Chlorophyll a concentration

Chlorophyll a concentration is an index of phytoplankton biomass and it is the most common property that characterizes marine productivity.

Satellite remote-sensing images of ocean colour, calibrated as chlorophyll concentration provide a unique approach to monitor the productivity of the oceans and seas worldwide.

SURFACE ALGAL BLOOMS

SUBSURFACE ALGAL BLOOMS

Seasonal algal blooms developing in the Omani shelf waters during the South-West and North-East monsoonsresult in periodic fish kill incidents, shortages in desalination plant functioning, and recreational problems for tourists and divers.

Our team (sponsored by the ONRG grant linking scientists and technicians from the Department of Marine Science and Fisheries and University of East Anglia) has launched several sea gliders, in order to scan the shelf waters throughout the year.

Sea gliders are autonomous robotic systems equipped with numerous sensors allowing recording of physical, chemical, and biological parameters of the water column. These records could be carried out every 6 hours, on the way to the surface (from the depth of several hundred meters) and back.In reaching the surface, the glider transmits recorded data via satellites and gets a new command- on what to do and where to sail.

Data on vertical distribution of temperature, salinity, water density, dissolved oxygen concentration, and phytoplankton biomass (based on fluorescence measurements), was complemented by sampling on board SQU research vessel “Al-Jamiah” coming from time to time to visit the glider. This sampling allowed us to understand what species have played the most important role in the formation of algal blooms and layers.

 

Overall, sea glider observations combined with plankton sampling and remote sensing provided insight into the termination of the winter monsoon algal blooms observed at sea surface and subsequent descending of these blooms to the depth of 25-55 m during the Spring Inter-monsoon season.

In comparison to the surface bloom, species diversity of the subsurface bloom is decreased by half. The dinoflagellate Noctilucascintillans dominated by biomass in all samples collected from the depth of subsurface fluorescence maximum shown in the figure. The subsurface algal blooms persist throughout inter-monsoon seasons, linking blooms initiated during the South-West and North-East monsoons.

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