Rena spill: ecosystems most at threat, plans for ongoing monitoring

Waikato University marine ecology and environmental science expert Professor  Chris Battershill has predicted the clean-up of fuel oil from the Rena will take months, and that though open sandy beaches may recover quite quickly, the region’s unique rocky reefs will take a lot longer.

credit: Massey University

Professor  Battershill is the inaugural Chair in Coastal Science for the Bay of Plenty, set up by the university and the local regional council, and plays a key role in the Intercoast programme involving Waikato University and Germany’s Bremen University.

With Bay of Plenty Polytechnic’s research vessel, Okiwa, and a University of Waikato survey boat, tutors and some senior students, Prof Battershill and the  president of the New Zealand Underwater Association, Shane Wasik, spent days after the grounding diving on sites near the Rena exclusion zone to assess the distribution and abundance of marine species to provide a  baseline by which impact and recovery from the oil spill could be assessed.

Monitoring of a representative set of habitats using a robust survey design will be started, with special attention will be paid to species of interest or of significance, due to their reef or sandy shore ecological dominance/influence or because they are kai moana or targeted recreational/commercial inshore fish and shellfish. The monitoring program will also incorporate a sampling program to assess petroleum hydrocarbon content (and other relevant chemistry) of tissues of key species (shellfish and fish) as well as sediments. The sampling/survey will be intense in the first weeks/months after the spill and then, depending on the rates of recovery, modified accordingly to record the ecosystems’ return to the background levels established before the ship grounding event.

The Science Media Centre asked Prof Battershill about what happens next:

What do you think are particularly vulnerable ecosystems on the Bay of Plenty coast  where oil in mudflats or other soft sediments might pose particular problems?

“Maketu and adjacent Waihi estuaries were two systems identified as being particularly vulnerable for the most part due to their cultural significance, food source importance for iwi and local resdients and also because of the high abundance and diversity of estuarine bird life seasonally present. These estuaries were found to be vulnerable in the early modelling projections for oil spill trajectory given the predicted at the begining of the incident and sadly those predictions appear to be now realised. Tauranga Harbour itself was also identified as being vulnerable should oil be directed by wind toward Matakana and Mount Maunganui. Although a narrow entrance somewhat shelded by the Mount, the strong currents on the incoming tide is likely to entrain surface slicks into the harbour. The landward side of Matakana (and the river like subestuary there) and Waikareo and Te Puna sub-estuaries were also likely to be in the line of fire. Seagrass beds of Otumoeti and Matua were also deemed vulnerable”.

What kind of monitoring programme do you think should be put in place to check on the longterm damage to coastal ecosystems?

“The Bay of Plenty is fortunate to have had a relatively long history of previous research and monitoring effort. In a search for relevant publications over the last 10 years, over 50 pages of references were readily assembled. There have been long term monitoring programs from the Bay of Plenty Regional Council and the Port Company, as well as research projects from the Polytechnic and the University of Waikato. Information is therefore available on the ‘before’ condition of many habitats, especially the estuaries and open coastal beaches. What was missing was information on the rocky islets adjacent to the Astrolabe Reef, and Motiti Island. In order to establish a baseline by which impact and recovery from the oil spill could be assessed, it was possible in the calm days immediately following the grounding, to mount a rapid survey. This was achieved by the University of Waikato, Bay of Plenty Polytechnic and the Mt Maunganui Dive club (represented by Shane Wasik)”.

“Samples of representative shellfish and some fish species were also collected for background data on their condition and this added to collections made by the Tauranga City Council. Therefore, a baseline data set was established by which to guage the level of impact of the spill. Monitoring of a representative set of habitats using a robust survey design will be set in place once … it is safe to dive. The ecological character of the habitats will be quantified. In addition, special attention will be paid to species of interest or of significance, due to their reef or sandy shore ecological dominance/influence or because they are kai moana or targeted recreational/commercial inshore fish and shellfish.

“The montioring program will also incorporate a sampling program to assess petroleum hydrocarbon content (and other relevant chemistry) of tissues of key species (shellfish and fish) as well as sediments. The sampling/survey will be intense in the first weeks/months following ease/cessation of the spill and then, depending on the rates of recovery, modified accordingly to record return to the background levels established before the ship grounding event. The selection of sites will be made to ensure the range of habitats present are covered. They will also overlap with those sites previously monitored in the BOP Regional council 10 year programme.”

At which sites has sufficient environmental data been previously gathered to benchmark such monitoring?

“The 10 year monitoring sites (estuaries and open beaches) get close to benchmarking the ‘impact’ monitoring program, but some of these have been lost in recent years due to logistic constraints. They do however collectively constitute a rare and valuable long term data set. This is rare. In a review of 10 other marine oil spill events none of them had any long term ‘prior’ information pertaining to the habitats affected, so it was therefore very difficult to prove recovery in any quantitative sense as information on what was ‘normal’ was absent.”

How expensive and how necessary is such monitoring ?

“The impact assessment and recovery monitoring is of paramount importance, not only to quantify the environmental damage and ecological cost sustained, but also to permit prediction of the time that ecosystem functioning will be restored and to determine how ecological services may come back ‘on line’, i.e. restoration of the environmental amenity which includes fisheries, kai moana services, recreational amenity, tourism services etc. Such monitoring can be expensive depending on the scale and the period over which it runs (in the millions of dollars over time if ecological function and elements of fisheries recovery are included).

“There is opportunity however, to build research and training capacity in the region in the process. Given the paucity of information pertaining to how New Zealand species respond to current petrochemical industry related products, there is also a clear need for new research in the eco-toxicology of pollutants utilising relevant experimental procedures. This will no doubt be a focus of future work for the tertiary education agencies in the region and others.”

An interview Dr Battershill gave Radio New Zealand can be heard here