IntegratedPlankton2

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

may set a minimum size
invertebrate predators choose small or medium size prey – opposite to vertebrate predation
example: Kerfoot - Bosmina and Epischura

So, why have a short form? greater reproductive output

Epischura versus sticklebacks

    D. Developmental polymorphisms
        1. inducible defenses
            a. chemical signals – morphogen chemicals

Gilbert:

Brachionus (loricate rotifer); predator Asplanchna releases a chemical (‘Asplanchnin’) that induces Brachionus to become spined;
spines induced only with the water from an Asplanchna culture;
inducibility only in early developmental stages

Daphnia with a Chaoborus predator

b. density

Asplanchna (cannibalistic at high densities) – 3 forms – sacchate, campanulate, cruciform (large, resistant to predation by campanulate form)

-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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	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