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
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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
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•
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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?