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ME lec 2


*Plankton are organisms that unable to move indep of surface currents
*How do holoplankton and meroplankton differ? holoplankton spend entire lives in plankton phase; meroplankton spend part of lives in plankton stage/phase
Give some examples of meroplankton benthic invertebrate larvae, many ostracods, larvae of nekon
*The frustule of a diatom is composed of silica
*How do diatoms avoid sinking to the ocean floor? Morphology increase vol to area, oil storage (less dense than water so reduces wt), ionic regulation by replacing heavy chemical ions w. lighter ones
Describe the morphology of diatoms. centric = usually radial, pillbox, pennate = elongate shapes pillbox, spines increase surface area-to-vol ratio w/o increasing much wt, various flattened body shapes or appendages to help surface resistance/sinking
How do pennate and centric diatoms differ? Gametes different for sexual reproduction, centric get smaller then get sperm or egg to sexually reproduce, pennate mostly benthic, half become egg and half become sperm
What is the raphe and what organisms have it? Raphe – opening or fissure on one or both valves of some pennate species; species w. raphe can glide by cytoplasmic flow that occurs along exterior part of fissure, cytoplasm acts similar to a belt or tread pulling cell fwd
*Describe asexual reproduction in diatoms. divide into 2 halves, each new valve secreted w/in old valve, so through generations, average size decreases, when too small to reproduce perform sexual reproduction
*Describe sexual reproduction in diatoms. centric: sperm break free of eggs w/in the wall, sperm fertilize egg, zygote swells to form auxospore, sheds old cell walls and produces larger wall to restore cell size; pennate: produce identical gametes that can’t swim so move like amoeba and fuse
What is an auxospore? protoplast that makes frustule (outside casing)
*Diatom populations are most likely to be limited by what three nutrients? nitrate, iron, and silicate
How do thecate and athecate dinoflagellates differ? thecate = thick cellulose cell wall (most species); athecate (naked) = no cell wall
When do dinoflagellate blooms typically occur relative to diatom blooms? Why? Blooms occur often in summer and fall after diatom blooms b/c flagella let them move down into nutrient rich water and back up into sunlit water
Describe asexual reproduction in dinoflagellates. simple division, doesn’t reduce in size like diatoms
less than 5% of photosynthetic dinoflagellates are toxic true
*In rodents brevetoxins affect what three things? Cognitive fxn, breathing, muscle control
What species (that we discussed) produces brevitoxins? Karenia brevis
*Prince et al. (2008) – what is the apparent purpose of the toxins that Karenia brevis produces? What is the scientific term associated with this phenomena? suppreses competitors, lowers photosynthetic efficiency and damaged cell membranes of competing phytoplankton to allow it to achieve blooms, chemical suppression of competitors = allelopathy
heterotrophic dinoflagellates are sometimes significant grazers on bloom-forming diatoms. true
*Some heterotrophic dinoflagellates can feed on large cells and chain forming diatoms using an extruded pseudopodial (temporary projection of cytoplasm of certain cells) membrane or pallium = highly plastic membranous organ that easily stretches, liquefies phytoplankton prey
*Leising et al. (2005) found that microzooplankton dominated by gymnodinoid dino’s were the major grazers of ????????? in Dabob Bay, WA. diatoms
*Phaeocystis is a photosynthetic flagellate that is able to exist in two forms. Describe them. as single cells, and can form colonies w. hundreds of cells embedded in a polysaccharide gel matrix
Prymnesiophyta (haptophytes) include about 500 living species in 50 genera, most notably the coccolithophorids and Phaeocystis
*Coccolithophores have an external shell composed of numerous plates made of calcium carbonate, plates called coccolids
In contrast to other phytoplankton species E huxleyi shows photoinhibition at relatively low light levels false
Coccolithophores often bloom after diatoms because they do better in conditions of higher ????????? and ???????? higher light and temp, lower nutrients, surface waters become stable w. shallow mixed layer
under conditions of elevated CO2, high light, nitrate-depletion the tow coccolithophores studied by Zondervan had reduced calcification and growth rates. false
*What is a diazotroph? organism that can grow w/o external sources of fixed N, they fix N themselves
*Name one genus that includes marine diazotrophs Trichodesmium
*Diazotrophic marine bacteria may support almost 50% of new production in what regions of the worlds oceans? nutrient poor waters of tropics and subtropics
Are prochlorphytes diazotrophs? no
*How important are prochlorophytes to global marine primary production? contributes 13-48% of net primary production in central gyres
*What type of organism are prochlorophytes? Phytoplankton, cyanobacteria
Thecosomes are a group of pteropods that feed using mucus
Gymnosomes are a group of pteropods that prey on thecosomes
Describe the typical feeding method used by copepods head appendages generate stream of water past mouth and actively grabs food particles, small particles accumulate in setae, larger particles seized in fling and cap method -throw feeding appendages laterally, open up a cavity that draws in the particle
*Why can’t most copepods filter feed? Reynolds number is too low
*Describe the copepod life-cycle. 12 stages separated by molting (adds segments and appendages), 6 nauplius stages, 6 copepodite stages (at last stage is mature adult)
Are all euphausiids planktonic? no
*Do euphausiids filter feed? yes
*How do pelagic tunicates such as salps feed? have cylindrical gelatinous body and water propelled through body used for feeding and locomotion, can catch food on mucus
How do appendicularians feed? How do they contribute to marine snow? make mucus box around the organisms and whip tail to get water to flow through mucus house from feeding filter, secrete mucus that contribute to marine snow aggregates
*Differentiate between standing stock and primary production. standing stock = # of organisms/unit area or per unit vol of water at moment of sampling, at any given time; primary production = rate at which plant material is produced
*What are the main factors affecting marine primary production? light, nutrients, water
*What macronutrient is often limiting in marine systems? Nitrogen
*What is the compensation depth? when rate of photosynthesis = rate of respiration, net photosynthesis = 0; for 1 given organism
*What is the critical depth? depth where total water column respiration = gross photosynthesis avg over 24hrs, looks at everything in water column; total plant production = total plant respiration; always lower than compensation depth; photosynthesis = 0 for total water column
*Where is the critical depth relative to the compensation depth? Critical depth is lower or at greater depth than compensation depth
*Describe in detail the Sverdrup model of primary production for the North Atlantic. Include all seasons and limiting factors. winter, spring, summer, fall
What is photoinhibition? damage to photosystems at high irradiances, damage can occur to cell membranes or electron-transport molecules
*Why do diatoms have an advantage over prochlorophytes when nutrients are abundant? b/c they can match their growth rates and have functional and numerical responses to blooms of small phytoplankton, have more top down control
*Why do prochlorophytes have an advantage over diatoms when nutrients are limiting? b/c uptake rates of prochlorophytes are high relative to cell vol allowing them to take up nutrients more effectively in low nutrient conditions, thin boundary layer to take nutrients
*What are the two key factors in seasonal trends in primary production and how do they act to determine what limits primary production in the oceans? depth of wind-mixed layer: influenced by wind speed, wave size, solar heating, too much mixing decreases sunlight, but just enough is good; solar position
*What is the F-ratio (in terms of primary production, not ANOVA!) ratio of new to total production, proportion of production in water due to nutrients in the system to what was regenerated and new (total)
*Why do regions with high F-ratios often support large fisheries? have shorter food chains = more efficient & highly productive, cut out the middle organisms = more transfer of energy from shorter food chain
Iglesias-Rodriguez et al. found that high CO2 resulted in _____ growth rates of Emiliania huxleyi. decreased
Iglesias-Rodriguez et al. found that high CO2 resulted in_____ cell volume. increased
*How was the Carbon to Nitrogen ratio affected by elevated carbon dioxide levels? How could this affect phytoplankton predators? (Riebesell et al., Nature 2007) increased C:N ratio w. more CO2, results in lower food quality for phytoplankton predators
*How do we expect higher surface temperatures reduce primary production in the oceans? (two reasons) enhanced stratification (building up of layers): decreases supply of nutrients to surface layer b/c harder to mix; decreased mixed layer depth: increase C:N ratios augmenting direct effects of increased CO2
*Beaufort et al. (2011): Coccolith mass was found to be most affected by ?????? concentration which was relatively high during the last glacial maximum. carbonate
*Coccoliths are secreted intracellularly in vesicles where __ and ____ are maintained at levels that stimulate calcite precipitation. Maintaining those levels may be more difficult when the waters become lower in __ and/or ___. pH, calcite saturation state; pH, carbonate
*Rossoll et al. (2012): What happened to the fatty acid concentration of diatoms when grown in high CO2 conditions? proportion of total essential FA declined almost tenfold in copepods
*Rossoll et al. (2012): How did the changes in fatty acid concentration of diatoms affect the diatom predator Acartia tonsa? In what ways were the copepods affected? Constrained growth and reproduction of A. tonsa; Copepods decrease in somatic growth and egg production
*Gao et al. (2012): How did doubling the CO2 concentration affect the energy of the diatoms to fix carbon? decreased production, increased pCO2 and seawater acidity increased light stress, increase respiratory carbon loss in phytoplankton
*By the end of this century global change will include shoaling of the upper mixed layer depths (increased mean light intensity) and increased CO2 levels. under those conditions the ambient phytoplankton community will support lower proportions of diatoms
*Gao et al. (2012): How did the diatoms respond to increasing light levels (daytime PAR) at constant (high) levels of CO2? depressed growth, less production
*Gao et al. (2012): The combination of increased light exposure, CO2 concentration and acidity acted synergistically to decrease phytoplankton production through: increased light stress and increase respiratory carbon loss in phytoplankton
Created by: 1224450232