Dr Alwyn Rees

BSc Liverpool
PhD Wales

Contact details
Phone: +64 9 373 7599 ext 83603
Email: ta.rees@auckland.ac.nz

Seaweeds exhibit an extraordinary range of size, morphology, structural complexity, productivity and life histories. In addition, they are important primary producers in coastal and estuarine ecosystems. For example, annual production of dry matter per unit area by intertidal seaweeds on exposed shores can exceed that of tropical rain forests or grasslands. However, this productivity can only be sustained through the acquisition and utilization of nutrients, particularly nitrogen and phosphorus. My main concerns are to understand the relationship between size, morphology and metabolism together with the ecophysiological mechanisms involved in seaweed growth, in particular the role of nutrients.

Specific areas of interest include the following:

Relationship between mass, surface area, volume, biochemical composition and metabolism in New Zealand seaweeds
Seaweeds have a range of size and morphologies from small filamentous to large laminate species. How does size and morphology influence the composition and metabolism of seaweeds?

Ammonium assimilation, phosphate uptake and growth rate in seaweeds
Assimilation of ammonium and uptake of phosphate are inhibited by methionine sulphoximine and furosemide, respectively. What is the effect of inhibitor titration (i.e. the increasing partial inhibition of ammonium assimilation and phosphate uptake) on growth rate in seaweeds?

The role of hyaline hairs in nutrient acquisition by seaweeds
Many seaweeds produce hyaline hairs and there is good evidence that they are involved in nutrient uptake. However, the mechanism(s) by which nutrients are transported from the hair (which can be up to 4 mm in length) to the thallus requires investigation. In addition, can hyaline hair characteristics be used to determine the nutrient status of seaweeds?

The physiology of reproduction in brown seaweeds
Of particular interest is the identity of the nutrient that limits gamete production and what controls the proportion of limiting nutrient released as gametes. Moreover, our understanding of reproduction in New Zealand brown seaweeds is very limited and, consequently, there are numerous opportunities to enhance our knowledge of the general biology of reproduction in this ecologically important group of algae.

• BEARDALL J., ALLEN, D., BRAGG, J., FINKEL, Z.V., FLYNN, K.J., QUIGG, A., REES, T.A.V., RICHARDSON, A. & RAVEN, J.A. (2009) Tansley Review. Allometry and stoichiometry of unicellular, colonial and multicellular phytoplankton organisms. New Phytologist 181, 295-309.
• REES, T.A.V. (2007) Metabolic and ecological constraints imposed by similar rates of ammonium and nitrate uptake per unit surface area at low substrate concentrations in marine phytoplankton and macroalgae. Journal of Phycology 43, 197-207.
• GEVAERT, F., BARR, N.G. & REES, T.A.V. (2007) Diurnal cycle and kinetics of ammonium assimilation in the green alga Ulva pertusa. Marine Biology 151, 1517-1524.
• REES, T.A.V., DOBSON, B.C., BIJL, M. & MORELISSEN, B. (2007) Kinetics of nitrate uptake by New Zealand seaweeds and evidence for two nitrate transporters in Ulva intestinalis L. Hydrobiologia 586, 135-141.
• TAYLOR, M.W., BARR, N.G., GRANT, C.M. & REES, T.A.V. (2006) Changes in amino acid composition of Ulva intestinalis (Chlorophyceae) following addition of ammonium or nitrate. Phycologia 45, 270- 276.
• BARR, N.G., TIJSEN, R.J. & REES, T.A.V. (2004) The contrasting effects of methionine sulfoximine on uptake and assimilation of ammonium in Ulva intestinalis. Journal of Phycology 40, 697-704.
• COOKE, R.R.M., HURD, C.L., LORD, J.M., PEAKE, B.M., RAVEN, J.A. & REES, T.A.V. (2004) Iron and zinc content of Hormosira banksii in New Zealand. New Zealand Journal of Marine and Freshwater Research 38, 73-85.
• REES, T.A.V. (2003) Safety factors and nutrient uptake by seaweeds. Marine Ecology Progress Series 263, 29-42.
• BARR, N.G. & REES, T.A.V. (2003) Nitrogen status and metabolism in the green seaweed Enteromorpha intestinalis: an examination of three natural populations. Marine Ecology Progress Series 249, 133-144.