Integrated Plankton Ecology, continued

II. Role of Predation, continued
    C. Cyclomorphosis – changes in body form/shape over seasons – development of spines and changes in body shape – WHY?
        1. resistance to sinking?

        2. temperature?

        3. predation?
            a. vertebrate – Tom Zaret; Lake Gatun (Isthmus of Panama); 2 forms of Ceriodaphnia cornuta – Melaniris fish
            b. invertebrate

                So, why have a short form?  greater reproductive output
      D. Developmental polymorphisms
        1. inducible defenses
            a. chemical signals – morphogen chemicals             b. density -SO, TO AVOID INVERTEBRATE PREDATORS – CHANGE SHAPE TO MAKE PREDATION MORE DIFFICULT
-TO AVOID VERTEBRATE PREDATORS -- REDUCE VISIBILITY
        2. pigmentation and light
            a. high altitude or saline lakes without fish – copepods are often pigmented bright red
                i. carotenoid pigment, astaxanthin;
                ii. when exposed to blue/uv light, clear copepodsl die
                iii. red pigment absorbs this light
            b. high altitude or saline lakes with fish – no pigmentation because makes them visible; remain deeper in the water column

III. Summary of effects of invertebrate and vertebrate predators

     Zooplankton community size
     Phytoplankton that can be grazed

IV. Plankton in rivers, reservoirs and natural lakes
 
 
Rivers  Reservoirs  Natural Lakes
Phytoplankton Diversity  Low in low order streams; increases in high order rivers  Low in riverine zone; increases in lacustrine zone  High diversity in oligotrophic, and mesotrophic lakes, decreasing in eutrophic lakes
Zooplankton Diversity  Small forms; rapid life cycles or mostly benthic life cycle  Small forms in riverine zone; lake forms in lacustrine zone  Micro and Macro-zooplankton
PhytoplanktonBiomass  Low in low order streams; increases in medium order rivers  High in nutrient-rich riverine zone; lower in lacustrine zone  Highly variable in temperate lakes (5 orders of magnitude); less variable in tropical lakes
Zooplankton Biomass  Low; inputs from lakes and floodplain pools; higher in higher order rivers  Most in transition zone; high degree of horizontal patchiness  High; vertical and seasonal gradients
PhytoplanktonProductivity  Low in low order streams and high order streams; limited by light and flow  High in transition zone; limited by light in riverine zone and nutrients in lacustrine zone  Increases with nutrient loading (until reach light limitation).  Pelagic productivity often less than littoral
Zooplankton Growth/Productivity  Low; higher in medium and high order rivers;eat detritus as well as algae  Moderate; most in transition zone; variable; some consumption of detritus  Moderate to high; extreme fluctuations due to resources and predation

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