studies, we first conducted the transcritpome assembly of Modiolus modiolus mussels living in coastal intertidal zones. Also, we conducted transcriptome comparison analyses between M. modiolus and Bathymodiolus platifrons living in hydrothermal vents and cold methane/sulfide-hydrocarbon seeps. De novo assemblies of the clean reads yielded a total of 182 476 and 156 261 transcripts with N50 values of 1 769 and 1 545 in M. modiolus and B. platifrons. A total of 27 868 and 23 588 unigenes were identified, which also displayed the similar GO representation patterns. Among the 10 245 pairs of putative orthologs, we identified 26 protein-coding genes under strong positive selection (Ka/Ks>1) and 12 genes showing moderate positive selection (0.5<Ka/Ks<1). Most of those genes are predicted to be involved in stress resistance. Overall, our study first provides the transcriptomic database forM. modiolus. Transcriptome comparison illustrates the genome evolution between M. modiolus and B. platifrons, and provides an important foundation for future studies on these two species.
key words: mollusc, transcriptome comparision, positive selection, stress adaptation
A model for calculating the erosion distance of soft sea cliff under wave loading
Fangqiang CHANG, Zhonglei SHU
doi: 10.1007/s13131-018-1245-x
A model for calculating the erosion distance of soft sea cliff under wave loading is established based on the erosion mechanism of soft sea cliff under wave loading and for considering wave hydrodynamic and sea cliff material parameters. The model is verified, and the parameters are regressed using an indoor flume experiment. The erosion distances of the sea cliff in the northeast of the Pingtan Island are calculated by the model, and the results are compared with the measured data. The maximum erosion occurs in static water level, the location of the maximum erosion moves up as the wave continues, and the erosion stops when the wave lasts for a period of time. The erosion does not occur until the wave height exceeds a critical value; however, the contribution of large waves to the erosion is not relatively substantial. The calculated erosion distances at two places in the northeast of Pingtan Island are 0.32 m and 0.26 m.
key words: wave, soft sea cliff, erosion
A spatial resolution effect analysis of remote sensing bathymetry
doi: 10.1007/s13131-017-1088-x
A spatial resolution effect of remote sensing bathymetry is an important scientific problem. The in situ measured water depth data and images of Dongdao Island are used to study the effect of water depth inversion from different spatial resolution remote sensing images. The research experiments are divided into five groups including QuickBird and WorldView-2 remote sensing images with their original spatial resolution (2.4/2.0 m) and four kinds of reducing spatial resolution (4, 8, 16 and 32 m), and the water depth control and checking points are set up to carry out remote sensing water depth inversion. The experiment results indicate that the accuracy of the water depth remote sensing inversion increases first as the spatial resolution decreases from 2.4/2.0 to 4, 8 and 16 m. And then the accuracy decreases along with the decreasing spatial resolution. When the spatial resolution of the image is 16 m, the inversion error is minimum. In this case, when the spatial resolution of the remote sensing image is 16 m, the mean relative errors (MRE) of QuickBird and WorldView-2 bathymetry are 21.2% and 13.1%, compared with the maximum error are decreased by 14.7% and 2.9% respectively; the mean absolute errors (MAE) are 2.0 and 1.4 m, compared with the maximum are decreased by 1.0 and 0.5 m respectively. The results provide an important reference for the selection of remote sensing data in the study and application of the remote sensing bathymetry.
key words: remote sensing, spatial resolution, water depth remote sensing inversion
Effects of nutrient limitations on three species of zooplankton
Lei CHEN, Chaolun LI, Konglin ZHOU, Yongqiang SHI, Mengtan LIU
doi: 10.1007/s13131-017-1122-z
Nutrient imbalance—a mismatch in nutrient ratios between the available food supply and the demands of consumers—has the potential to be transported up food chains, exposing zooplankton to nutrient limitations. In this study, the response of Calanus sinicus (copepod), Moina mongolica (cladocera), and Brachionus plicatilis (rotifer) to nutrient-limited (no-limited, P-limited, and N-limited) food were evaluated from the perspective of growth, reproduction, and stoichiometric homoeostasis. The results indicated that the growth of three species was suppressed under nutrient-limited (especially P-limited) conditions. However, the effect of nutrient limitations on their reproduction was species-specific. For C. sinicus, the dietary UFA (unsaturated fatty acid) as a major phospholipid component affected their egg production and total FA supporting energy promoted the hatchability of eggs. Furthermore, excess carbon in the diet promoted egg production but reduced hatching success. For M. mongolica, nutritional (P and UFA) and energy (total FA) support affected their fecundity. B. plicatilis fecundity exhibited the same pattern of growth (no-limited>N-limited>P-limited). In terms of stoichiometric homeostasis,B. plicatilis’s elemental compositions were less likely to be affected by nutrient limitations than M. mongolica. We suggest that the effects of nutrient imbalances could potentially become an evolutionary force affecting ecosystem structure and stability in eutrophic waters.
key words: zooplankton, nutrient, growth, reproduction, stoichiometric homoeostasis

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