CH9 Biological Productivity

primary productivity

the rate at which energy is stored by organisms through the formation of organic matter from inorganic materials and pure energy

what is the most common form of primary productivity?

mostly phytoplankton (90% of the oceans primary producers) via photosynthesis

heterotrophs

must consume preformed organic matter, do respiration process and feed via grazing, predation, scavenging, filter feeding, or deposit feeding

what are all ecosystems composed of?

producers, consumers, and decomposers

which role is the first organism to create organic matter from pure energy and inorganic nutrients?

producer

which role remineralizes organic matter to replenish the supply of plant nutrients to the ecosystem?

decomposers

what do herbivores consume?

only plants

what do omnivores consume?

plants and animals

what do carnivores consume?

only animals

food webs

networks of interconnected food chains

what is primary productivity?

formation of organic matter from inorganic nutrients and radiant energy from the sun

what are the products of photosynthesis?

oxygen

what is the most common type of primary production in the ocean?

photosynthesis

which two biological processes are opposite reactions of one another?

photosynthesis/respiration

which organisms obtain food by filtering bits or organic detritus out of the water?

filter feeders

bacterial decomposition/remineralization

heterotrophic bacteria (decomposers) convert organic compounds back into inorganic materials that plants can use again in photosynthesis

why are coastal oceans rich in life?

• they have nutrients wash off from land

• coastal upwelling brings deep nutrients to the surface of the ocean

• coastal oceans are shallow which allows light to penetrate the seafloor

why are polar oceans rich in life?

• very cold surface waters prevent strong pycnocline

• strong and persistent winds mix water deep

• deep nutrients mixed to surface where light is

why are equatorial oceans rich in life?

• equatorial upwelling occurs here

water that has recently upwelled to the surface is typically ___ and ___?

cold, nutrient rich

what is an example of a primary factor that controls levels of primary productivity in the ocen?

nutrients

what is an example of a secondary factor that controls levels of primary productivity in the ocean?

upwelling

why is upwelling such an important factor in creating areas of high biologic productivity?

upwelling brings nutrient rich deep water to the surface where productivity is limited by lack of nutrients

what two properties are typical for an upwelling region?

cold surface water and high biomass

major coastal upwelling regions

• east coast of US + Mexico

• northeast coast of south America

• north + south east coast of africa

• east coast of australia

where do we get our commercial fish?

upwelling and shelf regions

isothermal

nutrients come to the sunlit surface easily, sunlight is available for only half the year

the polar ocean

what is productivity in tropical ocean like?

productivity is low and steady year-round

winter ocean characteristics

• high nutrients

• low sunlight

• low productivity

spring ocean characteristics

• phytoplankton bloom

• sunlight increase

• plenty of nutrients

• spring bloom

summer ocean characteristics

• nutrients are low

• density stratification

• low productivity

fall ocean characteristics

• sunlight decreases

• wind mixing increases

• small fall bloom

• sunlight diminishes

• productivity stops

what is the dilemma which slows the growth of oceanic phytoplankton?

euphotic zone is high light but low nutrients

which ocean region has the lowest annual levels of production?

open ocean

in the mid-latitude (temperate) ocean regions, when does the large phytoplankton bloom typically occur?

spring

in the mid-lattitude (temperate) ocean regions, why does a large phytoplankton bloom occur in the spring?

this is when there is the right combination of sunlight and nutrients

given what you know about surface productivity, where do you think that sunlight penetrates deepest into the ocean?

middle of subtropical gyres

commercially imprtant pelagic fishes

• anchovy

• mackerel

• tuna

commercially important ground fishes

• hake

• haddock

• cod

maximal sustainable yield

the amount of standing stock that can be removed each year and still maintain a sustainable fishery

overfishing

when harvesting of fish stocks occurs so rapidly that it leaves behind a sexually immature stock that cannot sustain itself

reasons for overfishing

• high tech fishing (factory ships)

• ineffective fishery management

• lack of understanding of marine ecosystem and size of fish stocks

• targeting individual fish species rather than ocean ecosystems

incidental catch

marine organisms that are caught accidentally by fisherman seeking commercial species

side effects of overfishing

• larger fish are disappearing

• smaller fish are becoming more abundant

• induces inherited changes that slow growth size, maturing time, and fish size

• threatens human food supply and marine ecosystem