Background

24 artificial reef balls made of concrete were deployed in the Long Bay – Okura Marine Reserve in 2001 (Taylor, 2003; Taylor and Buckeridge, 2002). The balls were arranged in two groups of 12 reef balls each, the Zig Zag and the Octagon reefs, and are located approximately 500m offshore (subtidal) and at a depth of ~5m and ~6m respectively (at minimum spring low tide).

The reef balls were closely monitored by Auckland University of Technology’s research staff and students for a period of approximately 3 years after the deployment. During this time, four short reports were produced to inform of the overall state of the colonisation of the reef balls (Jaffrey et al., 2001; Jaffrey et al., 2002; Jaffrey et al., 2003; Jaffrey, 2004) and a thesis by Taylor (2003) was produced detailing the establishment and the colonisation process of the reef balls.

Despite multiple research works having been carried out at the reserves after 2004 (e.g., Kulins 2021) there are no references to the reef balls, probably due to a discrepancy with the recorded GPS coordinates. Presumably, the original coordinates were recorded using the New Zealand 1949 Datum, which was replaced in the early 2000s by the New Zealand Geodetic Datum 2000. It is highly likely that after the initial monitoring program ceased, following attempts to locate the reef balls were done using instruments (e.g., GPS) set to work with the newer NZ Geodetic Datum 2000, which would yield locations displaced 200m SE from the original locations (Fig. 1). Recently processed bathymetry data (NIWA, 2022) revealed the datums discrepancy (Fig. 1).

Rediscovery of the reefs

After multiple unsuccessful attempts to locate the reefs, due to the coordinates issue previously described, my diving buddy Shaun Lee was able to locate them in early 2023. You can read more about the rediscovery in this article that Shaun wrote for the Gulf Journal website, which includes great footage and pictures.

The reefs seem to be in good physical integrity. They are impacted by fine silt and sediment, but that is expected in an environment such as Long Bay. The impact is visually greater at the Zig Zag reef, probably due to it being closer to the shore than Octagon reef. The latter is located in a sandy environment, while Zig Zag is literally, on the mud.

iNaturalist Project

In order to keep track of what divers observe on these artificial reefs, we have setup the Long Bay artificial reefs project. The idea is to be able to build an inventory of species that make use of these reefs and then, perhaps, compare the results against the data recorded from the rocky reefs of the marine reserve.

If you are a diver and you happen to dive on these reefs, we encourage you to add your observations to the project :)

See below a couple of (terrible) images and some footage I took during my last dive at the Zig Zag reef.

References

Jaffrey, J., Taylor, T. W., Proesl, A., Buckeridge, J. (2001) Interim report on the artificial reef constructed in the Long Bay – Okura Marine Reserve, Auckland, New Zealand. 22nd November 2001. Earth & Oceanic Research Institute, Auckland University of Technology.

Jaffrey, J., Taylor, T. W., Murphy, P., Buckeridge, J. (2002). Interim report on the artificial reef constructed in the Long Bay – Okura Marine Reserve, Auckland, New Zealand. 29th July 2002. Earth & Oceanic Research Institute, Auckland University of Technology.

Jaffrey, J., Taylor, T. W., Murphy, P., Buckeridge, J. (2003). Interim report on the artificial reef constructed in the Long Bay – Okura Marine Reserve, Auckland, New Zealand. 11th August 2003. Earth & Oceanic Research Institute, Auckland University of Technology.

Jaffrey, J. (2004). Report on an observational dive visit by J. Jaffrey to the Long Bay artificial reefs, Auckland, New Zealand. 23rd January 2004. Earth & Oceanic Research Institute, Auckland University of Technology.

Kulins, S. (2021). Investigating the ecological effects of Long Bay-Okura Marine Reserve. University of Auckland.

National Institute of Water and Atmospheric Research, NIWA (2022). Benthic habitat analysis of approaches to Auckland. Desktop classifications using multibeam bathymetric data collected from hydrographic survey HS52. Prepared by the National Institute of Water and Atmospheric Research, NIWA for Auckland Council. Auckland Council technical report, TR2022/23

Taylor, T. W. (2003). The creation and colonisation of an artificial reef in the Long Bay-Okura Marine Reserve, Auckland, New Zealand. Unpublished Master of Applied Science thesis, Earth & Oceanic Research Institute, Auckland University of Technology. 118 pp.

Taylor, T., & Buckeridge, J. S. (2002). Environment Engineering in Action: Enhancing Marine Biodiversity Within the Long Bay Okura Marine Reserve. Auckland University of Technology.