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SMS 598: Application of Remote and In-situ Ocean Optical Measurements to Ocean Biogeochemistry Quick biology overview and Phytoplankton – taxonomic classification, pigments, photo-adaptation Mary Jane Perry 5 July 2007
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All you wanted to know about biology, but were afraid to ask
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Three Super Kingdoms: Eukaryotes Eubacteria Archaea single cells and metazoans Prokaryotes: single cells and consortia Bottom line: great diversity of organisms that interact with light in the ocean
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All you wanted to know about biology, but were afraid to ask Four basic functions of all organisms: EatAvoid being eatenDefecateReproduce energy & materials * light * reduced inorganics * organic C
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All you wanted to know about biology, but were afraid to ask Four basic functions of all organisms: EatAvoid being eatenDefecateReproduce toxins swimming bioluminescence morphology (spines, chains) etc.
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All you wanted to know about biology, but were afraid to ask Four basic functions of all organisms: EatAvoid being eatenDefecateReproduce dissolved organics (e.g., glycolate at high light)
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All you wanted to know about biology, but were afraid to ask Four basic functions of all organisms: EatAvoid being eatenDefecateReproduce vegetative (asexual) sex – spore/cyst formation – diatom size – other?
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All you wanted to know about biology, but were afraid to ask Four basic functions of all organisms: EatAvoid being eatenDefecateReproduce energy & materials * light – “primary producers” (phytoplankton; other photon users) * reduced inorganics – “primary producers” (chemosynthetic) * organic C – “consumers” (or secondary producers) consume DOM or POM; mixotrophs
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For the rest of this morning, will focus on “what’s a phytoplankton?” Photosynthetic (pigmented) Aerobic (oxygenated environment) Oxygenic (oxygen producing; use sunlight) Small, single-celled particle (usually)
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Three points: 1. Introduce you first to phytoplankton, and a little bit about their role in the ocean 2. What are the proxies based on interaction with light? – particles scatter light – pigments absorb light – chlorophyll a and phycoerythrin fluoresce light 3. How physiology changes the relationship between phytoplankton and their optical proxies
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Phytoplankton as particles – in the ocean, size matters related to function Size * efficiency of dissolved solute capture * motion – Brownian vs. intentional swimming * efficiency of encounter – surface area for contact * processing – if and how predator handles prey (match/not) * efficiency of aggregation * settling – Stokes Law (implications for carbon cycling) * carbon content * interaction with light – b : scattering (cross sectional area) – a : absorption (volume affects absorption efficiency)
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Two food webs (with interconnections) big little
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big particle vs. little particle energy/material cycling
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“Phytoplankton” as species What we call phytoplankton span the three Super Kingdoms: Archaea – rhodopsin (ATP); really phytoplankton? Eubacteria – cyanobacteria - oxygenic aerobic, anoxygenic, bacterial chlorophyll anaerobic, anoxygenic (sulfur bacteria) Eukaryotes – protists (very diverse) chlorophytes
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Do species matter? Some functions are species independent: photosynthesis and carbon fixation size - sinking and nutrient uptake Some functions are species specific: N 2 fixation (Trichodesmium) toxins (domoic acid, PSP, etc.) dominate oceanic carbon flux (diatoms) For optical identification, some pigments are taxon specific
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Synechococcus (~ 1 micron) arrow denotes thylakoid membrane which has both photosynthetic and respiratory functions Diagnostic: phycoerthyrin pigment fluoresces orange (in contrast to chlorophyll, which fluoresces red
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Prochlococcus ~ 0.7 microns Diagnostic: very small size, lack of orange fluorescence, divinyl chlorophyll a & b
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Trichodesmium (cyanobacterial nitrogen fixer; warm waters; patchy; Fe may regulate abundance)
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Prasinophyte
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Centric Diatoms, Thalassiosira and Chaetoceros
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Pseudonitzschia (some species have toxin, domoic acid)
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Alexandrium tamarense Ceratium Dinoflagellates
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Coccolithophorid, with calcite plates or coccoliths; look at the SeaWiFS website - blooms visible from space
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Phaeocystis (colonical and single cell) famous for producing foam on northern European beaches
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Chyrsophyte with silica scales
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Pigments definition: absorbing compound role:light harvesting for photosynthesis (PS) light protection when too much light (PP) types chlorophylls chlorophyll a - primary PS pigment in all oxygen producers chlorophyll b or c - accessory PS pigments; expand range; transfer energy to chlorophyll a (divinyl chl a and b) carotenoids light harvesting for photosynthesis (PS) light protection when too much light (PP) phycobilins water soluble pigments; phycoerythrin can fluorescence
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http://www.nyu.edu/pages/mathmol/library/photo/ www.ch.ic.ac.uk/local/projects/ steer/cloroads.gif Chlorophyll a (absorption peaks will vary, depending on environment – protein complex in membrane, polarity of solvent); in vivo fluorescence porphyrin ring w/Mg ++ phytol tail Degraded pigments: Pheophytin lost Mg ++ ; peak shifts to ~415 Pheophorbide lost Mg ++ and phytol tail
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Accessory pigments: Chl b and c inside chl a max peaks minor modification of ring in vitro fluorescence Chl c lacks phytol tail
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Carotenoids conjugated double bonds; role in photosynthesis (PS - absorb blue- green-yellow s) and photoprotection (PP - absorb excess photons, quenching free radicals, triplet oxygen); some taxon specificity
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Phycobilins (phycobiliproteins) – water soluble cyanobacteria and chryptomonads PUB phycourobilin PE (fluoresces orange) phycoerthyrin PC phycocyanin APC allophycocyanin
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