Coral and Other Benthos
Limiting Impacts around Construction
Sediment suspended during construction activities in the marine environment is primary cause of impacts spreading outside of direct footprints. Increased suspended sediments lead to light reduction, sediment smothering and interference with physiological processes. From our experience with many dredging and construction projects, we can predict critical thresholds of suspended sediment levels and advise on techniques to manage works to stay below such levels.
While habitat loss is best treated at the cause, there are simple and effective techniques available to create new areas of reefal habitat or accelerate the colonisation of bare substrates with benthic communities. Transplantation of benthos can be successful but is highly labour intensive and thus generally only suited to projects with local community participation. Restoring the basis of productive habitat and good water quality is cheaper and more sustainable, but can take time. See our guide to artificial reefs for more advice…..
MScience pioneered and published the techniques for monitoring nearshore Pilbara corals in Western Australia. Direct adaptations of these methods are now applied in all major dredging projects in the North-West of WA. We now run standard operating procedures for both diver-based and diver-less monitoring of corals, sponges, filter feeders, sea grass and macroalgae based on those methods.
Every monitoring design is different, being built around the specific needs of established for the program. We have experience with programs which cover large areas at low levels of precision to programs smaller areas with the capacity to detect small changes. While monitoring programs can be designed to detect very small effect sizes, we caution against programs which push detection limits lower than the capacity to explain that change.
As well as offering full monitoring services, we also provide a design and analysis capacity for projects where there is an existing field team in place from another agency. View our contract analysis services described in more detail.
- Pilbara Corals: we have conducted coral monitoring projects in Mermaid Sound, Onslow or Cape Lambert in every year between 2003 and 2014: with the largest data set being 30 months of fortnightly monitoring for a set of over 1500 corals across 24 sites;
- Ningaloo corals: we designed, analysed and reported a monitoring program amongst the branching staghorn corals surrounding a shoreline construction;
- Kimberley Islands: In this area safety concerns mitigate against diving and we have established diverless monitoring for corals and other benthos using a combination of images captured by RoV, drop cameras and reef walking at low tide.
Technical information on Monitoring
Intensive Programs – restricted area:
Detection of effects below a 10% change – often at the level of named species.
Mostly used for: Monitoring of impacts from point sources on small parts of the ecosystem.
- Surveys of coral in replicated transects or as tagged individuals, either by divers or Remotely Operated Vehicle
- Techniques: Marked individuals, replicated quadrats or transects, analysis of videos or stills
Rapid Assessment – Extensive Areas:
Detection of effect sizes of over 25% at scales of entire reef or island group – usually at a community level.
Mostly used for:
- Evaluation of the existing environment: Environmental Impact Assessment,
- Biodiversity assessment, Marine Protected Area planning.
- Looking for regional or reef-wide changes: assessment of diffuse effects like changes to underlying ecosystem processes.
Techniques: Principally those targeting moderate precision information over large areas: benthic lifeforms
Monitoring programs repeat the same sampling methods over time. It is essential that both the field and analysis components of these programs are subject to strict quality assurance to ensure that the results of different surveys are compatible. This is critical for high precision programs. We use standard operating procedures to deliver repeatable results. Our calibration and checking procedures for the analysis component of this work have been refined from experiences in scoring several hundred thousand images (read more…).