Phytoplankton 2
Community Dynamics
PHOTOSYNTHESIS
Photosynthesis: relationship between light & temperature
5C15C25C
Photoinhibition
Euglena with red masking pigment
FLOTATION MECHANISMS
Flotation Mechanisms
• Increase surface:volume to increase frictional resistance. e.g. Ceratium
Flotation Mechanisms
• Production of mucilage. e.g. Gloeocapsa and Staurastrum
Flotation Mechanisms
• Gas vacuoles. e.g. Anabaena
Flotation Mechanisms
• Accumulation of lipid. e.g. Botryococcus
Flotation Mechanisms
• Change buoyancy by exchanging monovalent and divalent ions. Documented for dinoflagellates in marine environments, not in freshwater.
Flotation Mechanisms
• Swimming by flagella. Ceratium
Pandorina
Euglena
Cryptomonas
GROWTH RATE & COMPETITION
Size and Growth Rate
Competition relative to the concentration of a limiting nutrient
Compare with Figure 15-4
Growth Rate
• Examples of growth and competition• = Cosmarium = Staurastrum
Competition between two diatoms
Vitamin Requirements
– Compare with Table 15-7
Metabolic Processes
MODES OF SUCCESSION
Seasonal Succession
Winter Populations and Spring Maximum
• Growth declines in winter when temperature is low and light is low (Figure 15-9).
• Sometimes production under ice cover can be significant (Figure 15-10).
• Sometimes spring maximum begins with growth under ice.
• Usually spring maximum after turnover and dominated by a single species (Figure 15-11).
Seasonal succession of major groups of phytoplankton in Lake Erken, Sweden
Winter production beneath ice
Production and loss of Asterionella in Lake Windermere, England (28 April – 30 June)
Spring Decline and Summer
• Decline in nutrients (especially Si) in the photic zone
• In very productive lakes (high phosphate loading)
Diatoms Greens Bluegreens
Fall Turnover and Autumn Circulation
• Temperatures decline• Reduced grazing by zooplankton• High nutrient availabilityDominated by large cells and filaments; usually
dominated by diatoms
Limitation and Availability of Growth Factors in Reservoirs
Consider differences between lakes and reservoirs
Parasitism and Grazing
• Parasites: – Chytrids– Viruses
• Grazers:– Heterotrophic Protists– Zooplankton (see Figure 15-13)• Cladocerans• Copepods• Rotifers
Competitive Interaction & Species Diversity
• Diversity indices– Species diversity declines as fertility increases– In eutrophic waters, diversity increases in the
summer and declines in the winter.
Vertical Distribution of Phytoplankton Biomass in Lakes and Reservoirs
• Figure 15-14 Chlorophyll a in Lawrence Lake
• Figure 15-15 Carotenoids in Lawrence Lake
• Figure 15-16 Phaeophyton in Lawrence Lake
Rates of Primary Production by Phytoplankton
Measured as mg carbon fixed per cubic meter per day Figure 15-22
for Lawrence Lake.
Figure 15-24 for Wintergreen Lake
River plankton production
LIGHT UTILIZATION
Efficiency of Light Utilization
• Utilization of light between 350 and 700nm (Table 15-10)
• In water column efficiency relatively low at surface (light above saturation)
• Efficiency increases slightly with depth but overall carbon fixation decreases (Figure 15-27)
Utilization of light between
350 and 700nm
Efficiency increases slightly with depth but overall carbon fixation decreases
CONCLUDING REMARKS
Extracellular Release of Organic Compounds
• Loss of photosynthate
• Many compounds are inhibitory (allelopathy)
Diurnal Changes in Phytoplankton
• Relative to light saturation
• Relative to synchronous division and metabolism
• Vertical migration
Horizontal Variation
• Related to morphometry of lakes and reservoirs (e.g. Figure 15-12)
• Related to longitudinal zones within reservoirs and streams
Summary Table 15-14RIVERS RESERVOIRS LAKES
PHYTOPLANKTON DIVERSITY USUALLY LOW LOW-MODERATE
HIGH (OLIGOTROPHIC)
LOW (EUTROPHIC)
PHYTOPLANKTON BIOMASS VERY LOW MODERATELY HIGH
HIGHLY VARIABLE (5 ORDERS OF MAGNITUDE)
PHYTOPLANKTON PRODUCTIVITY LOW
LIGHT LIMITED (RIVERINE ZONE)
HIGHEST (TRANSITIONAL
ZONE)NUTRIENT LIMITED(LACUSTRINE ZONE)
LOWER THAN LITTORAL
PRODUCTIONHIGHEST WITH
MODERATE LOADING