Phytoplankton and Primary Production Phagotrophic dinoflagellates Cryptomonads & photosynthetic Chain Forming diatoms Diatoms Green algae Blue Green algae (Cyanobacteria) Anabaena Productivity: rate at which organic matter is produced Microcystis Production: Total organic matter produced Relationship Between Primary Productivity Lakes are Categorized According to their Level of and Phytoplankton Biomass (Production) Productivity or “Trophic State” More Productive For conditions in which nutrients are limited Less Productive Biomass Productivity g Carbon . m-3. day-1 (Production) Oligotrophic Mesotrophic Eutrophic g Carbon . m-3 Greater Water Clarity : 10 m Less Water Clarity: 2.5 m Less Algae : 1.7 µg/L Chl a More Algae : > 14 µg/L Chl a Lower Phosphorus : < 8 µg/L More Phosphorus: 16 µg/L time PHOSPHORUS AND CHLOROPHYLL CONCENTRATIONS AND SECCHI DISK DEPTHS CHARACTERISTIC OF THE TROPHIC CLASSIFICATION OF LAKES Phosphorus Concentrations Vary Across the Western Finger Lakes MEASURED PARAMETER Oligotrophic Mesotrophic Eutrophic Total Phosphorus (µg/L) AVG 8 26.7 84.4 Range 3.0- 17.7 10.7- 95.6 16-386 Chlorophyll a (µg/L) AVG 1.7 4.7 14.3 Range 0.3 - 4.5 3 – 11 3 – 78 Secchi Disk Depth (m) AVG 9.9 4.2 2.45 Range 5.4 - 28.3 1.5 – 8.1 0.8 – 7.0 Table I – Data from Wetzel, 1983 Source: CSLAP data Chlorophyll Concentrations Are Relatively Low In Conesus Lake Cycle of Phytoplankton Production and Biomass in Temperate Lakes Source: CSLAP data Start of Spring bloom Autumn bloom fall Summer turnover Dry Period & fallout Surface temperature in a typical lake A: Spring Bloom: high nutrients, light, low herbivory B : Summer Clear Phase: low nutrients, high herbivory Herbivory peaks in summer months C: Late summer peak: declining herbivory D: Fall Bloom: high nutrients due to fall turnover Lake Mendota, near Madison WI SPRING SUMMER Diatoms Greens High nutrients Good competitors at low nutrients Low grazing Moderate grazing Low sinking High sinking rates (many flagellated) LATE SUMMER Blue-greens Lowest nutrients (N fix.) High grazing – resist by being unpalatable (sheath/toxin) Moderate sinking Dinoflagellates seem to thrive under low nutrient conditions many shift to phagotrophic diet Green WINTER – small phytoflagellates; sometimes motile dinoflagellates ` In most lakes the levels Coincides with increases of nutrients remain high in zooplankton (stars) and rates of herbivory (bars) .