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UCSC OS 130 - PLANKTON

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Ocean Processes and Ecology Spring 2004PLANKTONPLANKTON• Term actually defined by Professor Victor Hensen (Kiel Univ., 1887), comes fromthe Greek "planktos" to wander or drift• Ernst Haeckel (1890) critically defined the term 'plankton' to encompass all driftingorganisms including:i) plants phytoplanktonii) animals zooplanktoniii) bacteria bacterioplanktoniv) temporary meroplankton (only part of organism's life cycle)PHYTOPLANKTONPhotosynthetic marine organisms, as the primary producers of the marine ecosystem, are the firstlink in the marine food web. They convert solar energy to an energy form usable by themselvesand, in turn, by other marine consumers. Their importance to the biological economy of the seacannot be overstressed. The most significant contribution to the primary productivity of the worldoceans does not come from the obvious macroscopic attached plants that occupy the fringes ofthe continental masses. Rather, it is the microscopic, free-floating forms, collectively calledphytoplankton, that are the dominant primary producers.• Unicellular (singe-cell) plants, microscopic, benthic and pelagic, marine/fresh.Can form colonies (filaments, chains). Members include 3 kingdoms:i) Moneraii) Protistaiii) Plantae• Present in all lighted areas of the sea (including under ice)• Dominant plants in the sea - hence role in marine food chain very importantcalled the "grasses of the sea"If large enough to be caught in a fine-mesh net - net or macroplankton ( > 200 µm)If too small to be caught in a net - microplankton ( < 200 µm) this sizing is looseOcean Processes and Ecology Spring 2004• All phytoplankton are autotrophs (i.e., self-feeding), manufacturing their own food,in their case by the process of photosynthesis- hence are photoautotrophs and thusalso considered primary producers.PHOTOSYNTHESISBiological process of creating high-energy organic material from carbon dioxide,water and other essential nutrients utilizing the sun's energy6CO2 + 6H2O ⇒ ⇒ ⇒ C6H12O6 + 6O2DIATOMS• belong to the Phylum (division) Bacillariophyta,class Bacillariophyceae• most important and often most dominant (numerous) phytoplankters in temperate andhigh latitudes of the ocean (particularly upwelling areas)• occur singularly, or in chains, or in loose formations• most cells range in size from ~ 50 to 500 µmrange from 2 um to 2000 µm (=2 mm)• chains and other aggrecates held together by mucilagenous threads or SPINES• All species have a distinctive, rigid, external skeleton (cell wall) called a frustule or testFRUSTULE (TEST)- composed of (< 95%) of SILICA (4-50 % dry wt of cell)- gives structural strength, but allows cytoplasm outside contact with the aquaticenvironment- frustule is sculptured into patterns of spines, pores, channels, ribs- frustules fundamentlly composed of two valves: smaller fitting into larger like a petridishOuter - EpithecaInner - HypothecaNote Silcon is the element, SiSilica is short for silicon dioxide (SiO2), in all crstalline, amorphous, & hydrated or hydroxylated forms,Ocean Processes and Ecology Spring 2004Silicate is ionized from of monosilicic acid (Si(OH)4), aqueous (dissolved) diatoms have been abundant since at least the Cretaceous Period (135 million yrs)- first fossils from Jurassic period (191-205 million years ago)- (diatomaceous ooze or sediments)Two major types of diatoms based on cell shape (many varieties)CENTRIC round, pill-box shaped, two equal halves, > 1500 sppradially or concentrically symmetrical (from end view), all non-motilePENNATE - elongated shapes, mostly benthic some pelagic (e.g., Nitzschia)DINOFLAGELLATES• Belong to Phylum Pyrrophyta (Dinophyta):class Dinophyceae, (larger group - 1,500 to1,800 free-living species)class Desmophyceae (smaller group, two flagella at anterior end)- asexual division into two halves (e.g., Prorocentrum genus)• Second most abundant phytoplankton group, cell size 10 to 1,000 µm• Most exist exist singularly, some species (spp) form chains• Possess two flagella (whiplike appendages, flagellum singular) - so MOTiLE (capable of movement)• Different species utilize different energy sources:i) Autotrophic - building organic materials & obtaining energy from photosynthesisii) Heterotrophic - meet energy needs by feeding on phytos & small zooplankton(hence often also refered to as zooplankton)~ 50 % of dinoflagellates are strict heterotrophs (no chloroplasts)iii) Mixotrophic capable of both autotrophic and heterotrophic production (others are parasitic or symbiotic)• Dinoflagellates are divided on basis of possesion of a relatively thick cellulose wall calleda THECA THECATE forms (majority)NAKED formsOcean Processes and Ecology Spring 2004• Cell divided into anterior and posterior half by transverse groove - GIRDLEflagellua arranged such that one extends posteriorly from the celland the other wraps transversely around cell in girdle region• In thecate spp, the cell wall is divided into a number of separate cellulose platesornemented with pores and/or small spines• common thecate genera include Ceratium andLingulodinium polyedrum (basionym Gonyaulax polyedra forms local red tides)Ocean Processes and Ecology Spring 2004CYANOBACTERIA(also known as blue-green bacteria, or formerly as blue-green algae)• belong to the phylum (division) Cyanophyta - class Cyanophycea- the ‘typical’ cyanobacterium, approx. 150 genera, 2000 species recently Prochlorophytes have been added to the Cyanophyta (based on molecularevidence, previously they were their own division) - 3 genera• Procaryotic cells - lacking complex organelles- no chloroplasts, nuclear envelope, mitochondria, Golgibodies, endoplasmic reticula, theydo have thyllacoidsribosomes (protein production sites) are the smaller (70s) typical of bacteria• first algae to evolve (filamentous fossils found from 3.5 billion yr.)• PigmentationTypical - chlorophyll a, phycobiliproteins (phycocyanin gives distinctive blue-green colour)Prochlorophytes - divinyl chlorophyll a, chl b, (c), no phycobilins.Note: a phycobiliprotein is several phycobilins tightly bound to a protein)• Storage product: cyanophycean starch• Cells walls: peptidoglycan wall of amino sugars and amino acidssimilar to that of gram-negative bacteriaoften surrounded by mucilage polysaccharide sheath• Reproduction is asexual, no sexual reproduction Wide-spread distribution - freshwater,marine, terrestrial and symbiotic


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