oceanography exam 3
importance of upwelling for nutrient input to the photic zone
Upwelling is a largely wind-driven process, separate from the broad upwelling in deep ocean required to balance deep water formation. Upwelling completes cycle, bring cold, nutrient-rich water back to photic zone
examples of gelatinous holoplankton
Includes jellyfish, corals, and anemones
be able to understand why areas on the satellite map of productivity are productive.
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name two very important things the ocean has done to mitigate global climate change
-Ocean acts as a giant buffer to global warming - high heat capacity means large quantity of heat required to raise temp. -absorbs CO2
what are the 3 primary types of drag a fish must overcome?
1) surface drag - friction between fish body and water • increases as surface area increases • ideal shape would be a sphere, smallest surface area to volume ratio 2) form drag - force required to push water out of the way • form drag is proportional to cross-sectional area • ideal shape would be a needle 3) turbulent drag - highly turbulent fluid flow imparts drag on an object • ideal form is one that is rounded in front and tapered in the rear • promotes laminar (non-turbulent) flow
what are three main reasons that phytoplankton are small?
1. increases drag/friction so phytoplankton stay in photic zone 2. optimal for nutrient uptake through diffusion 3. optimal for waste excretion through diffusion
what is typical trophic efficiency and calculate efficiency of a 5 level trophic system versus one with 2 levels.
1000x 5-2 = 3. 10^3 = 1000
explain the premise of maximum sustainable yield (MSY) and the ecological factors that must be understood to predict stocks of a particular fish
3 primary approaches to fisheries management: o 1) eat lower on the marine food web (copepod sushi rather than yellow fin sashimi) o 2) marine aquaculture - farm the ocean as we do the land (e.g. salmon) o 3) use MSY approach - i.e. maximize # of fish caught while maintaining adequate standing stock to sustain yield Standing stock: biomass of a given population present at any given time o limited by food supply and predation MSY requires knowledge of: o 1) food supply for a given fishery o 2) rate of predation o 3) variability in #1 and #2 due to climate or ecological changes
approximately how large are adult tuna?
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why has MSY been an ineffective tool for fisheries management?
A number of variables make MSY a difficult management strategy to optimize: o excess food eaten by predators o climate variability o imperfect knowledge of species ecology o MSY sits at cliff's edge - hard to know how close to get o population age structure ♣ young fish increase biomass faster than old fish ♣ removal of old fish will increase biomass production rate, but decrease breeding population
is the Portuguese Man of War an individual or a colony? what is a siphonophore?
Appears to be an individual, but is actually a colony of 4 specialized polyps: • Polyp 1: provides flotation via a gas filled sac • Polyp 2: detects and captures food, and defends organism, using tentacles • Polyp 3: digests food (gastrozooids) • Polyp 4: reproduces polyps (gonozooids) • NOT a jellyfish, but rather a siphonophore, a colony of organisms working as one
at least how long has it been since atmospheric carbon dioxide levels were as high as today?
Atmospheric greenhouse gas concentrations are higher than at any time over the past 650,000 years, at least
why is productivity low in the high northern latitudes during winter, despite the high nutrient content of surface water?
Because productivity is higher with light, and light is more prevalent in the summer months (longer days). productivity.
is a whale a fish or a mammal? give two reasons.
Because they are mammals, they: o breathe air o are warm blooded o nurse their young
Are hydrothermal vent ecosystems completely independent of photosynthesis?
Chemosynthetic ridge ecosystems are not completely independent of photosynthesis because they require oxygen
what is the primary type of phytoplankton in non-productive temperature and tropical oceans? is their distribution limited by a nutrient for building of their shell?
Coccolithophores • Form higher proportion of phytoplankton biomass in non-productive temperate and tropical ocean waters • Armored by calcium carbonate plates, so they are typically preserved in sediments
what characteristic of caudal fin shape dictates its purpose? why?
Fin adaptations • Like fins on an airplane, fins on a fish are essential for controlling direction and stability • Fin functions: o 1) maneuvering: pelvic and pectoral fins, used to stop and execute turns o 2) stabilization: vertical dorsal and anal fins o 3) propulsion: caudal fin • Fish alternatively contract and relax muscles on each side of body to provide thrust, caudal fin provides final push
key factors that affect transmission of light through water (absorption and reflection)
Light traveling through water is affected by two key processes: absorption: -water absorbs sunlight, very little penetrates to depths below ~100 m -only short wavelength, high energy part of spectrum makes it to 10 m and below (blue-green light) reflection and scattering: o light rays encounter rough, uneven surface and reflect in different directions o upward scattering is termed backscattering o in clear water, scattering is limited and most red & yellow light absorbed, reflected light is blue-green o in turbid, i.e. high particle content water, most visible wavelengths are backscattered o what does yellow + blue + red produce? brown
what are holoplankton and meroplankton?
Meroplankton: planktonic larvae that become either benthic or nektonic Holoplankton: live entire life as plankton o Many varieties; dominated by copepods (upper picture) and euphausids (lower picture) which are both crustaceans o 60-70% of all zooplankton in most locations
key limiting nutrient in the ocean and why it is required for photosynthesis
Nitrogen o low nitrogen levels often limit primary production o an ecosystem constrained by lack of a key nutrient (e.g. N, P, Fe) is nutrient limited • Chlorophyll a requires nitrogen • ATP (key for energy storage) requires nitrogen and phosphorus • Left) The molecular structure of chlorophyll a, which is needed for photosynthesis. The molecule is complex and contains four nitrogen atoms. Right) • The molecular structure of ATP, a chemical essential to life, is complex. The molecule contains both phosphorus (P) and nitrogen (N) atoms.
know key areas where upwelling (divergence) and downwelling (convergence) occurs and put into context of the prevailing winds
Oceanic subtropical gyres are generally dominated by upwelling vertical motions. • Upwelling: vertical upward movement of water, often due to Ekman divergence o Divergence of water at surface causes deeper water (~100-200 m) to upwell to the surface o Upwelling brings cold, nutrient-rich water into the photic zone, causing thinner thermocline • Downwelling: vertical downward movement of water, often due to Ekman convergence o Convergence of water at surface prevents upwelling of cold, nutrient-rich water, causing thicker thermocline High productivity equatorial regions due to upwelling, low productivity subtropical gyres due to downwelling. Productive areas along coastlines are usually due to coastal upwelling... Upwelling-generated fog in San Francisco Bay. Redwoods harvest moisture from the fog - therefore they thrive in upwelling environments. Coastal upwelling - Northern Hemisphere**** • Here wind from north drives Ekman transport of surface water offshore • Deep water upwells to replace this surface water • Lot of biology • Wind from south drives onshore surface flow and downwelling • Will be on the final exam. Understand the logic. Know NSEW, many variants. Divergence brings upwelled nutrients into photic zone, increasing primary production. Convergence drives downwelling, which limits primary production.
where in the deep ocean are nutrient levels highest and oxygen levels lowest? explain in terms of respiration.
Old water has collected nutrients for a really long time! All this stuff has been rained down and respired, so not much oxygen.
in the water column, where does primary production typically exceed respiration? where does the reverse occur? how does this affect the nutrient concentrations in these two zones?
P>R in photic zone, R>P in aphotic zone, falling organic matter (marine snow) delivers nutrients to aphotic zone
difference between photic zone and aphotic zone
Photic zone: lots of production, respiration, bacteria makes it decay. Puts nutrients back into the water. All other steps in the ecosystem take place partly in the photic zone and partly in the aphotic zone. -zone in the upper ocean where light is of sufficient intensity to support photosynthesis (~1% of the surface value) -Most marine plants live in photic zone. -Primary production of organic matter takes place only in the photic zone (except for limited areas where chemosynthesis occurs). All other steps take place in photic and aphotic zones. Aphotic zone: The aphotic zone begins at the depth where the ambient light intensity is approximately 1% of that at the surface.
define difference between plankton, nekton, benthos
Plankton: unable to swim against currents; drifters o phytoplankton (plants) and zooplankton (animals) o plankton means CAN'T swim, they just drift. Nekton: active swimmers o e.g. fish, squid, marine mammals Benthos: sea-floor dwellers o E.g. clams, oysters, crabs, snails, lobsters, sea stars, sea urchins, corals, sea cucumbers o benthic plants live in shallow depths o benthic animals live at all depths, typically detritus feeders
what are some examples of meroplankton?
Planktonic eggs, larvae, and juveniles of species that spend their adult lives as benthos or nekton
understand the basic components of the carbon cycle: 1) volcanism-weathering, 2) photosynthesis-respiration, 3) ocean uptake and release, 4) the anthropogenic component.
The Carbon cycle, a 'biogeochemical' cycle • What is biogeochemistry? o The study of the biological, geological and chemical processes that cycle elements and molecules in natural systems. • Carbon is found in the atmosphere, ocean, biological organisms, and geological deposits (e.g. limestones, coal) • Oceans have a ton of carbon stored there o Atmospheres have a much smaller amount • Stores vs. fluxes (what's going in and out) Volcanism and weathering • Volcanic emissions of CO2 make rain water slightly acidic, leads to weathering of rocks, and carbon eventually returned to the sediments • Responsible for the long-term equilibrium of atmospheric carbon dioxide o greater volcanic input of CO2 balanced by enhanced weathering • Relevant on million-year timescales Photosynthesis and respiration • CO2 + H2O --> CH2O + O2 • CH2O + O2 --> CO2 + H2O (=reverse, respiration) • Photosynthesis uses carbon dioxide to create organic matter • Organic matter is respired, releasing carbon dioxide to the atmosphere • Some respire more than others... Oceanic uptake and outgassing • Carbon dioxide is absorbed by cold water - where is this? • Sinking of cold water at high latitudes removes carbon dioxide from the surface ocean and atmosphere • Carbon dioxide is released where water rich in carbon comes to the surface - where is this? • if [CO2]atm > [CO2]ocean , flux is into the ocean • if [CO2]ocean > [CO2]atm , flux is out of the ocean • carbon is constantly being exchanged between the atmosphere and ocean in both directions Anthropogenic effects (human-induced) • Burial of organic carbon in swamps, peatlands, and ocean sediments eventually produces fossil fuels (oil, gas, coal) • Typically oil, gas, and coal are unearthed on geologic time-scales (~million years) • We are mining and burning fossil fuels on a centennial time-scale, about 10,000 times faster than usual • Power plants, automobiles
about how much faster are we unearthing fossil fuels than would occur naturally?
We are mining and burning fossil fuels on a centennial time-scale, about 10,000 times faster than usual
what happens to water when carbon dioxide is dissolved in it?
When CO2 dissolved in seawater it forms carbonic acid, which releases hydrogen ions (H+) into solution.
anthropogenic carbon dioxide is going primarily into which reservoirs?
atmospheric and oceanic reservoirs
What type of organism forms the basis for all life in hydrothermal vent systems?
chemosynthetic bacteria
what aren't all fish shaped like balls?
fish compromise their form to minimize all three types of drag
2 ingredients for photosynthesis that are typically limiting
nutrients and energy
why are foraminifera and radiolaria important in paleoclimate studies?
o Both radiolaria and forams are highly sensitive to temperature change, so shells in sediments can be used to reconstruct past climates
What are the fundamental difference between hydrothermal vent ecosystems and almost all other ocean ecosystems?
other ecosystems work with photosynthesis and respiration
basic chemical equations describing photosynthesis and respiration?
photosynthesis: 6CO2 + 6H2O --> C6H12O6 + 6O2 respiration: C6H12O6 + 6O2 --> 6CO2 + 6H2O
name and understand 3 adaptations that most fish use to survive in the ocean (e.g. speed, accelerations, countershading, schooling...)
speed: chasing prey and escape predators camouflage: ambush and escape detection group cooperation: overwhelm prey and confuse predators/reduce chance of predation
what are the two main factors contributing to present-day sea level rise?
thermal expansion of seawater and melting of ice sheets
what are the two main classes of whales?
toothed and baleen whales
give an example of a fish with a lunate caudal fin
tuna, swordfish
4 ingredients for photosynthesis
water, CO2, nutrients, energy
what is the IPCC and why is it important?
• A scientific intergovernmental body • Role is to evaluate risk of climate change by human activity (fossil fuel burning) • Established in 1988 by the World Meteorological Organization and the United Nations Environment Program • Primary activity is to assemble and publish assessments of the science and impacts of climate change • Assessments based on peer-reviewed scientific literature • Written by top scientists from around the world, incorporates inputs from thousands of scientists • The premier source of information on climate change • IPCC has published 5 assessment reports, in 1990, 1995, 2001, 2007, and 2014
explain the basics of ocean acidification
• Acidity is a measure of the hydrogen ions in solution, measured on the pH scale. • pH = -log [H+] • as [H+] increases, pH decreases. log scale means every unit decrease in pH is a 10-fold increase in [H+] • pH is unit of measuring acidity • a soda can is a good example o pH of Coca Cola is 4 • scale is 0-14 o 0-7 is acidic o 7 is neutral o 7-14 is basic
what are the factors that led to the closing of the Georges Bank fisheries?
• Catch was under-reported by fishing industry • Fish more affected by fluctuations in other species than assumed • Migration complicated estimates of stock population • Politics o fisheries scientists recommended large reductions in harvest (~40%) o regulators imposed smaller reductions (~5%)
if either the Greenland or West Antarctic Ice Sheet melt completely, about how much will sea level rise?
• Complete melting of Greenland would raise globally averaged sea level by 7 m • Complete melting of West Antarctic Ice Sheet would raise globally averaged sea level by 5 m
two dominant types of holoplankton, and examples of the organisms they consume (or consume them)
• Foraminifera and radiolaria o Single-celled amoeba-like microplankton that secrete shells made of silica (radiolaria—upper picture) or calcium carbonate (foraminifera—lower picture) • Eating habits: o Use spines to capture prey, including diatoms, bacteria, and even copepods • Utility for climate studies: o Both radiolaria and forams are highly sensitive to temperature change, so shells in sediments can be used to reconstruct past climates
how do scientists monitor global sea level rise and the two factors which contribute to it?
• Global sea level rise is monitored by satellite altimetry • Thermal expansion is monitored by ARGO floats • Ice mass loss is monitored by the GRACE satelllite gravimetry mission
what are trophic levels, and what best describes trophic relationships in the ocean, a food chain or a food web? why?
• Heterotrophs congregate in areas of high primary productivity. • Food chain: phytoplankton consumed by herbivorous zooplankton, which are consumed by carnivorous zooplankton, which are in turn eaten by fish... o Each step represents a trophic level. • Oversimplified food chain. Top = killer whale • omnivores and carnivores eat multiple types of organisms, creating complex trophic linkages
how is nutrient content related to deep water age?
• How long it has been since the water has been in contact with the surface • 3 km down • 100 years is young • lot of nutrients in the old water! 1750 years old = oldest
What are hydrothermal vents and where do they occur?
• Hydrothermal circulation: heat driven circulation of water o sea water sinking through cracks in the sea floor o This sea water is heated by the warm lithosphere, causing convection. o Hot water at >350OC dissolved reduces chemicals. o Vent fluids are ejected into the deep oceans. occur along mid-ocean ridges (volcanic activity)
why is the ocean blue and the Huron River brown?
• Light transmission drops off sharply with water depth, with only the shorter wavelength, higher energy light (blue-green) penetrating deeper than 10 m ocean has clear water- absorbs red and yellow light- reflects blue and green back
what is the most abundant type of phytoplankton in highly productive parts of the ocean? what nutrient does it require?
• Most abundant phytoplankton in highly productive parts of the ocean o equatorial upwelling zones o Southern Ocean what nutrient does it require?
why is the example of the genus Prochlorococcus important? if it's so important, how did oceanographers not know about it until the 1980's?
• Play essential role in marine food web • Contribute 30-80% of photosynthesis in low nutrient environments • Is capable of fixing N2 gas into bioavailable compounds such as nitrate (NO3-) • If it's so important, then how was it missed for so long? o Filters were too coarse, Prochlorococcus slipped through the cracks o New technology of flow cytometry allowed scientists to see Prochlorococcus ♣ Pull a water sample through pipes and screen it out. Shoot a laser through it and if you have plants in the water, then the particles are going to scatter the light. • Laser is directed toward fluid stream • Particles scatter light and certain compounds emit characteristic wavelengths (e.g. chlorophyll) • Scattered and reflected light picked up by detectors revealing type and concentration of particles
how unusual is the rate of carbon dioxide increase in surface waters during the last 50 years?
• Rate of of CO2 increase in the atmosphere/surface ocean today is ~120 times larger than any time in last 650,000 years...
What factors are currently guiding our search for extraterrestrial life?
• Similar environments exist on earth in the form of cold seeps and drive our search for extraterrestrial life.
if there is less carbonate ion in the water, what happens to organisms that make their shells from calcium carbonate?
• Some organisms that build calcium carbonate shells are likely to be severely compromised by ocean acidification • As a result, carbonate ion content is low in deep water and calcium carbonate shells will tend to dissolve.
What is symbiosis and how do vent animals like tubeworms, clams and mussels make a living?
• Symbiosis - A type of living where two different organisms collaborate to ensure survival of both. • Tube worms, clams and mussels harbor symbiotic bacteria within their body. • The animals provide the bacteria with a safe home and the bacteria in turn provide organic carbon - the building blocks of life!
what are some of the possible explanations of baitball formation?
• The large size of the baitball may confuse some predators • Baitball formation is a nervous reaction to the presence of predators • Some prey fish get away • Gorging by predators reduces overall predatory feeding efficiency
what is the purpose of gills? do whales have gills?
• Water is taken through the mouth, passed across the gills to extract dissolved oxygen and exits through gills. no because they're mammals
why is deep water typically cold and rich in nutrients?
• Water that leaves surface to become a deep water mass gradually accumulates recycled dissolved nutrients. • The increasing age of deep water agrees with increasing nutrient concentration. • NB the difference between the Atlantic and the Pacific. • Pacific: old deep waters have had time to collect a large supply of nutrients from marine snow etc. - thus nutrient concentrations are high in the deep Pacific. Respiration of nutrients at depth depletes oxygen levels in deep Pacific • Upwelling completes cycle, bring cold, nutrient-rich water back to photic zone
difference between autotrophs and heterotrophs
• autotrophs - create their own food using external energy source through primary production (plants, algae, some bacteria) • heterotrophs - unable to make organic compounds from inorganic compounds, must eat autotrophs or other heterotrophs (all animals, most bacteria & fungi) • Heterotrophs live only where autotrophs provide food source.