Life In The Ocean

Life in the Ocean By Cristina B. June 8 2009 Music: Song for the Ocean by Kristin Hoffmann http://www.kristinhoffmann.com/

“ Earth”

70% of the planet’s surface is covered by water

Average depth of the ocean: 3000 meters

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!

What limits life in the Oceans?

Temperature

Influences the quantity of O 2 dissolved in the water

Influence on ocean currents

Salinity

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)

Nutrients (ditto)

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

Benthos

Communities that live asociated with the ocean floors (from the coast to the deep trenches)

Phytobenthos (plants)

Responsible for Primary Production (photosynthesis)

In “shallower” waters (euphotic layer, need light!)

Zoobenthos (animals)

Consumers

Decomposers

Benthos Posidonia oceanica

Plankton

Plankton are basically any and all organisms (plant or animal) that live in the water and are pulled this way and that by the currents. Generally microscopic.

Examples (and sizes):

Bacteria (0,1 - 1 µm)

Single-celled algae (0,1 - 100 µm)

Copepods (~ 1 mm)

Krill (~ 8 cm)

Medusas (up to 10 m with the tentacles)

Phytoplancton (single-celled algae) PRODUCERS = responsible for primary production via photosynthesis the ocean's lungs! 100 µm diatoms cocolithophorids Phytoflagellates dinoflagellates silicoflagellates

Zooplankton The CONSUMERS

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

Molluscs Echinoderm larvae (sea urchin) Salps

Chaetognaths: important predators of other planktonic groups 2 mm 2 cm

Medusas

Eggs and fish larvae

Nekton