Human impacts on the deep seafloor

ScienceDaily (Sep. 14, 2010) — Scientists have for the first time estimated the physical footprint of human activities on the deep seafloor of the North East Atlantic. The findings, published in the journal PLoS ONE, reveal that the area disturbed by bottom trawling commercial fishing fleets exceeds the combined physical footprint of other major human activities considered.

The deep seafloor covers approximately 60% of Earth's surface, but only a tiny fraction of it has been studied to date. Yet as technology advances and resources from relatively shallow marine environments are depleted, human impacts on the deep seafloor are likely to increase.

"Information on the location and spatial extent of human activities affecting the deep-sea environment is crucial for conservation of seafloor ecosystems and for governance and sustainable management of the world's oceans," said Angela Benn of the National Oceanography Centre, who led the new study.

The researchers focused on the OSPAR maritime area of the North East Atlantic, where human activities are particularly intense. The area covers over eleven million square kilometres, about 75 percent of which is deeper than 200 metres, and includes important fishing grounds such as those of Hatton and Rockall.

Using available data for the year 2005, they mapped and estimated the spatial extent of intentional human activities occurring directly on the seafloor as well as structures and artefacts present on the seafloor resulting from past activities.

They looked exclusively at the physical footprint rather than the consequential ecological effects of disturbance, contamination and pollution, which are harder to ascertain. One difficulty that they faced was that of accessing data on human activities that was accurate, up to date and comprehensive, and in a suitable format for analysis.

"Some governments, public organisations and private companies were far more forthcoming with information than others," explained Benn. "Significant improvements are needed in data collection and availability, and this requirement needs to be built into international conventions and treaties with a legal framework in place to ensure informed environmental management."

Despite difficulties and various uncertainties, the researchers' assessment suggests that, although now banned, previously dumped radioactive waste, munitions and chemical weapons together have the lowest physical footprint of the human activities considered, although they do not consider potential dispersal after leakage.

Non-fisheries marine scientific research also has a relatively small footprint, whereas those of fisheries marine scientific research, telecommunication cables and the oil and gas industry are moderate. However, even on the lowest estimates, the spatial extent of bottom trawling is at least ten times that for the other activities assessed, with a physical footprint greater than that of all the others combined.

The study estimated the total area of physical imprint in 2005 to be around 28,000 km2. However many human activities in the deep sea are concentrated in certain areas, particularly in shallower depths between 200 m and 1500 m, and in particular habitats which become disproportionally impacted. The OSPAR area comprises many different habitats each with different and diverse ecosystems. The percentage impact in each of these habitats would provide important information but unfortunately there is virtually no detailed seabed mapping to provide this information.

As demands drive human activities ever deeper the imprint will become more widespread. "Consequently," argues Benn, "there needs to be a much greater understanding of the relative impacts of human activities on the deep seafloor, and in particular how these activities affect seafloor ecosystems and biodiversity."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Oceanography Centre, Southampton (UK).

Journal Reference:

Angela R. Benn, Philip P. Weaver, David S. M. Billet, Sybille van den Hove, Andrew P. Murdock, Gemma B. Doneghan, Tim Le Bas, Peter Roopnarine. Human Activities on the Deep Seafloor in the North East Atlantic: An Assessment of Spatial Extent. PLoS ONE, 2010; 5 (9): e12730 DOI: 10.1371/journal.pone.0012730

Note: If no author is given, the source is cited instead.

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Human noise pollution in ocean can lead fish away from good habitats and off to their death

ScienceDaily (Aug. 13, 2010) — The growing amount of human noise pollution in the ocean could lead fish away from good habitat and off to their death, according to new research from a UK-led team working on the Great Barrier Reef.

After developing for weeks at sea, baby tropical fish rely on natural noises to find the coral reefs where they can survive and thrive. However, the researchers found that short exposure to artificial noise makes fish become attracted to inappropriate sounds.

In earlier research, Dr Steve Simpson, Senior Researcher in the University of Bristol's School of Biological Sciences discovered that baby reef fish use sounds made by fish, shrimps and sea urchins as a cue to find coral reefs. With human noise pollution from ships, wind farms and oil prospecting on the increase, he is now concerned that this crucial behaviour is coming under threat.

He said: "When only a few weeks old, baby reef fish face a monumental challenge in locating and choosing suitable habitat. Reef noise gives them vital information, but if they can learn, remember and become attracted towards the wrong sounds, we might be leading them in all the wrong directions."

Using underwater nocturnal light traps, Dr Simpson and his team collected baby damselfish as they were returning to coral reefs. The fish were then put into tanks with underwater speakers playing natural reef noise or a synthesised mix of pure tones. The next night the fish were put into specially designed choice chambers (long tubes with contrasting conditions at each end in which fish can move freely towards the end they prefer) with natural or artificial sounds playing. All the fish liked the reef noise, but only the fish that had experienced the tone mix swam towards it, the others were repelled by it.

Dr Simpson said: "This result shows that fish can learn a new sound and remember it hours later, debunking the 3-second memory myth."

His collaborator, Dr Mark Meekan added: "It also shows that they can discriminate between sounds and, based on their experience, become attracted to sounds which might really mess up their behaviour on the most important night of their life."

In noisy environments the breakdown of natural behaviour could have devastating impacts on success of populations and the replenishment of future fish stocks.

Dr Simpson said: "Anthropogenic noise has increased dramatically in recent years, with small boats, shipping, drilling, pile driving and seismic testing now sometimes drowning out the natural sounds of fish and snapping shrimps. If fish accidentally learn to follow the wrong sounds, they could end up stuck next to a construction site or follow a ship back out to sea."

The study is published in Behavioral Ecology and was carried out at Lizard Island Research Station. The work was supported with a fellowship for Dr Simpson from the UK Natural Environment Research Council and by the Australian Institute of Marine Science for Dr Mark Meekan.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bristol.

Journal Reference:

Stephen D. Simpson, Mark G. Meekan, Nicholas J. Larsen, Robert D. McCauley, and Andrew Jeffs. Behavioral plasticity in larval reef fish: orientation is influenced by recent acoustic experiences. Behavioral Ecology, 2010; 21 (5): 1098 DOI: 10.1093/beheco/arq117

Note: If no author is given, the source is cited instead.

View the original article here