Rain "greening up" our coastal waters

Recent above average rainfall in NSW has seen parched inland floodplains rejuvenated with birdlife and farmers anticipating bumper crops for the first time in decades. But the impact is felt far beyond the interior. UTS researchers, recently returned from a 17-day scientific voyage along the South East Coast of Australia, are predicting an explosion of life in the oceans as well.

"It's not only our gardens that are greening up. This amount of rain causes a large increase in runoff into our coastal areas and this is having a big effect on primary productivity in surrounding waters," said Dr Martina Doblin, UTS Senior Research Fellow and Sydney Institute of Marine Science researcher.

Dr Martina Doblin

Dr Doblin was the Chief Scientific Investigator aboard the National Marine Facility Southern Surveyor on a voyage to assess the impact of the East Australian Current (EAC) on primary productivity along the eastern seaboard of Australia. Primary productivity is a term used, in this context, by marine scientists to describe the growth and abundance of phytoplankton that are responsible for more than 40 per cent of global photosynthesis and are the energetic "base" of marine foodwebs.

"Phytoplankton need light and nutrients to grow but over the past 30 years we have seen changes in nutrient concentrations in coastal waters along Australia's east coast which have the potential to limit growth of some phytoplankton. We think this is linked to changes in rainfall or the activity of the EAC, or both," Dr Doblin said.

Like the dust storms last year, land runoff has the potential to introduce nutrients to coastal waters and result in large bursts of phytoplankton growth that provide food for the rest of the marine foodweb, including fish.

Dr Doblin lead a team of scientists from UTS Plant Functional Biology and Climate Change Cluster (C3), CSIRO, UNSW and NSW Department of Environment Climate Change and Water who sampled the river plumes in northern and southern NSW coastal waters and conducted a range of experiments designed to measure the response of natural phytoplankton communities to nutrient inputs.

The team also measured water chemistry and key parameters required to validate remotely sensed data (that estimate ocean colour and productivity from space for ecosystem modelling) along with critical processes associated with the EAC and eddies of the continental shelf region.

They found phytoplankton productivity increased in the vicinity of northern river plumes but was also high in coastal regions experiencing nutrient upwelling. Back in the laboratory, the scientists will now investigate the diversity of phytoplankton communities to better understand its links to productivity.

By bringing together a diverse group of researchers and technologies it is hoped that for the first time linkages can be established between the oceanography, nutrient and light climate and productivity of this important coastal region.