Nutrient dynamics in European water systems Snapshots of ELOISE results

1
Nutrient dynamics in European water systems
(Snapshots of ELOISE results)

• Vincent Escaravage, Peter M.J. Herman,
• and Carlo Heip

2
Eloise from start to present

• ELOISE, a European network for coastal zone
  research focusing on land-ocean interactions, and
  on how this is influenced by human activities.
• Operating since 1996, more than 60 ELOISE
  projects, rendering it the worlds largest
  coastal research initiative.
• ELOISE is intended to contribute directly to
  coastal zone management and spatial planning, and
  thus to European coastal policy.
• ELOISE has now entered a phase where scientific
  results have to be disseminated to all potential
  end-users in ministries to schools.
• All hereto ELOISE relevant material is gathered
  in so called digests. NIOO has compiled a digest
  on nutrient dynamics
• This presentation highlights snapshots from the
  digest

3
Topics addressed by the digest on nutrient
dynamics

• Relating nutrient fluxes to land-based
  activities, atmospheric and river processes
• Nutrient processing in estuaries and coastal
  areas what processes govern the fate?
• Effects of altered nutrient discharges on the
  functioning of coastal and estuarine foodwebs

4
Atmospheric Nutrient Inputs (1.4)

• Remarkable spatial resolution with 17 x 17 km
  boxes
• 30 of nitrogen input to sea comes from the air
• Wet deposition represents 81 of N-deposition
• 38 from agriculture, 72 from combustion sources

Hertel et al (2002)
5
Atmospheric Nutrient Inputs (2.4)

• N-Scavenging by sea salt aerosol
• HNO3NaCl gtNaNO3 HCl
• N-deposition enhanced by land-sea transition

From coast to sea
de Leeuw et al (2001)
6
Atmospheric Nutrient Inputs (3.4)

• Large deposition of nitrogen may occur during
  short periods (de Leeuw et al., 2003)
• Kattegat Strait events of high deposition
  increase chlorophyll by 20 (Hasager et al.,
  2003)
• About 30 of new production off Ireland supported
  by atmospheric N-inputs in May 1997 (Spokes et
  al, 2000)
• 38 of summer new production off Creta sustained
  by P-deposition (Markaki et al., 2003)

de Leeuw et al (2003)
7
Atmospheric Nutrient Inputs (4.4)

• Assessment of nutrient deposition requires a fine
  grided model dynamically coupled with a
  meteorological model.
• Efforts to be deployed Europe-wide instead of
  focus on North Sea and NW Mediterranean Sea.
• Both N and P-deposition to be addressed by
  monitoring efforts.

de Leeuw et al (2003)
8
River nutrient inputs (1.4)

• A full deterministic model was developed (INCA)
  to track N-fluxes.
• An independent P-version of INCA has also been
  developed (Wade et al., 2002b).
• All nutrient sources have to be individually
  measured
• Allow predictions on effects of changing policies
  (Jarvie et al., 2003)

Wade et al (2002a)
9
River nutrient inputs (2.4)
Garnier et al (2002)

• Other models make use of statistical rules and
  fuzzy logics (RIVERSTRAHLER, SOIL/SOILN).
• Less direct measurements are needed
• Lower computational demand allows combined N-P
  tracking in ecological coupled processes
• Most of N-retention occur when agricultural leach
  passes through riparian wetlands (Billen
  Garnier, 2000)
• But low predictive power for changes in
  individual sources

Forsman et al (2003)
10
River nutrient inputs (3.4)

• Residence time in upper aquifer 1-2000 yrs
  (Kunkel Wedland, 1997).
• Fertilizers added last century will continue to
  leach from aquifers to rivers for decades
  (Grimval et al., 2002)
• Significant amounts of nutrients are directly
  brought from groundwater to the sea (Gregerson,
  2003)

11
River nutrient inputs (4.4)

• Present models deserve conceptual refinements
• dynamic coupling with biological processes
• incorporation of major macronutrient (N,P,Si) and
  organic matter.
• merging of deterministic and statistic approaches
• incorporation of a groundwater module

Garnier et al (2002)
12
Fate of nutrients in coastal areas (1.6)

• Black Sea P, Si benthic regeneration is in the
  same range as Danube discharge, but intense
  denitrification occurs (Friedl et al., 1996).
• Intense nutrient regeneration sustains the high
  productivity in the Black Sea coastal zone
  (Friedrich et al., 2002)

Friedrich et al (2002)
13
Fate of nutrients in coastal areas (2.6)

• Benthic Fe and Ca act as buffer pools that
  sequester P, not available for primary production
  (de Wit et al. 2001)
• Increasing nutrient loadings push the system
  towards reduced states (Wijsman et al, 2002).
• Eventually toxic H2S and Ca/Fe-bound P are
  released (Heijs et al., 2000)
• Benthic system reaches a new stable state, highly
  reactive to nutrient enrichments (Heijs et al.,
  2000)

Stable states

• Sediment
• Buffering

H2S
Nutrient enrichment
Wijsman et al (2002)
14
Fate of nutrients in coastal areas (3.6)

• Empirically calculated denitrification rates
  f(NO3,O2) are no more accurate when micro/macro-
  benthic algae and/or macrofauna are active
  (Nielsen et al., 2001)
• Without model improvement, nitrogen retention
  should still been estimated by either mass
  balance or in situ direct measurements (Nielsen
  et al., 2001).
• Recently developed (N15 isotope pairing)
  technique allow to tightly track nitrogen
  transformation pathways (Risgaard-Petersen et
  al., 1998)
• Newly evidenced processes (DNRA, AMMANOX) are
  alternative pathways for denitrification (Welsh
  et al., 2001, Dalsgaard Thamdrup, 2002)

1.-Denitrification 2.-DNRA 3.-Nitrification
Kelso et al. (1997)
AMMANOX
15
Fate of nutrients in coastal areas (4.6)
Denitrification Nitrification

• Micro-algae efficiently incorporate mineralized
  nitrogen that is no more available to bacteria
  for denitrification
• The auto/heterotrophy of the system determines
  whether it acts as a sink or source of nutrients.
• (Risgaard Petersen, 2003)

16
Fate of nutrients in coastal areas (5.6)

• Seagrass beds act as N-sink biomass is
  eventually buried or exported (Welsh et al,
  2000).
• Denitrification is at low rates in seagrass beds
  but chemistry there is far to be understood
  (Welsh et al., 2001)

Welsh et al (2000)
17
Fate of nutrients in coastal areas (6.6)

• Much knowledge has been gathered on benthic
  nutrient fluxes that cannot be analytically
  solved with a single set of chemical equations
• Current progresses at the frontline of process
  modeling are developing the tools that will allow
  this integrative step (Meysman et al., 2003a,b)

Overview of different object types building
blocks within the MEDIA object orientated
modeling environment (Meysman et al., 2003a).
18
Effect of altered nutrient discharges on coastal
and estuarine food webs (1.4)

• A generic size structured food web model captured
  the patterns for scaled ecosystem experiments
  performed throughout Europa.
• Efficiency of the top-down control determines
  when nutrient accumulate in vegetal biomass or
  reach higher trophic levels.
• (Olsen et al., 2001)

19
Effect of altered nutrient discharges on coastal
and estuarine food webs (2.4)

• Six-fold increase of the non-diatom bloom
  (1960/1992) in Black Sea with increased nitrogen
  discharge (Humborg et al., 1997).
• Unbalanced nutrient additions (NP,Si) to North
  Sea ecosystem induce Phaeocystis colony blooms,
  not grazed by copepods (Rousseau et al., 2000).
• Field observations (Gasparini, 2000) and mesocosm
  experiments (Escaravage Prins, 2002) suggest
  efficient grazing on Phaeocystis cells by
  ciliates after collapse of the colony bloom

Rousseau et al (2000)
Escaravage Prins (2002)
20
Effect of altered nutrient discharges on coastal
and estuarine food webs (3.4)

• Balanced N/P discharges to the Black Sea (1991)
  promote the diatom-copepod food chain (preferred
  food for fish).
• Microbial food web predominates when nitrogen is
  provided in excess (1985)
• (Lancelot et al., 2002)

21
Effect of altered nutrient discharges on coastal
and estuarine food webs (4.4)
Detritus

• Acute eutrophication effects on benthic fauna
  through habitat alteration are rather well
  documented (Pearson Rosenberg, 1978).
• The effects on benthic food web functioning are
  far less understood
• Tracer experiments show that benthic organisms
  primarily feed on fresh vegetal matter rather
  than detritus (Herman et al., 2000)
• Macrofauna biomass also show a tight link with
  benthic primary production (Herman et al., 2000).

Microphytobenthos
Phytoplankton
22
Integrating knowledge and skills for modeling at
scale of basins

• The most complex models may not always be the
  most suitable lower boundary levels has to be
  considered regarding the question to be addressed
  (Soetaert et al., 2000).
• Simple LOICZ-type box models are well suited for
  large scale (e.g. ocean margin) nutrient budgets
  (Durrieu de Madron, 2003).
• When processes within the coastal systems are
  addressed, more complex models may be required
  (Soetaert et al., 2000).

Scheme for a fully coupled model (Soetaert et
al., 2000)