Nutrient Cycles in Marine Ecosystems Part II Section 4

Limited Productivity Inorganic nutrients (ex: nitrate and phosphate ions) are essential for growth of primary producers Productivity of primary producers will affect productivity of higher trophic levels Example: upwelling – high productivity

Benguela upwelling system

Removal of Nutrients Sink to sea floor In feces Detritus (decaying organic materials); organisms die Loss of nutrients from surface water Will only return to surface by upwelling Slow decomposition on sea bed (floor) due to cold/lack of oxygen

Removal of Nutrients Incorporated into coral reefs Deposition of calcium carbonate for growth of corals

Removal of Nutrients Removed by harvesting Removing/eating fish and other marine organisms

Nutrient Biological Uses Nitrogen Make proteins; synthesis of amino acids Carbon Synthesis of all organic materials (ex: carbohydrates, proteins) Magnesium Make chlorophyll for plants Calcium Production of bones, corals and shells Phosphorus Production of bones and synthesis of DNA

Summary of ways in nutrients are cycled in marine systems Nutrients derived from both Removal (3) Figure 4.1 Summary of ways in nutrients are cycled in marine systems

In Summary Fertilizers(N ,P and K)- plant growth. The level of dissolved nutrients increases from animal feces Surface water often lack nutrients because feces and dead matter tend to settle to the bottom of the ocean. Most decomposition is thus at the bottom of the ocean. Plants must be at the surface for the light. Nutrients are returned to surface waters by a special type of current called 'upwelling' and it is in these areas of upwelling that we find the highest productivity of marine life.

Website References http://www.seafriends.org.nz/oceano/seawater.htm#composition http://www.marinebio.net/marinescience/02ocean/swcomposition.htm