Photosynthesis

Almost all life on the earth depends on chlorophyll bearing organisms being able to use the sun's energy to convert inorganic molecules into organic molecules. This process is called photosynthesis.

There are significant differences in the location and extent in which photosynthetic organisms can operate due to the physical and chemical composition of the sea. This means that photosynthetic production is not uniform throughout the oceans, but occurs more in areas of high nutrient availability, for example, shelf seas and coastal regions. Phytoplankton are responsible for approximately 95% of all the marine photosynthesis.

Take a look at our Photosynthesis Fact Sheet and try our Photosynthesis questions

Plankton blooms are natural phenomenon, and they occur when conditions for growth and reproduction in phytoplankton are optimal. In early spring when the nutrients in the sea have been churned up by winter storms, phytoplankton starts to develop. By late spring and early summer the rate of growth is accelerated by warmer weather and more daylight hours. Sometimes plankton blooms can become so large satellites in space can photograph them. Coccolithophores are small phytoplankton with calcium plates surrounding their cell walls. This means that when it is in very large numbers it can turn the sea a milky white colour. Coccolithophore blooms are very common in the coastal waters of the British Isles.

Some blooms are vast in size and can be seen by satellites orbiting the earth. Look at these images of the British Isles and Europe taken by NASA:

Phytoplankton blooms are visible in the waters between the U.K and the Netherlands in this SeaWiFS image of the North Sea Region Click image to enlarge

A linear phytoplankton bloom is visible in the southern North Sea in this SeaWiFS image Click image to enlarge

Although the majority of plankton blooms are natural, some scientists believe that eutrophication of marine waters encourages blooms of phytoplankton and algae. Eutrophication is the process of water becoming more productive by increasing in nutrient rich substances such as nitrogen and phosphorus. This process happens naturally but takes hundreds or thousands of years. However, pollution of waters with plant nutrients (for instance fertiliser run off from farmland) can speed up this process. As consequence these blooms usually occur where rivers and estuaries meet coastal regions, and they can have drastic effects on the marine communities living there.

PREVIOUS