Ch. 13: Biological Productivity and Energy Transfer
Terms in this set (43)
What is primary productivity?
Rate orgs store energy through formation of organic matter (carbon-based compounds), using energy derived from solar radiation during photosynthesis or chemosynthesis
Chemo much less important than photo in worldwide marine primary production
99.9% of ocean's biomass relies directly/indirectly on organic matter supplied by photo
What is photosynthesis and respiration?
Photo: reaction where energy from Sun is stored in organic molecules
Plant cells capture light energy and store it as sugars
Photosynthetic equation is reversible = respiration
Photo: light energy input + water + CO2 => sugar & O2
Resp: sugar & O2 => heat energy released + water +CO2
What are photosynthetic organisms and chlorophyll?
Phytoplankton use green pigment to capture energy form Sun and perform photosynthesis
Color of surface waters strongly affect by amt of chlorophyll
What are the two main factors that limit the amt of photosynthetic primary productivity in the ocean?
Availability of nutrients and solar radiation (light)
How does the availability of nutrients affect primary productivity?
Distribution of life in ocean depends mainly of availability of nitrogen, phosphorus, iron, and silica and phytoplankton need
Runoff water carry material to oceans and deposit it as sediments on continental margins
Dissolves and transports nitrates and phosphates- main nutrients for phytoplanktons
Photosynthesis- combine nutrients w/ CO2 and water = carbohydrates, proteins, & fats
Continents = major source of nutrients = greatest concentration of marine life found along margins
Lack of certain nutrients esp. nitrogen (nitrate) and phosphorus can limit productivity
How does the availability of solar radiation affect primary productivity?
Photosynthesis can't proceed unless light energy (solar radiation) is available
Photo. in ocean is restricted to uppermost surface waters and areas of sea floor where water is hallow enough to allow light to penetrate
Compensation depth for photosynthesis: depth where net photo. becomes zero
Euphotic zone extends from surface down to compensation depth for photo. ~<100 m
How do the two factors necessary for photosynthesis differ b/w coastal areas and open ocean?
Open ocean (far from continental margins)
Solar energy extends deeper into water column, but concentration of nutrient is low
Light penetration much less, but concentration of nutrient is higher
B/c coastal zone is much more productive, nutrient availability must be most important factor affect distribution of life in oceans.
What are the different types of macroscopic (large) algae?
Largest members of attached species of marine algae
Mostly in middle lats, cold-water areas
Common in freshwater, not in ocean
most abundant and widespread
many are attached at bottom
Very rare in freshwater
What are microscopic (small) algae? What is their importance?
Either directly or indirectly source of food for more than 99% of marine animals
Most micro algae are phytoplankton (photosynthetic orgs that live in upper surface waters and drift w/ currents)
Some live on bottom
What are diatoms?
(cut in half)
Class of algae
Contained in micro shells - test
Diatom tests composed of silica
Accumulate on ocean bottom = diatomaceous earth
Most productive group of marine algae
Diatom tests have variety of shapes
All have top and bottom half that fit together
Single cell is contain in test
Exchanges nutrients and waste w/ surrounding water through holes in test
What is the reproduction style of diatoms?
Divide asexually until inner frustule becomes too small to support internal cell structure
Then cell forms naked auxospore of gamete that becomes either egg or sperm
Following sexual reproduction, new diatoms builds silicon case, and process repeats
What are coccolithophores?
(berry stone carrying)
Covered w/ small calcareous plates - coccoliths made of calcium carbonate
Each individual plate ~ size of bacterium
Entire org is super small
Live in temperate and warmer surface waters
Contribute significantly to calcareous sea floor deposits
What are dinoflagellates?
Possess flagella - small, whiplike structures - for locomotions
Slight capacity to move into areas more favorable for photosynthetic productivity
Rarely imp. geologically b/c tests are cellulose- biodegradable, not preserved
What is the red tide? What are blooms? What are harmful algal blooms (HABs)? What causes the red tides?
Such great abundance that they color surface water red
When conditions are right, phytoplankton populations can grow explosively and create bloom
HABs: Red tides and associated algal blooms that don't color water red but are detrimental to marine animals, human, and environment
Toxic blooms can kill marine life and ppl
Natural oceanographic conditions stimulate productivity of certain dinoflagellates
Nutrient-laden runoff from land
How do dinoflagellate toxins kill marine orgs and humans/
Dino responsible for many red tides produce biotoxins that can spread to many diff. organisms including humans
Karenia: kills fish and shellfishh
Gonyaulax: not poisonous to shellfish, but concentrates in tissues and is poisonous to humans who eat it = paralytic shellfish poisoning
Ciguatera: seafood poisoning caused by ingestion of certain tropical reef fish that have high lvls of naturally occurring dino toxins
What is eutrophication?
Artificial enrichment of waters by preciously scarce nutrient that can trigger overabundance of algae such as an HAB
How does regional primary productivity vary?
Primary photosynthetic production in oceans varies dramatically from place to place
Variability is result of uneven distribution of nutrients throughout photosynthetic zone and seasonal changes in availability of solar energy
What is the variation in nutrients depending on location, both depth and regional?
~90% of biomass generated in euphtoc (sunlit) zone of open ocean is decomposed into inorganic nutrients before descending below zone
Biological pump removes material from euphotic zone to sea floor b/c it "pumps" CO2 and nutrients from upper ocean and concentrates them in deep-sea waters and sea floor sediments
Subtropical gyres: permanent thermocline and pycnocline develops - forms barrier to vertical mixing, preventing resupplying of nutrients to sunlit surface layer
Mid lats: thermocline develops only during summer seasons
Polar: thermocline usually doesn't develop
Degree to which waters develop thermocline profoundly affects patterns of biological production observed at diff. lats
What is the productivity in polar (high lat) oceans?
Density and temp. change very little w/ depth
Waters are isothermal (same temp)
No barrier in mixing b/w surface waters and deeper, nutrient-rich waters
Summers: melting ice = thin, low-salinity layer that doesn't readily mix w/ deeper waters
Stratification is crucial to summer production b/c helps prevent phytoplankton from being carried into deeper, darker waters but are concentrated in sunlit surface waters when reproduce continuously
Nutrient concentrations (nitrates & phosphates) usually adequate in high lat surface waters
Availability of solar energy limits photo. moe than nutrients
What is the production in arctic and antarctic regions of polar oceans?
Winter- 3 months darkness; Summer- 3 illumination
Diatom productivity peaks during summer (may) when Sun rises high enough for deep penetration of sunlight in water
Zooplankton begin feeding on them = biomass peaks in June until Oct.
Productivity is greater
Upwelling of North Atlantic Deep Water- sinks the rises near Antarctic carrying high concentrations of nutrients
Sun provides sufficient solar radiation in summer = explosion of biological productivity
What is the productivity in tropical (low-lat) oceans?
Productivity is low in tropical regions of open ocean
Sun is more directly overhead, light penetrates much more deeply into tropical oceans then in mid-lats and polar waters, and solar energy is available year-round
Permanent thermocline produces stratification (layering) of water masses
Prevents mixing b/w surface waters and nutrient-rich deeper waters = eliminates any supply of nutrients from deeper waters below
Productivity limited by nutrients
What are the exceptions to the general pattern of low productivity in tropical oceans?
Trade winds and Ekman transport causes surface water to diverge toward higher lats
Surface water replaced by nutrient-rich water
Eastern Pacific Ocean
Prevailing winds blow to equator and along western continental margins
Surface water driven away from coast, replaced by nutrient-rich waters
West coast of continents
Orgs that comprise and live among coral reefs adapted to low-nutrient conditions
Symbiotic algae in tissues of coral and other species allow coral reefs to be highly productive ecosystems
Also retains and recycles existing nutrients
What is the productivity in middle latitudes (temperate) oceans?
Combo of two limiting factors control productivity
What is the productivity in middle latitudes (temperate) oceans during the winter?
Nutrient concentration highest;
Isothermal column, so nutrients are well-distributed
Sun at lowest position = less absorbed into surface water
Compensation depth for photo. so shallow that phytoplankton don't grow much
Absence of thermocline allows algal cells to be carried down beneath euphotic zone
What is the productivity in middle latitudes (temperate) oceans during the spring?
Sun rises higher in sky
Compensation depth for photo. deepens
Spring bloom of phytoplankton b/c solar energy and nutrients available
Seasonal thermocline develops (b/c increased heating) = algae in euphotic zone
Tremendous demand for nutrients in zone = supply limited = productivity decrease sharply
Phytoplankton populations decrease in April b/c insufficient nutrients and population consumed by zooplankton
What is the productivity in middle latitudes (temperate) oceans during the summer?
Sun rises even higher = surface waters continue to warm
Strong seasonal thermocline
Prevents vertical mixing = nutrients depleted from surface waters can't be replaced by deeper waters
Phytoplankton population remains low
Compensation depth for photo. at max
phytoplankton can actually become scarce in late summer
What is the productivity in middle latitudes (temperate) oceans during the fall?
Solar radiation diminishes
Surface temp. drop & summer thermocline breaks down
Nutrients return to surface layer as increased wind strength mixes surface waters w/ deeper waters
Fall bloom of phytoplankton = less dramatic than spring
Sunlight (not nutrient supply like in spring) is limiting factor as winter approaches
What is the comparison of regional productivity?
Dramatic peak in productivity in polar oceans during summer
Steady, low rate of productivity year-round in tropical ocean
Season pattern of productivity in middle lat oceans
Highest overall productivity in middle lat regions
What is a biotic community? What is an ecosystem?
assemblage of organisms that live together w/in os definable area
includes biotic community plus environment w/ which it exchanges energy and chemical substances
What are the two most important commodities passed along in marine ecosystems?
What is the energy flow in a photosynthetic marine ecosystem?
Unidirectional flow based on continuous supply of solar energy
Solar energy > algae > photosynthesis = solar to chemical > algae respiration > animals consume algae > mechanical and heat energy
What are the three basic categories of organisms within an ecosystem?
Can nourish self through either photosynthesis or chemosynthesis
Eat other organisms
Break down organic compounds that comprise detritus (dead and decaying remains and waste) for own energy requirements
What is the difference b/w autotrophic and heterotrophic organisms?
Producers- algae, plants, archaea, and photosynthetic bacteria
Consumers and decomposers
Depend either directly or indirectly on organic compounds produced by autotrophs for food supply
What can consumers be categorized as?
Feed directly on plants or algae
What is the flow of nutrients in marine ecosystems?
Matter doesn't dissipate (like energy) but is cycle from one chemical form to another by various members of biotic community
Chemical components of organic matter enter biological system through photo. (or chemo)
Passed on to animal populations (consumers) through feeding
Some material used and reused in euphotic zone, others sink as detritus - feeds orgs in deep water or sea floor
Undergoes bacterial or other decomposition processes
Converts organic remains into usable nutrients (nitrates & phosphates)
Upwelling hoists nutrients to surface gain to be used by algae and plants to begin cycle
What are different feeding strategies?
Suspension feeding/ filter feeding:
Use specially designed structures to filter plankton from seawater
Barnacles- legs to strain passing food
Claims0 extend siphons
Feed on food items that occur as deposit
Detritus- dead and decaying organic matter and waste
Sediment coated w/ organic matter
Worm- ingest and extract
Directly capture and eat other animals
Passive- waiting for prey and ensnaring them
Active- seeking prey
What are trophic levels? What is the energy flow?
Individual members of feeding population are larger then organisms they eat
[Exception= blue whale]
Transfer of energy from one population to another is continuous flow of energy
Small-scale recycling and storage interrupt flow = slows down conversion of potential (chemical) energy to kinetic, then heat, and finally energy is so dissipated it becomes useless
What is transfer efficiency? What is the gross ecological efficiency?
As biomass moves through food chain, there are losses at each lvl, such that only small percentage ultimately reaches highest trophic lvls
Typical transfer efficiency: 10%
Transfer of energy b/w trophic lvls is very inefficient
Efficiencies of diff. algal species vary, but ave. is only ~2% = 2% of light energy absorbed by algae is ultimately synthesized into food and made available to herbivores
Gross ecological efficiency- ratio of energy passed on to next higher trophic level divided by energy received from trophic level below
Ex: ecological efficiency of herbivorous anchovies = energy consumed by carnivorous tuna that feed on anchovies divided by energy contained in phytoplankton that anchovies consumed
Some chemical energy taken as food is excreted as feces, rest is assimilated
Assimilated: chemical > kinetic for respiration
What are food chains?
Sequence of organisms where energy is transferred
Primary producer > herbivore > one or more carnivore > "top carnivore" which is not usually preyed upon by any other org
Individual members of feeding population are generally larger in size and less numerous than prey
B/c energy transfer b/w trophic lvls is inefficient, is advantageous for fishers to choose population that feeds as close to primary producing pop as poss
What are food webs?
Top carnivores in food chain feed on number of diff. animals, ea. has own simple or complex feeding relationships
More likely to survive than chain b/c have alternative food to eat if own sources diminish in quantity or disappear
What is a biomass pyramid?
Ultimate effect of energy transfer b/w levels seen
Shows that for survival of ea. large marine org, many lvls of progressively larger populations of smaller-size orgs must exist to support those higher on pyramid
Number of individuals and total biomass decrease in successive trophic lvls b/c amt of available energy decreases
Also shows that orgs increase in size at successive trophic lvls up pyramid
What is symbiosis? What are the different types?
Two or more orgs closely associated such that one or more benefits from association
Commensalism: smaller or less dominant participant benefits w//o harming host
Mutualism: b/ benefit
Parasitism: parasite benefit at expense of host
What is standing stock? Overfishing? Maximum sustainable yield?
Standing stock: biomass present in an ecosystem at any time
Overfishing: harvesting so much biomass that remaining stock can't reproduce fast enough to replenish itself (~30% f world's fish stocks are now officially "overfished")
Maximum sustainable yield: max amt of biomass that can be removed yearly and still be sustained by ecosystem
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