Transcript Yager presentation to Schoolyard Saturday

Microbial control on the productivity of Barrow's coastal waters
Will the battle for nitrogen intensify under climate change?
Patricia Yager
University of Georgia
Debbie Bronk
Virginia Inst. Mar Sci
Marc Frischer
Skidaway Inst. Oceanogr.
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
•Introduction
•Why are microbes important?
•What’s special about the Arctic microbes?
•Our ideas about climate change impacts
•What are we going to do here?
•How can you be involved?
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Arctic Marine Food Web
http://www.arcodiv.org/
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
2007 minimum Arctic sea ice
[NSIDC, 2007; see http://www.nsidc.org]
Decline in September ice extent from 1979 to 2007
• September rate of sea ice decline: 1979-2007
• 2007 is the maximum ice retreat on record, with 2008 the 2nd lowest
Jacqueline Grebmeier
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
How will the loss of sea
ice affect the food web?
Hypothesis:
Reduced benthic?
Increased pelagic?
Nutrients required!
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Nutrients come from the
Bering Sea
or from upwelling near the
shelf break
[Courtesy Tom Weingartner]
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Yager et al. 2001
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Arctic Marine Food Web
?
http://www.arcodiv.org/
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Food Web
Don’t forget to recycle!
Detritus
(POM + DOM)
Decomposers
(bacteria etc)
Microbial
food web
Nutrients, CO2
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Adds to the classical
herbivorous food web
Bacteria in food webs
Decomposers
Prey for protozoans
Infected by viruses
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Aren’t bacteria bad?
E. coli
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Smallest marine organisms: 0.5 µm in
diameter (although largest marine
bacterium is 750 µm)
Three lifestyles: planktonic, attached,
symbiotic
2 million per drop (milliliter) of coastal
seawater
Decomposers
Significant metabolic diversity
Low morphological diversity
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Focus on
bacteria as
heterotrophs or
“decomposers”
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
NO3
Light
DOM
Phyto
Bacteria
Walsh Model – Original Construction
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
NO3 > DOM
NO3
Light
Stochiometric Converter
(5:1)
DOM
Phyto
Bacteria
Walsh Model – Direct Competition (Scenario I)
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
PRIMARY HYPOTHESES
H1: The balance of autotrophy and heterotrophy in the Arctic is regulated both
temporally and spatially by nitrate (NO3-).
Heterotrophic bacteria will utilize NO3- in response to intense N limitation in the pelagic
Arctic, allowing remineralization of refractory dissolved organic matter (DOM) with
high C:N ratios.
Heterotrophic bacterial uptake of NO3- will be greater during the dark winter and under
sea ice than in open water or well-lit summer conditions when bacteria are replete with
phytoplankton-derived DOM.
NO3-, combined with terrestrial DOM derived from riverine and groundwater flow, may
provide the means for bacterial growth and respiration during the dark winter.
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
H2: The composition and dynamics of bacterial communities will vary
significantly from summer to winter, correlating with concentrations and
sources of DOM and will be reflected in microbial communities by the
expression of key N-cycling genes, N-uptake and regeneration, and in
DOM uptake kinetic capabilities and growth efficiencies.
Lags in bacterial response to phytoplankton blooms will be due to required
community shifts.
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
H3: Climate change will enhance the competition for N in the
coastal Arctic as it reduces sea ice and increases terrestrial
organic inputs, without affecting the annual light cycle.
These changes will reduce the flux of C to the benthos, and
the efficiency of the biological pump.
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Field plan
Three seasons / Two years
December - January (Dark)
March – April (Light, high nutrients)
August – September (Light, low nutrients)
Sample pelagic water (10-50 m water)
-> Carbon and nitrogen inventories
-> Net community production
-> Algal production (primary production)
-> Nitrogen uptake by algae and bacteria
-> Algal species composition
-> Bacterial species composition, activity
-> Gene expression – esp. N-cycling genes
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
High precision carbon dioxide measurements
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Arctic currently has a highly efficient carbon pump:
Arctic shelves are
net autotrophic during the
open water season.
Tight bentho-pelagic
coupling
With an apparently strong
continental shelf carbon
pump to the deep basin.
Yager et al., 1995
Ducklow & McCallister 2004
Bates et al., 2005
Yager (in prep)
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Size-fractionated:
Bacterial Abundance
Bacterial Production
Respiration
Pyrosequencing
MAR-FISH
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Courtesy F. Heinrich
Microautoradiography – Fluorescent In situ Hybridization = MAR-FISH
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Radiation safety
14C is a pure beta emitter with a half-life of 5,730 years.
Its maximum beta energy is 0.156 MeV and its maximum
penetration range is 10 inches in air, 0.02 inch in water,
and 0.01 inch in plastic.
Because of its energy level, 14C is most damaging when
it comes into direct contact with human tissue.
For this reason, ingestion, inhalation, or internalization
through direct skin contact is the greatest hazard. Its
biological half-life ranges from minutes to 25 days, with
an average of 10 days.
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Radiation safety
Since we are measuring very small organisms, we will use very low levels of
14C in a safety-conscious way that will not harm humans or the environment.
While no one would suggest doing this, if one ingested the entire 250 µCi stock
we will use during our Barrow research, they would receive approximately:
150 mrem
14C is created naturally by cosmic rays entering the atmosphere. The average
annual effective background dose equivalent for a person living in the U.S.:
360 mrem/y
The UGA RSO restricts its radiation workers to a maximum dose of 500 mrem
per year (10% of the national safety standard of 5000 mrem per year).
All radioactive samples and waste will be returned to Georgia when
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
finished.
Nucleic Acids
Store and transmit genetic info
www.scienceclarified.com/ Mu-Oi/Nucleic-Acid.html
• DNA (deoxyribonucleic acid) - the genetic
template or “genome.”
– Double-stranded
– Four different nitrogenous bases (A,T,G,C)
– Sequence of nucleotides contains all genetic info
• RNA (ribonucleic acid) - the translator
– Single-stranded
– Four nitrogenous bases (A,U,G,C)
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
DNA collection for Bacterial Community Structure
(454 hypervariable tag sequencing)
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Eastern Arctic – Barents Sea
(isolates)
Subtropics (Savannah, GA)
Specific bacterial NO3 uptake
(nmol N l-1 d-1)
Specific bacterial NO3 uptake
(pmol N l-1 d-1)
How Do We Measure these two pathways?
Quantify key bacterial & phytoplankton genes
involved in N-cycling
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
How can you be involved?
PolarTrec teacher – Lollie Garay
Training and equipment to monitor conditions yourself
Turner Designs fluorometer for nutrient and chla monitoring
Links to GISS database?
Chris Cuomo (UGA), Wendy Eisner and Kenneth Hinkel, "Environmental Change,
Indigenous Knowledge, and Subsistence on Alaska's North Slope"
High School Student exchange with Jeff Peneston?
Oceans and Human Health interactions?
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Establish Barrow’s own nutrient time series
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010
Thank you!
A presentation by P. Yager to the BASC Schoolyard Saturday program – 2/27/2010