Algae declines in the water off Sydney

Mar 10, 2014
Electron microscope image of mixed phytoplankton taken from the coastal waters of southeastern Australia. Credit: Dr Penelope Ajani.

(Phys.org) —One of the longest time-series of phytoplankton (microalgae) data in the Southern Hemisphere has revealed that phytoplankton are declining in the waters off Sydney.

Phytoplankton are microscopic plants whose growth produces almost half of the world's oxygen, and supports the entire marine food chain. They can also result in blooms, including 'red tides'. They are closely linked to the climate system due to their sensitivity to ocean circulation and nutrient availability. Global warming may cause changes in phytoplankton abundance and diversity, and as such they are important indicators of climate-change effects on marine ecosystems.

"We know that the of southeast Australia have undergone significant climate-related changes over the past 60 years", says Dr Penelope Ajani from Macquarie University.

"We wanted to assess the effects of these changes on the phytoplankton".

For more than 10 years, Dr Ajani and colleagues have been collecting phytoplankton data from a monitoring station offshore from Sydney.

"We examined 11 years of samples. Our data confirmed the seasonal pattern of peak diversity in winter, and also that occur most consistently in March, September and December.

"Unexpectedly, we also observed a significant decline in total phytoplankton numbers over this eleven-year period. This decline in abundance was associated with a decline in water temperature."

Fellow researcher Dr Andrew Allen said: "What these findings tell us is that, although there has been a long-term increase in water temperature in our coastal waters, shorter-term fluctuations can and do occur.

"Such fluctuations significantly affect the , and therefore may have important implications for the entire marine ecosystem".

The phytotplankton dataset collected and analysed for this study represents one of the longest time series in the Southern Hemisphere. It therefore represents an important baseline for assessing the effects of future climate change on .

Explore further: One-celled plants key to understanding changes in the great lakes

More information: The paper "A decadal decline in relative abundance and a shift in microphytoplankton composition at a long-term coastal station off southeast Australia," in Limnology and Oceanography is available here: aslo.org/lo/toc/vol_59/issue_2/0519.pdf

add to favorites email to friend print save as pdf

Related Stories

Earth from Space: A southern summer bloom

Jan 16, 2012

(PhysOrg.com) -- In this Envisat image, a phytoplankton bloom swirls a figure-of-8 in the South Atlantic Ocean about 600 km east of the Falkland Islands.   During this period in the southern hemisphere, ...

Image: Phytoplankton Bloom in the Norwegian Sea

Jul 16, 2013

(Phys.org) —The waters off Iceland rank among the world's most productive fisheries. The reason for the abundance is an ample supply of phytoplankton, the base of the marine food chain. Like any plant, ...

Recommended for you

Coal-rich Poland ready to block EU climate deal

3 hours ago

European Union leaders meeting in Brussels to set their new greenhouse gas emissions plan are facing staunch opposition from coal-reliant Poland and other East European countries who say their economies would ...

EU leaders seek last-minute climate deal

8 hours ago

European Union leaders came under pressure Thursday to strike a deal aimed at bolstering Brussels as a trailblazer in fighting global climate change as negotiations went down to the wire.

Research team studies 'regime shifts' in ecosystems

10 hours ago

The prehistory of major ecological shifts spanning multiple millennia can be read in the fine print of microscopic algae, according to a new study led by researchers at the University of Nebraska-Lincoln.

User comments : 0