Photosynthesis (Primary Production)

Requirements for photosynthesis:

• sunlight (and chlorophyll to capture energy)

• nutrients (nitrogen, phosphorus..), space

CO2 + H2O C6H12O6 + O2 + H2Orespiration

photosynthesis

sugars, fixed carbon

Spatial Distribution

•Fig. 2.1 A spatial classification of marine organisms.

Trieste, 1960, 10,912m

(Marianas Trench, 10,923m)

octopus, 5000m

deepest fish, 8370m

sperm whale 1150mgiant squid 1500m

Light in the oceanWater not very transparent to light

Photic zone = where enough light penetrates for photosynthesisRange = few meters in coastal zone, to 200 m in clear, tropical ocean

Affected by: transparency of waterangle of sunlight hitting the wateratmospheric absorption of light

Primary Production in the Sea

•Fig. 1.21 Fate of sunlight as it enters sea water. The violet and red ends of the visible spectrum are absorbed first.

Factors that Affect Primary Production

Light in Water.

Primary Production in the Sea

• Measurement of Primary Production

Fig. 3.20 The results of a hypothetical light- and dark-bottle experiment.

Primary Production in the Sea

•Fig. 3.22 This phytoplankton bloom along the California coast, was imaged by SeaWiFS on 10-11 August, 2003 for true color (left) and for chlorophyll a concentrations.

Primary Production in the Sea

• Factors that Affect Primary Production

– Nutrient Regeneration. Marine producers rely on a number of mechanisms of nutrient regeneration, such as turbulent mixing, convective mixing, and upwelling.

Primary Production in the Sea Nutrient

regeneration

Fig. 3.35 Seasonal growth and decline of thermoclines in tropical (top), temperate (center), and polar (bottom) ocean waters.

Primary Production in the Sea• Factors that Affect Primary Production

– Nutrient Regeneration.

Fig. 3.36 Coastal upwelling in the Northern Hemisphere.

Productivity in the oceans

Primary Production in the Sea

• Factors that Affect Primary Production

– Grazing. Small herbivorous grazers routinely occur at such high concentrations that phytoplankton communities may be destroyed over a period of just a few weeks.

Primary Production in the Sea

• Fig. 3.24 Generalized population changes of a prey species and its predator, oscillating between unlimited (solid) and limited (dashed) phases of population growth.

Factors that Affect Primary Production

Grazing.

Contribution to Primary Production in Ocean

• One-celled plankton contribute 90%-95% of primary productivity in the ocean

• Macroalgae (large, attached algae in the coastal zone) contribute 5-10%

marine snow= particulate organic matter that

originates in the ocean

Formed by collisions of debrisand large particles, or decayingmaterial, with bacteria and protists attached. Sinks to bottom, carrying nutrients away from surface.

e.g., dead pelagic tunicate coveredwith bacteria and protistshttp://life.bio.sunysb.edu/marinebio/plankton.html

Vertical migration of zooplanktonDefinition: Migration pattern over 24 hrs, typically upwards at dusk and downwards at dawn,poorly understood, Why migrate? Several hypotheses:

*Avoid visual predators during daylight at greater depths and return to shallow zones with abundant food during night*Save energy during non-feeding daylight time in deeper, colder water*Exploit different currents at different depths and remain in same general area, or ascend to fresh, ungrazed food resources the next day

Range: up to 200 m (copepods) to 800 m (krill); speed 10 – 200 m/hourhttp://www.jochemnet.de/fiu/OCB3043_25.html

Vertical migration of zooplankton

*Consequences:

•faster transport of organic matter into deep water: animals capture prey at shallower depths and transport it downwards either as their body mass or fecal products; both are faster than sedimentation

*Not all individuals migrate the same range at the same time; population will lose some and gain others, enhances genetic mixing

*Samples from same depths taken during day and night will differ in species composition and total biomass

http://www.jochemnet.de/fiu/OCB3043_25.html

Vertical migration of zooplankton

*Deep Scattering Layers: False echosound signals by larger zooplankton (krill, shrimp) and fish, but sometimes also copepods, makes ocean seem to have a false bottom

Military interest in this DSL (submarines can hide under the layer)

http://www.jochemnet.de/fiu/OCB3043_25.html

sexual reproduction

Fig. 2.3 The basic components of sexual reproduction. The chromosome arrangement of each cell is shown to the right.

Sexual vs Asexual Reproduction

• Asexual reproduction = no genetic recombination: cloning, budding, fission

• Sexual reproduction = reduction division to produce gametes (half of parent DNA), combine to form a genetically mixed zygote different from either parent