Nutrient Cycles in Marine Ecosystems Part I Section 4

Surface Layer of Ocean Dissolved nutrients (N,*P) Elements/compounds that are essential to life Recall: algae require light for photosynthesis Intensity of light as depth Restricted to surface layer (photic zone) Depth 30 m to 150 m Obviously less in turbid water (high turbidity) *there due to animals releasing ammonia

What is an ion? atom or molecule in which the total number of electrons is not equal to the total number of protons, giving the atom a net positive (+) or negative (-) electrical charge.

SOME Surface Layer Ions

Surface Ions Those ions, together with nitrate and phosphate ions form nutrients for growth of algae and other producers Unit of measurement: ppm Nitrate and phosphate ions occur in low concentrations in seawater Nitrate = 0.5 ppm Phosphate = 0.07 ppm

Replenishment of dissolved nutrients (3) 1. Upwelling – movement of water from deep in the ocean to the surface layer, where nutrients become available to primary producers Replenishment=bringing back to use Wind driven Movement of dense water Movement of cooler water

Causes of Upwelling Deflection of deep water currents upwards Nutrients sunk to sea floor brought back up to surface of ocean Movement of water away from the coast by wind

2. Run-off from land Part of hydrological cycle Water leach nutrients (including nitrates and phosphates) from soil

3. Atmospheric Gases CO2 dissolved in seawater forming hydrogencarbonate ions (HCO3-) AKA bicarbonate Makes CO2 available for fixation in photosynthesis for primary producers *Ocean acidification N gas is fixed by blue-green bacteria in intertidal zones Forms nitrogen-containing organic compounds How nitrogen enters marine ecosystems *Show ocean acidification lesson

Intertidal Zone Area above water during low tide but underwater during high tide

Nitrogen Cycle

Recycled Nutrients like nitrates and phosphates are recycled at the ocean surface by excretion from zooplankton

Depletion of dissolved nutrients Uptake by primary producers like phytoplankton Synthesis of organic substances Example: nitrate ions used for synthesis of amino acids and proteins Phytoplankton  zooplankton  small fish Proteins passed to next trophic level and so forth