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Diversity of Aquatic Organisms Bacteria Part 1

Diversity of Aquatic Organisms Bacteria Part 1. Size Categories of Plankton. Bacteria and Archaea (0.1- 2.0 um) Small protists, cyanobacteria (0.5 - 10 um) Protists: protozoans and algae (10-500 um) Crustacean zooplankton (50-5000um) Examples: Microcystis (cyanobacteria) cell = 5 um

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Diversity of Aquatic Organisms Bacteria Part 1

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  1. Diversity of Aquatic OrganismsBacteriaPart 1

  2. Size Categories of Plankton • Bacteria and Archaea (0.1- 2.0 um) • Small protists, cyanobacteria (0.5 - 10 um) • Protists: protozoans and algae (10-500 um) • Crustacean zooplankton (50-5000um) Examples: Microcystis (cyanobacteria) cell = 5 um Rotifers (80 - 1500 um) Daphnia (2000 um) Common plankton net mesh sizes: 30 um: “phytoplankton net” collects colonial algae 60 um: collects most zooplankton, not algae 112 um: collects most crustacean zooplankton, some rotifers 150 um: collects most crustacean zooplankton

  3. Bacteria in Lakes • Very small in size, < 1 um • In contrast, most zooplankton can be captured with a 150 um mesh net • Some phytoplankton can be captured with a 60 um mesh net • Too small to be seen with ordinary microscope and stain. Therefore, until recently, bacteria were ignored or greatly underestimated. • Study of bacteria increased with the development of fluorescent dyes • Bacteria were found to make up 5-15 % of plankton biomass • Bacteria studies are now a thriving component of aquatic ecology www.epscor.dbi.udel.edu/outreach/science/images osl.gc.ca/sl_monitore/images

  4. Metabolic Types • It is almost impossible to identify bacteria by shape and size, therefore we identify them by what they do. • Photoautotrophs • Cyanobacteria (aerobic, act like autotrophic algae or green plants) • Photosynthetic bacteria (anaerobic purple sulfur bacteria) • Photoheterotrophs • Anerobic non-sulfur purple bacteria • Chemoheterotrophs • Denitrifier • Sulfate reducers • Fermenters • Decomposers aslo.org/photopost/data/502/0Purple-sulfur_bacteria_Great_Salt_Lake.JPG

  5. Abundance and Seasonal Cycles • Eutrophic lakes tend to have more bacteria than oligotrophic lakes • Peaks of bacteria abundance tend to coincide with peaks of phytoplankton abundance • Highest bacteria abundance in the summer starbulletin.com/1999/12/09/news/art.jpg

  6. Limiting factors for Heterotrophic Bacteria Growth • Temperature Growth slows significantly below 10-15o C • Inorganic Nutrients • Usually phosphorus • Oxygen • Aerobic metabolism is usually faster and more efficient that anerobic metabolism • Dissolved Organic Carbon • Quantity of DOC • Bacterial production is usually heavily “subsidized” by DOC inputs from the watershed and littoral zone (up to 80% of DOC) • Quality of DOC • Simple organic substrates (amino acids, sugars, fatty acids) can be used quickly • Complex organic substrates (tannins, cellulose) are utilized more slowly. • Predators • Zooplankton (Daphnia) eat large unicellular bacteria and colonies • Protozoa consume small unicellular bacteria (50% of predation by nanoflagellates) • Viruses account for 25% of bacteria mortality http://www.sacsplash.org/cimages/daphnia1.jpg wgbis.ces.iisc.ernet www.vet.upenn.edu/schoolresources/communications/publications/bellwether/55/images/bacteriophage.jpg

  7. Aquatic Food Web(Pelagic zone) • Traditional view • Fish are produced by organic material that originates in the phytoplankton • lakes are autotrophic Inorganic nutrients edoc.hu-berlin.de/dissertationen/goncalves-boechat-iola-2005-02-15/HTML/Goncalves-Boechat_html_21bf1373.png

  8. Aquatic Food Web • Modern View: Much DOC can enter lakes from the watershed, therefore fish production may rely on primary production from outside the lake (Lakes are heterotrophic) Microbial loop Autochthonous DOC

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