Biological Limnology Exam - Primary Producers & Zooplankton

primary producer

converts an abiotic source of energy into organic compounds (e.g. photosynthesis)

photoautotrophs

main primary producers in lake

chlorophyll

green pigment in plants/protist inside chloroplasts

algae

aquatic, plant-like organisms from single-celled phytoplankton to large seaweeds (kelp); not bacteria; unicellular/multicellar; photosynthetic eukaryotes

phytoplankton

photosynthetic microorganisms; adapted to live partly or entirely in open water

cyanobacteria

phylum of free-living photosynthesis bacteria; sometimes called blue-green algae, but NOT algae1

macrophytes

plant that grows in or near water; emergent, submerged, floating; rooted or uprooted

plankton

organisms unable to swim against the current (quasi-suspension); some incapable of independent movement; position determined by water movements

phytoplankton

photosynthetic plankton; microorganisms suspended, adapted to live partly or continuously in open water

features of cyanobacteria

• main pigment chlorophyll-a

• can have gas vacoules which help them float

• some can fix nitrogen from atmos. (N2 → NH4); energetically expensive

• some can produce toxins

• heterocysts - specialized cells that convert N2 → NH4

  • drive algal bloom production

eukaryotic algae

chlorophyta (green), diatoms

chloropyta

green algae; freshwater, unicellular, colonial, filamentous, chlorophyll-a & bdi

diatoms

unicellular & coenbial; cell walls contain cryptocrystalline silica, chlorophyll-a

coenobial

colony that always has the same # of cells once it is formed

how can so many phytoplankton species exist?

contradicts principle of competitive exclusion

• environment must be very stable - lakes are very unstable

• lots of symbiotic relationships

• selective grazing by predators

• resting stages

uses of chlorophyll-a

as a proxy:

• more chlorophyll-a = more phytoplankton —> deep chlorophyll maximum

  • more chlorophyll-a = higher DO

lifestyle of phytoplankton

• light: light affects amount of photosynthesis —> need alot, but too much = UV burns

• temp: all species have preferred temp ranges + temps of max growth

• buoyancy regulation: need adaptations to stay in photic zone (e.g. gas vacuoles, flagella, mucilage, etc.)

• nutrients: limiting resource —> too much = eutrophication

• death: pathogens (viral & bacterial), grazing by zooplankton

zooplankton

animal plankton

microzooplankton

protists (eurkaryotes that are not plant, fungi, or animal); rotifers (smal animals that feed on phytoplankton, detrius, protists) (reprod asexually, small biomass, large predator)

mesozooplankton

crustaceous zooplankton, cladocerans, zombie daphnea, predatory zooplankton

zooplankton diet

anything smaller than them

diel vertical migration

zooplankton reside in the metalimnion during the day to avoid predators in low light conditions, rise at night to warm water of epilimnion to feed, grow, and reproduce; avoid being eaten

affect of zooplankton predators

induce changes in morphology: helpment expression, neck tooth expression, crest expression, head + tail spine expression

seasonal zooplankton predator/prey dynamics

• winter: minimal biomass —> cold/low light

• spring: light, nutrients from mixing + still cold, bloom of diatoms, zooplankton react to food source + lake is vert clear (low algae); spring clear water phase

• summer: green algae/cyanobacteria

• fall: diatom bloom associated w/ lake mixing