ES101 Lecture Notes - Lecture 14: Ocean Acidification, Oxygen Saturation, Primary Production
Week 6, Lecture 2: Marine Biodiversity
Is the Great Barrier Reef Dead or Dying?
● Not dead yet
● However, last 12 months have seen a sudden “bleaching event” which killed large areas
of coral in northern parts of the reef
● Caused by unusually warm water temperatures
● Scientists fear larger areas of the reef will be lost in coming decades due to global
warming, ocean acidification
Environmental Characteristics
Aquatic Life Zones
Key Influences:
● Access to sunlight
● Temperature
● Dissolved oxygen availability
● Dissolved nutrients (carbon, nitrogen, phosphorus)
Penetration of Sunlight
● So as long as light can penetrate water, photosynthesis is possible
● Where photosynthesis occurs, oxygen is produced
● In shallow waters, nutrients are more available
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● Result: shallow, brightly lit waters tend to have high rates of primary productivity, larger
populations of animals
● 90% of marine species are found in coastal waters
Deep Waters
● Once you drop below the surface, primary productivity diminishes
● Oxygen becomes scarce with increasing death
● Nutrients are scarce except at upwelling zones and at the very bottom (benthic
environment)
Whale-Falls
● When a dead whale sinks to the floor of deep ocean, it brings a sudden influx of
nutrients
● Creates its own mini-ecosystem
More primary productivity in the north during northern summer because of extra sunlight,
northern winter has less but more near Antarctica
Upwelling
● Winds, currents cause water from deep to rise toward surface
● Upwelling water often brings additional nutrients
● Lots of coasts of North America, Greenland for example (mixing of water = lots of
primary productivity)
Categories of Aquatic Creatures:
Plankton:
● Ultraplankton
○ Free-floating, microscopic bacteria that photosynthesis
○ Collectively make a significant contribution to global primary productivity
● Phytoplankton
○ Larger, free-drifting, photosynthesizing plant-like organisms (e.g algae)
● Zooplankton
○ Free-floating
○ Includes primary consumers (herbivores) and secondary consumers (carnivores)
○ Vary in size from microscopic to jellies
Nekton: Free-swimming organisms (fish, replies, mammals, large invertebrates)
Benthic Organisms: Remain on the bottom (shellfish, crustaceans)
Decomposers: Includes microscopic organisms (bacteria, worms, etc)
Marine Biodiversity
● Is greatest at points of contact:
○ Between ocean and shore
○ At ocean-air boundary
○ Along benthic boundary
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
However, last 12 months have seen a sudden bleaching event which killed large areas of coral in northern parts of the reef. Scientists fear larger areas of the reef will be lost in coming decades due to global warming, ocean acidification. So as long as light can penetrate water, photosynthesis is possible. Result: shallow, brightly lit waters tend to have high rates of primary productivity, larger populations of animals. 90% of marine species are found in coastal waters. Once you drop below the surface, primary productivity diminishes. Nutrients are scarce except at upwelling zones and at the very bottom (benthic environment) When a dead whale sinks to the floor of deep ocean, it brings a sudden influx of nutrients. More primary productivity in the north during northern summer because of extra sunlight, northern winter has less but more near antarctica. Winds, currents cause water from deep to rise toward surface.
