"From Satellites to Microscopes: Studying Phytoplankton"

with guest scientists Ajit Subramanian and Andrew Juhl

Earth2Class Workshops for Teachers

Originally Presented 19 Nov 2005

¾ of Earth’s Surface is Ocean

• Phytoplankton form the base for marine ecosystems

• The ocean’s role in the global carbon cycle has become more understood in recent decades

• This and other biogeochemical cycles have major impacts on global climate

• Remote sensing has added much to our understanding of the marine ecosystem

Requirements for Marine Life

[Based in part on chapters 9 and 10 in DataStreme Ocean from the American Meteorological Society, © 2004]

All life requires:• an energy source• liquid water• nutrients• suitable environmental conditions

Differences between marine and terrestrial habitats

• Most plants on land extend only a few tens of meters above the ground

• Only a few birds fly higher than 100 m

• Marine plants can live as deep as 200 m

• Marine animals can exist in the deepest trenches, more than 10,000 m down

• By some estimates, there are more than 10 million marine species

Basic needs for marine organisms

• Liquid water• Energy source

sunlight (photosynthesis) chemosynthesis using H2S and other compounds consumer of other organisms

• Nutrients P, N, Ca, Mg Fe and other trace elements

Marine Environments (1)

• Neritic (near-shore) intertidal

• Pelagic (open-water) epipelagic (sunlit, 0 – 200 m) mesopelagic (200 – 1,000 m) bathypelagic (1,000 – 6,000 m) abyssal (6,000 – 10,000 m)

• Extreme conditions – hydrothermal vents, polar sea ice

Marine Environments (2)

• Plankton (drifters or floaters)

• Nekton (swimmers)

• Benthos (bottom-dwellers) mobile sessile burrowing

http://www.geo.arizona.edu/Antevs/nats104/00lect17marlifzon.html

There are many ways to represent marine environments and lifestyles

Marine Primary Producers

• Autotrophs (self-feeders) convert inorganic molecules into organic matter

• Seaweeds (large algae) and sea grasses (vascular plants); unicellular algae; certain photosynthetic bacteria and cyanophytes

• Phytoplankton comprise only 1% of total mass of plants on Earth, but responsible for major amounts of primary production

4 Major Groups of Phytoplankton: Diatoms

Ornate siliceous shell-like casesPhotosynthetic pigmentsDiatomaceous oozes

http://www.ucmp.berkeley.edu/chromista/bacillariophyta.html

Coccolithophores

Covered with calcareous plates

Thrive in nutrient-poor waters

Major contributors to “White Cliffs of Dover”

http://www-ocean.tamu.edu/Quarterdeck/QD5.2/pariente.html

Dinoflagellates

Two flagella (thread-like structure) and no solid covering

Some responsible for HABs (Harmful Algal Blooms, formerly know as “red tides”

http://www.geo.ucalgary.ca/~macrae/palynology/dinoflagellates/dinoflagellates.html

Marine bacteria

• Smallest, but most numerous organisms• Prokaryotes (no nucleus)• Many roles

autotrophs – photosynthetic/chemosynthetic heterotrophs decomposers mixotrophs (both autotrophic and heterotrophic)

Consumers

• Herbivorous Zooplankton microscopic (ex., copepods and krill) to macroscopic (ex., jellyfish and ctenophores)

• Carnivores larger zooplankton nektonic and benthic organisms secondary, tertiary, and higher consumers

• Approximately 10% ecological efficiency

Other Key Concepts in Marine Ecology

• Biomass

• Bioaccumulation

• Gross Production, Net Production, Recycled Production

• Nutrients and Trace Elements as Limiting Factors

Plankton and algae play key roles in the Nitrogen Cycle

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NitrogenCycle.html

The Nitrogen Cycle in the Oceans

• Recent research reveals that human impacts have greatly enhanced the rate at which nitrogen moves from land to sea

• In effect, we have doubled the amount of nitrogen “fertilizers” in the marine system

http://scicom.ucsc.edu/SciNotes/9801/ice/nitro.htm

One of the most effective nitrogen-fixers is Trichodesmium

• This cyanobacterium (blue-green algae) possesses nitrogenase enzymes

• Much research is underway to learn how Fe, Mo, and other elements may serve as bio-limiting factors

Trichodesmium

http://www.princeton.edu/~cebic/N-cycle-intro1.html

HAB – Harmful Algae Blooms

• Although most phytoplankton are harmless, some species contain toxins

• The misnomer “red tide” has been used for blooms of these dangerous organisms

http://www.whoi.edu/redtide/

http://www.whoi.edu/redtide/whathabs/whathabs.html

Global Carbon Cycle

• Ocean is major reservoir in C cycle• Important among “greenhouse gases”• CO2 transfer between ocean and

atmosphere occurs in several ways, which will be explained in the following slides

• Temporal and spatial exchanges occur over wide ranges, and may have temporary or permanent (by human standards) effects

The Physical Carbon Pump• The colder seawater is, the more CO2 is dissolved in it.• The oceans in tropical and subtropical regions release

carbon dioxide into the atmosphere, whereas large amounts of the greenhouse gas are in solution in the polar seas.

• The zones of deep-water formation, the Greenland Sea and the Arctic Ocean, in which the solute CO2 is pulled into the depths along with the sinking surface water, are therefore important elements in the physical pump.

• The CO2 is separated from the environment for several hundred years in these CO2 sinks until this deep-ocean water returns to the surface somewhere in the world in an upwelling.

                                                                              

Sketch illustrating the concept of vertical deep mixing, where carbon dioxide is transported from the ocean surface to the ocean depths by sinking cold water in the high latitudes. If brought to the surface (for instance, by upwelling) the cold water will warm up and release some of its carbon dioxide to the atmosphere.

http://calspace.ucsd.edu/virtualmuseum/climatechange1/06_1.shtml

The Biological Carbon Pump

• The photosynthetic process in algae consumes carbon dioxide, thus removing solute CO2 from the seawater.

• In parts of the ocean where massive proliferations of algae occur, consumption of the algae by zooplankton cannot keep pace with algae growth, whereupon the algae use up all the nutrients in the water such as nitrate and phosphate and, no longer able to proliferate, die and sink to the bottom.

• The carbon dioxide bound in their cells goes with them into the ocean depths in the form of organic carbon and is thus taken out of atmospheric circulation.

http://www.lighthouse-foundation.org/lighthouse-foundation.org/eng/explorer/artikel00294eng.html

http://calspace.ucsd.edu/virtualmuseum/climatechange1/06_2.shtml

The “Lime Counter-Pump”• The third pump, the "lime counter-pump," acts to counteract

the other two pumps by releasing carbon dioxide into the atmosphere.

• This biochemical pump begins with the formation of calcareous shells by marine life forms, above all corals and planktonic lime-forming algae.

• The first impression is that lime formation would bind large amounts of carbon dioxide, but in fact the opposite is the case: Lime formation produces CO2.

• Lime formation thus increases the CO2 concentration in the oceans, which is then balanced with the atmosphere by release of carbon dioxide.

• Recent calculations demonstrate that coral reefs produce about four times as much lime as the lime-forming algae. Since the reefs are also located in warm, shallow seas, there is also the contributing factor that carbon dioxide is not readily soluble in warm water, so that the gas leaves the seawater even more rapidly.

http://www.lighthouse-foundation.org/lighthouse-foundation.org/eng/explorer/artikel00294eng.html

Observing Marne Ecosystems

• Microscopic observations of collected water samples

http://www.enchantedlearning.com/subjects/invertebrates/plankton/Planktonprintout.shtml

SeaWIFS (NASA’s Sea-viewing Wide Field-of-View Sensor)

• http://oceancolor.gsfc.nasa.gov/SeaWiFS/

SeaWIFS can detect subtle changes in ocean color that signify various types and quantities of marine phytoplankton (microscopic marine plants), the knowledge of which has both scientific and practical applications.

http://seawifs.gsfc.nasa.gov/SEAWIFS/BACKGROUND/SEAWIFS_BACKGROUND.html

http://seawifs.gsfc.nasa.gov/SEAWIFS/IMAGES/SEAWIFS_GALLERY.html

AVHRR (Advanced Very High Resolution Radiometer)

• http://fermi.jhuapl.edu/avhrr/

Sea Surface Temperature (SST) imagery

How Can We Observe Earth from Space?

NASA provides an educational web site to explain remote sensing and other spatial information technologies at:

http://education.ssc.nasa.gov/fad/default.asp

The site includes a tutorial, lesson plans, and links to additional Internet resources.

• With this background, we’ll take a break and get ready to learn more from Drs. Ajit Subramanian and Andrew Juhl about their research investigations about these amazing organisms.