1EEOB 655 Limnology Fall 2011 Planktonic Secondary Production: From Microbes t Z l kto oop an on Jim Bauer Aquatic Ecology Lab Dept. of EEOB Secondary Production ? Rate of biomass growth regardless of the fate of an organism, population, or community ? Units are: gC/m2/y, gC/m3/y or similar; key point is SP is a rate and hence expressed per unit time ? Represents energy/mass available to predators Assim=I-E-R Rigler 1973; IBP No. 17 (~equivalent to Production) 2High Biomass = High Production Kalff 2002; from Plante & Downing 1989 Secondary Production - Microbes ? Major Groups ? Archaea (third domain of life) ? Bacteria ? Viruses ? Fungi ? Microbial diversity and metabolism ? Heterotrophic bacterial biomass and production Bacteria ? An explosion of techniques to determine community abundance, biomass, metabolic rates, and production began in the 1960s and continues ? A second and more recent thrust employs a suite of molecular methods to characterize ?taxa? of bacteria and their activity 3Photomicrographs of bacterioplankton cells from Wascana Creek, Saskatchewan, filtered onto 0.2-?m pore-size cellulose nitrate filters: (a) stained with Syto 9 for total cell counts; cells appear green (b) the same preparation stained with the commercial Live Dead stain for determination of ratio of live to dead cells, live cells appear green while putative dead cells red a) (c) filtered cell preparation stained with 5 mmol l?1 cyanoditolyltetrazolium chloride incubated for 60 min and counterstained with Syto 9; yellow cells are active while green cells are not metabolically active as determined by this assay. Note: Magenta cells and filaments are cyanobacteria imaged using autofluorescence of their photosynthetic pigments. b) c) Microbial Identification ? Most microbes (particularly archaea, bacteria, viruses) cannot be identified based on morphology (in contrast with plants, animals) ? Traditional identification based on culturing microbes and determining the metabolic capabilities and growth requirements ? Today an array of methods allow characterization of molecular sequences (e.g. nucleic acids) and diagnostic molecules (e.g. fatty acids) for microbes in natural samples Only a Small Percentage of Bacteria Grow in Culture ? Traditional culture methods use rich medium but bacteria in aquatic systems often live under resource scarcity ?So most bacteria have not been cultured ? New methods (very low nutrients low substrate other , , refinements) may allow cultivation ? For now emphasis is on understanding bacteria through molecular characterization (gene sequencing, etc) from natural samples ? Genetic information also can reveal metabolic capabilities (e.g. genes present to make nitrogen fixing enzyme) 4Distribution and Abundance of Bacterial ?Taxa? Just Starting to be Understood Yannarell & Kent 2009 Typical Vertical Distribution in A Lake Archaea (The Third Domain of Life) dw4.unl.edu Initially considered to be mainly methanogens, extreme halophiles, extreme thermophiles. Now being discovered in many habitats including water columns Energy Source Chemical Chemo- Light Photo- Electron donor Inorganic -litho- Classification of Microbial Metabolism Photo-litho-auto-troph Chemo-organo-hetero-troph Examples: Organic -organo- Carbon source CO2 -auto- Organic -hetero- Both -mixo- -troph Majority of bacteria 5Bacteria are Essential to Ecosystem Function ? Decomposition of detritus, DOC, DON, DOP and recycling of CO2 and nutrients (N and P) ? Nitrogen conversions (nitrification, denitrification) ? Drivers of other biogeochemical transformations ? Food source for filter feeders and detritivores ? Can also be primary producers (important in a few types of systems: cyanobacteria, chemoautotrophs) Why do we care about bacteria and dissolved organic matter natural waters? CO2, N&P nutrients Respiration Primary Production Diffusion of CO2 from atmosphere DOM (100%)Bacteria The ?Microbial Loop? , remineralization back to CO2, N&P Nutrients (~90% efficient) Dead, decaying organic matter Microzooplankton MacrozooplanktonGr Gr Gr ? Very important concept Patterns of Abundance, Biomass and Secondary Production of Bacteria ? As with other groups bacteria typically increase with nutrients and primary production 6Bacterial Abundance (Biomass) Patterns General but Variable Some of this variation due to methods Gasol & Duarte 1990 Sources of Organic Carbon Supporting Bacteria ? Primary production - authochthonous ? Release of DOC by phytoplankton, macrophytes, benthic algae ? Death of phytoplankton macrophytes benthic , , algae ? Secondary producers (DOC release and death) - authochthonous ? Inputs of terrestrial organic carbon (DOC)- allochthonous Cole et al. MEPS 1988 General pattern of bacterial productivity: BP about 20% of NPP 7Carbon Budget at 1m Depth of Frains Lake, MI ?shows importance of bacteria Small Pool but Large Flux! Wetzel 1983; modified from Saunders 1972 Fluxes are ?g C/L/d ? In hypolimnion, however, bacterial biomass dominates! Ratio high in oligotrophic systems Simon et al. 1992. Mar. Ecol. Prog. Ser. 86:103-110) Ratio low in eutrophic systems BOC = Bacterial Organic Carbon Summary of Patterns and Productivity - Bacteria ? Bacteria abundance, biomass and production increase with TP, Chl ? Bacteria key processors of organic carbon ? Rule of thumb BP is about 20% of NPP for planktonic systems, but large range ? But many systems with high allochothonous C which also supports bacterial production ? Ratio of bacterial biomass to phytoplankton biomass declines with phyto biomass 8Viruses ? Pathogen for bacteria, phytoplankton, and other organisms Two Life Cycles: Lysis and Lysogeny Pedruzzi and Luef 2009 Bacterium Viruses ?Recent studies have found that upwards of 80% of all bacteria and phytoplankton in aquatic systems can be infected with viruses! 9Fungi Important in Flowing Waters: Significant Decomposers of Leaf and Detrital Material Spores of aquatic hyphomycetes. A. Flabellospora sp. B. Alatospora acuminata s.l. C. Anguillospora sp. D. Unidentified conidium. E. Condylospora sp. All spores are from a single sample from a stream in Alabama. Photomicrographs V. Gullis Zooplankton: Heterotrophic Protists (protozoa) ? In general these consumers represent a small component of the zooplankton community biomass, but can account for a substantial component of zooplankton production. ? Primary groups are ciliates flagellates and amoebae , , ? Flagellates are mainly 2-20 microns; ciliates are 20-200 microns in maximum length ? Protozoa consume bacteria and small phytoplankton and in turn are prey for larger zooplankton like copepods ? Rapid population growth possible via cell division ?Key component of the microbial loop Why do we care about bacteria and dissolved organic matter natural waters? CO2, N&P nutrients Respiration Primary Production Diffusion of CO2 from atmosphere DOM (100%)Bacteria The ?Microbial Loop? , remineralization back to CO2, N&P Nutrients (~90% efficient) Dead, decaying organic matter Microzooplankton MacrozooplanktonGr Gr Gr 10 Note diversity and heterogeneity of vertical distribution Feeding of Herbivorous Zooplankton ? Feeding rates ? magnitude ? factors influencing feeding ? Food selectivity ? particle size ? particle type Feeding Rate vs Filtering Rate ? Filtering rate (FR) is the volume of water cleared of particles of a given type per unit time (e.g. ml/animal/day) - often measured using tracer particles ? also called ?grazing rate? ? Feeding rate (Ingestion) is the actual amount of food ingested per unit time, e.g., mass/animal/time or mass/population/time 11 How Much Do Zooplankton Filter? Feeding Varies with: ?food concentration (I) ?particle size (FR, >I) di d i f Peters and Downing 1984 ?crow ng an nter erence (
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