Global Nutrient Fluxes at the Land-Ocean Interface (G-NUX)

(2005-2009)

Introduction

Nutrient availability is a key control of ocean carbon cycling and atmospheric CO₂ . Rivers and groundwater discharge are major sources of nutrients to coastal waters. Studies so far focused on quantifying riverine fluxes of nutrients and deriving empirical relationships between these fluxes and possible controlling factors.

In this joint project of the Departments of Physical Geography and Earth Sciences – Geochemistry, we will develop spatially-explicit, process-based models of particulate-bound and dissolved nitrogen and phosphorus fluxes along the terrestrial water cycle and at the land-ocean interface.

Objectives are to assess

(1) the controls on both river and groundwater fluxes

(2) their impact on coastal biological productivity

Regional models will be calibrated for well-documented river basins and adjacent coastal waters. By combining available global databases with these models, we will estimate global-scale nutrient fluxes to coastal waters and their impact on primary productivity. Finally, we will assess the effects of global change (climate, population, land-use) on these fluxes and the implications for the marine carbon cycle.

This project provides employment for 4 researchers:

Sibren Loos (PhD) Nutrient dynamics in large river basins (Physical Geography)
Aim: to analyse, model and identify the major controls of the transport of N and P from point and diffuse emission sources through selected major river basins towards the coastal zone.
Approach: establishment of a Geographical Information System (GIS) for a set of well-documented river systems, development of a spatially-distributed process-based model using PCRaster (link), assessment of the sensitivity of total annual nutrient fluxes to global change.

Hans Duerr (Postdoc) Global nutrient fluxes at the land-ocean interface: quantification and analysis of controls (Physical Geography)
Aim: to estimate global, spatially-explicit river and groundwater fluxes of nutrients (N, P and Si) to the coastal zone, and to assess the response of these fluxes to global change.
Approach: extrapolation of regional data to the global scale using global databases and modeling.

Goulven Laruelle (PhD). Regional impact of changes in terrestrial nutrient fluxes to coastal waters (Geochemistry)
Aim: to develop a generic, regional coastal zone model to assess the impact of human-induced changes in riverine and groundwater nutrient inputs on regional coastal nutrient and carbon cycling. The model should also form the basis for a coastal zone module in an Earth System Model.
Approach: extension of existing biogeochemical models describing coastal zone nutrient dynamics and assessment of the sensitivity to changes in nutrient fluxes.

Iana Tsandev (PhD). Global impact of changes in terrestrial nutrient fluxes to the ocean (Geochemistry)
Aim: to evaluate the global impact of natural and human-induced changes in terrestrial nutrient fluxes from rivers and groundwater on nearshore and oceanic C, N and P cycles on decadal to millennial time scales.
Approach: modification of existing box models and global oceanic circulation models for C and nutrient cycling in the oceans and assesment of the sensitivity to changes in global nutrient cycles.

For further information contact:

Caroline Slomp ( slomp@geo.uu.nl ) or +31-(0)30-2535514

Hans Middelkoop ( h.middelkoop@geog.uu.nl ) or +31-(0)30-2532167

(Inter-)national partners (selection)

• Participants IGBP-LUCIFS

• Participants EU-RTN Siwebs

• Prof. Dr. S. Kempe, TU Darmstadt

• Dr. C. Kroeze, Wageningen University , the Netherlands

• Prof. Dr. M. Meybeck, Paris.

• Prof. Dr. C. Heinze, Univ. of Bergen, Norway.

Key references

Asselman, NEM, Middelkoop, H & Van Dijk, PM. The impact of climate change on soil erosion, transport and deposition of suspended sediment in the river Rhine . Hydrological Processes 17 , 3225-3244 (2003).

Brovkin, V et al. Carbon cycle, vegetation, and climate dynamics in the Holocene: Experiments with the CLIMBER-2 model. Global Biogeochemical Cycles 16 , Art. no. 1139 (2002).

Caraco , NF . Influence of human populations on P transfers to aquatic systems: a regional scale study using large rivers in Phosphorus in the global environment. Transfers, Cycles and Management. (ed. Tiessen, H.) 235-244 (Wiley, 1995).

De Wit, MJM. Nutrient fluxes in the Rhine and Elbe basins. PhD-thesis. Nederlandse Geografische Studies 259: 176 (Utrecht University, 1999).

Handoh, IC & Lenton, TM. Periodic mid-Cretaceous oceanic anoxic events linked by oscillations of the phosphorus and oxygen biogeochemical cycles. Global Biogeochemical Cycles 17 , art. no.-1092 (2003).

Humborg, C et al. Silica retention in river basins: far reaching effects on biogeochemistry and aquatic food webs. Ambio 29 , 45-50 (2000).

Lancelot, C et al. Modelling the Danube-influenced North-western Continental Shelf of the Black Sea . II: Ecosystem Response to Changes in Nutrient Delivery by the Danube River after its Damming in 1972. Estuarine, Coastal and Shelf Science 54 , 473-499 (2002).

Meybeck, M. Carbon, nitrogen, and phosphorus transport by world rivers. American Journal of Science 282 , 401-450 (1982).

Middelkoop, H & Van der Perk, M. Modelling spatial patterns of overbank sedimentation on embanked floodplains. Geografiska Annaler 80A , 95-109. (1998).

Rabouille, C, Mackenzie, FT & Ver, LM. Influence of the human perturbation on carbon, nitrogen, and oxygen biogeochemical cycles in the global coastal ocean. Geochimica Et Cosmochimica Acta 65 , 3615-3641 (2001).

Seitzinger, SP et al. Global patterns of dissolved inorganic and particulate nitrogen inputs to coastal systems: Recent conditions and future projections. Estuaries 25 , 640-655 (2002).

Slomp, CP & Van Cappellen, P. Groundwater inputs of nutrients to the coastal ocean: controls and potential impact. Journal of Hydrology 295 , 64-86 (2004).

Van Drecht, G et al. Global modeling of the fate of nitrogen from point and nonpoint sources in soils, groundwater, and surface water. Global Biogeochemical Cycles 17 , Art. No. 1115 (2003).