Photosynthesis (Primary Production) Requirements for photosynthesis: sunlight (and chlorophyll to capture energy) nutrients (nitrogen, phosphorus..), space CO 2 + H 2 O C 6 H 12 O 6 + O 2 + H 2 O respiration 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 1150m giant squid 1500m

Light in the ocean Water not very transparent to light Photic zone = where enough light penetrates for photosynthesis Range = few meters in coastal zone, to 200 m in clear, tropical ocean Affected by: transparency of water angle of sunlight hitting the water atmospheric absorption of light

Primary Production in the Sea Fig 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 The results of a hypothetical light- and dark-bottle experiment.

Primary Production in the Sea Fig This phytoplankton bloom along the California coast, was imaged by SeaWiFS on 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 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 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 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 debris and large particles, or decaying material, with bacteria and protists attached. Sinks to bottom, carrying nutrients away from surface. e.g., dead pelagic tunicate covered with bacteria and protists

Vertical migration of zooplankton Definition: 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/hour

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

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)

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