Monthly Archives: February 2008

Flood waters on the Great Barrier Reef – a report from the Keppels

Posted on by
Reply

On the topic of Great Barrier Reef flood waters posted last week, a rapid response team from my lab, headed by Dr Guillermo Diaz-Pullido and backed by the remote sensing capabilities of Dr Scarla Weeks was busy conducting coral and algal surveys in the Keppels region to determine baselines of coral health before the flood waters hit the reef. Dr Diaz-Pullido and two volunteers (Pim Bongaerts and Norbert Englebert) joined researchers from JCU to determine levels of coral and algae at reefs across the region. Flying out from Rockhampton over the ever rising flood waters confirmed the MODIS satellite images (see bottom left), and shows the level of water damage to the region (see centre): the waters were clearly heading outwards of the reef forming a freshwater lens (see bottom right picture).

Satellite image showing the Fitzroy river (Jan 21st 2008) View of the Fitzroy River in full flood (22nd Jan 2008) Flood plume extending out to the inshore reefs (22nd Jan 2008)

 

As a bit of background to this region: the Fitzroy catchment at nearly 150,000km2 is the largest of the Great Barier Reef, and is dominated by agriculture (grazing, irrigated cotton and horticulture) and by mining (coal production of 100 million tonnes/year, magnesite and nickel), and significant flooding events have been recorded in 1918, 1954, 1978, 1983, 1988 and 1991 (see below from the Bureau of Meterology). The ABC News site has some astounding images from the 2008 flood here.

 

Following the high levels of rainfall in January this year, many have predicted significant flooding and impacts to the inshore coral reefs of the Keppel region. Such disturbances are far from unusual in the Keppels – in 1991, over 85% of coral in shallow reefs died following severe flood events, and again on November 2006, significant mortality occured within 8 hours on the reef flats in the Keppels due to a lethal combination of high rainfall and low tides.

The team surveyed shallow and deep reefs of five islands using belt transects, including more than 300 1×1 m photo quadrats. At the time of the surveys, the freshwater plume from the Fitzroy River had already reached the leeward side of some islands, although at the time of surveying Dr Diaz-Pullido reported no visible impacts on the coral reef benthic community. Benthic macroalgae (seaweeds) usually colonise weakened and dead corals, and during the last coral beaching event in 2006, seaweeds experienced an unprecedented macroalgal bloom. Despite the severity of these disturbances and algal blooms, many coral reefs of the area have recovered and currently flourish (see images below)

 

Dr Guillermo Diaz Pullido surveying coral and algal cover prior to the flooding Research assistants Pim Bongaerts and Norbert Englebert collect algal samples Healthy inshore reefs at the Keppels with high coral cover (Acropora sp.

 

The impacts on the reef communities will depend on the residence time of the freshwater plume on the area, the nature and quantity of the sediments and contaminant associated. The team are closely monitoring the oceanographic and meteorological patterns, and depending on the developments of the plume, the research team will head back to the Keppel Islands in the coming weeks. The offshore surface flow in the region is strongly influenced by wind direction, whilst surface flow is primarily offshore (cross-shelf) limited in offshore extent by the frontal boundary created by inflow of oceanic waters due to eddy dynamics further south. Therefore, the Fitzroy outflow will be deflected to the left due to geostrophy (due to rotation of the Earth ) moving along this front.

Coral Reefs May Be Protected By Natural Ocean Thermostat

Posted on by
1

Science Daily, Feb 8th 2008

Natural processes may prevent oceans from warming beyond a certain point, helping protect some coral reefs from the impacts of climate change, new research finds. The study, by scientists at the National Center for Atmospheric Research (NCAR) and Australian Institute of Marine Science (AIMS), finds evidence that an ocean “thermostat” appears to be helping to regulate sea-surface temperatures in a biologically diverse region of the western Pacific.

The research team, led by NCAR scientist Joan Kleypas, looked at the Western Pacific Warm Pool, a region northeast of Australia where naturally warm sea-surface temperatures have risen little in recent decades. As a result, the reefs in that region appear to have suffered relatively few episodes of coral bleaching, a phenomenon that has damaged reefs in other areas where temperature increases have been more pronounced.

The study lends support to a much-debated theory that a natural ocean thermostat prevents sea-surface temperatures from exceeding about 88 degrees Fahrenheit (31 degrees Celsius) in open oceans. If so, this thermostat would protect reefs that have evolved in naturally warm waters that will not warm much further, as opposed to reefs that live in slightly cooler waters that face more significant warming.

“Global warming is damaging many corals, but it appears to be bypassing certain reefs that support some of the greatest diversity of life on the planet,” Kleypas says. “In essence, reefs that are already in hot water may be more protected from warming than reefs that are not. This is some rare hopeful news for these important ecosystems.”

Continue reading →

Floodwaters ‘threatening Great Barrier Reef’

Posted on by
2

Brisbane Times (29th Jan 2008)

Scientists from across Queensland are converging on the mouth of the Fitzroy River in Rockhampton over fears that sediment and toxic chemicals carried by floodwaters in central Queensland now reaching the ocean may damage the Great Barrier Reef.

Marine scientists from James Cook University, the Queensland Environmental Protection Agency and the Department of Natural Resources will be collecting water samples, measuring flow rates and diving on the reef to assess its condition first hand.

Dr David Haynes, acting director of water quality and the Coastal Developmental Unit of the Great Barrier Reef Marine Park Authority, said that sediment could pose a significant threat to the health of the reef.

“The main problem with sediment is one of the things it will do is settle on coral and physically smother them in high enough concentrations,” he said.

“It can also make the water highly turbid and reduce the amount of light that can penetrate through the water and corals are very dependent on light to obtain food; they use algae in their cells to manufacture food.

“If the corals are in dirty water then the coral’s food source is cut off for as long as the water is dirty.”

Continue reading →

More on sunscreen and coral bleaching

Posted on by
Reply

Here is an excerpt from a recent news article (click below for full story):

Sunscreen may be killing corals

Cosmos, Monday 4th October

Some experts are yet to be persuaded by the findings, however.

“Any contaminant can experimentally damage a coral under artificially high concentrations. The amount [in the wild] must be tiny due to dilution,” commented Terry Hughes, director of the Australian Research Council’s Centre of Excellence for Coral Reef Studies at James Cook University in Queensland.

“Imagine how much water a tourist wearing one teaspoon of sunscreen swims through in an hour-long snorkel. Compared to real threats like global warming, runoff and overfishing, any impact of sunscreen is unproven and undoubtedly trivial,” he said.

However, Pusceddu argued that the coral response to sunscreen exposure was not dose dependent, “The mechanism appears to be on-off: thus once the virus has been switched on by [the chemicals in] sunscreen, toxicity is irrelevant.”

Ove Hoegh-Guldberg, director of marine studies at the University of Queensland in Brisbane, said the study is interesting, but notes that many factors are likely to be responsible. “Bleaching is like a runny nose: there are lots of things that could cause it.”

Though sunscreens may contribute to coral death, virus-caused bleaching is only a small part of the big picture, he said: “Climate related bleaching is a direct consequence of heat stress and does not involve viruses or bacteria.”

Coral reefs and climate change

Posted on by
Reply

A colleague of mine, Dr John Bruno forwarded me an excellent article that he wrote for The Encyclopedia of the Earth, titled “Coral Reefs and Climate Change”

“A healthy reef ecosystem literally buzzes with sounds, activity and colors and is populated by incredibly dense aggregations of fish and invertebrates. In this respect, tropical reefs are more reminiscent of the African Serengeti than of the tropical rainforest they are often compared to, where the resident birds and mammals can be secretive and difficult to see. A coral reef can contain tens of thousands of species and some of the world’s most dense and diverse communities of vertebrate animals. Unfortunately, very few remaining coral reefs resemble this pristine condition; on most, corals and fishes are much less abundant than they were only a few decades ago”

John’s expert write-up and summary of threats to coral reefs related to climate change (coral bleaching, disease, ocean acidification) provides an excellent background of the literature and current threats, and is a worthy read for scientists, managers and the general public alike.

Healthy Great Barrier Reef reefscape A recovering Jamaican coral reef Bleached corals off Puerto Rico in 2005

 

2005 a deadly year for Caribbean coral

Posted on by
Reply

Following close on the heels of IUCN report …

PARIS (AFP, Jan 28 2008) — The Caribbean’s fragile coral reefs were devastated in 2005 by a doubly whammy of record-high temperatures and 13 full-on hurricanes, according to a UN-sponsored report released Monday.During the last 50 years many Caribbean reefs have lost up to 80 percent of their coralacp-palmata.jpg cover, damaging or destroying the main source of livelihood for hundreds of thousands of people, said the report, prepared by a team of scientists and experts at the Global Coral Reef Monitoring Network.

The study was jointly sponsored by UNESCO and the Intergovernmental Oceanographic Commission.

Coral-based ecosystems are extremely sensitive to temperature increases, which have led over the last 50 years to massive bleaching — affecting up to 95 percent of the reefs around some islands, including the Cayman Islands, Jamaica, Cuba, and the French West Indies.

2005 was the warmest year since records were first kept in 1880, and global warming is likely to increase in years to come, climate scientists have warned.

Continue reading →