65 terms

Oceanography Chapter 13

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What are the two primary factors that control biologic productivity in the surface oceans?
sunlight and oxygen
Why is upwelling such an important factor in creating areas of high biologic productivity?
a) Upwelling brings nutrient-rich deep water to the surface where productivity is limited by the availability of nutrients.
Primary productivity
The RATE at which ENERGY IS STORED by organisms through the formation of organic matter (carbon compounds)
Photosynthesis
Energy that comes from solar radiation
Chemosynthesis
Energy that comes from CHEMICAL reactions
99.9 % of the ocean's biomass gets its carbon directly or indirectly from what process?
photosynthesis
What do chemosynthetic organisms; such as those around hydrothermal vents and deep-sea archaea do to synthesize food?
oxidize hydrogen sulfide and methane
Most primary productivity in the ocean is carried out by what group?
phytoplankton
Photosynthetic Productivity
CHEMICAL REACTION that STORES solar energy in organic molecules
Gross primary production
TOTAL amount of organic carbon produced by photosynthesis per unit time in certain area
Cellular Respiration
Used by algae and other organisms to sustain life functions which RELEASES ENERGY
Net primary production
- Gross primary production minus cellular respiration (growth, reproduction)
- Total OM produced minus OM used by cellular respiration
- Is eaten and used by other organisms
- Supports entire ecosystem
Plankton nets
Method used to sample plankton. Tells scientists who is there, but NOT what they are doing, i.e. samples of plankton can be used to find out the composition of the phytoplankton and zooplankton, but not their rates of primary productivity.
Phytoplankton biomass
- how it can be estimated
Can be estimated by using chlorophyll (green pigment used in photosynthesis) by capturing phytoplankton on filters and measuring the amount of chlorophyll on the filter after extracting the chlorophyll using solvents.
Phytoplankton biomass
- how it can be measured
What can be measured using satellite instruments to measure ocean color, which is strongly affected by the presence of chlorophyll containing phytoplankton.
SeaWiFS
Sea-viewing Wide Field-of-view Sensor
Provides global coverage of the color of the Earth's surface every two days, used to estimate ocean chlorophyll concentrations and vegetation cover on land.
Rates of productivity can be ESTIMATED by measuring what?
photosynthesis and respiration rates
Photosynthesis rates are usually measured by what?
production of oxygen or the assimilation of inorganic carbon into organic carbon
Oxygen production (photosynthesis) and uptake (respiration) can be measured by enclosing samples of seawater in bottles and measuring what in the bottles?
change in oxygen concentration
Solar radiation
Light PENETRATES the atmosphere, despite its thickness of over 80 km. However, <1% of light penetrates below 100 m in the ocean.
Photosynthesis restricted to what place which extends from the surface to the compensation depth for photosynthesis?
euphotic zone
The compensation depth for photosynthesis is where net production is equal to what?
zero
The compensation depth for photosynthesis is approximately how deep in the open ocean and may be less than how deep in the coastal zone where the waters are more turbid?
100 m, 20 m
Ocean selectively absorbs visible light of the (longer , shorter) wavelengths (red, orange and yellow).
longer
Red light is usually absorbed within what part of the ocean?
upper 10 m
Yellow light is usually absorbed within what part of the ocean?
100 m
Life in the oceans depends on the availability of what such as nitrate, phosphate, silicate and iron?
nutrients
Nutrients
brought into marine ecosystems VIA RUNOFF from the land (including both natural and human inputs such as fertilizer) and are also brought into marine ecosystems by AEOLIAN deposition (e.g. iron containing dust carried by the wind from deserts to the open ocean)?
Open Ocean
In this area solar energy penetrates deeper into the water column, but the concentration of nutrients is LOW
Coastal Ocean
In this area the penetration of solar radiation into the water column is less, but the concentration of nutrients is much HIGHER.
Most important factor for productivity
Nutrient availability
In addition to the coastal ocean, what area of the ocean is highly productive?
Western Margin of Continents
Primary productivity in a region varies from very low to very high depending on what?
Distribution of nutrients and seasonal changes in solar radiation
Where is the productivity cycle of polar oceans found?
1 Winter darkness
2 Summer sunlight
3 Phytoplankton (diatoms) bloom
4 Zooplankton (mainly small crustaceans) productivity follows
Tropical Oceans
• SOLAR RADIATION HIGH, but NUTRIENTS LOW as sunlit, surface waters are separated from deeper nutrient-rich waters by a permanent thermocline.
• Productivity occurs at a relatively LOW, STEADY RATE.
• Exceptions includes areas of equatorial upwelling, coastal upwelling and coral reef ecosystems.
In the tropical ocean, solar radiation is high, but nutrients are low as the sunlit, surface waters are separated from deeper nutrient-rich waters by what?
a permanent thermocline
Where is the productivity cycle of temperate oceans found?
• Winter - nutrients concentrations highest, water column well mixed and isothermal, light relatively low. Light limited.
• Spring - Compensation depth for photosynthesis increases as sun is higher in the sky, spring bloom occurs. Spring bloom becomes nutrient limited as a thermocline develops.
• Summer - more solar radiation, but phytoplankton nutrient limited as a strong thermocline forms at a depth of about 15 m.
• Fall - solar radiation reduced as sun gets lower in the sky, thermocline becomes unstable and breaks up. Nutrients return to surface water resulting in a fall bloom. Fall bloom becomes light limited.
Anthophyta
Photosynthetic marine organism
Seed bearing, true plant
Only in shallow coastal waters
Primarily grasses and mangroves
Microscopic Algae
- Produce food for 99% of marine animals
- Most planktonic
Golden algae
• Microscopic Algae
- _______
• Diatoms (tests of silica)
• Coccolithophores (plates of calcium carbonate)
Dinoflagellates
• Microscopic Algae
- _______
• Red tide (HAB-Harmful Algal Bloom)
• Toxins
• Fish/marine animal kills
• Human illness
An ecosystem includes what?
living organisms and environment
Consumers
Eat other organisms for energy
- Herbivores
- Carnivores
- Omnivores
- Bacteriovores
Decomposers
break down dead organisms or waste products for energy
heterotrophic
Consumers and decomposers are what?
Biogeochemical cycling
the movement of water and nutrients back and forth between biotic (living) and abiotic (nonliving) realms
10
About ___% of energy transferred to next trophic level
Biomass pyramid
Number of individuals and total biomass decrease at successive trophic levels
Organisms increase in size
Need 10,000 times the mass of 1 Orca in producers to sustain that 1 Orca
Food chain
A simple diagram to show a community of organisms where each member is eaten in turn by another member for energy.
Food web
A complex arrangement of interrelated food chains illustrating the flow of energy between interdependent organisms.
Trophic Levels
Marine fisheries
• Commercial fishing
• Most from continental shelves
• Over 20% from areas of upwelling that make up 0.1% of ocean surface area
Standing stock
Mass present in an ecosystem at a given time
Overfishing
Occurs when harvesting takes place so rapidly that the majority of the population is sexually immature and unable to reproduce
Maximum sustainable yield
Maximum fishery biomass that can be removed yearly and still be sustained by the fishery ecosystem.
80
In U.S. waters ___% of 191 commercial stocks are fully or overexploited.
90
___% of fish from large species have been removed; fishing industry moving down the food chain and concentrating on smaller and smaller fish. This leads to top predators becoming smaller in size - many half to one fifth the size that they once were.
80 and 120
Estimates of the total amount of fish that can be harvested are between ______ million metric tons.
30
About ___% of fish stocks depleted or overfished
47
About ___% fish are fished at the biological limit
Why are global fish stocks in decline?
We are too good at finding and catching fish.
We don't understand enough about the factors that determine the population dynamics of marine fish.
Management of the fishing industry.
'The tragedy of the commons.'
Non-fishing human impacts, e.g. pollution.
Bycatch.
Bycatch
Marine organisms that are caught incidentally with the target species which are usually thrown back, but most die.
On average how much of the catch is discarded as bycatch?
a quarter
In shrimp fisheries the bycatch may be ___ times larger than the catch of target species.
8
Estimated that bycatch is ____ million metric tons per year.
18 to 36
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