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Restoration Ecology

 

“Returning a system to a close approximation of its condition prior to disturbance, with both the structure and function of the system recreated” 

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Restoration Ecology is a relatively new research field and most projects with a pre-defined scientific approach focused on ecological restoration has been in terrestrial environments. In marine environments the use of "artificial reefs" has earlier been addressing other issues than attempting to restore ecosystem function, e.g. fisheries enhancement or shore protection. The conservational aspect has emerged during the last decades but then with the persistent heritage of artificial reef construction for other purposes.

Many purely expermimental studies on settling of marine benthic organisms has resulted in a broad knowledge of different species preferences of a number of substrate qualities like; rugosity, orientation, cryptic or exposed, depressions or elevations etc. The lessons from these experiments has often been that the more complex the substrate is, the richer the settled fauna will be. Substrate heterogeneity gives a multitude of different nisches attracting a larger number of different species.

These lessons has rarely been adopted to the applied field of coral habitat restoration. Still, many restoration programmes are using simple pre-fabricated concrete units with smooth surfaces as previously used in projects aiming at shore protection or fish attraction. Few has attempted to mimic natural habitats, and so far the only projects to my knowledge that has used hydrodynamics as a factor in artificial reef design has been aiming at shore protection.

In this restoration project I will try to mimic the natural habitat, and work with hydrodynamics in the design of the artificial reefs. I'm hoping that this will increase settling success and shorten the time needed for the artificial reefs to reach a similar species diversity as a natural reef.


Habitat Restoration

Habitat restoration aiming at returning an ecosystem to a pre-impact state of structure and function requires that you know what this state was. Often in deeper marine environments you don't. The technology to get in situ information about the deep-sea ecosystems is recently gained. Before that, the development of the bottom-trawling fisheries to heavier gear able to plow their way through the delicate reef habitats had already destroyed much of the habitats we now can go down and look at by means of unmanned (ROVs) or manned submersibles equipped with strong headlights and video cameras. We will often have to make a "best guess" of the pre-impact state of the system we want to restore.

An ecosystem is built by both abiotic and biotic derived structures, and in cold-water coral reefs the main structure is built by one stony coral species - Lophelia pertusa is the main ecosystem engineer of its habitat. There are other stony corals, but they play in another league than Lophelia. Replanting Lophelia is therefore the number one priority, however, it's a slow growing species and you need an abiotic foundation as a substitute for the dead matrix of coral skeleton that usually is present in a reef, i.e. an artificial reef.

What then is the function of a CWC reef? The coral skeleton matrix act as a hydrodynamic trap of nutritious particles and pelagic larvae, thus concentrating nutrients and settling of marine benthos within the reef. It also provide shelter and foraging grounds to animals higher up in the trophic food web. This is the ecosystem function you want to restore.

The key factors you need to identify are:

  • the pre-impact state (from available data and/or a reference site)
  • the proper restoration endpoint (guided by the above)
  • the local restoration potential or constraints (limited larval pool?)
  • the functional groups (in this case Lophelia is the key functional species, but there can be more less obvious ones)
  • the key linkages (e.g. food web interactions, symbiotic relationships)
  • the essential matters to be cycled within the system
  • the natural or human induced disturbance regimes that the restored habitat will need to buffer against
  • and, finally, what are the key factors that you need to include in the analysis to assess the success?

This 'restoration ecologist's checklist' is derived from a paper written by Palmer et. al (1997), an excellent paper linking Community Ecological Theory with Restoration Ecology and the possibility of cross-fertilization between the two fields. This paper is my map and compass throughout this PhD project. The examples are from ecological restoration in terrestrial habitats, but the authors have managed to generalize so well that you can apply the thinking in any environment. In fact, you could read it solely to understand the magic of generalization. That is a trick that could get your papers into the highest ranked international journals. After reading it the first time I couldn't really tell whether it had a marine or terrestrial focus. It was applicable to my work, so I assumed that it had some marine examples. Reading it again, however, I realized they're talking beetles and grassland. The closest they get to aquatic environments are examples from wetlands and river regulation. They were nowhere near coral reef restoration.



Reference

Palmer M.A., Ambrose R.F., Poff N.L. (1997) Ecological theory and community restoration ecology. Restoration Ecology 5:291-300pp

 

   
 

 

 

 

 

 

 

"Every year an area twice the size of the contiguous USA is being trawled"

bottom-trawling video

In many areas the deep coral habitats has been severely reduced. In Norway it is estimated that 30-50% of the reefs have been damaged or destroyed. In Australia and New Zealand as much as 90% of the reefs have been destroyed due to the orange roughy fisheries.

 

 

There are many scientific references of trawling impacts, here are two examples:

Fosså J.H., Mortensen P.B., Furevik D.M. (2002) The deep-water coral Lophelia pertusa in Norwegian waters: distribution and fishery impacts. Hydrobiologia 471:12

Koslow J.A., Gowlett-Holmes K., Lowry J.K., O'Hara T., Poore G.C.B., Williams A. (2001) Seamount benthic macrofauna off southern Tasmania: community structure and impacts of trawling. Marine Ecology Progress Series 213:111-125