15. 2 Diversity of Ocean Life & 15.3 Oceanic Productivity

15. 2 Diversity of Ocean Life&

15.3 Oceanic Productivity

Classification of Marine Organisms

• Classified based on where they live & how they move– Plankton: floaters– Nekton: swimmers– Benthos: bottom dwellers

Plankton

• Include all organisms – algae, animals, & bacteria

• Move with the ocean currents• Can swim• Algae that undergoes photosynthesis =

phytoplankton • Microscopic • Animal plankton = zooplankton

Nekton

• Include all animals capable of moving independently of the ocean currents by swimming

• Can migrate long distance• Include most adult fish, squid, marine

mammals, & marine reptiles

Benthos

• Describes organisms living on or in the ocean bottom

• Shallow coastal ocean floor contains a wide variety of physical conditions & nutrient levels

• Deeper parts = photosynthesis can not occur– They feed on each other and whatever falls from

above

Marine Life Zones

• 3 factors used to divide the ocean into life zones:– Availability of sunlight – Distance from shore– Water depth

Availability of Sunlight

• Photic zone = sunlight• Euphotic zone = portion of the photic zone

near the surface where photosynthesis can occur (up to 100 m deep)

• Aphotic zone = no sunlight

Distance from Shore

• Subdivided based on distance

• Intertidal Zone = land & ocean meet & overlap– Harsh living conditions due to crashing waves,

drying out time to time, quick temperature changes, salinity, & oxygen concentrations

– Adapted

• Neritic Zone = covers gently sloping continental shelf

• Narrow – hundreds of km from shore • Shallow enough for sunlight to reach ocean

floor = photic zone• 90 % of the worlds commercial fisheries

because it is so rich

• Oceanic Zone = beyond continental shelf• Surface waters have lower nutrient

concentrations because nutrients sink out of the photic zone to the deep ocean floor– Smaller populations than the more productive

neritic zone

Water Depth

• Pelagic Zone = open ocean of any depth• Animals = swim or float freely– Photic area of the pelagic zone home to:

phytoplankton, zooplankton, nekton– Aphotic area fo the pelagic zone home to: giant

squid & other species that have adapted to deep waters

• Benthic Zone = any sea – bottom surface (regardless of the distance from shore)

• Mostly inhabited by benthos organisms

• Abyssal Zone = subdivision of the benthic zone• Extreme pressure• Low temperatures• No sunlight• Little life forms

Hydrothermal Vents

• Along the oceanic ridges• Seawater seeps into the ocean floor through

cracks in the crust• Becomes heated and saturated with minerals• Minerals precipitate out when it comes in

contact with cold ocean water (black smoke color)

15.3 OCEANIC PRODUCTIVITY

Primary Productivity• Production of organic compounds from inorganic

substances through photosynthesis or chemosynthesis• Photosynthesis – use of light energy to convert water

and CO2 into glucose molecules• Chemosynthesis – process by which certain

microorganisms create organic molecules from inorganic nutrients using chemical energy

• 2 factors influence a area’s photosynthetic productivity: – Available nutrients – Amount of solar radiation

Productivity in Polar Oceans

• Density & temperature change very little with depth in polar regions

• Summer = melting ice = lower salinity• Availability of solar energy is what limits

photosynthesis productivity in polar areas

Productivity in Tropical Oceans

• Productivity is low & limited bc of lack of nutrients

• The sun is more directly overhead > light penetrates deeper into the tropical ocean than in temperate and polar waters

• Solar energy is available year around• Permanent therocline prevents mixing btw

surface waters and nutrient rich deeper waters

Productivity in Temperate Oceans

• Found at mid-latitudes • Winter• Spring• Summer• Combination of these 2 limiting factors to

control productivity– Sunlight– Nutrient supply

Oceanic Feeding Relationships

• Tropic Levels– Feeding levels– Zooplankton = herbivores (eat algae)– Herbivores eaten by Carnivores

• Transfer efficiency – The transfer of energy btw tropic levels is inefficient

• Food Chain / Food Web– Sequence of organisms where energy is transferred

starting with a primary producer– Feeding relationships = Food Web

Review Questions

• What factors influence a region’s photosynthetic productivity?

• Compare/Contrast Food Web & Food Chain• Compare/Contrast Photosynthesis &

Chemosynthesis• How are marine organisms classified?• Why is the neritic zone rich in life?