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: Algorithm finds missing phytoplankton in Southern Ocean

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

Tracking giant kelp from space

2 hours ago

Citizen scientists worldwide are invited to take part in marine ecology research, and they won't have to get their feet wet to do it. The Floating Forests project, an initiative spearheaded by scientists ...

Heavy metals and hydroelectricity

3 hours ago

Hydraulic engineering is increasingly relied on for hydroelectricity generation. However, redirecting stream flow can yield unintended consequences. In the August 2014 issue of GSA Today, Donald Rodbell of ...

What's wiping out the Caribbean corals?

4 hours ago

Here's what we know about white-band disease: It has already killed up to 95 percent of the Caribbean's reef-building elkhorn and staghorn corals, and it's caused by an infectious bacteria that seems to be ...

User comments : 0