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Residues and sources of HCHs and DDTs in the sediments of land-based sewage outlet to the Zhanjiang Bay, China
Lirong Zhao, Yuzhen Shi, Hui Zhao, Jibiao Zhang, Xingli Sun
doi: 10.1007/s13131-019-1432-4
Due to the large usage of DDT-containing antifouling paints and lindane in China, heavy residuals of DDTs and HCHs have been found in many fishing harbors, but there is lack of studies on this issue for the Zhanjiang Bay which is an important fishing harbor and mariculture zone in South China. To evaluate the pollution status and sources of HCHs and DDTs in the Zhanjiang Bay, the concentrations, spatial distributions and sources in the sediments of 11 land-based sewage outlets to the Zhanjiang Bay were investigated. Since the 1980s, HCHs residuals had obviously decreased in studied areas, but DDTs had little change, even abnormally high levels were found in some sites. The content percentages and diagnostic ratios of HCHs isomers and DDTs showed that the source of HCHs was derived from soils around the bay and recent input of lindane, and DDTs were from historical residues of technical DDTs and fresh input of DDT-containing antifouling paints on fishing ships. Based on sediment quality guidelines, DDTs would be of more concern for the ecotoxicological risk on marine environment and adverse effects on benthonic organisms. This study indicated that lindane and DDT-containing products may be still used in some places of Zhanjiang City. It should be urgent to control their usage and clean the DDTs-contaminated sites by the local government.
key words: Zhanjiang Bay, sediment, DDTs, HCHs
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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