Important Links and adresses
Optical Methods of Remote sensing
Detecting Algal bloom and specifically HBA was for a long time a matter of heavy logistics where on board and off board instrument were used like buoy , mooring probs, in situ Lab analysis, but a big shift happened after 1979 where Mueller demonstarate the possibility of detecting HAB through remote sensing.Quantifying “discoloration” is problematic and associating a discoloration with a HAB is even more difficult. As a result, research on HAB detection using optical techniques has varied and includes methods which examine water discoloration, chlorophyll concentration, absorption spectra, and optical characteristics. Optical techniques are based on the simple premise that HABs cause discoloration of the water, hence the term “red tide”. Blooms that dominate the biomass will change the color of the water, providing an indication of the potential risk. As a result, many monitoring programs respond to reports of water discoloration. Research on open ocean blooms beginning with the use of CZCS imagery, has shown that distinctive color patterns can aid in the detection of various types of algal blooms.
Compared to discoloration interpretation, spectral analysis of distinctive characteristics for HABs is more reliable at identifying monospecific blooms and extracting helpful information. Broadly, spectral characteristics involve two optical types: Apparent Optical Properties (AOP) and Internal Optical Properties (IOP). AOP is determined by the ambient light field and IOP is the absolute property of the medium itself . Unique remote sensing reflectance (a typical AOP) are determined by phytoplankton and have a close relationship with discoloration. Different classification algorithms or HAB identification rules are developed based on reflectance characteristics to discriminate HABs from other optical water types . On the other hand, IOP such as absorption and backscatter are also widely examined to create optical models with the purpose of accurate identification of HABs . Although influence by other components can contribute to the spectral shape of HAB waters,
This step focuses on investigating corresponding oceanographic parameters obtained by ocean color techniques when monitoring a HAB event. The primary ocean color parameters, such as Chl-a and NPP, are known to be biochemically informative. Therefore, tracing the spatial and temporal variation of such ocean color factors enables us to discover the presence of a changing HAB, especially large-geographic HABs lasting for a considerable period. High Chl-a and NPP zones in continuous sequential daily-images are promising indicators of the occurrence and movement of HABs. Finally, the retrieval and spatial-temporal analysis of aforementioned ocean color parameters are expected to provide a substantive explanation from the biochemical perspective, leading to a more deep understanding of the true HAB mechanism.
The development of optical models for HABs has taken two approaches: the examination of absorption spectra alone, and the examination of the entire suite of optical properties, which include both scattering and absorption characteristics. Absorption techniques focus on both photosynthetic and auxiliary pigments. with a given species seems to be a logical approach. However, direct measurements of visible absorption spectra allow for the characterization of only some phytoplankton properties. Schofield discussed the issues involved with using optical absorption methods for phytoplankton identification, through the use of in situ instrumentation. Millie et al.(1997) showed that a single pigment was unique between Karenia brevis and a diatom, allowing possible discrimination of the two species through the use of fourth-derivative analysis of the absorption spectra. Similarly, in situ measurements of specific absorption bands, combined with discriminate analysis, to aid in the separation of toxic and non-toxic phytoplankton in Norwegian waters.
Optical Characterisation
Discoloration
Color Analysis
Algal Bloom Status ,forcast, and Metigation.
How the smallest creature affect the biggest eco-systeme
