1. Diversity of Aquatic Organisms Bacteria Part 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.  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 Abundance and Seasonal Cycles starbulletin.com/1999/12/09/news/art.jpg

6. Limiting factors for Heterotrophic Bacteria Growth   Temperature Growth slows significantly below 10-15 o 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.ce s.iisc.ern et www.vet.upenn.edu/schoolr esources/communications/p ublications/bellwether/55/im ages/bacteriophage.jpg

7. Inorganic nutrients   Traditional view Fish are produced by organic material that originates in the phytoplankton lakes are autotrophic Aquatic Food Web (Pelagic zone) 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) Autochthonous DOC Microbial loop