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Dai L.,CAS Qingdao Institute of Oceanology | Dai L.,University of Chinese Academy of Sciences | Li C.,CAS Qingdao Institute of Oceanology | Yang G.,CAS Qingdao Institute of Oceanology | Sun X.,Jiaozhou Bay Marine Ecosystem Research Station
Journal of Marine Systems | Year: 2016

Horizontal changes in mesozooplankton abundance, biovolume and size spectra at western boundary currents in the subtropical North Pacific during winter 2012 were evaluated by ZooScan measurement on samples collected by net towing from 23 stations. Zooplankton abundance and biovolume ranged from 35.1 to 456.8ind.m-3 and 4.3 to 231.7mm3m-3, respectively. Copepoda were the most dominant species, followed by Chaetognatha and Tunicata. According to the Bray-Curtis cluster analysis based on biovolume of zooplankton size classes of each taxonomic group at intervals of 1 (log2 mm3ind.-1) between -6 and 12 and considering the effect of regional factors, zooplankton communities were classified into four groups, which basically coincided with the geographical patterns of different currents: the North Equatorial Current (NEC), the North Equatorial Counter Current (NECC), the Kuroshio Current (KC), and the Mindanao Eddy (ME), respectively. The largest and lowest biovolumes were observed in the NECC region and the NEC region, respectively, and both were dominated by the 0.3 to 1mm equivalent spherical diameter (ESD) size class, while the ME region was dominant by the 1 to 2mm ESD size class. The slopes of the normalized biovolume size spectra for each group were slightly lower than -1 (range from -0.85 to -0.92), which indicates that zooplankton communities in the study area were characterized by low productivity and high energy transfer efficiency. © 2015 Elsevier B.V.

Shi Y.-Q.,CAS Qingdao Institute of Oceanology | Shi Y.-Q.,University of Chinese Academy of Sciences | Sun S.,CAS Qingdao Institute of Oceanology | Sun S.,Jiaozhou Bay Marine Ecosystem Research Station | And 3 more authors.
Hydrobiologia | Year: 2015

Because jellyfish are sensitive to the availability of prey, their distribution likely is linked to the distribution pattern of zooplankton functional groups. We studied the regional and interannual variations of zooplankton functional groups in the Yellow Sea using data from six cruises conducted in June between 2000 and 2009. We compared these data to previously collected data on giant jellyfish distribution and biomass. Our results indicate that different zooplankton functional groups have their own relatively fixed distribution patterns and that the distribution of zooplankton can affect the distribution of the jellyfish community. Giant crustaceans and large copepods were found to be mainly distributed offshore, small copepods and small jellyfish tended to be located in the coastal region, and chaetognaths were mainly sampled along the 50 m isobath. Sea bottom temperature and salinity, determined by the Yellow Sea Cold Water Mass, are shown to have been major factors affecting the distribution of zooplankton functional groups. Among zooplankton functional groups, small copepods and giant jellyfish show similar distribution patterns, suggesting that the abundance of small copepods is feeding that of giant jellyfish. The observed interannual biomass of small copepod was positively related to temperature, and we suggest that this relationship may explain the rarity of giant jellyfish outbreaks in cold years. © 2014, Springer International Publishing Switzerland.

Feng S.,CAS Qingdao Institute of Oceanology | Feng S.,University of Chinese Academy of Sciences | Zhang F.,CAS Qingdao Institute of Oceanology | Sun S.,CAS Qingdao Institute of Oceanology | And 3 more authors.
Hydrobiologia | Year: 2015

In recent decades, massive outbreaks of the giant jellyfish, Nemopilema nomurai have been appearing frequently in coastal seas of China. In the life cycle of N. nomurai, asexual reproduction by its benthic polyps may largely determine the jellyfish population size, and it was thought that asexual reproduction leading to medusae might be affected by differences in the duration at low winter temperature on different parts of the coast. To test this hypothesis, polyps were first stored at low temperature for two different durations, 5°C for either 40 or 117 days. They were then maintained at seven temperatures, (maintained at 5°C, and separately elevated to 10, 13, 16, 19, 22, 27°C) reached by raising the temperature 1°C every 2 days from 5°C, as well as a control temperature: 5°C. Polyps were fed with three frequencies (once per 5 days, once per 10 days, and unfed, prey concentration, 0.1 mgC l−1, being supplied once). The percentages of polyps strobilating, strobilation duration, ephyra and podocyst production were recorded. The results showed that longer duration at low temperature accelerated strobila formation at warmer temperature, as well as significantly enhancing podocyst production, but not for the strobilation percentage or ephyra production. Temperature had a marked influence on strobilation percentage, as well as on ephyra and podocyst production. The optimum temperature for strobilation by N. nomurai polyps ranged from 10 to 13°C. The maximum numbers of ephyrae appeared after polyps had been stored at longer low temperature then warmed to 10°C and fed once per 5 days, while the maximum production of podocysts occurred in polyps warmed to 27°C and fed once per 5 days. We conclude that longer duration at low temperature in winter, a continuous 10–13°C period in spring, and increasing food supply all accelerate the strobila formation, increase jellyfish production and are tend to increase blooms of N. nomurai medusae. © 2015, Springer International Publishing Switzerland.

Wang N.,CAS Qingdao Institute of Oceanology | Wang N.,University of Chinese Academy of Sciences | Li C.,CAS Qingdao Institute of Oceanology | Liang Y.,University of Chinese Academy of Sciences | And 5 more authors.
Hydrobiologia | Year: 2015

Aurelia spp. are among the main blooming jellyfish species. The polyp stage plays an important role in its outbreaks. To determine how temperature and food conditions may affect the process of reproduction, we maintained Aurelia sp. 1 polyps in the laboratory at three temperatures (10–15°C) and four food concentrations (0–0.1 mg C l−1) to test their combined effects on the strobilation process and the production of buds and ephyrae. The length of the strobilation preparation period significantly decreased with increased temperature, but was not affected by food conditions. With sufficient food supply, the polyps that had already released ephyrae restart the strobilation process. Food condition positively affects both the production of buds and ephyrae. Temperature, however, had different effects: at the three temperatures tested, 13°C was most appropriate for polyps to release ephyrae, while bud production was highest at 15°C. These results suggest that eutrophication (as a proxy for food condition) would affect both the size of the Aurelia sp. 1 polyp population and juvenile medusa population, whereas temperature adjusts the reproductive energy distribution between budding and ephyra release to regulate the strobilation process. This temperature adjustment mechanism likely helps match the production of juvenile medusae with the peak of zooplankton biomass. © 2014, Springer International Publishing Switzerland.

Ning J.,CAS Qingdao Institute of Oceanology | Li C.,CAS Qingdao Institute of Oceanology | Yang G.,CAS Qingdao Institute of Oceanology | Wan A.,Jiaozhou Bay Marine Ecosystem Research Station | And 2 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013

Calanus sinicus, a dominant calanoid copepod in the Yellow Sea, is an important link in the food web between phytoplankton and higher trophic levels. Its populations typically start to develop in later winter with a maximum of individuals in early summer. To study the correlation between changes in the abundance of this species and changes in food resources and the physical environment, RNA and DNA concentrations and egg production rates (EPR) were measured, and RNA:DNA ratios were calculated as indices of growth and nutritional conditions of copepods collected in the Yellow Sea from February to July. We observed pronounced seasonal and spatial variations of RNA concentrations and resulting RNA:DNA ratios. There was a positive correlation between the EPR and RNA:DNA ratios. The copepods collected in March and April, when phytoplankton were more abundant, had high RNA:DNA ratios, and contained more RNA than copepods collected during the other months. There was no significant correlation between the growth indices (RNA:DNA ratios and EPR) and chlorophyll-a concentrations (Chl a) or temperature at large temporal and spatial scales. We tracked the development of two phytoplankton blooms in April, which were dominated in turn by diatoms and dinoflagellates. We observed high concentrations of RNA and a high RNA:DNA ratio at both bloom sites during the respective blooms. During the diatom bloom, the RNA:DNA ratios in copepods increased at the onset of the bloom and decreased thereafter. In addition, we observed a positive correlation (. P<0.001) between RNA-based indices and Chl a. Our results suggest that food availability plays a more important role than temperature in controlling the growth of C. sinicus in the field. Thus, the spring phytoplankton blooms in the Yellow Sea are important regulators of copepod abundance. © 2013 Elsevier Ltd.

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