Coral Reefs Can Turn Growth On and Off
by Sara Coelho
Coral reefs do not grow continuously and some reefs off Australia are dead structures, relics from past periods of growth. But this is not necessarily a sign of major ecological catastrophe - when the opportunities arise, reefs know how to make the most out of it and can grow very quickly.
The Great Barrier Reef
Reef growth depends on a number of environmental factors, but two are especially important: sunlight and space to expand. This means that reefs can grow extensively in clear water, mud free environments where sunlight penetrates deep into the water column. In the long term, rising sea levels also come in handy as they provide vertical space for reef expansion.
'We don't know fully what is going to happen to coral reef growth under changed environmental conditions, but the potential for reef growth and recolonisation is there.'
Professor Chris Perry,
Manchester Metropolitan University
'Our recent studies demonstrate that whole suites of reefs on the innermost parts of the Great Barrier Reef grew very rapidly between about 8000 and 5000 years ago, but not much since,' says Professor Chris Perry, a specialist in tropical coastal geosciences at the Manchester Metropolitan University.
Perry analysed two areas of reef within one small bay on Dunk Island off Queensland to see how rates and styles of reef growth have changed there over time. Together with Dr Scott Smithers, from the Australian James Cook University, he extracted cores from the reef to analyse mud content, carbonate sediments and the coral species preserved in each core. They also collected samples for radiocarbon dating.
'We found two distinct areas of coral reef development within this area around Dunk Island,' says Perry. Radiocarbon dating shows that the reefs grew at very different times, one between about 6500 and 4500 years ago, and one much more recently, in the last 1500 years or so.
'Both, however, have grown rapidly to sea level and have reached the end of their natural life under present sea level conditions,' he adds. The reefs cannot continue to grow up because the sea level is stable and further seawards growth is probably limited by the muddy water conditions around the island that restrict sunlight penetration.
Some of these reefs look alive and are covered by a thin layer of coral. But scratch the surface and the structure below 'is an old, relict reef,' says Perry.
The findings, published this month in Geology, show that these reefs grew only at certain depths. But when the opportunities arise, 'these reefs can grow very quickly - they appear to be very good at making the most out of their opportunities,' Perry says.
Although the coral reef off Dunk Island is dead, if the conditions change the reefs may be able to switch back into active growth. And this might happen sooner rather than later with the sea-level rises predicted for the next few decades.
In practice a rising sea level could provide new space for corals to grow, but Perry cautions that global warming and climate change may also bring other less beneficial effects, such as coral bleaching and ocean acidification, limiting the ability of corals to recolonise these surfaces.
'We don't know fully what is going to happen to coral reef growth under changed environmental conditions, but the potential for reef growth and recolonisation is there,' Perry concludes.
Deep-Sea Octopuses' Origin Traced Back To Antarctica
Octopuses now found throughout the world's deep oceans share a common origin in the waters around Antarctica, according to new research conducted as part of the ground-breaking Census of Marine Life project.
Dr Jan Strugnell with a Megaleledone setebos octopus, thought to be the closest living relative of the deep-ocean octopuses.
This ancestral octopus species evolved in the waters around the South Pole around 33 million years ago.
It then spread outwards into new ocean basins around 15 million years ago, as the Antarctic cooled and began to develop the ice sheet that still covers it today. The pattern may prove relevant to the spread of many other kinds of marine animal.
The cooling Antarctic led to what the paper's authors call a 'thermohaline expressway', a northbound flow of cold, nutrient-rich water with high levels of salt and oxygen, along which octopuses travelled into new habitats.
The expressway formed because pure water crystallised into ice, leaving its salt content in the water that remained. The extra salt content made this water denser, so it flowed down into the deep oceans. The octopuses of the Antarctic went with it, as they were already adapted to deep, cold water.
Scientists have long suspected that many modern deep water species have their origins in the Antarctic, but this is the first research to quantify this through detailed genetic analysis of different octopus species.
Other creatures could have spread in a similar way. 'We think that if octopuses colonised the deep sea by this route, it's very likely that other organisms did so as well,' said Dr Jan Strugnell of the University of Cambridge, who is among the paper's authors. The work is based on research conducted while she was a postdoctoral researcher at Queen's University Belfast, funded by NERC's Antarctic Funding Initiative.
'In recent years it has become clear that diversity of species in the deep ocean is far greater than we had thought,' adds Strugnell. 'This research sheds light on how this diversity came about.'
'It is clear from our research that climate change can have profound effects on biodiversity, with impacts even extending into habitats such as the deep oceans which you might expect would be partially protected from it,' comments Dr Louise Allcock of Queen's University Belfast, another of the paper's authors.
A secondary factor behind the movement of octopuses may have been that scouring of the seabed by icebergs and other new phenomena caused by the spreading ice sheet made the waters of the Antarctic less hospitable.
Once the plucky molluscs made it to new habitats along the thermohaline route, their evolution diverged, leading to the development of the various species of deep-water octopus. Many have undergone major physiological changes to adapt to their new environment. Several species have lost their ability to squirt ink to confuse predators, since doing so is of little use in the lightless ocean depths where few predators rely on sight.
The researchers relied on tissue samples of octopuses collected over the last ten years on many different research cruises. These allowed Strugnell to conduct DNA analysis to investigate the deep-ocean octopuses' descent. Statistical work on the creatures' family tree led her to conclude that modern deep-sea octopuses most probably have an Antarctic origin.
The Census of Marine Life aims to catalogue the variety of life in the oceans in unprecedented detail. It is the first effort of its kind; it started in 2000 and should be finished by late 2010. It involves more than 2000 scientists from 82 countries.
The deep-sea octopus research was published in the journal Cladistics.
Sea Turtles To Hatch Fewer Males
by Sara Coelho
Global warming is likely to make marine turtles to hatch more females than males and may reduce nesting success, according to a review of the effects of increasing temperature on the turtles' biology.
Sea-level rises will also affect sea turtles by reducing the beach area available for nesting.
Marine turtles spend most of their lives at sea, hunting for prey. Females come ashore only every few years to lay their eggs on beaches.
'The problem is that marine turtles can be very faithful to their hatching site,' says lead author Dr Matthew Witt from the University of Exeter. 'They can come back to lay their eggs on the beach where they hatched,' he says. This makes the turtles vulnerable to local environmental changes caused by global warming.
Rising temperatures are likely to become a problem. 'The sex of marine turtles is determined by temperature during the middle third of the incubation period,' explains Witt. Warmer conditions lead to clutches with a higher proportion of females. Males are favoured by colder incubation temperatures, for example in white beaches where sand reflects lots of sunlight.
Witt and colleagues looked at 30 years of data collected at key turtle rookeries around the Atlantic Ocean and Mediterranean Sea and tried to see how global warming is likely to change local breeding conditions. The findings, published in the Journal of Experimental Biology, show that raising temperatures at nesting sites are likely to affect sea turtles.
'It's reasonable to say that sex ratio will be skewed towards females,' says Witt. Also, 'hatching success is also likely to decline with global warming.'
'But we don't know how female turtles will react to the changes,' says Witt. 'Maybe they'll compensate for the increasing temperatures by laying their eggs earlier in the year, or by burying them deeper in the sand where it's cooler.'
Marine turtles are cold-blooded reptiles and their distribution depends mostly on seawater temperature. 'Global warming may open new areas for marine turtles, but we also need to find out if there is an upper limit to the temperature they can tolerate,' he says.
The sea-level rises predicted by climate change models are also going to bring consequences for marine turtles. As seawater rises, 'the area available for nesting will decrease and some rookeries may be lost,' says Witt. This 'coastal squeeze' is most likely to happen in popular tourist areas where buildings and roads constrain beach area and prevent sand to retreating as the sea levels rise.
Plastics Found In The Seas Around Antarctica
by Tamera Jones
Man-made plastics have found their way to the most remote and inaccessible seas in the world off the coast of Antarctica, scientists have discovered.
The seas around continental Antarctica are the last place on Earth scientists have looked for plastic, mainly because they're so difficult to get to.
'We were going to the Amundsen Sea on board the RRS James Clark Ross to collect biological specimens for the first time ever, and were well placed to look for plastics at the same time,' explains David Barnes from the British Antarctic Survey, who led the research.
Barnes linked up with other researchers from Greenpeace's MV Esperanza and on board the ice patrol vessel HMS Endurance, making an unusual collaboration, to look for one of the most abundant and persistent scourges of the global ocean - floating debris. They found that rubbish made of plastic was most common compared with debris made from metal, rubber or glass.
They report in Marine Environmental Research how they found fishing buoys and a plastic cup in the Durmont D'Urville and Davis seas off the coast of east Antarctica and fishing buoys and plastic packaging in the Amundsen Sea in western Antarctica.
Although some countries have highlighted plastic bags as a serious environmental concern, of the 51 pieces of debris spotted in the South Atlantic, only two were plastic bags.
They found no evidence of natural debris like branches, shells or plants.
There are no scientific research stations or other bases anywhere near the Amundsen Sea, suggesting the plastic debris must have got there via ocean currents.
Harmful to marine wildlife
The researchers also sampled seabed sediments around Antarctica for minute degraded plastics.
Plastic fragments have found their way as far south as South Georgia in the South Atlantic, so the researchers were surprised to find no evidence of fragments in seabed sediments around the continent.
But with pieces of plastic floating on the surface of the Amundsen Sea, it seems that this is likely to change in the not-too-distant future.
Plastics harm wildlife in a number of ways. Plastic banding often ends up round seals' or birds' necks. Not only that, but the material's surface easily absorbs toxic organic pollutants. When the stuff degrades into minute fragments, tiny marine creatures like zooplankton inadvertently feed on them.
'The possibility of tiny pieces of plastic reaching the seafloor is especially worrying, because the continental shelves around Antarctica are dominated by suspension feeders, which are essentially at the bottom of the food chain.'
'But what's really worrying about plastics getting to Antarctica, apart from aesthetics, is the fact that they can carry non-native animals. We don't have this problem in Antarctica yet, but with warming seas, they stand a much better chance of surviving,' says Barnes.
Barnes is keen to go back to sample the Amundsen Sea at some point in the future to keep track of changes in this remote part of the world.
'Plastics will continue to make their way to Antarctica and we need to keep a handle on this change,' he adds.
The fact that plastic debris is floating into the most far-flung of places is a strong measure of man's influence on the surface of the planet.
Deepest Black Smokers Found In Caribbean
by Tom Marshall
Scientists have found the deepest known hydrothermal vents, some 5 kilometres down beneath the waves of the Caribbean in the Cayman Trough.
They used submersibles to probe the vents, finding slender spires of copper and iron ores around the vent, amid jets of water hot enough to melt lead.
'Seeing the world's deepest black smoker vents looming out of the darkness was awe-inspiring,' says Dr Jon Copley, a marine biologist at the University of Southampton's School of Ocean and Earth Science who is based at the National Oceanography Centre (NOC) and led the whole research programme. 'Superheated water was gushing out of their two-storey high mineral spires, more than three miles beneath the waves.'
Autosub6000 is launched from the RRS James Cook
Hydrothermal vents, also called black smokers, are spots on the seabed where fluid and gases from deep volcanic systems leak up into the seawater. They often host extraordinary communities of plants and animals. These creatures are adapted to high pressure and lightless, scalding conditions.
Unlike most ecosystems on Earth, these communities get their energy not from sunlight, but from the chemical energy found in the fluids pumped out by the vents. The first black smokers were discovered decades ago, but most are in much shallower water.
The submersibles launched from the British research vessel RRS James Cook. They also took samples of the fluids jetting out of the vent, which will now be analysed and compared with samples from other black smokers.
The Cayman Trough is the world's deepest undersea volcanic rift, found on the seabed between the Cayman Islands and Jamaica. At its lowest point, the pressure is equivalent to the weight of a large family car pressing down on every square inch.
The scientists first launched an underwater robot called Autosub6000, which moves around the aquatic environment under its own control. Designed and built by scientists at NOC in Southampton, it carried out a detailed survey of the seabed in the area. They then followed it with another deep-sea vehicle, named HyBIS; this descended under remote control to the vent site Autosub6000 had identified and took samples and pictures. HyBIS was developed by team member Dr Bramley Murton alongside engineering firm Hydro-Lek Ltd.
The deepest black smoker ever found
'It was like wandering across the surface of another world', says Murton, who controlled HyBIS for the mission. 'The rainbow hues of the mineral spires and the fluorescent blues of the microbial mats covering them were like nothing I had ever seen before.'
The team will stay in the Caribbean continuing the research until 20 April. They then hope to return to the area over the next year or two with ISIS, the larger of NOC's remotely-operated vehicles, once they can secure ship time to do so. ISIS was recently used to seek out the first black smokers ever found in the Southern Ocean, and has a wider range of abilities than HyBIS. It can take high-resolution images and video of what it finds, and can even bring up animals in specially-pressurised vessels so they can be studied on the surface.
As well as the researchers from Southampton, the expedition also includes scientists from the University of Durham in the UK, from the University of North Carolina Wilmington and the University of Texas in the US, and from Norway's University of Bergen. Colleagues ashore at the Woods Hole Oceanographic Institution and Duke University will help them analyse the data on the newly-discovered vents.
Coral-Like Creatures Survived The Last Ice Age
by Sara Coelho
Bryozoan colonies may look like frail miniature corals but they were sturdy enough to survive being bulldozed by advancing glaciers during the last ice age. When the ice retreated, they evolved into the unique bryozoan fauna of the Antarctic continental shelf.
Bryozoans are tiny bottom-dwelling organisms that build coral-like colonies that can reach up to one metre tall and wide. They may not be a household name, but they are very common: 'you would have to try hard to find an aquatic environment without them, apart from the deepest trenches,' says Dr David Barnes, a biologist based at the British Antarctic Survey.
They are exceptionally common in Antarctica's Weddell Sea, where scientists have identified around 300 species, many of them not found anywhere else. The extraordinary biodiversity of bryozoans in Antarctica is puzzling, since the continental shelf was covered with glaciers at the height of the last ice age.
'So how do you account for this diversity, especially of endemics, in an area that is supposed to be wiped out whenever there is a glacial maximum? Where do they come from?,' asks Barnes.
Barnes joined forces with Dr Piotr Kuklinski, from the Natural History Museum in London, and set out to catalogue the many hundreds of bryozoan samples dredged out during research cruises in Antarctica. The team analysed bryozoans from many island locations around Antarctica, including the shallow Antarctic continental shelf, the continental slope and the deep abyssal plain of the Southern Ocean.
The idea was to create a combined distribution map for most bryozoan species, to see which assemblages live where and at what depth.
Bryozoan colony (Melicerita obliqua) from the Southern Ocean. Bryozoans live inside individual units called zooids. Scale bar is 200 micrometers in A and 100 micrometres in B.
They found that the bryozoans living in the deep sea were very different from the ones thriving on the continental shelf – 'it's a completely different fauna,' stresses Barnes. This means that the bryozoans that live on the shelf now did not come from the deep sea.
It is also unlikely that they migrated from distant areas that remained free from the advancing glaciers. 'Bryozoans are attached to the ground as adults, their larvae are short-lived and do not travel far,' explains Barnes, adding that here too, as in the deep sea, the fauna show few species in common.
'The simplest explanation to the patterns we have found is that many bryozoans are indeed endemic to the Weddell Sea continental shelf,' says Barnes. The bryozoans did not recolonise most of the wide and deep shelf until after the glaciers retreated – they managed to survive there in refuges and secluded areas, even at the height of the last ice age.
'This is the first convincing evidence that life survived on the Antarctic shelf during the last glacial maximum,' he concludes. The hunt is now on for the smoking gun of exactly where those refuges are.
Getting To The Bottom Of Biodiversity
The new technique of macro ecology lets ecologists take isolated samples of plant and animal life and piece the results together to understand how species are spread across a wide area. Tom Webb explains how marine science is helping in the search for a general theory of biodiversity.
The chilly waters of the North Sea don't feature on many eco-tourists' lists of must-see marine biodiversity hotspots. Yet despite the oil rigs, the fishing and the ferries, the surprisingly diverse animal communities of this humdrum sea are revealing important new facts about how life on earth is distributed. By linking the natural history of individual species to patterns in diversity across the entire sea, we are also beginning to understand how future impacts such as climate change may alter biodiversity across large areas.
In a study funded by NERC's Strategic Oceans Funding Initiative, we looked at the North Sea benthos - that is, those animals living on or in the sea-bed - and showed that we can predict the distribution of species based on their biological characteristics. In particular, traits such as body size seem to determine the spatial patterns of the whole North Sea benthic community. But these effects are subtle: big species are not necessarily more widely distributed than small species; rather, they are more evenly distributed within their ranges. On the other hand, small species, and species which can't move long distances, appear to have very clustered distributions.
This is important because human activities in the North Sea affect some species more than others. Commercial fishing, in particular trawling, has a disproportionate effect on large species, even those not deliberately targeted by the fishery. If those large species are lost from the system, this has implications for the structure of the whole community. It does suggest, though, that we can monitor an activity's effects on the system by looking for changes in the relative degree of clustering of species. This may be useful because it is easier and faster to assess the numbers of species in samples than it is to obtain detailed knowledge of their biology.
In fact, as part of the same project we're finding out just how difficult it is to get information on the biological characteristics of most marine animals. For many species, there is simply no documented knowledge of their ecology and behaviour - things like what they eat, how many offspring they produce, or how long they live. Typically we have this data for fewer than a quarter of species. If this is true for the North Sea, our ignorance surely plumbs even greater depths in less well-studied and less accessible regions, including much of the developing world and the vast abyssal plains of the deep sea.
The sea potato, Echinocardium cordatum.
A lack of available information may explain the fact that our study did not identify other facets of animal biology as important drivers of species distribution. For instance, most bottom-dwelling species are relatively sedentary as adults, and so their best chance of moving large distances comes when they reproduce. Broadly speaking, species fall into two camps: those which launch their larvae into the plankton where they drift around for days or even weeks before settling back to the sea floor as adults; and those which keep their offspring close to them. We expected that the choice of larval developmental strategy would have a big effect on adult distributions, with species with a planktonic phase spread more widely. Although we did observe a trend in this direction, it was not statistically significant - but this may be because we had data on developmental mode for only 124 of 575 species.
Body size is the trait that bucks this trend for lacking data - it is far easier to measure an organism than to find out anything about its lifestyle, and we can usually find basic estimates of size for around two thirds of the species in our samples. Studying body size in combination with information on the distribution and abundance of species thus promises more insights in future.
Such insights are possible due to a 'macro ecological' approach - a relatively new technique well suited to address the difference in scales between ecological samples and the big environmental questions that we face. Most field ecologists work at small spatial scales, typically identifying and counting organisms in a series of small samples - the classic ecologist's quadrat usually measures between 10cm and 1m on each side.
The equivalent sample for marine benthic systems is the grab sample, where sediment from a small area (most often 0.1m2) of the sea-bed is extracted, brought up to the surface and then sieved to reveal the species living in it. Macro ecology lets us combine many such samples - in this case, taken from more than 230 locations throughout the North Sea - so that ecologists can address far bigger questions, such as how species are moving in response to climate change.
Biodiversity on land and sea
Our study is unusual because most of our knowledge of biodiversity comes from ecosystems on land. Macro ecology, in particular, has developed largely through the study of a few well-known groups like birds and butterflies. But any study of birds is only focused on a small component of diversity. In taxonomic terms, all birds belong to a single group called a class; the next level up in the taxonomy, the phylum, groups birds with all other vertebrates.
The catworm, Nephtys hombergii.
Other animal phyla include molluscs, arthropods and annelid worms. So although birders might get excited by small differences between bird species, all birds are more similar to each other than any worm is to any mollusc, and it's only by studying more diverse systems that we can start to understand how major differences in biology affect patterns in geographical distribution.
This is where the advantages of working in marine systems become most apparent. For example, a single 0.1m2 sample of North Sea sediment may contain up to 90 species, and these species are very diverse - there are many worms, but also molluscs, starfish and crustaceans. In the dataset we used, single samples contained representatives of as many as seven different phyla. Studying systems with such taxonomic diversity means that in the same set of samples, there is tremendous variety in biological characteristics too.
There are other good reasons to study marine systems. Over 90 per cent of the so-called 'habitable volume' of Earth - regions suitable for life - is marine. Life originated in the sea, and the diversity found in the North Sea is not a fluke of sampling: around 2/3 of animal phyla are found only in the oceans. But the seas are increasingly threatened by many human activities.
As well as climate change, which is not only warming the oceans but also making them more acidic, marine fish make up an important part of the diet of a large proportion of the world's people, and the sea-bed is an important source of natural resources including oil and gas.
Any general theory of biodiversity therefore has to encompass the marine environment. 1.2 billion people live near the coast and this total is expected to continue increasing rapidly. If this happens, then understanding how marine species are distributed may be crucial to our future well-being.
Giant Steps Help Predators Find Food
by Tamera Jones
Large ocean predators like tuna, sharks and ocean sunfish use two different tactics to search for food depending on whether it's abundant or sparse, scientists have shown for the first time.
A mako shark.
When their prey is patchy, open-ocean predators make long swims followed by lots of smaller ones – called Lévy flights – to find their prey. But when fish are abundant, they use a local 'scattergun' approach to find food.
Lévy flights are specialised random walks made up of long steps followed by lots of short steps occurring at every spatial level. If these fish were tracked from space or from a boat, you'd see the same pattern,' explains Professor David Sims from the Marine Biological Association, who led the research.
It may seem obvious that large predators have to swim for miles and then make shorter swims to optimise their chances of finding prey. Indeed scientists have hypothesised since the 90s that in unproductive waters, predators would use Lévy flights to locate prey, while in rich waters, they should make smaller, more localised movements.
But finding evidence to back these ideas up has, until now, proved challenging.
'The fact is this is an idea that's been extremely difficult to test. You need very large datasets,' says Sims.
Earlier research that claimed to demonstrate Lévy flights in albatrosses, bumblebees and deer has since been discredited, because the data was problematic or the statistical methods the scientists used weren't accurate enough.
'Part of the difficulty has been in dividing up foraging behaviour and other behaviours like resting, travelling or interacting that are unlikely to have patterns best approximated by Lévy flights. We now have better statistical methods to identify the laws that govern these complex patterns making it easier to distil a pure signal,' says Sims.
The research team – made up of 16 scientists from five countries – describe today in Nature how they attached electronic tracking tags to 55 individual predators from 14 different species of shark, tuna, ocean sunfish and swordfish. This produced a large dataset of more than 12 million movements collected over 5700 days.
Using complex statistical methods, they divided up this data so that they could analyse it in detail.
They found ample evidence for Lévy search patterns in nearly all 14 species. And, as predicted by the Levy flight hypothesis, individuals switch between Lévy and a localised approach to foraging depending on what habitats they're in.
The researchers call these localised movements Brownian searches after the term scientists use to describe the random movement pollen grains make when they're suspended in water and are being bombarded by water molecules.
One blue shark swapped Brownian behaviour in the rich waters of the continental shelf edge off northern Spain for Lévy searching in the comparatively empty waters of the Bay of Biscay.
Another fish, a bigeye tuna in the central eastern Pacific near the Galapagos Islands made big steps followed by small steps to find food, but when it moved to cooler waters full of fish, it switched to Brownian-type movements.
The researchers are keen to test their statistical methods on animals like octopus, cuttlefish and snails next.
'If this is a universal law of searching it should occur everywhere. The next question is, did animals evolve Lévy flights when faced with challenging environmental conditions at some time in prehistory?' says Sims.
Deep-Sea Fish Stocks Threatened
11 March 2009
Commercial fishing in the north-east Atlantic could be harming deep-sea fish populations a kilometre below the deepest reach of fishing trawlers, according to a 25-year study published on Wednesday.
Orange roughy on the processing line of a factory bottom trawler.
Scientists have long known that commercial fishing affects deep-water fish numbers, but its effects appear to be felt twice as deep as previously thought.
Dr David Bailey of the University of Glasgow, who led the study - published in the journal Proceedings of the Royal Society B - said:
"Commercial fishing may have wider effects than anyone previously thought, affecting fish which we assumed were safely beyond the range of fishing boats. We were extremely surprised by this result and believe that it has important implications for how we manage the oceans."
Populations of north-east Atlantic commercial deep-water fish such as black scabbardfish, orange roughy and roundnose grenadier have dwindled since deep-water fishing started in the area in the late 1980s, but it wasn't until 2003 that catch quotas were introduced.
"Each deep-water species has a defined depth range and very often the juveniles live at depths shallower than the adults. Removal of fish by commercial trawling down to 1600 metres is likely to affect populations in deeper waters."
Dr John Gordon, Scottish Association for Marine Science
Researchers started mapping the distribution of deep-water fish on the slopes off the west coast of Ireland in 1977 in an effort to understand more about the fish living there and their biology. They used Natural Environment Research Council-owned ships RRS Discovery and RRS Challenger to continue recording species over an 11-year period until 1989 - before any fishery was established in the region. They then mapped the slopes again from 1997 until 2002 using the same ships and the same fishing methods to get a consistent data set.
As part of a European Union-led project to study species in deep-sea environments - HERMES, the researchers then compared the abundance of fish in the two different periods.
They unexpectedly found that deep-sea fish numbers down to 2500 metres - a kilometre below the deepest reach of fishing trawlers - were lower in the later 1997 to 2002 period. Not only this, but target species and non-target species were both affected and in much deeper parts of the ocean. Numbers of one species of eel has dropped by half. Some deep-water trawlers harvest down to 1600 metres.
"This study is unique in that we have over ten years of scientific data from before 1990 when the commercial fishery took off so we can accurately detect the decline," said Professor Monty Priede of the University of Aberdeen's Oceanlab.
"The deep-seas fishing industry targets relatively few species, such as roundnose grenadier and orange roughy: unwanted species are discarded. These can make up around 50 per cent of the catch and because of the extreme change in pressure and temperature when they're brought to the surface, none of these will survive. This explains why the study has shown a decrease in abundance of target and non-target species.
"Each deep-water species has a defined depth range and very often the juveniles live at depths shallower than the adults. Removal of fish by commercial trawling down to 1600 metres is likely to affect populations in deeper waters," said Dr John Gordon of the Scottish Association for Marine Science and a member of the study team.
Scientists say the implications for fishery managers is that to protect deep-sea fish stocks, they should take into account adverse ecosystem effects, not just the abundance of the fish stocks being targeted. They say that trawling may need to be restricted more than it is now.
There are plans for Marine Protected Areas in the north-east Atlantic, which are being considered by the OSPAR Convention. But this might not be enough.
"Marine Protected Areas need to be much bigger than the existing coral-protecting MPAs. They are not very effective for mobile fish species unless the fishing effort itself is reduced," said Professor Priede.
"MPAs might not be as effective as we'd hoped since we can detect the depletion of fish up to over 50 miles outside the fishing zone," added Dr Bailey.
The study, funded by the Natural Environment Research Council, European Commission and the Marine Conservation Biology Institute, involved researchers from the University of Glasgow, the British Antarctic Survey, the Scottish Association for Marine Science, Highland Statistics and the University of Aberdeen's Oceanlab
Corals In A Changing World
Coral reef in Indonesia.
7 May 2010
Coral reefs are among the world's richest ecosystems, but environmental change is fast putting them at risk. Scientists are revisiting fundamental questions in coral research to understand how corals will fare in the future. David Suggett and colleagues explain.
Productive and diverse coral reef ecosystems exist because of coral growth. To grow optimally, corals need specific conditions of light intensity, temperature and pH. But these conditions appear to be changing faster than ever, as tropical waters are subjected to both global climate change and local problems like pollution and sedimentation. How such altered environments will affect reefs is still largely unknown, but certainly any change to the rate and extent of coral growth will be vital in determining reefs' future form and function.
We can already see the effects of rapid environmental change on how fast corals grow. For example, slower growth rates of Porites, a key reef-building coral, have been recorded within the Great Barrier Reef over the last two decades, alongside accelerated increases of seawater temperature. However, it is unlikely that temperature alone is fully responsible. Warmer waters are ultimately driven by more CO2 in the atmosphere; this CO2 also dissolves into seawater to lower pH, making it more acidic - a process known as Ocean Acidification (OA).
Several experimental studies now show that OA not only slows corals' growth, but may also make them more vulnerable to temporary stresses that can cause coral bleaching - this is when corals turn pale and ultimately die. Physiological resistance to transient stresses, such as unusually warm or cool waters, requires corals to use energy that they would otherwise be able to invest in growth. The findings to date are alarming but highlight a key issue: we need to consider the combined effects of multiple climate change variables to accurately predict future coral growth. Curiously, many studies have focused on temperature and OA, but little attention has yet been paid to the key limiting resource for coral growth in every reef - light.
Too much of a good thing?
The availability of light is the main regulator of coral growth, and is also predicted to change in future environments, along with temperature and CO2, and hence acidity. The tiny animals that build coral reefs are dependant on a symbiotic relationship with algae, called zooxanthellae. These algae live within the coral animals' surface tissue; the carbon they fix by photosynthesis is used to 'feed' the coral. Up to a point, more light means more photosynthesis, to the benefit of the coral.
But too much light eventually makes the zooxanthellae - and in turn the corals - more susceptible to the stresses that lead to coral bleaching. Photosynthesis increases the rate at which corals can 'calcify', or lay down their calcium carbonate skeletons. But unfortunately, calcification also becomes compromised as seawater becomes more acidic - hence the lower growth rates seen under OA. So the ultimate effect of climate change on the form and function of tropical reefs depends on the combined changes of light, temperature and OA, as well as on how specific corals and zooxanthellae respond to these changes. This is where we come in.
Since 2004, several NERC-funded research projects within the University of Essex's photosynthesis laboratory have focused on the responses of marine organisms, in particular a globally abundant phytoplankton species, Emiliania huxleyi, to OA. Unfortunately, mimicking the effects of OA in the laboratory is not as easy as simply tweaking water's pH by adding acid or alkaline substances! Adding biology to the picture further complicates the inorganic carbon chemistry that determines the pH of seawater. Organisms change the pH of their surroundings through photosynthesis and/or respiration, and by producing calcium carbonate (chalk) skeletons or shells.
This meant that from the outset of our OA projects, we needed to develop and optimise experimental 'microcosm' systems to provide full control over the continually-changing chemistry. In developing this technology, we produced the crucial tool needed to examine the complex interactive effects of light, temperature and pH on coral growth. This is the subject of a new NERC-funded project within Essex's Coral Reef Research Unit (CRRU) entitled A community metabolism approach to examine the environmental regulation of coral growth'.
How Do Corals Grow?
This new project has re-ignited a key question. Just how - and how fast - do corals really grow? This may seem like an obvious question, yet it still remains unanswered. Surprisingly few publications report coral growth rates. Such a lack of core information highlights a central problem: How does a coral grow and how is growth best measured?
The growth form, or 'architecture', of a coral colony is highly variable. Environmental conditions such as exposure to currents and light levels can play major roles in sculpting a coral colony, but the extent to which environments regulate architecture varies within and between species. The complexity and variability of coral architecture makes assessing colony growth - defined as the change in a reef's size per unit of time - extremely difficult. No single measure can be truly reflective of growth. So to find out how changing climates will influence colony growth, we need to learn how to assess coral growth accurately, as well as to identify the factors that control it.
We can already see the effects of rapid environmental change on how fast corals grow.
This has led to another new NERC-funded project, the Coral Aquarist Research Network (CARN), also run within Essex's CRRU. To assess what drives growth requires the capacity to carefully control (and manipulate) the environment for as many species as possible; the resources for this are far outside the scope of most research facilities.
But they are readily available in the industrial sector, specifically from coral growers and national and public aquaria, which for many years have independently been establishing the best way to grow coral species. CARN was launched to provide a forum through which UK coral researchers and academics could exchange information with the nation's aquarist and coral husbandry industry. It is primarily focused on how to benefit industry by exchanging detailed knowledge of coral growth, mortality and fecundity.
Initiating these two new NERC-funded projects alongside existing research within the CRRU has encouraged further investment by the University of Essex, which has funded a new coral growth aquarium facility.
This facility has been designed in close collaboration with the coral husbandry industry and will provide a resource for researchers to continue the UK's momentum in coral science, which until now has largely been based on studies in the field. Such investment is certainly a sign of the times. Our environment is changing quickly, and so are the priorities for the research community. We are re-visiting perhaps the central issue in coral research, so as to shed new light on how corals grow, both now and in the future.
Jellyfish Sting Survivor 'Shouldn't Be Alive'
By Kylie Bartholomew
A 10-year-old girl's survival after an encounter with a box jellyfish in Queensland last year could be a one-of-a-kind story, experts say. Rachael Shardlow was stung by the world's most venomous creature while swimming 23 kilometres upstream from the ocean mouth in the Calliope River, near Gladstone, in December.
Rachael's 13-year-old brother, Sam, pulled her onto the riverbank. She told him she could not see or breathe, and fell unconscious with the jellyfish's tentacles strapped to her limbs. Zoology and tropical ecology associate professor at James Cook University, Jamie Seymour, says the girl's survival after such an extensive sting is unheard of. "I don't know of anybody in the entire literature where we've studied this where someone has had such an extensive sting that has survived," he said. "When I first saw the pictures of the injuries I just went, 'you know to be honest, this kid should not be alive'. I mean they are horrific."Usually when you see people who have been stung by box jellyfish with that number of the tentacle contacts on their body, it's usually in a morgue."
Associate professor Seymour says the university is interested to see how long it takes for Rachael to recover, as well as whether there are any long-term effects. "From our point of view it's really useful information that you very seldom, if ever, get your hands on," he said. Rachael's father, Geoff Shardlow, says his daughter has scarring as well as some short-term memory loss.
"We've noticed a small amount of short-term memory loss, like riding a pushbike to school and forgetting she's taken a pushbike," he said. "The greatest fear was actual brain damage [but] her cognitive skills and memory tests were all fine." Mr Shardlow says it is vital there are more jellyfish warning signs erected throughout central Queensland.
Rachel Shardlow survived after being stung by a box jellyfish near Gladstone in the Calliope River in central Queensland. (ABC News)
Deadly Jellyfish Head South In Threat To Tourism
By Kirrin McKechnie for the 7.30 Report
Swimmers in far north Queensland have long lived with the threat of irukandji and box jellyfish stings, but the dangerous marine creatures could soon be headed further south. This season about 50 people in Queensland have been hospitalised after being stung in waters from the far north to the central coast, and both potential killers close affected beaches for six months each year. Scientist Jamie Seymour has been researching the deadly creatures for nearly 20 years and says global warming means the irukandji will eventually end up as far south as the Gold Coast.
His assertion is a worrying prospect for tourism operators along the Sunshine and Gold coasts. Dr Seymour, an associate professor at James Cook University in Cairns, says global warming has already extended the irukandji's habitat.
"For irukandji, 30 or 40 years ago the length of the season was about a month to a month-and-a-half," he said. "The length of the season now is about five-and-a-half to six months. It's increasing as water temperatures go up. "The other thing we're seeing is they're getting further and further south. Give it time, it'll be a problem down in Surfers Paradise. "It's just going to take a little bit of time, an increase in water temperatures, then it's all going to hit the fan."
He says the Sunshine Coast could have a jellyfish problem in just five years. "You put one degree, half a degree rise in sea water temperature, they'll be there no doubt about it at all," Dr Seymour said. "I don't think you'll see big box jellyfish down there because it's a completely different way of life, and they need coral reef to stop the waves and things."Irukandji, I can see it happening, and it'll happen in my lifetime."
Tourism Sunshine Coast chief executive Russell Mason says the threat of irukandji stings could damage the industry. "The whole concept of global warming is going to affect tourism across the globe," Mr Mason said. "The government - state, federal and local - all need to be really aware that tourism is a critical component of the Australian economy, and in places like the Sunshine Coast it is the biggest driver of our economy. "Any threat to that needs to be managed very carefully."
Mr Mason says quelling public panic will be the biggest challenge for the industry. "It's a bit like shark attacks in the fact that people don't know a lot about the irukandji at the moment, and because people don't know about them they get very worried," he said. "Fortunately James Cook University is doing a lot of research in this area and they'll be able to tell us how to deal with the irukandji problem. "Probably more importantly, they'll tell us where the irukandji are likely to turn up and that way we can monitor those areas very closely."
The race is on for Dr Seymour to come up with more answers about the mysterious marine killer. "You come to north Queensland and when you want to swim on the beach everybody's crammed into these little stinger nets," he said. "And I've got this vision of being able to see people all the way down the beach enjoying themselves. "What we need to be able to do is get a handle on the jellyfish, and the only way we can do that is [work out] how they actually operate, what their biology is, and go from there. "I liken it to what happens with snakes. Twenty or 30 years ago, certainly when I was a kid, if there was a snake in the backyard your dad would go down with a 12-gauge (gun) and blow its head off. "Do we do that with snakes now? No we don't. "Now we understand what snakes do. We have anti-venoms. We know how to treat snake bites. "People don't really worry that much. Yes, we know they're there but it doesn't change the way we act.
"If we can work out what the jellyfish are doing and where they are and under what circumstances, then we make it safer for the average punter down on the beach."