Attendance was high at a recent presentation on the biodiversity of Lyttleton Harbour/Whakaraupo. About forty people— including representatives from Environment Canterbury (ECan), members of local government, and a lively crew of schoolkids from the nearby Governor’s Bay School— crowded into the Governor’s Bay Fire Station to hear about and discuss the state of the harbour with local marine biologists Tommaso Alestra and Mads Thomsen.
Tommaso Alestra, a member of the University of Canterbury’s Marine Ecology Research Group (MERG), started off the talks with an overview of his recent work on the biodiversity of Lyttleton Harbour/Whakaraupo. This project started a little over a year ago, when ECan approached MERG with a problem: they didn’t have any information about the harbour’s rocky reef communities. While Lyttleton Port itself has been studied repeatedly, no one had ever completed a comprehensive study of the surrounding area. Given the possibilities of future development in the harbour— dredging the channel, instating a new Catchment Management Plan, and so on— this knowledge gap needed to be addressed. What plants and animals are present in Lyttleton Harbour? And how might these communities change in the future?
Tommaso, along with other researchers from MERG including Stacie Lilley and Jan McKenzie, set out to start answering these questions in June of 2015. The researchers identified 20 sites spread across both coasts of the middle section of the harbour. At each site, they carefully surveyed the rocky reef communities, documenting the presence and abundance of plants and animals at the upper tidal, mid tidal, and low tidal zones. It took six months to complete the surveys and another six to compile and analyze the data.
The fruits of this effort have been worthwhile. Tommaso’s research has shown that Lyttleton Harbour /Whakaraupo reefs are typically highly diverse, with a high number of plant and animal species. Canopy-forming algae, which are essential to creating habitat in most intertidal rocky reefs, are doing well in Lyttleton. Where canopy-formers are missing, mussel beds are present and play a similar role in turning rocky substrate into liveable habitat for a slew of marine plants and animals.
There are some challenges facing Lyttleton Harbour/Whakaraupo, however. One of these is the presence of invasive species. As Tommaso said, “they’re everywhere.” His surveys have revealed twelve invasive species spread across the reefs. One of the most nefarious of these is the North Pacific kelp, Undaria pinnatifida. You may be familiar with Undaria– it’s also known as wakame, and it features prominently in Japanese cuisine.
This is where Mads Thomsen took over. He began with “Invasion Biology 101”, a high-speed lesson on the different definitions and impacts of invasive species. New Zealand, though geographically isolated, is deeply connected to the global network of marine invaders. These species arrive, predominantly, as a byproduct of shipping, whether carried along in ballast water or clinging to the hulls of ships. Many species don’t survive the process of transport and arrival in a new environment, but those that do, and that become established in the new environment, can have major impacts.
They don’t always have the impacts you’d expect, however. Undaria pinnatifida, Mads’ research shows, is an invasive species that’s prevalent across New Zealand. But here’s an important distinction in invasion biology: while Undaria is a highly successful invader, blooming in massive swathes across the reefs, it’s not a particularly impactful one. It doesn’t seem to kill off local species, or result in lower overall biodiversity in the areas where it’s present. This might be related to the fact that Undaria blooms on a seasonal basis, present in high densities in the winter but dying back to vegetative stalks in the summer. This vegetative period might allow native species to withstand the pressure of invasive Undaria. No one knows, absolutely, the reason for the lack of impact. Ultimately, in local reefs, where Undaria is highly abundant, this invasive seaweed might not be so nefarious as we thought.
With that conclusion emphasized, the floor was opened for questions, and a lively discussion ensued. The questions from the listening audience were well-considered, critical.
One listener challenged the way findings had been presented during the talk, pressing the researchers on their conclusions and allowing them to explain some of the limitations of studies like these. Another listener suggested an economic market for Undaria, while others commented on the impact this research might have on the forthcoming decisions about dredging the channel into Lyttleton Port. All seemed to agree, it was a pity we did not have earlier data to compare to 2016, but good that we had it now. And overall, there was enthusiasm about continuing this work in the future.
For me, a student in ecology and aspiring science communicator, it was an event that inspired a lot of appreciation for the local community. I was left impressed with the quality of the conversation between researchers and concerned locals— listeners were engaged and lively, but also critical, making sure the scientists understood the value of their comments. I was inspired by the clear communication between local scientists, members of government, schoolkids, and an interested public. Collaborative conversation like this is necessary for effective and inclusive local conservation, and I’m excited to see that it’s thriving in Lyttleton.
Until next time,