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DOM

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Núria Catalán

on 29 April 2014

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Transcript of DOM

C Cycling
Sources, transformations and controls of dissolved organic matter (DOM)
in a Mediterranean catchment

Núria Catalán García
Barcelona, 13th September 2013
Introduction
Chapter 1
Chapter 2
Sources : Tranvik et al. 2009; Aufdenkampe et al. 2011
from land 2.7
Chapter 3
Chapter 4
Thesis goal
Determine the sources, controls and transformations affecting DOM in a Mediterranean catchment
Current conception
State of the art
Natural DOM variability
DOM transformation processes

What is DOM?
to atmosphere 1.2
to sediments 0.6
to sea 0.9
-1
Units: Pg C y
INLAND WATERS
"DOM is the great modulator, the variable that modifies the influence of other variables"
Glucose
Humic acid
Complex composition
Microbial loop
C cycling
Aquatic food webs
Pollutants toxicity
Underwater light regime
Availability of nutrients
Landscape perspective
Export
Sources
Modified from Soranno et al. 2010
Sept 2007 - Dec 2008
16 Runoff events

Mediterranean ephemeral washes
Seasonality and landscape factors drive dissolved organic matter properties in Mediterranean ephemeral washes
Catalán N., B. Obrador, C. Alomar, and J.Ll. Pretus, Biogeochemistry 2013, 112: 261-274
21st December

23th December



Chronological clustering allowed distinguishing
two periods
from the DOM properties in the ephemeral washes





DOM
concentrations
show
seasonal variability
Factors

F

P-value

Explained variance

Seasonal cluster

90.8

<0.001

Subcatchment

7.4

<0.001

Interaction

2.1

<0.05

5.2 %



AU
samples present a more
terrestrial-like
character






Microbially-like
character of DOM increases in
WS


Catchment characterization
S’Albufera des Grau catchment (56km2)
7 subcatchments

Summer drought
Autumn
Winter-spring
Autumn
AU
AU
WS
18.6%
37.9%
During
AU
, hydromorphological factors are the main drivers of DOM variability

Landscape
DOM
DOM characterization of 16 runoff events in the 7 subcatchments
Spectroscopy and concentration
Seasonality
Natural vegetation
Farming centre
Humid areas
Artificial surfaces
PERMANOVA RESULTS
During
WS
, subcatchments landscape influence DOM properties
Higher reactivity of allochthonous vs autochthonous DOC sources in a shallow lake
Catalán N., B. Obrador, M. Felip and J.Ll. Pretus, Aquatic Sciences (in press)
Context
Linear dynamics
Exponential dynamics
Irregular pattern
The dynamics of DOM qualitative parameters show different patterns
Qualitative changes in DOM during its degradation cannot be assumed to follow a regular decay pattern
The initial character of
AutoDOM
was more colored and aromatic than
AlloDOM
The
AlloDOM
showed more extensive changes in a monthly basis
Experimental design and methodology
Bacterial abundance and production
Bacterial growth efficiency and
cell-specific production
DOM descriptors from EEMs:
Total fluorescence, peaks and HIX, BIX and FI index
DOM concentration

DOM quality Spectroscopy:
Absorbance (SUVA and a350)
Fluorescence
UV radiation in the range of natural radiation
Bacterial growth efficiency (%)
Cell-specific production (pg C cell-1 h-1)
Incubation time (days)
The initial bioavailability is higher for
AlloDOM
than for
AutoDOM
(faster attainment of

BGE and CE maxima)
Later increase of
AutoDOM
bioavailability
Rapidly available DOM
Short exposure to degradation pathways
Macrophytic origin of DOM, aromatic
Longer exposure to degradation pathways
AlloDOM
undergoes faster and more intense changes in DOM properties
28 days

final 4

final 3

final 2

final 1

initial 4

initial 3

initial 2

initial 1

DOCInitial- DOCfinal → DOC degradation (ΔDOC)

Priming effect in freshwater ecosystems:
response of lake DOC to labile C additions
Catalán, N., A. Kellerman, H. Peter, F. Carmona and L. Tranvik (in prep.)
Context
Photodecay
Sorption
Complexation
Other controls
The priming effect
“changes in C inputs that modify the decomposition rate of the organic C initially present”
Kuzyakov, 2008
Labile
Does it occur in the water column of aquatic systems?
Are there evidences of priming effect in the water column of inland waters?

Does the DOC consumption vary depending on the lake water used or the labile C source added?

Is DOC mineralization facilitated by the addition of nutrients or the availability of surface?
Objectives
Experimental design and methodology
DOC present in the system

LAKE WATER
Labile C source added
Primer concentration
As a % of the initial DOC:
0 0.05 0.2 1 5
Nutrients availability
With and without nutrients
C limiting (C:N:P of 45:7.4:1)
Surface availability
PRIMER
GLASS BEADS
Acetate
Cellobiose
Glucose
Only in the clearwater and humic lakes
Only in the clearwater and humic lakes
Measurements and detection method
Primer concentration (%)
Primer concentration (%)
Primer concentration (%)
DOC consumption
Positive priming
Negative priming
No priming
ANCOVA approach
If H0 accepted, no sig. differences and no evidences of priming effect
Differences between slopes?
DOC consumed in the control + amount of primer added
MASS BALANCE:
Humic extract (Artificial)

Valloxen (eutrophic)

Ljustjärn (clearwater)
No nutrients
No Glass Beads
Nutrients
No Glass Beads

No nutrients
Glass beads
Nutrients
Glass beads
No significant
No significant
p <0.001
p<0.001
Svartjärn (polyhumic)
No nutrients
No Glass beads
Nutrients
No glass beads
No nutrients
Glass beads
Nutrients
Glass beads
No significant
No significant
No significant
No significant
The nutrient and surface availability do not facilitate the occurrence of priming effect

Context
t
Objectives
To characterize DOM on a seasonal basis
To assess the effect of sources and processes over DOM quality
To evaluate spectroscopic descriptors as tools to capture the complexity of ecosystemic processes affecting DOM
Mediterranean Sea
Torrential pulses entrance
Torrential pulses entrance
Surface
150cm

250 cm
Extraction of leachates
Darkness, 4ºC, 48h gently stirred
Endmembers
Macrophytes leachate
Sediment leachate
Seawater
AU torrential water
WS torrential water
DOM concentration and spectroscopic properties
Methods and sampling strategy
Lagoon dominated by humic-like DOM

Peak C relevant in torrential water
The lack of relationship between DOM concentration and FDOM indicates variation in the sources influencing DOM
"Better tracing DOM variability by quality
than by concentration "
Low intensity seawater but high Peak T
Sediment is displaced towards longer wavelenghts
Ruppia is similar to the lagoon but higher peak T
Jaffé et al. 2008
Significant differences between month ( PERMANOVA: 69.4%, F=15.3, p< 0.001), but not between sites
Vertical variability of DOM properties allows identifying sources and ecosystem processes
Aromatic DOM in the surface after torrential inputs
Conclusions
The quality of dissolved organic matter present in ephemeral washes is influenced by landscape factors, and this influence varies in a seasonal basis.
Two seasonal periods are distinguished in terms of DOM quality in ephemeral washes: autumn, showing an aromatic terrestrially-derived DOM, and winter-spring with a microbial-like DOM.
In autumn, the main drivers of DOM properties in ephemeral washes act at a broad scale, including hydromorphological variables such as runoff or catchment slope and the precedent summer drought. During winter-spring, more local processes dominate DOM quality, and differences between subcatchments arise linked to local landscape features such as soil type or land uses.
The classical paradigm that links autochthonous DOM with lability and allochthonous DOM with unreactive materials is not supported.
The allochthonous DOM draining from the ephemeral washes into the lagoon is more reactive than autochthonous DOM when it is subject to photo- and biodegradation processes.
The short exposition to degradation pathways of DOM in ephemeral washes leads to the presence of rapidly degradable compounds, while the longer history and macrophytic origin of lagoon DOM decreases its reactivity.
The instantaneous rates of change in DOM quality show that DOM degradation cannot be assumed to universally follow a regular decay pattern.
No evidences of enhanced DOM mineralization in freshwater systems due to priming effect are found. None of three labile carbon sources added increase the decomposition rates of the existing DOM in water bodies presenting different trophic states.
The nutrient availability and the role of cell attachment to a surface do not play any significant role on the priming effect.
The seasonal variability in the quality of DOM in the studied lagoon reflects the phenology of macrophytes and the pulses of torrential episodes draining the catchment. Other processes like bottom hypoxia, phytoplanktonic peaks or seawater entrances are reflected in the dynamics of DOM quality.
DOM inputs from the catchment contribute with aromatic DOM and generate heterogeneities in the water column during autumn. Macrophytes affect DOM in spring and summer emitting labile materials that are likely to be rapidly consumed, remaining the more humic fraction in the lagoon water.
Context
Methods
Sub-catchments characterization
THANK YOU!
Mediterranean landscape
Prairie, 2008
"The humic fraction is the main component of DOM"
McKnight et al. 2003
Spectroscopic techniques provide extended information on the chemical properties of DOM
Stedmon and Markager, 2005; Jaffé et al. 2008, Fellman et al. 2010
Absorbance spectra
Aromaticity
A254/DOC = SUVA
A440
CDOM
Spectral slope
Molecular weight
... in inland waters
DOM

characterization
Experimental laboratory designs
Temporally and spatially
extended field designs
Objectives
To determine if DOM quality in ephemeral washes is related to landscape properties
To assess spatial variability in DOM quality and its potential link with landscape
To determine the relevance of these drivers along the year
EEMs-derived descriptors also relate
AU
with humified and
WS
with protein-like DOM
Models assume constant rates for [DOM ] reactivity patterns
Guillemette and del Giorgio, 2011
What about the reactivity patterns of DOM quality properties
Objectives
Are there differences in the
reactivity
of
Allochthonous
and
Autochthonous
DOM?

Do
instantaneous rates of change
capture the dynamics of DOM quality changes?
No significant
No significant
Ljustjärn (clearwater)
No significant
Svartjärn (polyhumic)
No significant
Priming in lake water column is unlikely to happen for waters with different trophic states

C budgets show that the consumption of the samples are lower or not different from the controls + the amount of primer added
WHAT IS THE MECHANISM BEHIND
PRIMING?
Bianchi, 2011
Could DOM be protected from enzymatic degradation?
Are other "protective states" besides bioenergetics determining DOM persistence (recalcitrance)?
Lower humification and biological origin in the surface during macrophyte growth
Hydrological inputs
Macrophyte phenology
Bottom hypoxia
Phytoplankton activity
Seawater entrances
The Global C Cycle, 4th IPCC report
Water courses are ephemeral washes

Diverse lithology and mixed land uses

Natural park (from 1995)
S'Albufera des Grau, Menorca, WE Mediterranean
Enclosed coastal lagoon (Obrador et al.2008)

78ha, Medium depth 1.37m

Macrophyte dominated (Obrador et al. 2007) with very intense C cycling (Obrador and Pretus, 2012)
Farming land
Irrigated croplands
Humification
Protein-like
Both
season
and
subcatchment
and their
interaction
explain DOM properties variability
The landscape factors influencing DOM quality vary between seasons
Allo
Auto
The stronger decrease of DOC and faster attainment of CE and BGE reflect a more labile character of
AlloDOM
Guenet et al. 2010; Bianchi, 2011
"The interactions between substrates, microbial communities and abiotic conditions of the system determine organic matter persistence"
Kleber, 2009
Seasonal variability in dissolved organic matter properties as a fingerprint integrating ecosystem processes in a Mediterranean lagoon
Catalán, N., B. Obrador and J.Ll. Pretus (submitted)
Materials with higher fluorescence than expected from [DOC]
Presence of non-fluorescent materials as carbohidrates
Central point representative of the whole lagoon DOM

Bacteria
Complexation
Sorption
Photodecay
Flocculation
Uptake
DOM
Concentration and composition
Mineralization and sedimentation
Bioavailability
Recalcitrance
"A fraction of DOM has fluorescence properties"
Ewald et al., 1983
Excitation-emission matrices (EEMs), 3D fluorescence spectra
Mopper and Schultz, 1993
Fluorescence regions are excellent indicators of ecological processes, functional properties and sources of DOM
Flow intermittency
Seasonality
determines DOM properties
Prairie, 2008
Links DOM - landscape
Mediterranean systems
Recalcitrance and reactivity
Sources and quality
Knowledge gaps
NMDS, the arrows are hydromorphological factors significantly (p<0.01) related

"the origin determines the reaction"

Adapted from Wetzel, 2003
Current view
Del Giorgio and Cole, 1998
DOC
SUVA
a350
Sr
FI
BIX
HIX
PeakC
PeakA
PeakB
PeakT
PeakM
AlloDOM
presented higher reactivity rates than
AutoDOM

Incubation time (days)
DOC
SUVA
a440
Sr
Ruppia
Sediment
River-AU
River-WS
Sampling time
Sampling time
Full transcript