Life in the oceans is distributed over 3 dimensions
There is a very high diversity of marine environments
Our Oceans Atlantic Pacific Indian Arctic Antarctic “ ONE OCEAN” All are interconnected thanks to an important system of oceanic currents both at surface and in the depths.
Oceanic Circulation The centres of the Oceans (within the Gyres) are like deserts, with little biological production... Whereas the western coasts are frequently very rich areas of high productivity thanks to vertical currents known as UPWELLINGS.
Upwellings Vertical currents bring nutrient-rich waters from the ocean depths to the surface where the presence of sunlight allows phytoplankton to shift photosynthesis into a higher gear. This results in more food available for all.
Primary Production (gC/m 2 /year) Notice how productive certain areas are, like the North Sea, a region intensly fished!
Influences the quantity of O 2 dissolved in the water
Influence on ocean currents
Importance for marine animals’ capacity for osmoregulation (process by which we control the quantities of minerals in our cells).
Along with Tº has an influence on water density
Sunlight (necessary for photosynthesis)
Light Euphotic layer Receives enough light for photosynthesis Aphotic layer Total Darkness Oligophotic layer Dusk Zone PROBLEM: PHOTOSYNTHESIS REQUIRES LIGHT + NUTRIENTS , BUT LIGHT IS FOUND IN THE UPPER LAYER WHEREAS NUTRIENT-RICH WATERS ARE NEAR THE BOTTOM! SOLUTION: UPWELLINGS + STORMS (mix up the water column) DEPTH REMINERALIZATION PHOTOSYNTHESIS
Vertical Distribution of Life Nekton Pelagos Benthos Plankton
Copepods 2 mm You don’t want to know how many of these you can swallow in a bucket full of sea water…
Other crustaceans Many animals that live on the sea floor actually live in the water column as plankton when they’re young. As they grow older and bigger (and go through several metamorphosis) they migrate back down to the bottom. krill amphipod Lobster larvae