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”