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

Monitoring heavy metals using mussels

1 hour ago

A research team in Malaysia has concluded that caged mussels are useful for monitoring heavy metal contamination in coastal waters in the Strait of Johore. Initial results indicate more pollution in the eastern ...

Climate change report identifies 'the most vulnerable'

3 hours ago

Extreme weather events leave populations with not enough food both in the short- and the long-term. A new report by the Environmental Change Institute (ECI) at the School of Geography and the Environment ...

Obama readies climate change push at UN summit

6 hours ago

President Barack Obama will seek to galvanize international support in the fight against climate change on Tuesday when he addresses the United Nations, with time running out on his hopes of leaving a lasting ...

New toxic spill traced to Mexico mine

6 hours ago

Civil protection authorities have confirmed new toxic spills in northwestern Mexico, where a massive acid spill from a copper mine contaminated waterways.

User comments : 0