Dr Rob Middag
- Dr Rob Middag
- Tel: (03) 479 7907
- Location: Science II, 3n13
Trace metals in the marine environment.
Our research focusses on the biogeochemistry of trace metals in sea water. This research involves large oceanic expeditions as well as local field work to determine the sources, sinks and cycling of metals in the world’s oceans and seas.
Analysis of dissolved aluminium and manganese with flow injection systems at sea
Biogeochemistry of Trace Metals
Many trace elements are critical for marine life and therefore influence the functioning of ocean ecosystems. For example, iron, zinc and cadmium play a crucial role in the growth of phytoplankton, the microscopic unicellular plants that form the basis of the ocean food chain (primary production). Metals like lead on the other hand, are toxic contaminants, negatively affecting primary production. Through their effect on primary production, trace metals affect the amount of atmospheric CO2 sequestered in the deep ocean via the biological pump, thereby affecting global climate. Other trace metals, together with a diverse array of isotopes, are used to assess modern-ocean processes and the role of the ocean in past climate change. For example, manganese can be used as a tracer of input from hydrothermal vents and the relationships between the metals cadmium, zinc and nickel with the major nutrients nitrate, phosphate and silicate are used to estimate ocean nutrient concentrations in the past. In 2014 we took part in an expedition to the Bellingshausen Sea, west of the Antarctic Peninsula to collect samples for 11 different metals, iron and uranium isotopes as well is iron binding ligands that keep iron in solution. Our most recent cruise was just north of New Zealand and this transect will be repeated in 2016.
Sampling for trace metals in the Titan Ultra-Clean sampling van.
You can see part of the Titan sampling system (white PVDF water samplers and the titanium frame)
and some of the sample bottles to be filled with a sub-sample of water for a variety of parameters.
We have several flow injection systems that can be used to determine concentrations of iron, manganese and aluminium while at sea. Moreover, we have a SeaFAST system, an ultra clean, low pressure ion chromatography system for seawater extraction and a High Resolution Sector Field Inductively Coupled Mass Spectrometer (Nu Attom). The SeaFAST is an automated system that buffers a small volume (typically 10-20 mL) of seawater to a pH of 6 before it is loaded onto a column containing a chelating resin. The resin binds the trace metals in the sample, but not the sea salts that cause interfere with the measurements on the mass spec. Additionally, the sample gets pre-concentrated as volume of the sample decreases by 5-50 fold, depending on the volume of seawater passed over the resin and the volume of acid used to elute the metals of the resin. This way we can accurately and precisely determine the low levels of metals that occur in the open ocean to study their distribution in influence on the marine ecosystem.
PhD Projects available!
Please contact me if you are interested in conducting a PhD in this research area. Scholarships are available for international and domestic students. The next research cruise will probably be north of New Zealand.
Mari112: Global Marine Systems
CHEM 201: Physical and Environmental Chemistry
CHEM 204: Environmental Chemistry
CHEM 304: Environmental Chemistry (Coordinator)
CHEM 400 (Honours Module): Chemical Oceanography
|Dec 2012-present||Lecturer Chemical Oceanography at the University of Otago|
|Oct 2010-Nov 2012||Joint post doc with prof de Baar (Royal Netherlands Institute for Sea research; NIOZ) and prof Bruland (University of California Santa Cruz) stationed in Santa Cruz (USA)|
|Oct 2006-Sept 2010||PhD student with prof de Baar (NIOZ, the Netherlands)|
|Aug 2010-Sept 2006||Undergraduate and Msc in Marine Biology at the University of Groningen (the Netherlands)|
See http://www.researchgate.net/profile/Rob_Middag for full list of publications
Peer reviewed papers
- Rijkenberg, M.J.A., de Baar, H.J.W., Bakker, K., Gerringa, L.J.A., Keijzer, E., Laan, M., Laan, P., Middag, R., Ober, S., van Ooijen, J., Ossebaar, S., van Weerlee, E.M. and Smit, M.G., 2015. “PRISTINE”, a new high volume sampler for ultraclean sampling of trace metals and isotopes. Marine Chemistry, http://dx.doi.org/10.1016/j.marchem.2015.07.001.
- Middag, R., Seferian, R., Conway, T. M., John, S. G., Bruland, K. W. & de Baar, H.J.W., 2015. Intercomparison of Dissolved Trace Elements at the Bermuda Atlantic Time Series Station. Marine Chemistry, http://dx.doi.org/10.1016/j.marchem.2015.06.014.
- The GEOTRACES group (Middag, R. 1 of 135 authors), 2015. The GEOTRACES Intermediate Data Product 2014. Marine Chemistry, http://dx.doi.org/10.1016/ j.marchem.2015.04.005.
- Rolison, J.M., Middag, R., Stirling, C.H., Rijkenberg, M.J.A., de Baar, H.J.W., 2015. Zonal distribution of dissolved aluminium in the Mediterranean Sea. Marine Chemistry. http:// dx.doi.org/10.1016/j.marchem.2015.05.001.
- Middag, R., van Hulten, M.M.P., van Aken, H.M., Rijkenberg, M.J.A., Gerringa, L., Laan, P. and de Baar, H.J.W., 2015. Dissolved aluminium in the Ocean Conveyor of the West Atlantic Ocean: effects of the biological cycle, scavenging, sediment resuspension and hydrography. Marine Chemistry, http://dx.doi.org/10.1016/j.marchem.2015.02.015.
- Dulaquais, G., Boye, M., Middag, R., Owens, S., Puigcorbe, V., Buesseler, K., Masqué, P., de Baar, H.J.W. and Carton, X., 2014. Contrasting biogeochemical cycles of cobalt in the surface western Atlantic Ocean. Global Biogeochemical Cycles: 2014GB004903.
- van Hulten, M.M.P., Sterl, A., Middag, R., de Baar, H.J.W., Gehlen, M., Dutay, J.C., Tagliabue, A., 2014. On the effects of circulation, sediment resuspension and biological incorporation by diatoms in an ocean model of aluminium. Biogeosciences, 11, 3757–3779, 2014.
- Rijkenberg M.J.A., Middag R., Laan P., Gerringa L.J.A., van Aken H.M. Schoemann, V., de Jong, J.T.M., de Baar, H.J.W., 2014. The Distribution of Dissolved Iron in the West Atlantic Ocean. PLoS ONE 9(6): e101323. doi:10.1371/journal.pone.0101323
- Klunder, M.B., Laan, P., De Baar, H.J.W., Middag, R., Neven, I. and Van Ooijen, J., 2014. Dissolved Fe across the Weddell Sea and Drake Passage: impact of DFe on nutrient uptake. Biogeosciences, 11(3): 651-669.
- Abouchami, W., Galer, S.J.G., de Baar, H.J.W., Middag, R., Klunder, M., Mezger, K., Feldmann, H., Andreae, M.O., Vance, D., Zhao, Y., 2014. Biogeochemical cycling of cadmium isotopes in the Southern Ocean along the Zero Meridian. Geochimica et Cosmochimica Acta 127, 348-367.
- Xue, Z., Rehkämper, M., Horner, T.J., Abouchami, W., Middag, R., van de Flierdt, T., de Baar, H.J.W., 2013. Cadmium isotope variations in the Southern Ocean. Earth and Planetary Science Letters 382, 161-172.
- Middag, R., De Baar, H.J.W., Klunder, M.B., Laan, P., 2013. Fluxes of dissolved aluminum and manganese to the Weddell Sea and indications for manganese co-limitation. Limnology and Oceanography 58 (1), 287-300.
- Bruland, K.W., Middag, R., and Lohan, M.C., 2014. 8.2 - Controls of Trace Metals in Seawater. In: H.D. Holland and K.K. Turekian (Editors), Treatise on Geochemistry (Second Edition). Elsevier, Oxford, pp. 19-51.
- Research Cruises
- ANTXXII/3 from 18-Jan-2005 until 6-Apr-2005 aboard R.V. Polarstern to the Southern Ocean (from Cape Town (South Africa) to Punta Arenas (Chile) through the Weddell Sea).
- IPY/GEOTRACES test cruise between April 11 and April 26, 2007 aboard R.V. Pelagia, in the North East Atlantic Ocean off the coast of Portugal.
- IPY-GEOTRACES expedition ARK XXII/2 aboard R.V. Polarstern from 28 July until 07 October 2007 from Tromsø (Norway) to Bremerhaven (Germany).
- IPY-GEOTRACES expedition ANT XXIV/3 aboard R.V. Polarstern from 10 February until 16 April 2008 from Cape Town (South Africa) to Punta Arenas (Chile) through the Weddell Sea.
- Dutch GEOTRACES test cruise aboard R.V. Pelagia from April 22-28 2010. Cruise from Texel (the Netherlands) to Scrabster, Scotland to test the newly develop sampling bottles to replace the GO-FlO’s for trace metal clean samples.
- Dutch GEOTRACES West Atlantic expedition leg 1 64 PE 319 aboard R.V. Pelagia from April 30 till May 25 2010, from Iceland to Bermuda.
- Dutch GEOTRACES West Atlantic expedition leg 2 64 PE 321 aboard R.V. Pelagia from June 12 till July 7 2010, Bermuda to Fortaleza (Brasil).
- Dutch GEOTRACES West Atlantic expedition leg 3 JC0057 from March 1 till April 6 2011, Punta Arenas (Chile) to the Canary Islands aboard the RRS James Cook.
- Dutch GEOTRACES Mediterranean expedition leg 1 64 PE 370 aboard R.V. Pelagia from May 7th 2013 till June 6th, Texel (the Netherlands) to Istanbul (Turkey).
- Phantastic II expedition to the Bellingshausen Sea (Antarctica) NBP 14-09 (B-244) aboard R.V. Nathaniel B Palmer from October 26 2014 till November 26 2014.
- Cross Shelf Exchange voyage TAN1506 aboard R.V. Tangaroa crossing the continental shelf from the Hauraki Gulf into the Pacific Ocean from May 3 till May 22 2015.
The all-titanium ‘Titan’ Ultra-Clean sampling system for trace metals coming on deck after
a deep deployment in the Atlantic Ocean aboard RV Pelagia.
In this picture: Patrick Laan (yellow helmet, Royal Netherlands Institute for Sea Research),
Rob Middag (red jacket), Jeroen de Jong (bottom of the picture, Université Libre de Bruxelles)
and Cor Stevens (Pelagia technician)