Doctoral Programme on Marine Ecosystem Health and Conservation
 The MARES Researchers and their Research
Recovery pathways of damaged ecosystems: identifying relationships between ecosystem attributes (diversity, functioning and services) and human pressures in saltmarshes
PhD Code: MARES_12_02:
  • Host institute 1: P3 - University of Bologna
  • Host institute 2: P6 - Stichting Koninklijk Nederlands Instituut voor Zeeonderzoek (NIOZ)
  • Host institute 3: Ghent University
Research fields:
  • T2 - Understanding biodiversity effects on the functioning of marine ecosystems
  • T6 - Habitat loss, urban development, coastal infrastructures and Marine Spatial Planning
  • Airoldi Laura
  • Bouma Tjeerd
  • Peter Herman (
  • Carl Van Colen (Ugent)
Contact Person and email: Airoldi Laura -

Subject description
Coastal systems are threatened by multiple anthropogenic activities, such as urban development, organic and inorganic pollution and over-exploitation of resources. Nonetheless, current management activities are still almost exclusively developed in an impact-by-impact framework. Over the past decades, efforts have been made to incorporate natural capital into political and management decisions (Millennium Ecosystem Assessment 2005). However, there is still insufficient scientific understanding of how multiple human actions and potential interacting effects between those actions affect the provision of ecosystem services (Daily et al 2009). The concept of Ecosystem Based Management (EBM) is especially relevant when managing ecosystem resilience, i.e., the capacity of an ecosystem to absorb perturbations while retaining its essential structure, function and services, including the identities of the component species (Folke et al 2004). If ecological system’s resilience is ‘‘eroded’’, the system becomes vulnerable to sudden regime shifts, i.e. critical transitions where after the ecosystem will be characterised by a different set of species, structures, processes, functions and services (Scheffer et al. 2009).
A key challenge of EBM is to assess thresholds and trade-offs associated with alternative management choices. A threshold can be set as the level of human induced pressure (e.g., pollution) at which a small change produces a substantial alteration of the ecosystem’s structural (e.g., diversity) and functional (e.g., resilience) attributes (Samhouri et al. 2010). Thresholds are thus characteristic for non-linear responses. As thresholds exist for multiple human pressures, trade-offs (i.e. tradings between different properties of the system) can occur if management measures affect multiple thresholds in different ways. Unfortunately, thresholds relationships are only quantified for a few cases, and often they focus on one direction only (i.e., the risk of increasing human pressures), without exploring the reverse pathways following management actions geared towards recovery. Further, in natural systems the cumulative impact from several stressors tend to result in synergistic and antagonistic effects rather than additive ones (Crain et al. 2008, Halpern et al. 2008a). For example, fisheries exploitation and increased nutrient loadings jointly affect food webs and production in estuaries, and each affects the sensitivity of species and ecosystems to the other (Breitburg et al. 2009). As a result, there could be levels of fisheries and nutrient loadings that lead to threshold responses  and are resistant to remediation through fisheries removals and nutrient management (Scheffer et al. 2001; Breitburg & Riedel, 2005). EBM aimed at long-term sustainability requires the identification of the causes and non-linear interplay between multiple stressors. However, so far, experiments have not progressed sufficiently to identify trade-offs in management options of interacting multiple stressors.
Coastal wetlands and associated saltmarshes have suffered some of the most serious declines (Dugan 1993, Rippon 2000) with some estimates suggesting global losses ≥ 60-70 % (Lotze et al. 2006,  Airoldi & Beck 2007). Pollution, eutrophication, drainage, conversion to agriculture land and aquaculture uses, changes in sedimentation and hydraulic regimes, global warming, invasive species, fisheries, urban development, shipping, tourism and water sports are generally considered the most serious threats to present day coastal wetlands (e.g. Dugan 1993, Cencini 1998, Kennish 2002). Global changes in sea levels are also beginning to pose severe threats to saltmarshes and coastal wetlands because of the strong dependence of these habitats on water-level fluctuations and tidal regimes (Adam 2002, Morris et al. 2002). Wetlands are now the target of numerous international and national initiatives and regulations for conservation, wise use and restoration of critical ecosystem services. However, the degree of actual recovery of ecosystem functioning and structure from these efforts remains uncertain (Moreno-Mateos et al. 2012).
The objective of the proposed MARES PhD project, for which The University of Bologna and the Royal Netherlands Institute for Sea Research will join their complementary expertise and infrastructure, is to assess the interactive impacts of, and recovery pathways from multiple human pressures in degraded saltmarshes. The candidate will identify potential options for restoration, based on mitigation of interactive stresses (e.g. nutrient inputs, soil permeability, prolonged flooding, trampling or marine litter), and will test their effectiveness experimentally. Responses to experimental manipulations of multiple interactive stressors will be measured both in terms of biogeochemical functions (e.g. storage of carbon, nitrogen, and phosphorus, etc) and biological structure (patch habitat size, primary production, biodiversity, etc), from which recovery of ecosystem services will be derived. Particular attention will be spent on understanding how local environmental and biological settings can affect the rate and degree of recovery of damaged systems. For example there are suggestions that rates of recovery might differ between warm and cold climates,  the size and degree of fragmentation of the habitat, riverine inputs or tidal amplitude, etc. The latter will be achieved by combining field work in The Scheldt (NIOZ-Yerseke), Waddensea (NIOZ-Texel) and the Adriatic sea (Univ. Bologna) in combination with mesocosm experiments enabling the manipulation of multiple stressors (cf. La Nafie et al. 2012).  Along the Adriatic coastline large-scale diebacks of Spartina have occurred and this habitat has been replaced by Salicornia spp. with major losses of structural complexity. The underlying drivers of this shift are not jet fully known, but preliminary data show that recovery of Spartina grasslands is particularly slow in areas with anthropogenic stressors (i.e. nutrient enrichment, deposition of algae, and trampling).
  • Adam P (2002) Saltmarshes in a time of change. Environ Cons 29: 39-61
  • Airoldi L, Beck MW (2007) Loss, status and trends for coastal marine habitats of Europe. Oceanogr Mar Biol Annu Rev 45: 345-405
  • Breitburg DL, Craig JK, Fulford RS, Rose KA, Boynton WR, Brady DC, Ciotti BJ, Diaz RJ, Friedland KD, Hagy JD, Hart DR, Hines AH, Houde ED, Kolesar SE, Nixon SW, Rice JA, Secor DH, Targett TE (2009) Nutrient enrichment and fisheries exploitation: interactive effects on estuarine living resources and their management. Hydrobiologia 629: 31-47
  • Cencini C (1998) Physical processes and human activities in the evolution of the Po delta, Italy. J Coast Res 14: 774-793
  • Crain CM, Kroeker K, Halpern BS (2008) Interactive and cumulative effects of multiple human stressors in marine systems. Ecol Lett 11: 1304-1315
  • Dugan P (1993) Wetlands in danger. A world conservation Atlas. In: Dugan P (ed) Oxford University Press. New York
  • Halpern BS, Mcleod KL, Rosenberg AA, Crowder LB (2008) Managing for cumulative impacts in ecosystem-based management through ocean zoning. Ocean Coast Manag 51: 203-211
  • Kennish MJ (2002) Environmental threats and environmental future of estuaries. Environ Cons 29: 78-107
  • La Nafie YA, de los Santos CB, Brun FG, van Katwijk MM, Bouma TJ (2012) Waves and high nutrient loads jointly decrease survival and separately affect morphological and biomechanical properties in the seagrass Zostera noltii" Limnol. Ocean. In press
  • Lotze HK, Lenihan HS, Bourque BJ, Bradbury RH, Cooke RG, Kay MC, Kidwell SM, Kirby MX, Peterson CH, Jackson JBC (2006) Depletion, degradation, and recovery potential of estuaries and coastal seas. Science 312: 1806-1809
  • Millennium ecosystem assessment (2005) Ecosystems and human well-being: synthesis. Island Press, Washington, D.C.
  • Moreno-Mateos D, Power ME, Comin FA, Yockteng R (2012) Structural and functional loss in restored wetland ecosystems. Plos Biology 10:
  • Morris JT, Sundareshwar PV, Nietch CT, Kjerfve BCDR (2002) Responses of coastal wetlands to rising sea level. Ecology 83: 2869-2877
  • Rippon S (2000) The transformation of coastal wetlands: exploitation and management of marshland landscapes in North West Europe during the Roman and medieval periods. British Academy, London
  • Samhouri JF, Levin PS, Ainsworth CH (2010) Identifying Thresholds for Ecosystem-Based Management. Plos One 5:
  • Scheffer M, Bascompte J, Brock WA, Brovkin V, Carpenter SR, Dakos V, Held H, Van Nes EH, Rietkerk M, Sugihara G (2009) Early-warning signals for critical transitions. Nature 461: 53-59
  • Scheffer M, Carpenter S, Foley JA, Folke C, Walker B (2001) Catastrophic shifts in ecosystems. Nature 413: 591-596

Employment Details
The Ph.D. candidate will be employed as research scientist at The University of Bologna. He/she will have full benefits of the Italian public health and social insurance scheme. The EU-funded gross contribution to the employment costs of monthly Euro 2800 will result in a salary of approx. Euro 2000 per month depending on individual characteristics of the Ph.D. candidate. The candidate will work under the integrated and coordinated supervision of UNIBO and NIOZ, and will spend 24 months at Bologna University and 12 months at NIOZ. That will allow the replication of experiments at different study sites providing insight on how local environmental and biological settings can affect the rate and degree of recovery of damaged systems

Expected outcomes
The candidate is expected to produce at least four scientific publications with the supervisors on the results of experimental tests. The results will also be used to formulate and refine best practices and approaches to the management of multiple human pressures acting in saltmarshes. The candidate will benefit from close exchange with (inter)national projects (e.g., THESEUS, COMTESS, BwN, etc) which will facilitate access to a variety of engineering and environmental data and will ensure that the outcomes of the PhD project will have direct relevance for real case studies

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