Biological Productivity

Conditions for Life in the Sea Consider the main biochemical reaction for life in the sea, and on earth in general: 6H 2 O + 6CO 2 + energy + nutrients = C 6 H 12 O 6 + 6O 2 Focus on left side of equation What is in short supply in the sea and thus limits the amount of life in the ocean??

Absorbing Nutrients 6H 2 O + 6CO 2 + energy + nutrients = C 6 H 12 O 6 + 6O 2  Phytoplankton are base of the food chain  Most important primary producers of complex sugars and oxygen Lauderia sp.

Open Ocean Food Webs Barrie Kovish Vicki Fabry Pacific Salmon Copepods Coccolithophores Pteropods

Sinking Organic Debris Present Ocean Food Web – Complex ecosystem interactions based on a low CO 2 ocean MicrobialRemineralization Primary Producers Zooplankton Food Web Upper Trophic Levels Seafloor community Provided by James Barry MBARI Ocean Food Web

Absorbing Nutrients  Nutrients absorbed by plants through diffusion across a semi-permeable membrane Lauderia sp.

Diffusion: molecules move from high to low concentrations

Which Nutrients are in Short Supply?  Nitrogen (N) as Nitrate NO 3 (-2)  Phosphorus (P) as Phosphate PO 4 (-2)  Silicon (Si) as Silicate SiO 4 (-2)

Phosphate and Nitrate in the Pacific

Silicate in the Pacific

Biolimiting Nutrients  N, P, and Si are exhausted first in Eq. surface waters during photosynthesis  Essential to the growth of phytoplankton  If these biolimiting nutrients increase in sea water, life increases  If these biolimiting nutrients decrease in sea water, life decreases  Where would you expect to find the highest biomass in the Pacific??

CZCS Global Primary Production

 O 2 is high in the surface and mixed layer  O 2 decreases to a minimum at base of thermocline  O 2 then steadily increases with depth How Does Nutrient Distribution Compare w/ Dissolved Oxygen? 6H 2 O + 6CO 2 + energy + nutrients = C 6 H 12 O 6 + 6O 2

Dissolved O 2 Reverse of Nutrients

Why is the Concentration of Oxygen High in the Mixed Layer?? Hint #1: How and where is oxygen produced in the sea??? 6H 2 O + 6CO 2 + energy + nutrients = C 6 H 12 O 6 + 6O 2 Hint #2: How can oxygen be mixed downward from the atmosphere into the ocean?

How is Oxygen Removed from the Thermocline & Slightly Below??

Dead and decaying organic matter sinks downward from surface waters  Rate of sinking decreases as it encounters the cold, dense water of the thermocline  Material decays (oxidizes) at the thermocline, which strips O 2 out of the water and returns nutrients to the sea  Cold, nutrient-rich water of the thermocline is returned to sunlit surface waters by way of upwelling

CZCS Global Primary Production

Marine Ecology

Basic Ecology  physical and chemical parameters affecting distribution and abundance  An ecosystem includes both the living (biotic) and non-living (abiotic) portions of the environment. –Examples include: salt marshes, estuaries, coral reefs, the North Pacific Gyre.

Classification of Organisms by Environment  horizontal: neritic | oceanic  vertical: –epipelagic (top) / euphotic (good) –mesopelagic (middle) / disphotic (low) –bathypelagic (deep) / aphotic (without) –abyssopelagic (“bottomless”)

Divisions of the Marine Environment Figure 9-1

Classification of Organisms by Lifestyle  Scientists have established another classification scheme to categorize biota on the basis of lifestyle. The major groups are: –plankton (floaters) –nekton (swimmers) –benthos (bottom dwellers)

Plankton  weak swimmers, drifters, unable to counteract currents. –Phytoplankton (plants) –Zooplankton (animals)

Nekton  active swimmers capable of counteracting currents. –Fish –Squids –Reptiles –Birds –Mammals

Distribution of Marine Lifestyles  16.7% of Earth’s animals are marine  2% inhabit pelagic environment (most of the oceans are cold and dark)  98% are benthic!

Benthos  Epiflora or epifauna live on the sea bottom.  Infauna live in the sea bottom.  Benthic plants - restricted to shallow waters (light)  Benthic animals occur everywhere from shallow depths to the deep sea.

Research Video Clips: “Live fast, die young...”

Hydrostatic Pressure  Pressure caused by the height of water.  Function of water height and water density  Pressure generally increases at a rate of 1 atm per 10 m of water. ( or 16 psi per 10 m depth)

Think You’re Under Pressure Now?

Hydrostatic Pressure (Cont.)  enormous in the deep sea yet animals live there.  Animals do not contain gases.  However, mesopelagic fish which have gas-filled swim bladders to help maintain neutral buoyancy –unable to move rapidly between depths –pressure change could cause bladder explode.