Underwater vision

Nicole Miller helps us see what is happening to Wellington's coastline (14 minute read)

In a week of weather warnings and wearing waterproof clothing, Sunday was an unexpected respite. The wind dropped, the clouds dispersed and there was even some warmth in the air. Earlier in the week, the forecast had been dire, and it looked as if we might have to cancel the event a group of us had been planning at a local reserve. But Wellington showed us its gentler side that day.

Our planned event was to show people some of the work underway in the reserve. We had educational activities for children, an area ready for planting with native grasses and shrubs, and gloves for anyone who wanted to help me with weeding tradescantia. We didn’t have a lot of people – we hadn’t expected to – but we did have enough to make it a good morning. It was wonderfully satisfying to see some native sedges I hadn’t realised were there emerge from a mass of tradescantia. When we had finished our work and were having a hot drink, we even saw a kārearea (New Zealand falcon) flying overhead.

When it comes to helping people connect with our birdlife and forests, we have the advantage that they are conspicuous. It’s a very different challenge to connect people with life under the sea. Most of us, especially those living somewhere with a climate like Wellington’s, never see beneath the water’s surface. But our actions are affecting the undersea environment, particularly in places like Wellington Harbour. How can we show people what is happening hidden from view?

This is a question which has been troubling Nicole Miller. She discovered scuba diving as a university researcher, and she tells me that she was first entranced by seaweed on a visit to the Channel Islands off the California coast. “The seaweed there was amazing, a lush, thick kelp forest. As a diver, I found it so impressive being immersed in these towering underwater forests.”

Californian kelp forests (image credit: Nicole Miller)

On her return to Wellington, she contacted marine scientists to ask whether she could see similar giant kelp forests anywhere in New Zealand. “They said, oh yeah, we’ve got those right here in Wellington. And I said, how come nobody talks about this? This is just incredible.”

Nicole was delighted to find she could dive in seaweed forests around Wellington – even inside Wellington Harbour – but she soon realised that not all was well. The giant kelp forests of Wellington Harbour are disappearing at a rate which would horrify us if it happened on land. But because it’s underwater, most of us don’t notice.

The loss of seaweed in Wellington Harbour led to Nicole becoming both a citizen scientist and a marine advocate. Now, her efforts are the subject of a recently released documentary: Seaweed, a Love Story. It tells of the hundreds of hours she has spent underwater, documenting the state of seaweed on, so far, 46 kilometres of Wellington coastline. I saw the film’s premiere advertised, through my work on the Wellington Glean Report, so I decided to see the film and speak with Nicole to learn more about seaweed, and how she connects people with our underwater forests.

Before I go on, I think it’s useful to define exactly what seaweeds are, because to someone used to working on the land, they can be confusing. When we look around us on the land, almost every living thing we see is either a plant, an animal or a fungus. There are a few biological weirdos which you might notice if you are looking for them, such as lichens, but without a microscope these are all you are likely to see.

In the sea, however, it’s more complicated. The term seaweed encompasses three groups which we commonly call green algae, red algae and brown algae¹. This makes it sound simple, but these three groups are less closely related to each other than carrots, pine trees and mosses. Green algae are usually considered to be plants, but they are in a separate group from land plants. Red algae are not considered plants but belong to a group which sits alongside plants in the family tree of life. Brown algae aren’t even close to being plants. They are off in a completely separate group from plants, animals and fungi. Among the relatives of brown algae are the parasites which cause potato blight and kauri dieback.

In this image, you can see brown, green and red algae (image credit: Nicole Miller)

A walk along the seashore can reveal all three kinds of seaweed, but the largest number of species, by far, belong to the red group. However, in terms of mass, the brown algae dominate. They are the marine equivalents of imposing kauri trees, lofty kahikatea, dense canopies of kohekohe or our gnarled mountain beech.

I wrote about seaweed a couple of years ago, and looked into the range of threats seaweeds face in Wellington Harbour. Since that was a while ago, I’ll summarise what I learned first, and then explain some of what Nicole and her colleagues have been learning more recently.

The mightiest of the seaweeds is the giant kelp, which lives in cooler waters in both the northern and southern hemispheres. In Wellington, it’s living right at the edge of its temperature tolerance, which means that as the climate warms it will struggle more and more. Marine heatwaves, which are prolonged periods where the sea is unusually warm, are already contributing to the loss of giant kelp and other kelp species in some areas.

As well as climate, seaweeds in Wellington Harbour are affected by sediment. Especially during storms, rain has always washed soil into streams and rivers, which have then carried it into the sea as sediment. However, the destruction of forest cover has accelerated the loss of soil from the land and has massively increased the amount of sediment in the sea. Seaweeds need light, because, like plants, they make their food using sunlight, but sediment in the water blocks the light they need. Sediments smother marine life and can also scour rocks, making it difficult for young seaweeds to establish.

The third problem is the way that humans have unintentionally disrupted the food chain in the sea². Seaweeds, along with some kinds of microscopic plankton, perform the same role in the sea as plants on land – they are the base of the food chain, on which everything else depends. The next level in the food chain contains the herbivores, which directly eat the plants on land or the seaweeds in the sea. Some fish are herbivores, as are shellfish such as pāua, and sea urchins such as kina. Then there are the animals which eat other animals, the carnivores or predators. Important predators in our coastal waters are large fish such as snapper and blue cod, as well as crayfish.

However, people love to eat snapper, blue cod and crayfish, and the result is that there are far fewer predators in places such as Wellington Harbour than there used to be. The reduction in predators means that nothing is eating the herbivores, and some, particularly kina, have seen a large increase in numbers. The balance between the species has shifted because we have removed the predators. For seaweeds already struggling with high temperatures and waters full of sediment, this is a disaster.

It’s difficult to know exactly when and how seaweeds are being lost from the harbour, because we can’t observe under the sea in the same way we can the land. Even for a diver like Nicole, it’s difficult. “We had to put permanent markers in, because otherwise nobody believes you, in fact, sometimes you question yourself. If you’ve got a sloping reef, you’ve only got visibility somewhere between 2 and, if you're lucky, 4 meters. You don’t really have distinct landmarks, and it’s hard to see how things change. So we used permanent markers and took photos in the same area over time.”

The hundreds of hours that Nicole has spent diving have given her an understanding of the way kina are affecting the areas of seaweed forest. “It's quite hard to capture the initial impact of kina grazing, because kina move around quite a lot. It seems that they move in waves. The first time they move through a kelp forest, it just gets a bit thinner. If I see an area like this, I can tell something has changed, but I'm not sure what. And then they come in second and third waves, often bunching up against the remaining kelp forest in high numbers. That’s where we see drastic change and fast change - from kelp forest to a few little stumps left - but eventually the seaweed is all gone.”

The following videos show the decline resulting from kina overgrazing as well as recovery resulting from kina control.

Seaweed decline

Seaweed recovery

The resulting bare rock is known as a kina barren. There’s nothing much living there apart from kina. They’re bold kina too, Nicole, points out, they don’t have to hide, because there are no predators. “I was cycling into town one day, on one of those glorious Wellington days that you can’t beat, and the harbour was completely flat. I was just north of the fountain and the rotunda, and I looked over the sea wall, and I could see the urchins coming right to the sea wall. I'm taking photos and telling people who stopped that it's a destroyed ecosystem. One lady I spoke to looked at it and she said I've seen it worse. It seems as if people think that if there's no rubbish or no sediments currently in the water, it's great.”

Part of what Nicole has been doing is documenting what’s happening to the seaweed in the harbour and on the south coast. If she doesn’t do it, nobody else will, because there’s no formal monitoring of seaweed forests in place. She aims to cover 70 kilometres of coastline, so she’s well over half way there, and has over 36 hours of footage so far. This is the citizen science part of what she’s doing.

But there’s no point in documenting the decline of our seaweed forests if people aren’t aware of it, or don’t care. So, she has also been looking at innovative ways to advocate for the harbour and seaweeds. “Where there's some sort of a personal connection of people to an environment we can see, we're really good with looking after that in New Zealand. People see birds, and they love birds. We really put a lot of money and effort into protecting bird species.

“With the marine environment, I’m in it all the time, so I see it. I feel it. But I have to go right back and remind myself: hang on, don’t assume that because we're an island nation, people have a connection to the marine space. Not everybody does. So then the question is, how do you communicate that, not just to the public, but councils and ministries too.

This is where Nicole has combined her love of diving with her love of photography, to make the underwater world visible to the people of Wellington. She has been photographing seaweeds, creating stunning images which show people the intricate beauty and gracefulness of the seaweed forms. She has used her 360^o underwater video camera to create virtual tours of Taputeranga Marine Reserve and other underwater sites around Wellington (check them out at the link here, and if you only look at one, look at this one, because it has the best diversity of seaweeds). She even has virtual reality headsets which allow people to watch her videos, as if they were actually underwater but without getting wet. You can also explore Taputeranga Marine Reserve on a self-guided video tour. Short videos of different dive and video sites can be accessed, via QR code, from information boards on the shore near where the tours were filmed. And, of course, there’s the documentary about her work.

You can watch the documentary trailer here.

Helping people to build that connection is only the first step. Another project has been to try controlling the kina in a limited area, to see if that can protect the seaweed and even allow it to recover. She has a joint project with Taranaki Whānui, and the results so far have been encouraging. “I was really surprised at how quickly the kelp forest actually grows back if there's still enough seaweed nearby. Just taking that feeding pressure off by removing the urchins, within 5 months we saw recovery in areas close to existing kelp forest. It won't come back in all places around the harbour, because some places will be too warm now. We might not get all the species either, because it’s like a rainforest, once it’s cut down, you lose all the other bits underneath as well, and it's not quite the same without efficient protection. Still, it’s been really good to show that in this area, if you remove the urchins the seaweeds come back.”

But removing the kina by hand isn’t the answer. All it can really do is prove the ability of seaweed forests to recover, and maybe provide a sanctuary for the seaweed in the same way Zealandia’s fence provides a sanctuary for some of our most vulnerable species. If Zealandia was the only place without introduced predators in Wellington, then our city wouldn’t have the thriving birdlife it does. All the predator control work going on outside the fence is important too. But we can’t control kina right around the harbour by manual harvesting.

There’s a crucial difference between what we need for our land forests and birdlife to recover, and what we need for our underwater forests to recover. On land, it takes constant effort to control the introduced predators, browsers and weeds, but with that effort our forests thrive. In the sea, we are acting like an invasive predator, killing the fish and crayfish which naturally keep the kina population stable and at a level which allows the seaweed forests to thrive. We are taking too many fish.

Nicole tells me that local fisheries officers have reported “30% of people who are checked in Wellington have illegal or wrong sized fish, or just too many. The national average is 10%. What is it that makes Wellingtonians three times more likely to poach? That mindset really has to change. People are taking away the chance for their kids and anyone in the future to have the same opportunities. I get that the economy is bad at the moment, to a certain extent. But there are a lot of people who feel entitled to it rather than need it or take illegal catch for financial gain. And where there is a need, then we, as a society, should make sure there's enough for those who really need it.”

It's not a simple problem to fix, but for somewhere like Wellington Harbour it shouldn’t be impossible. Nicole explains that “There are people who've done participatory, mediated processes to make decisions about resource management. I’d love to see that done here. We need to make decisions transparent – what is important to people, what are our ambitions for the marine environment and what is it currently like, who benefits, who loses out, all of those things. It’s also really important for mana whenua³ to be at the heart of it, because they're really the ones who have that long term view - back into the past and future. Then we need to collectively come up with decisions.”

It isn’t only overfishing which threatens our harbour and other coastal environments. Nicole points out that there are other decisions we are making on land or above the water which are damaging our coastal environments. We have invasive species in the marine environment, as we do on land, and keeping new ones out is crucial, since they are extremely difficult to control once established⁴. Climate change is already having an impact, such as through warming water temperatures and changes in where species live. We are using indiscriminate, destructive fishing methods, and we are discharging too much sediment and pollution from both urban and rural areas.

If we can agree to stop taking too many fish from our harbour and manage other actions which are harming it, then Nicole sees cause for optimism. “If you allow the marine environment to fix itself, it actually does quite well. The capacity of the ocean to bounce back is amazing, as long as you stop putting too much bad stuff in, like sediments and pollution, and you stop taking too many good things out. The ocean is resilient, and there's a lot we can do if we respect the marine environment, and make the right decisions on land. But we need to change what we are doing, to allow it to be resilient.”

Some of Wellington’s underwater forest (image credit: Melanie Newfield)

1. I should add here that the names do approximate what we see when we look at the different kinds of seaweed, with green algae the brightest green, red algae often tinged in various shades of pink, red, or purple and brown algae in shades of greenish-brown. However, there are exceptions, including a kind of green algae which grows on land, on surfaces such as rock, which is bright orange-red, red algae which are brownish-green and brown algae which are green.

2. Ecologists today talk about food webs rather than food chains, because different species are linked in many different ways and a web is a better analogy than a chain, but for this article, a chain is sufficient to explain the issue.

3. Māori groups who have the rights and responsibilities related to a particular area.

4. This is a topic I intend to get to in the future.