Underwater optical environment in the Upper Gulf of Thailand

Matsumura, Satsuki,Siripong, Absornsuda,Lirdwitayaprasit, Thaitherworn

Coastal marine science. Vol.30No.1, 2006.4, pp. 36-43

Abstract

Because the composition of coastal water is full of variety by each region, relationship between chlorophyll-a (chl.a) concentration as a indicator of primary productivity derived by satellite ocean color data and in situ data of chl.a may not be same always. Those relations or algorithms should be verified at each coastal water for managing coastal environment. Coastal ocean color algorithms should be built up at each coastal water or at least should be verified by wide range field data for practical application at each region. Intensive research cruises were conducted at the Upper Gulf of Thailand. Optical survey using PRR (Profiling Reflectance Radiometer) showed the character of the Upper Gulf water. Under water optical algorithms for that water were suggested by these survey data. Optical depths in the Gulf of Thailand were also measured to know the compensation depth for primary production. Although the transparency measured by Secchi disk is not so large and surface water looks very turbid, the light energies are reaching to near bottom at almost all stations of the upper Gulf. It suggests that the turbidity of this water were mainly composed of scattering material like as clay mineral rather than absorbing material like as phytoplankton pigment or CDOM.

Keywords:

  • coastal water algorithm
  • PAR
  • compensation depth
  • chlorophyll-a
  • CDOM
  • SS
  • satellite
  • remote sensing

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Spatial and seasonal variability of Chlorophyll-a and associated oceanographic events in Sabah water

Abbas, Alaa A.,Mansor, Shattri B. ; Pradhan, Biswajeet ; Tan, C.K.,2012. Spatial and seasonal variability of Chlorophyll-a and associated oceanographic events in Sabah water.The Second International Workshop on Earth Observation and Remote Sensing Applications (EORSA 2012), pp 215-219. DOI 10.1109/EORSA.2012.6261168.

Abstract

This study investigated the spatial and temporal distributions of Chlorophyll-a (Chl-a) in Sabah coastal water using satellite data, and identified the associated oceanographic events which caused large scale water enrichment in the surface layer. Results showed that surface Chl-a experienced seasonality in Sabah waters. At the northwest coast, very obvious increase in the Chl-a was observed from January to March, attributed to wind-driven coastal upwelling during the northeast monsoon (NEM). The southeast coast depicted high Chl-a at Labuan offshore water, related to the reversing direction of Baram River plume towards Sabah during NEM. Labuan bay water had higher Chl-a during the southwest monsoon (SWM) due to the effect of discharged materials from the Padas River during the rainy season at Labuan. On the other side, a slight increase in surface Chl-a was illustrated along the entire northeast coast during NEM, with higher concentrations at the southern part compared to the northern region. The high Chl-a at the southern part (southern Sandakan) was owing to alongshore water transport from the northern region driven by NEM winds and effect of discharged materials from the Kinabatangan River during the rainy season at Sandakan. Water characteristic at the southeast coast was highly influenced by surface water transport from the Sulu and Sulawesi seas and prevailed surface currents. Both inshore and offshore waters off Semporna had peak Chl-a in December, related to Sulu Sea water transport towards Semporna and occurrence of cyclonic eddy at the offshore water during early NEM. Tawau water showed very high Chl-a throughout the year due to the effect of coastal discharge. The discharged material near Tawau was transported to a wider area offshore during SWM. That in turn caused another peak Chl-a at Semporna inshore water in August during SWM.

Keywords:

  • Asian monsoon
  • Sabah water
  • chlorophyll-a
  • seasonal variation
  • upwelling

An extensive Cochlodinium bloom along the western coast of Palawan, Philippines

Rhodora V. Azanzaa, ,Laura T. Davida,Roselle T. Borjaa,Iris U. Baulaa,Yasuwo Fukuyob
a The Marine Science Institute, University of the Philippines, Diliman, Quezon City 1101, Philippines
b Asian Natural Environmental Science Center, The University of Tokyo, Yayoi 1-1-1 Bunkyo-ku, Tokyo 113-8657, Japan
http://dx.doi.org/10.1016/j.hal.2007.12.011

Abstract

A massive fish kill and water discoloration were reported off the western coast of Puerto Princesa, Palawan, Philippines in March 2005. Phytoplankton analysis revealed a near monospecific bloom of the dinoflagellate, Cochlodinium polykrikoides, with cell concentrations ranging from 2.5 × 105 to 3.2 × 106 cells per liter. Ground truth data were supplemented by processed satellite images from MODIS Aqua Level 2 data (1 km resolution) from January to April 2005, which revealed high surface chlorophyll-a levels (up to 50 mg/m3) offshore of west and southwest Palawan as early as February 2005. The bloom extended 310 km in length and 80 km in width at its peak in March off the central coast (Puerto Princesa). By April, the bloom declined in intensity, but was still apparent along the northern coast (El Nido). Fluctuations in chlorophyll levels off the western coast of Sabah, Malaysia and Brunei during this time period suggested that the bloom was not limited to the coast of Palawan. Satellite imagery from Sabah in late January revealed a plume of chl-a that is believed to be the source of the C. polykrikoides bloom in Palawan. This plume drifted offshore, advected northward via the basin-wide counterclockwise gyre, and reached nutrient-rich, upwelled waters near Palawan (due to a positive wind stress curl) where the dinoflagellate bloomed and persisted for 2 months from March to April 2005.

Keywords

  • Cochlodinium polykrikoides;
  • Fish kills;
  • Philippines;
  • Remote sensing