Spatial and temporal variability of chlorophyll-a in Bohai Sea, China.

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Friday 3 july 2015

12:36 - 12:39h at North America (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology, Poster pitches

Parallel session: Poster pitches: 15F. Environment - Ecohydraulic

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Chlorophyll-a is the main component of the color of phytoplankton. Patterns of chlorophyll-a gives a reflection of primary production in the ocean. It also has an economic effect on fishery resources and hydro-environment. Its detection helps to identify possible eutrophication in a region. Largest inner sea of China-Bohai Sea is located in northern part of China. It is semi-enclosed with one only passage to Yellow Sea. It is relatively shallower than connected waters. The unique marine geo–environment makes it vulnerable to phytoplankton blooms. In this study, the spatial and temporal variation of chlorophyll-a (MChl-a) concentration in Bohai Sea were analysed with data remotely sensed by Moderate Resolution Imaging Spectroradiometer (MODIS) over the period from 2003 to 2013. Local forcings of temperature, wind speed, relative humidity and Huanghe River discharge were also analyzed. Results of the Mann-Kendall (MK) tests showed that MChl-a blooms occurred in spring and summer. Its concentration in the surface layer was higher in costal zones, especially Laizhou Bay, Bohai Bay and Liaodong Bay. The concentration of MChl-a except for Laizhou Bay kept increasing during the last 11 years, which increases the possibility of eutrophication. The time that blooms occurred had a one or two month shift back and forth in different places. The main factors that affect MChl-a concentration were explored. MChl-a concentration was negatively correlated with wind speed, while positively correlated with air temperature and relative humidity. Huanghe River discharge showed positive correlation to MChl-a near coastal areas, but a negative one in the deep water.