Recommendations

This project presented the author with three wonderful opportunities to travel to remote parts of the Australian and Antarctica continental shelves, with the challenge of mapping the benthic habitats from select sites. Apart from the great variation in the physical environment of the study sites, the scales of observation and assessment techniques used were also vastly different. With the benefit of the experience gained through this project, the following issues are raised,

some with recommendations, and others with predictions of the future use of certain technologies for marine benthic habitat mapping.

5.2.1 Multibeam sonar

An essential technology used in this project was multibeam sonar. The high-resolution 100% sea floor coverage has revolutionised bathymetric and geological maps of the ocean. This technology is the key to linking the traditional geological and biological approaches to benthic habitat mapping. Yet it can come at a large cost in time and money. The huge leap in the amount of data collected, taxes post-processing time if applied line by line. Area-based editing is by far a quicker method to clean the data of outliers, however, this software is expensive and is not easily available for students. Another impediment for using this technology is the predominant use of proprietary-formatted survey data. This project used three different expensive multibeam sonar systems and each had a different output data format. Big delays were experienced in obtaining post-processing software which could view the data, then convert it into simple XYZ format for viewing in a GIS. One can only hope that multibeam

manufacturers realise that making their data formats accessible on open-source processing packages, such as MBSystem and Caraibes, will encourage more use of their equipment.

5.2.2 Underwater video

Underwater video is considered the priority tool for groundtruthing marine habitats. Single long transects are recommended to image the patchiness of benthic communities, which occurs at all scales. In contrast, still cameras are limited in their ability to 'capture' the patchiness of benthos. The resolution of underwater video is becoming closer to the image quality of still cameras with the development of digital video, and improved processing techniques will enable better taxonomic identification of megabenthos. Analogue video should be avoided as it usually requires conversion to digital for analysis and loses resolution in the process. Statistical analysis of video imagery is time consuming, however, this project benefited greatly from the

megabenthos patterns revealed by multivariate analysis of the video data. In the future, we will see greater use of video imagery within a GIS, whereby screenshots of video imagery are mosaiced and then georeferenced for overlay on multibeam data. This technique will greatly enhance interpretation of geophysical data and the relationship with biota.

5.2.3 Sediment grabs

Sediment grabs are a traditional method of sampling the seabed to detect patterns in macrobenthos distribution. Certainly grabs are a low-impact technique compared to benthic trawls for collecting infauna. In this project, much use was made of sediment samples for trying to determine whether the biogenic composition of sediment could indicate macrobenthos distribution. Sediment composition did also prove useful in helping to establish the variation in environments of deposition. However, much time and effort was spent looking at skeletal components under a microscope, and underwater video was found to be a far better

groundtruthing technique to establish benthos distribution. As gravel weight was found to be a useful proxy for benthos, analysis should focus on the size classification of sediments.

Classifying the detailed biogenic components of sediment is not recommended.

5.2.4 GIS

GIS is indispensable to scientists and managers to provide a comprehensive view of the ocean's natural processes. Yet it does present some problems. Again, propriety-formatted data formats cause large delays in converting from one format to another for viewing in the GIS of choice. One should not underestimate the time needed to convert data formats, particularly if dealing with raster datasets from different sources. Any GIS chosen for ocean modelling should, ideally, view both raster and vector data together from a large variety of data sources. In addition, quality metadata is important if one is to share GIS models between colleagues or to present maps to the public on the internet. Care should be taken to keep detailed notes of how each GIS map was produced so as to compile the metadata. It is also important that the verbal descriptions of processes acting on the seabed match the spatial distributions of benthic habitat boundaries in a GIS. In this project, the author found the use of conceptual model diagrams to be useful in describing the geology-benthos relationships, and for communicating other processes acting on the seabed. In the future, we will see greater use of interactive 3D models of seabed bathymetry and benthic habitats through the internet as the next step from traditional 2D mapping in a GIS.

5.2.5 Proxies

Finding geophysical proxies for benthos distribution was an important objective of this thesis. Amongst the benthic habitat mapping fraternity, there are many projects looking for the right proxy so as to automate datasets and derive benthic habitats. This project found that slope and gravel weight were useful physical variables to predict megabenthos patterns, but these

study. We recommend that future benthic habitat mapping studies are conducted which prioritise the collection of these two geophysical variables, to explore whether they are

potentially useful as universal proxies in other marine environments. However, it is unlikely that there is actually a single 'Rosetta Stone' proxy, which can automatically predict all benthos assemblage patterns. In this project, the author found that the use of proxies can only be taken so far and should only be used as a guide for characterising the seabed. One should then stand back and consider all physical and biological patterns in light of what one knows about the processes, asking questions, such as 'Do the patterns make sense?' As this project found, it takes a wide view, considering all information on the geology, oceanography and biology to derive benthic habitats.

5.2.6 Habitat definition

The concept of 'habitat' means many things to many people. Scientists and managers appear to spend a lot of time and effort trying to define a 'one-size-fits-all' definition. Similarly, there are many different schemes to classify marine benthic habitats. It is generally accepted that habitats should be viewed within a hierarchy at progressively finer-scales of observation. For this project, a classification scheme was used which is being developed for the bioregionalisation of Australia. This author found the scheme quite user-friendly as the finer-scales of observation described the seabed habitats in terms of the Secondary Biotopes (the geology type) and the Biological Facies (the biological assemblages associated with the geology). Even though this is a top-down hierarchy, it is important to note that the boundaries of the lower levels define the boundary limits of the upper levels. However, this author believes that one should not get too pedantic about which scheme is used for interpreting benthic habitats of study areas. A

recommendation is to select a scheme, modify it for ones own use, and make the definitions and scale of each level clear for the reader to understand.

5.2.7 Maps

This project has raised questions about how should one report the scale and resolution of electronic maps produced in a GIS. The traditional method of map making involved the production of paper hard copies where reporting scale is quite standard. Scale for GIS is a very dynamic because it can be changed in an instant. When dealing with raster imagery in a GIS, knowing the resolution of the grid size is probably as important as knowing the scale. For this project, the resolution of gridded data in the digital elevation models were reported in the text, however, for screen shot images of bathymetric maps produced in a GIS, it may be of use to also include the grid size along with a distance scale within a legend on the map. To enable

people to understand the uncertainties and the technology used in collecting and interpreting benthic habitat maps, a reliability diagram could be attached to images. The diagram could be a matrix of the technology used, line-spacing, age of survey etc. for users to judge the quality of the data behind the interpretations. This author believes that hard copy paper maps of fixed scale are quite limiting in their ability to communicate the spatial distribution of benthic habitats. In the future, greater use will be made of the internet for users to access GIS data, and to

interactively change the presentation, scale and colours of electronic maps.