Rising seas could drown turtle eggs: new research


James Whitmore, The Conversation

Immersion in seawater kills sea turtle eggs, suggesting that sea turtles are increasingly at risk from rising seas, according to research published today in Royal Society Open Science.

In a laboratory experiment, researchers immersed green turtle eggs in seawater for varying lengths of time. The researchers tested eggs of various ages, and then counted the number of eggs that hatched. They found that immersion for six hours reduced survival by a third.

The study partly explains reduced numbers turtle of hatchlings recorded at Raine Island, home to the largest population of green sea turtles in the world.

David Pike, lecturer in tropical biology at James Cook University and lead author of the study, said turtle nests low down on beaches could be underwater for six hours during abnormally high “king” tides or storm surges.

Michele Thums, ecologist at the Australian Institute of Marine Science, said that given climate projections for increased severe weather events, this could mean fewer hatchlings survive in the future.

But every beach will see different impacts from rising seas, said Tim Dempster, senior lecturer in marine biology at University of Melbourne.

“You can’t just take [a…] scenario of a certain degree of warming, say that will lead to a certain amount of sea level rise, project how much land will be inundated and then project what proportion of nesting habitat will be affected,” he said.

Turtle embryos need oxygen to develop into baby turtles, and immersion in water prevents oxygen from the soil entering the eggs. The embryos effectively suffocate, a process known as “hypoxia”.

Thums said that while most turtles nest above the high tide line and are rarely immersed for six hours, “there are always inexperienced turtles that will lay further down the beach and also there is competition at high density nesting sites like Raine Island”.

Compared to the rest of the world, green sea turtles on Raine Island have a much lower level of breeding success, which could lead to a large decline in the number of breeding adults in the future.

Pike said the low level of success could be partly explained by inundation, but there were likely other factors at work.

“One possibility is that the sand is full of bacteria from all of the rotting eggs that are beneath the sand, and that any fresh eggs laid there may be exposed to bacteria that overgrow the egg and kill the embryo,” he said.

“Another possibility is that contaminants (heavy metals, pesticides) are being passed from the mother turtle to the eggs, and that may cause the embryos to die.”

The Queensland Department of Environmental Heritage and Protection is currently trying to raise low lying spots on Raine Island by moving sand. The island could lose between 7 and 27% of its area thanks to rising seas.

With Janelle Braithwaite, editor at The Conversation.

The Conversation

James Whitmore is Editor, Environment & Energy at The Conversation.

This article was originally published on The Conversation.
Read the original article.

Following Nemo: marine life is heading south


Tim O'Hara, Museum Victoria

Changing wildlife: this is the first article in a series looking at how key species such as bees, insects and fish respond to environmental change, and what this means for the rest of the planet.

The seas are warming. Collectively the oceans have absorbed more than 80% of the energy retained by the Earth through recent climate change.

However, actual warming of the water has been very uneven, with some seas heating up much more quickly than others. Temperate rises have been most extreme where there are strong currents flowing from hot tropical regions towards the poles.

And as warmer seas move further south, tropical wildlife is going with them, giving us a dramatic insight into how global warming is changing our oceans.

The EAC

The East Australian current (the famous “EAC” used by migrating turtles in the movie Finding Nemo) brings warm water from off Queensland down the New South Wales coast to Tasmania. Similar currents also exist off southwestern Australia, Japan, the eastern United States, southeastern Africa and southern Brazil.

Many marine creatures have a wandering larval stage in their life cycle. These are often microscopic creatures that are transported by waves and currents far from their parents. Some larvae can travel for months or even years before settling down in suitable habitat and metamorphosing into the more recognisable crab, shell, sea-star or fish that we see along the coast.

This life history means that marine animals can respond rapidly to changing water temperatures and currents. Like Nemo they can be swept down the coast and survive in newly warming environments.

So let’s follow Nemo and find out what is happening along the eastern coast of Australia right now.

Heading south, permanently

The Solitary Islands are off the New South Wales Coast, just north of Coffs Harbour. They are the front line in the tropicalisation of temperate oceans. Tropical herbivorous fish are settling in increasing numbers; parrotfish and surgeonfish scrape at rocks and coral to remove and eat seaweeds.

These fish demolish existing kelp beds and eat any young plants that attempt to grow. This in turn allows coral larvae brought down by the EAC to settle and thrive. Coral reefs are on the move.

Further south, the eastern coast of Tasmania is being invaded by animals that previously were only found in New South Wales. Recreational fishers, naturalists and scientists have recorded almost 50 newly arrived species, some in abundance.

The best documented is the long spined or black sea-urchin, which also grazes kelp and has created large “barrens” on rocky reefs all the way to southern Tasmania.

No room to move

So does this matter? Who cares if everything just gets moved around? Coral reefs in New South Wales may sound attractive but there are a variety of reasons why warming of marine environments is bad news.

The long spined sea urchin, which creates ‘barrens’ by grazing seaweeds, has become established in warming seas off Tasmania.
John Turnbull / Flickr

One big problem happens at the poleward end of large continents. Cooler species have nowhere to go. There is no suitable habitat to migrate to.

For example, there is a whole cluster of species that only occur in southern Tasmania, like the cute spotted handfish. Rising temperatures and invading species could easily drive this and other species off Tasmania to extinction.

The critically endangered spotted handfish lives only in southern Tasmania.
Rick Stuart-Smith / Reef Life Survey

Not all species have a larval stage that can travel long distances, and such species could become marooned in areas with unsuitable temperatures. Many economically important animals such as rock lobsters, abalone and scallops like cool water and will become restricted in range and abundance.

It’s not just the heat

Rising temperatures are not the only calamitous result of climate change.

Sea levels are rising as a result both of melting ice and of the expansion in volume that occurs when water warms. This will not only affect the hundreds of millions of humans that live next to the coastline, as their properties are inundated and they are forced to migrate, but also the specialised animal and plants that live along the coastline.

The additional carbon dioxide in the atmosphere is also a pollutant in its own right. Its effect on ocean chemistry is to make it more acidic. But this is perilous for animals like corals and molluscs that make their skeletons from calcium carbonate.

The deep sea will be affected as well. Coral beds living a kilometre or so below sea level on seamounts off southern Tasmania will get squeezed by rising temperatures and ocean acidification.

With rising seas, animals and plants that live on this wide Victorian rock platform will be pushed upwards to occupy a thin band on the cliff behind.
Museum Victoria

We do not lack scientific data on these issues. Nothing has arisen that has shaken the scientific consensus that there will be lethal problems for marine animals and plants from a changing climate.

It is now a social and engineering problem. They key thing is that we move rapidly to decarbonise the global economy.

We will be publishing more articles in this series in the coming days.


Tim will be on hand for an Author Q&A between 2 ans 3pm AEST on Wednesday, July 15. Post your questions in the comments section below.

The Conversation

Tim O'Hara is Senior Curator of Marine Invertebrates at Museum Victoria.

This article was originally published on The Conversation.
Read the original article.

AUSTRALIA: THE NORTH MARINE REGION


Peter Garrett, Australia’s Minister for the Environment, Heritage and the Arts, today released a report on the biodiversity, ecosystems and social and economic uses of the oceans of northern Australia. The report entitled ‘The North Marine Bioregional Profile,’ brings together and explores the available knowledge of the Arafura and eastern Timor Seas, from the Northern Territory/Western Australia border to Torres Strait, including the Gulf of Carpentaria.

The report is expected to assist the government to better understand and protect our marine environment, conserve biodiversity and determine the priorities in our marine conservation efforts. It will also assist industry to better plan and manage their activities in the region.

A Marine Bioregional Plan for the region covered in the report is expected to be handed down in 2010. In total there will be five plans covering Australia’s marine regions.

View The North Marine Bioregional Profile at:
http://www.environment.gov.au/coasts/mbp/north/index.html