Transparent Exopolymer Particles (TEP):A frequently ignored, but extremely active component of NOM
Uta Passow & Tom Berman
Israel Oceanographic & Limnological Research
Marine Science Institute, Univ. California Santa Barbara
NOM-Conference July 2011
1.What are TEP?2.Where do they come from? How are they formed?3.What is their role in aquatic systems?
Transparent Exopolymer Particles (TEP):
TEP • are gel particles• ubiquitous in every water (lakes, streams, oceans)• are transparent• increase viscosity• behave like gels• are very flexible,• are very sticky• are very surface reactive• are very abundant during phytoplankton blooms (high Chl.a)• exist in the dissolved-particulate continuum• are very difficult to quantify
TEP-like substances are particulate biopolymers rich in acidic polysaccharides
sulfated deoxy-sugarsfucose, rhamnose, arabinose, galactose
but they also contain proteins, lipids, nucleic acids…
1. What are TEP?
TEP = Transparent Exopolymer Particles
1. What are TEP?
100 µm
100 µm
50 µm
0.00.11.0
10.0100.0
1000.0
1 10 100Diameter (μm)
TEP exist in different sizes
0
200
400
600
800
1000
1200
1400
0 5 10 15 20
Time (days)0 5 10 15 20
TEP exist at different concentrationsTE
P (μ
g Xa
ntha
neq
. L-1
) diatom bloom
Net heterotrophic systemdN
/dl (
# m
l-1μm
-1)
Up to 106 liter-1
Passow 2004
Small phytoplankton flagellates
1. What are TEP?
TEP = transparent exopolymer particles exist as
large webs
matrix of aggregates
small particles
1. What are TEP?
0
10
20
30
40
50
60
70
80
90
1 2 3 4
Filtration of gel-particles such as TEPT
EP
(ug
Xeq
. l-1
)
0.2
–1
um>
1 um
> 0.
2 um
> 0.
2 um
Filtration pressure: 125-150 mm Hg 250-300 mm Hg
Passow & Alldredge 1995
TEP, gel properties make them difficult to isolate and quantify
1. What are TEP?
1.What are TEP?2.Where do they come from? How are they formed?3.What is their role in aquatic systems?
Transparent Exopolymer Particles (TEP):
Phytoplankton
generate polysaccharides for capsules, slimes or they are released directly into the water.
diatoms coccolithophoresPhaeocystis
and bacteria
The formation rate and composition of these biopolymers depends on species and growth conditionsDiatom with attached bacteria
2. How are TEP formed?
1 um
Leppard 1995, Leppard et al 1977
Phytoplankton exude dissolved polysaccharides into the water
2. How are TEP formed?
These polysaccharides assemble to form gels
up to 107 fibers per literAssembly of gels
– Nanogels (nm, 10-20 kDa)– Macrogels (mm)
IEntanglement
IIGelation & Annealing
IIICompaction & Aggregation
2. How are TEP formed?
Hydrophobic and electrostatic bonding to colloidal sized nano-gels, which coalesce to form larger gels and porous networks
These gels have a high interfacial area and have charged sites: very surface active!
AbsorptionFe+++Fe+++
Fe+++
Fe+++Fe+++
Fe+++
Fe+++
Fe+++
Fe+++ Fe+++
Fe+++
Fe+++
Fe+++
Fe+++
Fe+++
Fe+++
Fe+++
Fe+++
Fe+++Fe+++
2. How are TEP formed?
TEP exist in a size continuum from colloidal to large particles
1nm
1um
1mm
POC
DOC
Free Fibrils
Transparent Exopolymer Particles, TEP
Nano & Micro-hydrogels
Time (minutes - hours)
Interface DOC & POC
Size Continiuum of Marine Gels
gelation & annealing
aggregation
alignment on hydrophopic surfaces
Free Polymers
HMW
LMW
collo
idal
Solu
tes
1-10 kDa
2. How are TEP formed? Passow 2004
TEP form abiotically from dissolved precursors
Incubation time (hours)
TEP
ug
Xeq
. L-1
0
2000
4000
6000
0 48
insideoutsidecontrol
Experiment: Incubate raw seawater in dialysis bags (8 kDa) for 48 hours: TEP release inside bag by diatoms, no TEP or TEP-precursors outside bag (0.2 µm filtered seawater). Control: 0.2 µm filtered seawater.TEP-precursors pass through the 8 kDa dialysis bags and form TEP
2. How are TEP formed? Passow 2000
Formation of TEP from 0.2 um prefiltered seawater in a flocculator
0
100
200
300
400
500
600
700
800
900
1000
6/17/1995 6/18/1995 6/19/1995 7/12/1995
TEP
ug
Xant
han
equi
v. p
er li
ter
t = 0shear 24 hcontrol 24 h
bloom peak clouding flocced deep water
Passow 20002. How are TEP formed?
TEP formation is a function of precursor concentration
TEP are scavenged by solid surfaces like fibers
> 500 Dalton & < 0.2 µm
Experiment.: Suspend silicious fibers in seawater with a Phaeocystis sp. bloom filtered into 2 size fractions, < 500 Dalton & 500 Da to 0.2 µm
SiO2-CA-Hybridnanofaser
< 500 Dalton2. How are TEP formed?
2. How are TEP formed? Mopper et al 1995
TEP formation is enhanced by bubbling or shear
Aggregates in rolling tankTEP collected by bubbling
Formation of TEP by phytoplankton
DIC
nutrients
Precursors, nm,AFM contact mode
TEP > 2 µm
Phytoplankton
release
abiotic formation
Santschi et al. 1998
1.What are TEP?2.Where do they come from? How are they formed?3.What is their role in aquatic systems?
Transparent Exopolymer Particles (TEP):
Why is it important that particles are formed abiotically from dissolved matter?
DOC &colloids
TEP
Cycling of toxins,metals, carbon
Micro-environment
Distribution dependant on
water movement
Partially independent:aggregation
filterable
Structured:substrate, refugia,
micro-zones
unstructured
3. The role of TEP
In the ocean TEP play a central role • for biofilm formation• for settlement of organisms• for aggregation (clumping)• for the viscosity of seawater• as a surface • as a substrate• vertical transportation of organic matter: “bacterial shuttles”• as a protection against antibiotics and toxins• as a protection against damage of the photosynthetic apparatus• as a ligands for trace metals, e.g. Fe• ……….
⇒ many potential uses
3. The role of TEP
TEP easily attach to solid particlesand form the matrix of aggregates
3. The role of TEP: aggregation
Gaerdes et al. 20103. The role of TEP: aggregation
Total Aggregate Formation is a Function of TEP concentration
3. The role of TEP: aggregation
Natural marine or lake snow storms
Gulf of Mexico: Marine snow formation in the presence of oil
May 2010, Golf of Mexico, V. Asper
3. The role of TEP: aggregation
Azam 1998
The microbial loop: an impressionist version!
3. The role of TEP: bacteria interaction
Microstructure in the aquatic environment is essential for bacteria
Bar-Zeev et al 2011
Vertical transport of TEP to depths
TEP as microbial shuttles
3. The role of TEP: bacteria interaction/ flux
DAPI staining of bacteria reveals that many of the bacteria are attached to TEP.
3. The role of TEP: bacteria interaction
TEP provide surfaces, structure as well as substrate for bacteria
Passow 1994
TEP provide surfaces, structure as well as substrate for bacteria
The majority of bacteria appear attached
Berman & Parparova 20103. The role of TEP: bacteria interaction
Membrane
Modified Paradigm for Aquatic Biofilm Formation including TEP
Biofilm
Berman & Passow 2007
TEP contribute appreciably to biofilm formation
3. The role of TEP: bacteria interaction
Thank you!
Teaching students oceanography on “the Bill of Rights”