EVPP 550 Waterscape Ecology and Management – Lecture 9

1. EVPP 550Waterscape Ecology and Management – Lecture 9 Professor R. Christian Jones Fall 2007

2. Lake Biology – OverviewHabitat 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

3. Lake Biology – OverviewHabitat 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

4. Lake Biology – OverviewHabitat 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

5. Lake Biology – OverviewBiotic 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

6. Lake Biology – OverviewBiotic 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

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

8. Lake Biology – OverviewBiotic Communities • Nekton • Organisms controlling their own movements • Can move freely and inhabit all lake zones • Includes fish and larger invertebrates

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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)

16. 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

17. 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

18. Lake Biology - Phytoplankton • Factors affecting growth • Parasites • Chytrid and biflagellate fungi • Infect desmids and diatoms • Viruses • Can infect cyanobacteria • Sedimentation

19. 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