Study underway into algal bloom on Cook's Muri Lagoon

Transcript

There have been more concerns this month with water quality on Rarotonga in the Cook Islands.

In the latest development two piggeries were forced to shut down because water they were discharging was leaching into the Ngatangiia waterway.

The famed Muri Lagoon is part of this waterway and the most recent concerns there have been an algal bloom which had the local community out trying to clear it last week.

Steve Lyon, who runs Pacific Dive and is based at Muri, is also a marine scientist, and part of a team looking into why it is worse this year.

He told Don Wiseman about the algae and its probable origins.

STEVE LYON: It's definitely making the lagoon look a bit different. The lagoon looks a little darker from the beach and I guess that's the aspect that is most concerning for the operators in and around that area, that the lagoon doesn't have the same aesthetic appeal. It actually isn't that far established into the lagoon offshore. The lagoon is about 300 or 400 metres wide at that point and [the algae] only exists within about 50 or 70 metres of the shore. But from the shore it does have quite a visual impact. So that is one of the key problems we have identified and why have we moved forward with a programme to do more investigations on this and figure out what is going on.

DON WISEMAN: What do you put it down to?

SL: Well, this algae, as I say is current in the environment anyway, it's not new and it's not something we haven't seen before. But the extent of the bloom this year is new for us. Obviously nothing can be definitive without understanding what we had up to this, and there hasn't been ongoing research on this, so we are coming midway through the event if you like. But it would appear that it is a combination of several things. Firstly this algae doesn't settle very well when this water is turned over a lot. And this year we have had calmer weather, less large southern swell, less wind than we would normally get through that part of the lagoon. So the lagoon has been more settled than usual, and that may have contributed to it. Another contributing factor is nutrification, so higher nutrients in the lagoon, that can come from things like laundromats, laundry soaps, detergents, agricultural run-offs and of course septic run-off as well. So that can all contribute to higher nutrients in the lagoon. However we haven't really seen that as an issue because there haven't been other indicators, we haven't had any human health issues or anything like that, and the water is still testing pretty clean actually. I mean as far as I know it's fine within the lagoon itself, it's only some streams we have some issues with.

DW: In terms of controlling that run-off, I know there were two piggeries that are in the gun close by at the moment, and there have been issues going back a while. But in terms of that run-off that you're talking about from the laundromats and that sort of thing, what sort of effort goes into trying to control that?
 
SL: Well first of all it's important to note that our tourism industry here is very, very concerned about any potential problems because this is one of our key natural assets, and we certainly want to make sure we are doing the right thing to keep our environment as clean as pristine as possible. We have had an aid funded project for several years now called the water and sanitation project funded in part by NZ Aid, and that has gone a long way to making improvements in how we manage our waste. So the focus of that project itself so far has been upgrading domestic sewerage systems so essentially upgrading septic systems in households in the Muri area. And I think they've done over 200 upgrades in that area. And we would expect that to have an improvement. The project is still ongoing so there is now work to be done in commercial sectors, and of course hand in hand with that is an increase in the capacity and the will of the government to tidy up some of the issues around animal husbandry and things like that. And lately we have seen two piggeries shut down as a result of community complaints about their environmental impact and the government has done something about it.