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INTRODUCTION TO PHYTOPLANKTON

INTRODUCTION TO PHYTOPLANKTON. BIOL 202-MARINE BOTANY FALL 2009 Dr. Mitra. PHYTOPLANKTON. OVERVIEW OF PHYTOPLANKTON COMMUNITIES CLASSIFICATION AND DIVERSITY RESPONSES TO LIGHT NUTRIENTS ADAPTIVE STRATEGIES STRATEGIES TO PREVENT GRAZING. PHYTOPLANKTON. Autotrophic Free-floaters

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INTRODUCTION TO PHYTOPLANKTON

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  1. INTRODUCTION TO PHYTOPLANKTON BIOL 202-MARINE BOTANY FALL 2009 Dr. Mitra

  2. PHYTOPLANKTON • OVERVIEW OF PHYTOPLANKTON COMMUNITIES • CLASSIFICATION AND DIVERSITY • RESPONSES TO LIGHT • NUTRIENTS • ADAPTIVE STRATEGIES • STRATEGIES TO PREVENT GRAZING

  3. PHYTOPLANKTON • Autotrophic • Free-floaters • Microscopic • Mostly unicellular although some are colonial and filamentous

  4. CLASSIFICATION • Phytoplankton ----Picoplankton-0.2 to 2µm ----Nanoplankton-2.0 to 20µm ----Microplankton-20 to 200µm Picoplankton are important contributors to primary productivity of plankton. Biomass in surface waters range from 40-50Pg C/year (P=peta, and 1 Pg is equivalent to 10 15 g). CYANOPHYTA, CHLOROPHYTA, PYRRHOPHYTA, CRYPTOPHYTA, CHRYSOPHYTA, BACILLARIOPHYCEAE

  5. Factors influencing Phytoplankton Growth Light Reference: Biology of Algae By Sze

  6. LIGHT Irradiance is inversely proportional to water depth. COMPENSATION DEPTH --- Different species have different compensation depths. Rate of photosynthesis equals rate of respiration. No production of biomass takes place. Cells below the compensation depth are unable to grow and deplete their resources.

  7. Growth in response to a nutrient Reference: Biology of Algae By Sze

  8. MONOD EQUATION-Requirement for a specific nutrient μ = μmax S/K+S μ=growth rate μmax=maximum growth rate S=nutrient concentration K= Half saturation constant. Value of S at 1/2μmax K and μmax vary with temperature.

  9. Growth of two species Which population will grow at low nutrient concentrations? Reference: Biology of Algae By Sze

  10. NUTRIENTS Nutrient concentrations vary in different bodies of water. EUTROPHY-Nutrient enrichment OLIGOTROPHY-Low nutrient level Macroelements-C, H, O, S, K, Ca, Mg, P, and N. Microelements-cofactors-Fe, Mn, Cu, Zn, Mb. Si is required by all diatoms.

  11. Limiting Nutrients for Growth • Nitrogen---N2, NH4+, NO3-, NO2-, and urea. • Phosphorus---Inorganic phosphate can occur in a number of forms (HPO42-,PO43-;and H2PO4- • Sulfur—SO42-,H2S

  12. NITROGEN FIXATION IN CYANOBACTERIA Reference: Biology of Algae By Sze

  13. NITROGEN • Nitrate is the primary source of nitrogen utilized by algae • Nitrate----(nitrate reductase)Nitrite---(nitrite reductase)--Ammonium. • Ammonium is utilized in cell metabolism.

  14. PHOSPHORUS • Phosphate in different forms • Organic phosphates---broken down by phosphatases in the membrane of algae.

  15. ROLE IN SULFUR CYCLE Reference: Biology of Algae By Sze

  16. NUTRIENTS-MODE OF NUTRITION • AUXOTROPHY- Requirement for a specific vitamin. Some algae require additional vitamins (biotin, thiamine). • MIXOTROPHY-”Mixed feeders”. Mixotrophy involves uptake of organic matter from the surrounding water or ingestion of organic particles (phagocytosis).

  17. FLOATING AND SINKING Accumulation of polysaccharides Photosynthesis goes up Buoyancy increases Cells rise Gas vesicles collapse Increased vacuolation Buoyancy decreases Cells sink Photosynthesis decreases

  18. ADAPTIVE STRATEGIES OF PHYTOPLANKTON • Frictional drag of water (water viscosity) creates a “sticky” environment that sticks to cell surfaces. • Smaller cells have a greater surface: volume ratio. Elongate cells have greater surface ratio. • Cyanobacteria-have gas vesicles that aid in buoyancy. • Some phytoplankton accumulate low-density materials (lipids). • Phytoplankton with flagella swim toward light.

  19. STRATEGIES TO PREVENT GRAZING • Increased rates of cell production. • Increased abundance of species that are resistant to herbivory. • Mucilaginous sheaths, thick cell walls, and external coverings protect the species. • Some form colonies---too large to handle. • Chemical deterrents ---repel the herbivores. Photos by Lesley Bensinger Dr. Mitra’s Research Group

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