Phytoplankton: diversity and ecology
● Phytoplankton shaped our climate and the air we breath
○ Marine cyanobacteria evolved 3.8 billion years ago and started to alter earth’s chemistry through the process of
photosynthesis
○ 2h2o + co2 → suhar + h2o + o2
○ The utilization of co2 reduced carbon dioxide concentrations in the atmosphere and the process of organic
photosynthesis simultaneously increased earth’s oxygen content
○ Two major oxygenation events
■ Early proterozoic
■ Late proterozoic
● Roles of phytoplankton in the ecosystem
○ Marine phytoplankton play crucial roles in the marine ecosystems
■ Farming the base of the marine food web
● Phytoplankton → zooplankton → small fish → large fish
■ Contributing 50% of the global primary production
● Coastal areas, equator (upwelling), north and south poles are where primary production is
highest
● Tropics and equator (rainforest) is where primary production is highest on land
■ Driving biogeochemical (elemental) cycles (carbon, nitrogen)
● Basics of marine productivity
○ Productivity fuels life in the ocean, drives its chemical cycles, and lowers atmospheric carbon dioxide
○ Ocean primary productivity largely refers to the production of organic matter by phytoplankton, microscopic,
single cells plants suspended and floating in the ocean
○ Phytoplankton are “photoautotrophs” harvesting light to convert inorganic to organic carbon
○ This organic carbon is used by diverse heterotrophs
● What are phytoplankton?
○ Cyanobacteria was the first phytoplankton
○ Phytoplankton
■ Phyto = plant
■ Plankton = wanderer
○ Phytoplankton is an ecological term (rather than taxonomic)
■ Organisms that get their energy from sunlight
■ Cannot outswim a current
○ Phytoplankton are found within two major domains in life:
■ Bacteria (cyanobacteria)
■ Protists (diatoms, dinoflagellates, coccolithophores)
, ○ Despite the high species diversity and obvious difference in morphology, genetic variation, and ecosystem function
all phytoplankton utilize…
■ Nutrients from the oceans interior
■ The co2 dissolved in the ocean
● Phytoplankton growth
○ In response, to light, cells take up carbon and accumulate protein and other key metabolics
■ As they “grow bigger”, cells ultimately divide, which results in population increase expressed as the cell
division rate of population growth rates!
○ Growing requires sufficient substrate (nutrients, light) and optimal environmental conditions (temperature, pH)
■ Phytoplankton reproduce better in cold/warm water, since nutrients and co2 dissolve better in colder
waters
○ Phytoplankton succession: diatoms, green algae, and cyanobacteria take turns with their blooms
■ Diatoms have two peaks: april/may and october/november
● Less hot temperature
■ Green algae peaks in the summer (july/august), as well as cyanobacteria (august/september)
● The life cycle
○ A series can alternate in its life cycle between four distinct phases
■ Growth → sex → quiescence → cell death
○ The population of a phytoplankton species found in any particular sample will contain cells that undergo
different fates
● Reproduction in general
○ Asexual: resulting in two identical “daughter” cells; binary fission (prokaryotes) and mitosis (eukaryotes)
■ Mitosis: interphase → prophase → metaphase → anaphase → telophase
○ Sexual: resulting in four cells (gametes) in eukaryotes
■ Meiosis: prophase 1 → metaphase 1 → anaphase 1 → telophase 1 → prophase 2 → metaphase 2 →
anaphase 2 → telophase 2
● Reproduction in diatoms
○ Goes through both mitosis (asexual) and meiosis (sexual)
■ Mitosis: wall formation around cell; larger of two cells undergoes mitosis again or once the smaller of
the two reaches a minimum size, it undergoes meiosis
● In asexual, it divides into two cells: one is identical to the mother cell and the other is a
smaller cell that produces the gametes
■ Meiosis: gametes → fusion of gametes → zygotes
● Exponential growth
○ Occurs when conditions are ideal
○ Lag phase → exponential growth → stationary phase → decline/death phase
○ As growth is exponential, nutrient supply is inversely exponentially declining
, ■ Growth is exponential (g = 2^n)
● The major causes of variations in phytoplankton growth and productivity are related to light, nutrients, and temperature
○ Each species or group responds differently to these variations
● Factors affecting growth in the ocean:
○ Light
○ Dissolved nutrients
○ Temperature
○ Salinity
○ Dissolved gasses (co2, o2)
○ pH
● Light intensity
○ Light penetration goes much deeper in open ocean (oligotrophic waters)
○ Light penetration in coastal waters is lower but there is more nutrients
● Photosynthesis
○ Photosynthesis occurs in eukaryotic chloroplasts and internal membranes of some prokaryotes
○ Photosynthesis can be separated into light and dark reactions
○ Harvesting light and produces energy
■ Light harvesting and energy transfer to reaction center
■ H2o splitting and electron donation (o2 evolution)
■ Electron transport to form atp and nadph
■ Atp and nadph required
■ Rubisco fixes co2 and sugar is produced
■ Calvin cycle regenerates substrate
● Photosynthesis - pigments
○ Photosynthetic pigments are arranged as antenna complexes in the thylakoid membrane
○ Accessory pigments to capture a wide spectrum of the sun’s energy
■ Chl a (all groups)
■ Chl b (green algae)
■ Chl c (phaeophyta, dinophyta)
■ Carotenoids like xanthophyll (phaeophyta) and carotene (dinoflagellates)
■ Phycobilins like phycoerythrin and phycocyanin (cyanobacteria, rhodophyta)
● Photosynthesis measurements
○ Photosynthesis can be measured by:
■ Winkler titration (o2 concentration)
■ Using 18o stable isotope (h218o) and measure 18o2 evolution
■ Use of optodes/electrodes to measure oxygen concentration (ctd-o)
■ Isotopically labeled co2 (13c, 14c)
● Phytoplankton shaped our climate and the air we breath
○ Marine cyanobacteria evolved 3.8 billion years ago and started to alter earth’s chemistry through the process of
photosynthesis
○ 2h2o + co2 → suhar + h2o + o2
○ The utilization of co2 reduced carbon dioxide concentrations in the atmosphere and the process of organic
photosynthesis simultaneously increased earth’s oxygen content
○ Two major oxygenation events
■ Early proterozoic
■ Late proterozoic
● Roles of phytoplankton in the ecosystem
○ Marine phytoplankton play crucial roles in the marine ecosystems
■ Farming the base of the marine food web
● Phytoplankton → zooplankton → small fish → large fish
■ Contributing 50% of the global primary production
● Coastal areas, equator (upwelling), north and south poles are where primary production is
highest
● Tropics and equator (rainforest) is where primary production is highest on land
■ Driving biogeochemical (elemental) cycles (carbon, nitrogen)
● Basics of marine productivity
○ Productivity fuels life in the ocean, drives its chemical cycles, and lowers atmospheric carbon dioxide
○ Ocean primary productivity largely refers to the production of organic matter by phytoplankton, microscopic,
single cells plants suspended and floating in the ocean
○ Phytoplankton are “photoautotrophs” harvesting light to convert inorganic to organic carbon
○ This organic carbon is used by diverse heterotrophs
● What are phytoplankton?
○ Cyanobacteria was the first phytoplankton
○ Phytoplankton
■ Phyto = plant
■ Plankton = wanderer
○ Phytoplankton is an ecological term (rather than taxonomic)
■ Organisms that get their energy from sunlight
■ Cannot outswim a current
○ Phytoplankton are found within two major domains in life:
■ Bacteria (cyanobacteria)
■ Protists (diatoms, dinoflagellates, coccolithophores)
, ○ Despite the high species diversity and obvious difference in morphology, genetic variation, and ecosystem function
all phytoplankton utilize…
■ Nutrients from the oceans interior
■ The co2 dissolved in the ocean
● Phytoplankton growth
○ In response, to light, cells take up carbon and accumulate protein and other key metabolics
■ As they “grow bigger”, cells ultimately divide, which results in population increase expressed as the cell
division rate of population growth rates!
○ Growing requires sufficient substrate (nutrients, light) and optimal environmental conditions (temperature, pH)
■ Phytoplankton reproduce better in cold/warm water, since nutrients and co2 dissolve better in colder
waters
○ Phytoplankton succession: diatoms, green algae, and cyanobacteria take turns with their blooms
■ Diatoms have two peaks: april/may and october/november
● Less hot temperature
■ Green algae peaks in the summer (july/august), as well as cyanobacteria (august/september)
● The life cycle
○ A series can alternate in its life cycle between four distinct phases
■ Growth → sex → quiescence → cell death
○ The population of a phytoplankton species found in any particular sample will contain cells that undergo
different fates
● Reproduction in general
○ Asexual: resulting in two identical “daughter” cells; binary fission (prokaryotes) and mitosis (eukaryotes)
■ Mitosis: interphase → prophase → metaphase → anaphase → telophase
○ Sexual: resulting in four cells (gametes) in eukaryotes
■ Meiosis: prophase 1 → metaphase 1 → anaphase 1 → telophase 1 → prophase 2 → metaphase 2 →
anaphase 2 → telophase 2
● Reproduction in diatoms
○ Goes through both mitosis (asexual) and meiosis (sexual)
■ Mitosis: wall formation around cell; larger of two cells undergoes mitosis again or once the smaller of
the two reaches a minimum size, it undergoes meiosis
● In asexual, it divides into two cells: one is identical to the mother cell and the other is a
smaller cell that produces the gametes
■ Meiosis: gametes → fusion of gametes → zygotes
● Exponential growth
○ Occurs when conditions are ideal
○ Lag phase → exponential growth → stationary phase → decline/death phase
○ As growth is exponential, nutrient supply is inversely exponentially declining
, ■ Growth is exponential (g = 2^n)
● The major causes of variations in phytoplankton growth and productivity are related to light, nutrients, and temperature
○ Each species or group responds differently to these variations
● Factors affecting growth in the ocean:
○ Light
○ Dissolved nutrients
○ Temperature
○ Salinity
○ Dissolved gasses (co2, o2)
○ pH
● Light intensity
○ Light penetration goes much deeper in open ocean (oligotrophic waters)
○ Light penetration in coastal waters is lower but there is more nutrients
● Photosynthesis
○ Photosynthesis occurs in eukaryotic chloroplasts and internal membranes of some prokaryotes
○ Photosynthesis can be separated into light and dark reactions
○ Harvesting light and produces energy
■ Light harvesting and energy transfer to reaction center
■ H2o splitting and electron donation (o2 evolution)
■ Electron transport to form atp and nadph
■ Atp and nadph required
■ Rubisco fixes co2 and sugar is produced
■ Calvin cycle regenerates substrate
● Photosynthesis - pigments
○ Photosynthetic pigments are arranged as antenna complexes in the thylakoid membrane
○ Accessory pigments to capture a wide spectrum of the sun’s energy
■ Chl a (all groups)
■ Chl b (green algae)
■ Chl c (phaeophyta, dinophyta)
■ Carotenoids like xanthophyll (phaeophyta) and carotene (dinoflagellates)
■ Phycobilins like phycoerythrin and phycocyanin (cyanobacteria, rhodophyta)
● Photosynthesis measurements
○ Photosynthesis can be measured by:
■ Winkler titration (o2 concentration)
■ Using 18o stable isotope (h218o) and measure 18o2 evolution
■ Use of optodes/electrodes to measure oxygen concentration (ctd-o)
■ Isotopically labeled co2 (13c, 14c)
