All life depends ultimately on primary producers, the organisms which capture the energy in sunlight by photosynthesis. On land, they are easily recognized as plants. Although marine primary production by coral reefs, mangroves and seagrasses is relatively better-known, the vast majority of primary production in the sea is by microscopic single-celled plants called phytoplankton. These tiny plants depend on sunlight in the upper pelagic layers of the ocean and absorb nutrients from the water in order to reproduce and grow. They are the first step in the food chain that provides the fish that humans consume.
All primary producers, such as marine phytoplankton, use a variety of chemical pigments to capture the energy from sunlight. The best known of these is the green pigment chlorophyll that is present in virtually all primary producers. The concentration of chlorophyll and other pigments in the marine plankton can be measured from space by analysing the colours coming from the oceans surface. Combining information from satellites with measurements and experiments performed at sea allows estimates of the ocean’s production to be made and mapped.
Primary production in most of the open ocean is quite low, limited by supplies of the chemical nutrients needed by plants to grow. Highly productive areas are found where sources of nutrients are available from deep water upwelling and large river inflows.
In the LAPE area the main sources of nutrients are from the flows from the Amazon, Orinoco and other South American rivers. The overall primary production of the LAPE is quite low, and consistent with other tropical open sea areas. There are seasonal variations and peaks of productivity in the southern-most area off Trinidad and Venezuela, which are driven by the nutrient supplies in the outflows of the Orinoco and other rivers.
Phytoplankton are the microscopic plants that provide the primary production in pelagic ecosystems. The vast majority are single-celled although chain-forming and other colonial forms exist. In spite of their small size, when they are abundant enough they can colour the ocean waters enough to be visible from space. The two most important groups are dinoflagellates and diatoms and both groups include thousands of species.
Plate 1 Dinoflagellates
Plate 2 Dinoflagellates
Plate 3 Dinoflagellates
Plate 4 Dinoflagellates
Plate 5 Dinoflagellates
Plate 6 Chain Diatoms
|Plate 7 Diatoms|
Coccolithophores & Filamentous Algae