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