Transcript EVPP 550 Waterscape Ecology and Management – Lecture 9

EVPP 550
Waterscape Ecology and
Management – Lecture 9
Professor
R. Christian
Jones
Fall 2007
Lake Biology – Overview
Habitat Regions
• Littoral zone
– Ztotal < zPZ
– Bottom is within photic
zone
– Trophogenic: Psyn>Resp
– Autotrophs and
heterotrophs
– Supports benthic algae,
rooted macrophytes which
add structure
– Substrate-associated
plants and animals are
characteristic
Lake Biology – Overview
Habitat Regions
• Pelagial zone
– Ztotal > zPZ, z < zPZ
– Open water within
photic zone
– Trophogenic:
Psyn>Resp
– Autotrophs and
heterotrophs
– Species that can
suspend in water
column or actively
swim are
characteristic
Lake Biology – Overview
Habitat Regions
• Profundal zone
– Ztotal > zPZ, z > zPZ
– Open water and
bottom below
photic zone
– Tropholytic zone:
Resp > Psyn
– Heterotrophs only
– both suspended
and substrate
associated
Lake Biology – Overview
Biotic Communities
• Plankton
– “wanderers”
– Suspended in the water column
– May demonstrate limited mobility, but location
chiefly controlled by currents
– Found principally in the pelagic region, but
sometimes also in littoral or profundal
– Phytoplankton: “plant”-like/photoautotrophs
• Algae, cyanobacteria
– Zooplankton: “animal”/heterotrophs
• Rotifers, cladocera, copepods
Lake Biology – Overview
Biotic Communities
• Benthos
– Organisms associated with the bottom &
sediments
– Found in both littoral and profundal
– Phytobenthos
• Includes aquatic macrophytes and benthic
algae
– Zoobenthos
• Invertebrates of many groups
• Most diverse in the littoral
Lake Biology – Overview
Biotic Communities
• Periphyton
– Attached microbial community
– “slime” growing on underwater surfaces
– Coats macrophytes, rocks, logs, etc.
– Includes algae, bacteria, protozoa, and
microinvertebrates
Lake Biology – Overview
Biotic Communities
• Nekton
– Organisms controlling their own
movements
– Can move freely and inhabit all lake
zones
– Includes fish and larger invertebrates
Lake Biology - Phytoplankton
• Characteristics
– “plant” component of the plankton
– Primary producers
– All have chlorophyll a
– Conduct standard photosynthesis
– H2O + CO2 + light  (CH2O) + O2
– All require N, P, trace elements
– Some also can utilize DOM or even may feed
suplementally on bacteria
Lake Biology - Phytoplankton
• Characteristics
– Vary in taxonomy and morphology
– All divisions of eukaryotic algae represented
• Greens, diatoms, dinoflagellates, cryptophytes,
euglenoids
• Cyanobacteria (blue-green algae) can be very
important
• Range from very small unicells (<1 um) to large
colonies and filaments (up to 1 mm or more)
• Size categories: 0.2-2 um picoplankton, 2-30 um
nanoplankton, 30-200 um microplankton
Lake Biology - Phytoplankton
• Adaptations
– Avoid sinking
• General morphology: hairs, projections, anything to
increase friction
• Flagella: can swim against gravity
• Lower density: gas vacuoles, lipids
– Nutrient uptake
• Sinking: breaks down boundary layer facilitation
diffusion
• Small size: higher surface area/volume
Lake Biology - Phytoplankton
• Adaptations
– Predation avoidance
• Colonial habitat
• Projections
• Indigestable muscilage
– Reproduction
• Mostly asexual: binary fission, autocolony
formation
• Sexual: When stressed some produce zygote,
diatoms use zygote to restore size
Lake Biology - Phytoplankton
• Factors affecting growth
– Light
• Light energy required for photosynthesis
• Light varies with latitude, season, time of day,
cloud cover, attenuation coefficient, depth
• Photosynthesis shows an assumptotic relationship
to light
• To estimate photosynthetic production in the field,
need to account for time of day and depth
variations in light
Lake Biology - Phytoplankton
• Factors affecting growth
– Light
• Photosynthetic rate/primary production quantified
by measuring either: O2 production or C-14 uptake
• Can use either:
– Bottle string in situ
– P-I curve in lab extrapolated to field condition using light
extinction and ambient light data
Lake Biology - Phytoplankton
• Factors affecting growth
– Nutrients
•
•
•
•
•
•
N required for proteins, amino acids
P required for ATP, nucleic acids
Si for diatom frustules
Trace metals in enzymes
Vitamins by some algae
Nutrients can be taken up in excess of current
need for future use (luxury uptake)
Lake Biology - Phytoplankton
• Factors affecting growth
– Nutrients
• P generally limiting in most fw systems, but
sometimes N
• Si for diatoms, Mo for N fixers
• Relationship between P and:
–
–
–
–
Cell size
Chl a
Pico biomass
Group biomass
Lake Biology - Phytoplankton
• Factors affecting growth
– Grazing
• Spines and projections may increase effective size and
inhibit grazing
• Cladocerans esp Daphnia are most efficient grazers
• Heavy grazing may reduce abundance and productivity of
phytoplankton
• Light to moderate grazing may actually stimulate production
by increasing nutrient availability
• Differential grazing may favor certain cyanobacteria and
colonial green algae by removing their competitors since they
are resistant to grazing
• Nanoplankton vs. Daphnia
Lake Biology - Phytoplankton
• Factors affecting growth
– Parasites
• Chytrid and biflagellate fungi
– Infect desmids and diatoms
• Viruses
– Can infect cyanobacteria
– Sedimentation
Lake Biology - Phytoplankton
• Factors affecting growth
– Washout
• Important in lakes receiving large inputs of water
– Mainstem reservoirs, urban lakes
• Washout processes may not be simple
– Displacement without mixing - Linear decrease in
plankton with time
– Complete mixing – exponential decline in plankton with
time
• Washout may keep plankton low even when
nutrients are available