What is primary production in the ocean, and what limits it?

The creation of organic matter by photosynthetic organisms (phytoplankton and algae) using sunlight and nutrients; limited by light availability and nutrient supply (especially nitrogen and phosphorus) The breakdown of dead organic matter by bacteria; limited by water temperature The total amount of fish produced in an ecosystem each year Energy production at hydrothermal vents through chemosynthesis

What is the biological pump, and why is it important for Earth's climate?

The process by which marine organisms capture CO2 through photosynthesis and transport it to the deep ocean when they die and sink, removing carbon from the atmosphere for centuries The circulation of water between the ocean surface and the deep ocean, which pumps oxygen to deep-sea organisms The action of whales diving deep and returning to the surface, which mixes ocean layers The evaporation of seawater that pumps water vapor into the atmosphere

What is the role of marine bacteria in nutrient cycling?

Marine bacteria decompose dead organic matter and recycle nutrients (nitrogen, phosphorus) back into dissolved inorganic forms that phytoplankton can use Marine bacteria are primarily harmful pathogens that cause disease in marine animals Marine bacteria produce oxygen that supports deep-sea animal life Marine bacteria are not important — they are only significant in freshwater

What is ocean stratification, and how does it affect productivity?

Stratification is when warm, light surface water sits in a stable layer above cold, dense deep water, preventing mixing and blocking nutrient-rich deep water from reaching the sunlit surface Stratification is the layering of different salinity water, where freshwater sits above saltwater near river mouths only Stratification increases ocean productivity by keeping nutrients concentrated in the surface layer Stratification refers to the layering of different ocean habitats by depth zone

How do whale populations contribute to ocean productivity — the 'whale pump'?

Whales feed in deep or polar waters and defecate at the surface, bringing nutrients (especially iron and nitrogen) into the sunlit zone where they fertilize phytoplankton growth Whale bodies decompose slowly on the seafloor, releasing nutrients too deep to affect surface production Whales have no significant effect on ocean productivity Whales increase productivity by mixing ocean layers with their swimming movements

What is iron fertilization, and why is it significant for both ocean productivity and climate?

Adding iron to nutrient-limited ocean areas stimulates phytoplankton blooms; since iron is often the limiting nutrient in large ocean regions, this could increase carbon sequestration Iron fertilization refers to adding iron pipes to the ocean to attract fish Iron is toxic to phytoplankton, so iron fertilization reduces ocean productivity Iron enters the ocean only from rivers and has no effect on open ocean productivity

What is 'ecosystem resilience' and what factors increase or decrease it in marine systems?

The ability of an ecosystem to absorb disturbance and recover; increased by high biodiversity and redundancy; decreased by overfishing, pollution, and climate stress Resilience refers only to the ability of coral to survive bleaching events An ecosystem with fewer species is more resilient because competition is reduced Ecosystem resilience is a fixed property that does not change with human impacts

What is a 'dead zone' in the ocean and what causes it?

A hypoxic (low oxygen) area where most marine life cannot survive, caused by excessive nutrient runoff that triggers algal blooms, which deplete oxygen when they decompose The deepest part of ocean trenches where no sunlight reaches Areas of the open ocean naturally devoid of life due to low temperatures Regions affected by oil spills where no recovery is possible

How does marine physiology adapt to the extreme pressure of the deep ocean at the cellular level?

Deep-sea organisms have pressure-adapted enzymes with flexible structures that maintain function at high pressure, and cell membranes rich in unsaturated fatty acids that stay fluid under compression Deep-sea cells have rigid cell walls like plants to resist being crushed Deep-sea organisms avoid pressure effects by not having any cells — they are acellular Deep-sea organisms survive by reducing all metabolic activity to near zero

What is a 'keystone species' and can you name two marine examples?

A species whose impact on its ecosystem is disproportionately large relative to its abundance; marine examples include sea otters (controlling urchins/kelp) and sea stars (maintaining intertidal diversity) The most numerically abundant species in an ecosystem — the species that all others depend on for food Any species that is endangered — its rarity makes it precious to the ecosystem The species at the base of the food web, such as phytoplankton