Doctoral Programme on Marine Ecosystem Health and Conservation
 The MARES Researchers and their Research
Tolerance of deep-sea benthic ecosystems to trawling disturbance
PhD Code: MARES_12_10:
  • Host institute 1: P13 - University of Aveiro
  • Host institute 2: P1 - Ghent University
  • Host institute 3: P16 – Hellenic Centre for Marine Research (HCMR)
Research fields:
  • T2 - Understanding biodiversity effects on the functioning of marine ecosystems
  • T4 - Natural Resources: overexploitation, fisheries and aquaculture
  • Cunha Marina R.
  • Vanreusel Ann
  • Lampadariou Nikolaos (
Contact Person and email: Cunha Marina R -

Subject description
Deep-sea sediments represent one of the major ecosystems on earth and, the continental margins in particular provide essential goods and services (e.g. oil and gas, fisheries, CO2 sink) (Levin and Dayton, 2009).  Because of the difficulties associated with its exploration, the full variety of habitats and spectrum of functions and services provided by the deep-sea are poorly known Results from the limited number of deep-sea studies have provided convincing evidence that human activities are leaving spatially wide footprints at the deep-sea floor (Ramirez et al., 2010; Glover & Smith, 2003), but the full impacts associated with the exploitation of deep-sea resources (e.g. mining, oil and gas, fishing) and dumping of waste (mining and litter) is poorly known. Determining the sensitivity of deep-sea organisms and ecosystems is crucial for impact assessment as anthropogenic activities will increase significantly in the near future. Recent studies suggest that, in contrast to shallow water and terrestrial ecosystems (Cardinale et al. 2006), even small losses in deep-sea biodiversity can have exponential impacts on functions such as biomass and productivity (Danovaro et al., 2008; Loreau, 2008).
Before we can conclusively state that European deep-sea ecosystems are threatened by human activities, we need to better understand their ecology, in particular the biodiversity-functioning relationships,  and the potential impacts of the exploitation of biological, energetic and mineral resources along the European continental margin which mostly lie within the national Exclusive Economic Zones. Knowledge on biodiversity and its relation with functioning is therefore crucial for providing information relevant to the identification and implementation of technical options for their conservation and sustainable use (UNESCO, 2009).
Fisheries are the most widespread human activity in the marine environment (Benn et al. 2010). Bottom trawling, in particular, have been shown to damage or destroy long-lived emergent epifaunal animals such as corals and sponges, harming the three-dimensional complexity of the seabed, and subsequently reducing species diversity and faunal biomass (Althaus et al. 2009; Clark & Rowden 2009; Koslow et al. 2001). Therefore, fishing impacts on soft sediments will be investigated in different regions (e.g. the South Ionian Sea and the West Iberian margin) .  Areas of disturbance versus virtually undisturbed sites in similar environmental settings within these regions will be identified and compared in terms of biodiversity, community structure and ecosystem functions in order to assess the (in) tolerance to disturbance of the benthic assemblages.
The following main Hypothesis was therefore identified for this PhD project :Disturbance will alter biodiversity (loss of species and/or functional groups) affecting various functions (depletion of nutrients in sediment, inefficiency in carbon mineralization, reduced sediment-seawater fluxes etc.).
This hypothesis is translated in specific tasks:
1) to identify areas and degrees of disturbance;
2) to identify and compare biomass (C), taxonomical and functional composition and diversity of macro, meio and microbenthic communities of disturbed and reference areas;
3) to compare ecosystem functions in relation to biodiversity between disturbed and reference areas
Two potential study areas are identified: In the central and eastern Mediterranean, the main trawling areas are located along the south Ionian Sea, and are exploited mainly by Italian multiple-gear vessels of small gross tonnage with a length of less than 12 m (Sardà et al. 2004). Studies of the effects of fishing on deep-sea ecosystems in the Mediterranean Sea have mostly addressed the population structure and dynamics of target species, while little is known of the impact of fishing on non-target species and biodiversity, and the resilience of benthic communities (Sardà et al. 2004). In the Western Iberian Margin an area of interest is located at the Southwest coast of Portugal (depths of 200-800 meters), where otter trawling has occurred on a continuous base, targeting Norway lobster (Nephrops norvegicus).. Today, trawling extends to depths above and below the Nephrops grounds targeting several species of deep water shrimps. This activity yields a diverse catch of fish and invertebrate species, from which only a few are of commercial interest, producing very high levels of by-catch (50 to 90% of the total weight caught) (Erzini et al. 2003). The area of interest includes fishing grounds with different levels of impact (from no fishing to intense trawling and fixed nets). Depending on timing of the planned multidisciplinary cruises soon to be confirmed at least one of these will be investigated for the above tasks in the context of this PhD.
Project’s success will be best attained by following a well-designed workplan with four predefined phases including specific activities scheduled in order to meet the time limits of the PhD project.
Phase 1: Project set-up (months 1-4). Literature review; detailed design of the field experiment and sampling strategy (selection of site(s), stations, frequency of sampling and sampling technique, selection of appropriate methodology for applying the studied disturbance, determination of variables to be measured, etc); compilation of a list of laboratory and field equipment and consumables; construction and/or maintenance of laboratory and field equipment that will support the planned experiments.
Phase 2: Field work (months 6-9 and 18-21). Collection of field samples will be performed within the first two years of the project. The field campaigns will be multidisciplinary as they will be part of other larger research projects. Benthic samples will be collected and ROV surveys performed in both trawled areas and control stations in order to characterize the benthic environment and to assess the effect of deep-sea fishing activities on the different benthic components (microbial, meio-, macrofaunal communities). Sediment cores will be collected for an onboard incubation experiment using benthic chambers and micro-electrodes in order to estimate the rate of nutrient fluxes in disturbed and undisturbed samples, used as a proxy for ecosystem functions.
Phase 3: Sample analysis (months 6-29). Sample processing; identification of organisms; measurement of community and population dynamics variables, such as diversity, mortality rates, reproduction success, sex and life stages ratio, etc; stable isotope analysis; laboratory analysis of important environmental variables (e.g. sediment granulometry, indicators of food availability).
Phase 4: Data analysis, synthesis and dissemination (months 16-36). Data analysis using the most advanced statistical techniques in population and community ecology
  • Althaus F, Williams A, Schlacher TA, Kloser RJ, Green MA, Barker BA, Bax NJ, Brodie P, Schlacher-Hoenlinger MA (2009) Impacts of bottom trawling on deep-coral ecosystems of seamounts are long-lasting. Marine Ecology Progress Series 397:279-294
  • Cardinale BJ, Srivastava DS, Emmett Duffy J, Wright JP, Downing AL, Sankaran M, Jouseau C (2006) Effects of biodiversity on the functioning of trophic groups and ecosystems. Nature 443:989-992
  • Clark MR, Rowden AA (2009) Effect of deepwater trawling on the macro-invertebrate assemblages of seamounts on the Chatham Rise, New Zealand. Deep Sea Research Part I: Oceanographic Research Papers 56:1540-1554
  • Danovaro R, Gambi C, Dell' Anno A, Corinaldesi C, Fraschetti S, Vanreusel A, Vincx M, Gooday AJ (2008) Exponential decline of deep-sea ecosystem functioning linked to benthic biodiversity loss. Current Biology 18:1-8
  • Erzini K, Monteiro P, Araújo A, Castro M (2003) Journal of the Marine Biological Association of the U.K. 83, 731
  • Glover AG, Smith CR (2003) The deep-sea floor ecosystem: current status and prospects of anthropogenic change by the year 2025. Environmental Conservation 30:219-241
  • Koslow JA, Gowlett-Holmes K, Lowry JK, O'Hara T, Poore GCB, Williams A (2001) Seamount benthic macrofauna off southern Tasmania: community structure and impacts of trawling. Marine Ecology Progress Series 213:111–125
  • Levin LA, Dayton PK (2009) Ecological theory and continental margins: where shallow meets deep. Trends in Ecology & Evolution 24:606-617
  • Loreau M (2008) Biodiversity and Ecosystem Functioning: The Mystery of the Deep Sea. Current Biology 18:126 - 128
  • Ramirez-Llodra EZ, Brandt A, Danovaro R, De Mol B, Escobar E, German CR, Levin LA, Arbizu M, Menot L, Buhl-Mortensen P, Narayanaswamy BE, Smith CR, Tittensor DP, Tyler PA, Vanreusel A, Vecchione M (2010) Deep, diverse and definitely different: unique attributes of the world's largest ecosystem. Biogeosciences 7:2851-2899
  • Sardà F, Calafat A, Flexas MM, Tselepides A, Canals M, Espino M, Tursi A (2004) An introduction to Mediterranean deep-sea biology. Scientia Marina 68 (Suppl. 3):7-38
  • UNESCO. 2009. Global Open Oceans and Deep Seabed (GOODS) – Biogeographic Classification. Paris, UNESCO-IOC. (IOC Technical Series, 84)
Employment Details
The candidate will be employed by the University of Aveiro under a "Researcher" contract, for a 3-year period. The gross monthly salary will be approximately 1800 €, subjected to legal taxes. The host will provide office space including access to computer facilities as well as workbench space in the Marine Ecology laboratory including access to the equipment therein. All basic equipment and material for performing the proposed research is available at the host institution. In addition, the candidate will also have access through short term research visits to equipment and facilities of the partner institutes (HCMR and Ghent University).

Expected outcomes
The expected results of this PhD project are to attain a better insight in the relationship between disturbance, deep-sea diversity and ecosystem functions integrated over different size components of the benthos.
A “comparative experimental approach” (Menge et al., 2002, 2003) will be employed to identify the influence of anthropogenic stressors on the biodiversity and functions of deep-sea sedimentary environments. By integrating aspects of biodiversity and ecosystem functions in a context of disturbance, this project aims to contribute significantly in the development of management tools for maintaining sustainable maritime activities while preserving the integrity and the good environmental status of margin ecosystems.
Four deliverables are suggested for helping assess the progress of the different phases of the PhD project and achievement of objectives:
  • Deliverable 1: Report on field and laboratory experimental design and the methodology to be used (month 5)
  • Deliverable 2: Report on the results from laboratory and field experiments related to the first cruise (month 17)
  • Deliverable 3: Report on the results from laboratory and field experiments related to the second cruise (month 29)
  • Deliverable 4: Effects of deep-sea fishing activities on benthic communities: results from field and laboratory experiments). The deliverable will consist of a set of publications in peer-reviewed journals, most likely 3, describing the overall results of the study which will be submitted at the end of project (month 36)
We expect at least 3 papers to be generated in the context of the PhD:
  • 1) on the comparsion of the biodiversity of the three size groups between impacted and non impacted sites.
  • 2) on the impact of trawling on ecosystem functioning and its relation with biodiversity
  • 3) on the tolerance of specific taxa and their use as indicator taxa.
Throughout the duration of the project important scientific results will be communicated to the scientific community through participation in International conferences (e.g. 15th International Meiofauna Conference, Korea 2013). In addition, the candidate will be encouraged to develop and/or participate in outreach and education activities directed to enhance awareness of the general public (including school-age children and teenagers) on deep-sea scientific and conservation issues.

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