EVPP 550 Waterscape Ecology and Management – Lecture 9 - PowerPoint PPT Presentation

EVPP 550Waterscape Ecology and Management – Lecture 9

Professor

R. Christian Jones

Fall 2007

• 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

• 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

• Profundal zone
• Ztotal > zPZ, z > zPZ
• Open water and bottom below photic zone
• Tropholytic zone: Resp > Psyn
• Heterotrophs only
• both suspended and substrate associated

• 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

• 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

• Periphyton
• Attached microbial community
• “slime” growing on underwater surfaces
• Coats macrophytes, rocks, logs, etc.
• Includes algae, bacteria, protozoa, and microinvertebrates

• Nekton
• Organisms controlling their own movements
• Can move freely and inhabit all lake zones
• Includes fish and larger invertebrates

• 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

• 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

• 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

• 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

• 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

• 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

• 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)

• 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

• 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

• Factors affecting growth
• Parasites
• Chytrid and biflagellate fungi
• Infect desmids and diatoms
• Viruses
• Can infect cyanobacteria
• Sedimentation

• 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