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Protoraphis Simonsen, a newly recorded marine epizoic diatom genus for China
Lang Li, Changping Chen, Lin Sun, Jiawei Zhang, Junrong Liang, Yahui Gao
doi: 10.1007/s13131-019-1467-z
Epizoic diatoms on marine copepods are common in nature and may have a special ecological relationship with their hosts. However, this special ecological group is not well known, and it has only rarely been studied in the China seas. To address this knowledge gap, the species diversity and classification of epizoic diatoms on planktonic copepods were studied with samples collected from the East China Sea. In the present study, a marine araphid diatom genus Protoraphis and its type species, Pr. hustedtiana, were observed and identified by light and electron microscopy, thus representing the first record of this genus and its type species in China. This genus is characterized by a median sternum strongly bent to opposite sides and terminate in two transapical grooves at the valve ends. Protoraphis hustedtiana was found to be epizoic on the posterior body appendages and segments of the marine calanoid copepod Candacia bradyi. An internal view shows a complex, ear-shaped process that is close to the apical slit field. The ecological habitats and geographical distributions of Protoraphis were also discussed, and, together with complementary morphological studies, our results have increased the number of records for marine epizoic diatoms to three genera with three species in China, including Pseudohimantidium and Pseudofalcula.
key words: marine epizoic diatom, copepod, Protoraphis, newly recorded genus, ear-shaped process
Succession of causative species during spring blooms in the East China Sea: coupled biophysical numerical modeling
Ke SUN, Zhongfeng QIU, Yijun HE, Wei FAN, Zexun WEI
doi: 10.1007/s13131-016-0964-0
In the East China Sea (ECS), the succession of causative species responsible for blooms is a recurrent phenomenon during the spring, which changes from diatoms to dinoflagellates. Observations from space andin situ cruises captured this pattern of succession during spring of 2005. In this study, we coupled two biological models, which were developed previously forSkeletonema costatum andProrocentrum donghaiense, into a circulation model tailored for the ECS. The coupled biophysical model was used to hindcast the blooms and to test the hypothesis proposed in earlier studies that phosphate (PO43–) is the first-order decider of the succession. The coupled model successfully reproduced the hydrodynamics (as described in a companion paper by Sun et al., the spatiotemporal distribution of the chlorophylla (Chla) concentration, and the species succession reasonably well. By analyzing the effects of different factors on the surface Chla distribution, we confirmed that the offshore boundaries of the blooms were confined by PO43–. In addition, we suggest that surface wind fields may modulate the horizontal distribution of blooms. Thus, during the dispersal of blooms, surface winds coupled with PO43– may control the succession of blooms in the ECS. The proposed coupled model provides a benchmark to facilitate future improvements by including more size classes for organisms, multiple nutrient schemes, and additional processes.
key words: Skeletonema costatum, Prorocentrum donghaiense, species succession, biophysical model, East China Sea
A new merged dataset of global ocean chlorophyll a concentration with higher spatial and temporal coverage
Yanfang XIAO, Jie ZHANG, Tingwei CUI, Ling SUN
doi: 10.1007/s13131-018-1249-6
Understanding the ocean’s role in the global carbon cycle and its response to environmental change requires a high spatio-temporal resolution of observation. Merging ocean color data from multiple sources is an effective way to alleviate the limitation of individual ocean color sensors (e.g., swath width and gaps, cloudy or rainy weather, and sun glint) and to improve the temporal and spatial coverage. Since the missions of Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and Medium-spectral Resolution Imaging Spectrometer (MERIS) ended on December 11, 2010 and May 9, 2012, respectively, the number of available ocean color sensors has declined, reducing the benefits of the merged ocean color data with respect to the spatial and temporal coverage. In present work, Medium Resolution Spectral Imager (MERSI)/FY-3 of China is added in merged processing and a new dataset of global ocean chlorophyll a (Chl a) concentration (2000–2015) is generated from the remote sensing reflectance (Rrs (λ)) observations of MERIS, Moderate-resolution imaging spectra-radiometer (MODIS)-AQUA, Visible infrared Imaging Radiometer (VIIRS) and MERSI. These data resources are first merged into unified remote sensing reflectance data, and then Chl a concentration data are inversed using the combined Chl a algorithm of color index-based algorithm (CIA) and OC3. The merged data products show major improvements in spatial and temporal coverage from the addition of MERSI. The average daily coverage of merged products is approximately 24% of the global ocean and increases by approximately 9% when MERSI data are added in the merging process. Sampling frequency (temporal coverage) is greatly improved by combining MERSI data, with the median sampling frequency increasing from 15.6% (57 d/a) to 29.9% (109 d/a). The merged Chl a products herein were validated by in situ measurements and comparing them with the merged products using the same approach except for omitting MERSI and GlobColour and MEaSUREs merged data. Correlation and relative error between the new merged Chl a products and in situ observation are stable relative to the results of the merged products without the addition of MERSI. Time series of the Chl a concentration anomalies are similar to the merged products without adding MERSI and single sensors. The new merged products agree within approximately 10% of the merged Chl a product from GlobColour and MEaSUREs.
key words: merged data, ocean color, chlorophyll a, CIA, FY-3 MERSI, VIIRS

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