Phytoplankton
bloom in the Barents Sea.
These chlorophyll-rich microalgae are at the bottom of the oceanic food chain, and play a fundamental role in the carbon cycle, as they absorb carbon dioxide, acting as a carbon sink.
It is a fragile equilibrium: the quantity of phytoplankton is often increased by the release into the sea of agricultural fertilisers, especially phosphates. The process of plant decomposition can deprive the ocean of all its oxygen because the bacteria that digest the plants release hydrogen sulphide, creating dead zones where fish are unable to survive.
The most important example of this has occurred in the Black Sea, where the huge inflow of polluted freshwater and the particular shape of the basin, with a very low level of vertical mixing, have led to the formation of a completely anoxic zone, which is devoid of life at a depth of below 200 metres.
Some species of algae also give off toxic substances, which are harmful to natural resources and humans; the well-known red tides of the Caribbean are an example of this Harmful Algal Bloom (HAB).
Macroscopic algae too can bloom abnormally, as happened some years ago in the Adriatic, and more recently in 2008, in the northern Yellow Sea near the port of Qingdao. The radar image from COSMO-SkyMed shows numerous filaments of emerging algae.
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image:
A massive proliferation of macroscopic algae in the bay of Qingdao, a major port in China.
The COSMO-SkyMed radar picks out filaments of the algae emerging a few centimetres from the surface of the water.
The image shows several boats engaged in clean-up operations.
The COSMO-SkyMed radar picks out filaments of the algae emerging a few centimetres from the surface of the water.
The image shows several boats engaged in clean-up operations.
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