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Ploughing the deep-sea floor

Article taken from: Nature | News

Fish trawling reshapes deep-sea canyons

Dredging stirs up slow silt storm and may disrupt marine life.

Lucas Laursen


Ploughing the deep sea floor

Pere Puig, Miquel Canals, Joan B. Company, Jacobo Martín, David Amblas, Galderic Lastras, Albert Palanques & Antoni M. Calafat

Original article: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11410.html

Deep-sea trawling smoothes out the wrinkles of canyons on the continental slope, making marine mountainsides look more like ploughed fields, changing the habitat of deep-sea creatures. The process rivals landslides and storms as a shaper of the deep sea, according to work published today in Nature1.

For almost a century, fishing fleets have trawled for shrimp off Spain's Mediterranean coast by dragging nets along the flat, shallow coastal sea floor. But in the 1960s, they also started to pursue shrimp farther offshore and into rugged canyons as deep as 800 metres. The impact they had on this rougher terrain was a mystery.

In 2006, geoscientists surveying canyons off Spain's coast found smooth slopes which they attributed to an underwater cascade, but one of the smoothed slopes was in the lee of the proposed cascade2. While trying to come up with reasons, Pere Puig, a marine geologist at the Institute of Marine Sciences in Barcelona, Spain, and his colleagues realized that the anomalies occurred in a trawling zone and hypothesized that trawlers were scraping silt off ridge tops and dropping it into canyon bottoms.

For six months, the researchers measured silt flow in the canyons and took core samples from the sea floor and video footage of a canyon. Then they plotted the silt disturbances on a high-resolution map of the canyons and compared them with four years of detailed fishing records. They found higher silt flow during hours when the trawling fleet operated and smoother canyon walls in areas with the greatest trawling activity, and different sediments in trawled and untrawled regions. The team estimates that trawling has doubled the amount of sediment flowing down into the canyons since the 1970s.

Smoothing out the structure of marine canyons will reduce the number of species that can live there, says Elliott Norse, chief scientist at the Marine Conservation Institute in Bellevue, Washington. If shallower waters are any guide, it will also change the make-up of species, adds marine biologist Callum Roberts of the University of York, UK: "Big fish like complex habitats," he says, "things like prawns and scallops live fast, die young and like their habitats open and unstructured." Yet researchers do not yet know which species the prawns may be replacing. Puig says his team is planning surveys of the biodiversity of trawled and untrawled slopes next.

Yet fishing the stock this way may not be sustainable in the long term: in 2011 the United Nations Food and Agriculture Organization listed the shrimp as overfished and many conservation groups support a total ban of deep-sea trawling, though some marine managers think that the species can recover if left alone for long enough. In July, the European Commission said it wanted to ban the activity throughout the waters of the European Union, but Javier Garat, secretary-general of Spain's Fishing Confederation (Cepesca) says that industrial fishing groups would prefer regional bans, such as those enacted over the past decade in marine reserves, accompanied by scientific monitoring. They will lobby to modify the proposal when it is considered by the European Parliament and European Council this autumn. Puig agrees that bans should be evaluated on a case-by-case basis rather than as a blanket approach because sustainable fisheries may emerge in some places where the geological and ecosystem damage is "already done".

Journal name: Nature

DOI:10.1038/nature.2012.11356

References

    1. Puig, P. et al. Nature advance online publication http://dx.doi.org/10.1038/nature11410 (2012).

      Show context
    2. Canals, M. et al. Nature 444, 354–357 (2006).

 

Cold-water corals and oxygen content

New study on Mediterranean cold-water corals reveals their sensitivity on low oxygen contents

MARUM, Bremen, Germany

fig1A recently published HERMIONE study on continuous sedimentary records from an eastern Mediterranean cold-water coral site revealed a temporary extinction of these deep-sea organisms during the Early to Mid Holocene (11.4–5.9 cal. kyr BP). The timing of the corals' demise coincides with the sapropel S1 event, during which the deep eastern Mediterranean basin (>1,800 m) turned anoxic. The results of this study show that during the sapropel S1 event low oxygen (dysoxic) conditions of 2 ml l-1 even extended to intermediate depths (~600 m), where the cold-water corals formerly thrived. The corals clearly suffered under these extreme conditions, which might have had a negative effect on their growth rate and reproductive processes, and eventually caused their temporary extinction. This very first evidence for the sensitivity of cold-water corals to low oceanic oxygen contents suggests that the projected expansion of tropical oxygen minimum zones resulting from global change will threaten cold-water coral ecosystems in low latitudes in the same way that ocean acidification will do in the higher latitudes.
Above: Schematic NW-SE cross-section across the Apulian margin showing the Santa Maria di Leuca (SML) cold-water coral province in the Ionian Sea. a: Phases of sustained coral growth in the late deglacial and Mid to Late Holocene that were associated with the formation of Adriatic Deep Water (AdDW) resulting in enhanced bottom currents and a well-ventilated water column. b: Temporary demise of cold-water corals during Early Holocene sapropel S1 event in the eastern Mediterranean Sea. Anoxic (>1,800 m water depth) to dysoxic (~500-1,800 m water depth) conditions were caused by enhanced water-mass stratification associated with increased freshwater input, enhanced eutrophication and reduced AdDW formation.

Reference: Fink HG, Wienberg C, Hebbeln D, McGregor HV, Schmiedl G, Taviani M, Freiwald A (2012). Oxygen control on Holocene cold-water coral development in the eastern Mediterranean Sea. Deep Sea Research Part I 62: 89-96.

 

Management of deep-sea fisheries on the high seas and their impacts on deep-sea ecosystems

Phil Weaver

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Over the past decade, the United Nations General Assembly has addressed international concerns over the environmental impacts of deep-sea fishing in international waters.  A series of resolutions have been adopted committing flag States and regional fisheries management organizations (RFMOs) to manage deep-sea fisheries for sustainability and minimal impact on the environment or else prohibit such fishing from taking place. In September 2011 the General Assembly will review the actions taken by States and RFMOs to implement the UNGA resolutions on deep-sea fisheries with a view to calling for further measures as need be.  There is a clear need to provide scientific input into the UNGA review and I obtained funding from the PEW Environment group, among others, to hold a workshop in early May 2011 to bring together scientists from around the World to assess what progress had been made in deep-sea fisheries management.   A number of HERMIONE scientists participated including David Billett, Anthony Grehan, Monty Priede, Telmo Morato and Ricardo Santos whilst others contributed images and other information.  A report from this meeting has been produced and is available on the HERMIONE website.  This report summarises the workshop conclusions, identifying examples of good practice and making recommendations in areas where it was agreed that the current management measures fall short of their target.

Five topics were identified in the UNGA resolutions where scientific assessment was needed. These were:  1. impact assessments; 2. identifying vulnerable marine ecosystems (VMEs); 3. sustainability of deep-sea fish stocks and bycatch species; 4. move-on rule (where vessels must move away if they encounter VMEs); 5. monitoring, control and surveillance.  Overall the report concludes that:

  • the UNGA resolutions have not been fully implemented
  • deep-sea fisheries are not being managed for long-term sustainability, and
  • vulnerable marine ecosystems (VMEs) are not being given sufficient protection from significant adverse impacts (SAIs).

Phil presenting at the UNGenerally, there has been a failure of RFMOs to collect the necessary data for environmental impact assessments, so these assessments have been non-existent, partial or inconclusive. Many areas where VMEs are likely to occur are still being fished and the precautionary principle is not being applied. When VMEs have been identified, they have been restricted to corals and sponges, whilst other vulnerable fish species caught as bycatch have been ignored. The move-on rule is often the only management regulation in place to protect VMEs but most RFMOs have set threshold limits of bycatch so high that the regulation is ineffective. The workshop expressed concern about the effectiveness and appropriateness of the move-on rule, in that it may actually increase impacts on VMEs in some areas where VMEs are closely spaced; for example, previously unfished seamounts.

Monitoring control and surveillance of remote deep-sea bottom fisheries is a further complication hindering effective management. Better use of tracking systems such as vessel monitoring systems (VMS), with more frequent and detailed reporting, should be combined with effective port state controls. Finally, the workshop condemned the current data policies of most RFMOs, which are reluctant to share fisheries data, including VMS, with the wider scientific community.

In June I was invited by the United Nations to be a panellist on the UN open-ended Informal Consultative Process on Oceans and Law of the Sea (UNICPOLOS).  This involved presenting preliminary results of the report to a plenary session of the United Nations in New York.  My talk was well received with many very positive interventions made subsequently by member states including the EU.  I also gave a talk at a side event organized by the Deep Sea Conservation Coalition.  I am due to appear again in New York in September for the UN General Assembly where we will distribute copies of the report and hold a side-event to promote it.  It seems that the UN are now getting the message that their conservation measures are not being properly applied and that they will need to do more – for example a complete moratorium on bottom trawling in the deep-sea.

Phil Weaver

   

EC Green Paper

Consultation: Green Paper on a Common Strategic Framework for future EU Research and Innovation Funding

inno_union_logo2On 9th February 2011, the European Commission presented a Green Paper which proposes major changes to EU research and innovation funding to make participation easier, increase scientific and economic impact and provide better value for money. The changes, to be introduced in the next EU budget after 2013, would bring together the current Framework Programme for research, the Competitiveness and Innovation Programme, and the European Institute of Innovation and Technology.

The Commission is seeking the views of all interested individuals and organisations on these proposed changes and on the specific questions set out in the Green Paper. The deadline for contributions is Friday 20 May 2011, and you can participate in the consultation process via an online questionnaire, or by submitting a written response, and you can also read the online blog. In parallel, a competition for the name of the Common Strategic Framework is being organised.

This marks the start of a public consultation on the key issues to be taken into account for future EU research and innovation funding programmes.

 

Camouflaged crabs carry the world on their shoulders

paramola_cuvieriA new paper by Braga-Henriqes, A. et al. explores observations of “carrying behaviour” in a species of crab (Paramola cuvieri) in the Azores.  These crabs carry artefacts from their surrounding environments, such as sponges and corals, on their backs.  When startled, for example by the floodlights of the manned submersible LULA used to make these observations, the crabs lower the carried object over themselves and stay still, producing a camouflage effect.  This clever behaviour is made more interesting by the fact that the types of objects carried by the crab were not necessarily those that were the most readily available, suggesting that the behaviour is complex. Morphology, size and weight of objects, as well as palatability seem to be more important in the process of selection than their availability on the seabed.
The article is currently in press and will soon be available in the journal Marine Biodiversity.

Reference: Braga-Henriques A, Carreiro-Silva M, Tempera F, Porteiro FM, Jakobsen K, Jakobsen J, Albuquerque M, Santos RS (accepted) Carrying behaviour in the deep-sea crab Paramola cuvieri (Northeast Atlantic). Marine Biodiversity

   

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