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Posts Tagged marine

Now we can all be deep sea explorers Rebecca McLeod Aug 20

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It is now possible to explore the deep sea without having to leave the couch. No need to get cold and cramped sitting for hours inside the confined space of a submersible.

NIWA have just released an incredible online resource of seafloor images covering the whole of New Zealand’s Exclusive Economic Zone. Have you ever wondered what lies beneath the blue as you have flown over Cook Strait? Did you know that there is a massive network of undersea canyons off Otago? And have you ever realized just how quickly you can plunge into the deep ocean just off the coast of Fiordland? It is also very cool to explore the abyssal Pyuseger and Kermadec trenches that mark the fault line to the south and north of the country.

I am often awed by how little we know about the marine area that makes up more than 90% of our country! But then on the other hand, perhaps the fact that much of this approximately four million square kilometers of seafloor is classified as “deep sea” provides a pretty good excuse. One of our resident deep sea explorers Peter Batson published an excellent book called Deep New Zealand: Blue Water, Black Abyss a few years ago. This, or his website www.exploretheabyss.com is a must see if you want to learn more and see some beautiful photos and drawings of crazy deep sea life forms.

NIWA has only just launched these maps and it seems there are a few small teething issues – for now to download you can right click, open the link in a new window/tab, then save each image. For those interested in how the seabed in such deep areas is mapped, there is great information here.

Science in danger of being diluted in marine reserve decisions Rebecca McLeod Feb 02

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In light of recent marine protection developments on the South Island’s West Coast, I have reposted a piece I wrote for the Science Media Centre back in 2008. I will write more soon about the West Coast – I am still trying to figure out the extent to which scientific information guided the decision making process there.

I recently went to a talk by Kim Hill entitled “Is science something we should fear?”

Being a scientist, I thought Kim was joking. Why would the public not value and embrace the knowledge and lessons learned by people that in essence, spend their time trying to better understand and improve the world? It started me thinking about the role that scientists should have in guiding decisions about how we manage our environment, in particular our coastal marine areas.

New Zealand has an excellent reputation for marine conservation, due to initiatives including our quota management system and the growing numbers of marine reserves. The Government is currently developing a framework that will essentially allow locals to decide how they want marine protection measures to proceed around their coasts.

This move is occurring partly in response to very vocal opposition to proposed marine reserves in some parts of the country. The idea is that by involving the community in the decision process, people will have a vested interest in the outcomes, resulting in a higher level of support for the introduced protection measures.

The framework for these local groups will be similar to that of the Fiordland Marine Guardians; a group of “stakeholders” (e.g. fishers, tangata whenua, tourism operators etc.), who proposed a series of conservation measures to be established in the fjords. Following many years of discussion, negotiation, and compromise, the Guardians presented a proposal to Parliament in 2003, and in 2005 the Fiordland Marine Management Act was established. The protection measures include 10 marine reserves, reductions in recreational quota, and restrictions on commercial fishing areas, anchoring etc. These decisions were guided by the expert opinion and knowledge of a marine ecologist from Otago University.

In February 2008 the Department of Conservation and the Ministry of Fisheries released an implementation strategy for this new regional approach to marine management. The document outlines how a forum of up to 14 stakeholders will be appointed in each of the defined regions in NZ. These stakeholders will encompass tangata whenua, commercial fishers, recreational users, conservation groups, tourism operators, aquaculture industry, minerals industry… and scientists.

It will be the task of each forum to reach a consensus on areas to be proposed for marine protection, and make recommendations of what the protection measures should involve. Each of the stakeholders will have equal status in discussions and decision-making. This is the part that concerns me.

Processes that occur in the marine environment and marine ecosystems are inherently complex and can vary significantly over small distances, and also over time. The effectiveness of protection measures are likely to be dependent upon what they consist of, where they are placed, and how big an area they cover.

For example, in the fjords it appears that the new marine reserves are differing in their ability to “recover”. In Doubtful Sound, we have found that changes in crayfish numbers can be related to the amount of food that is available at each location. Near the output of the Manapouri hydroelectric power station, where increased freshwater has led to a decline in mussels and other clams (crayfish food), crayfish are not recovering.

In contrast, in other marine reserves where there is plenty of crayfish food, crayfish numbers are rapidly increasing. This is just one of many examples that demonstrate the success of a marine protected area (MPA) can vary significantly depending on its location, shape and size.

Whilst it is incredibly important to have the support of the local community for MPAs, it is equally, if not more important to get the characteristics of the MPA correct in the first place. Otherwise, it is possible that no amount of protection will lead to “recovery” of the marine ecosystem. To increase the likelihood of designing an MPA that is going to be effective, management recommendations put forward by the regional forums need to critically evaluate all reliable knowledge and data pertaining to the marine environment in question.

And keep in mind that this information will not necessarily come solely from scientists. The extensive local knowledge of other interested parties such as fishers and tangata whenua has a large role to play here too. My point is that debate and negotiation from all interested parties should be based upon the best available knowledge, and where available, data.

To provide advice about how to design effective MPAs, scientists need answers to questions such as: What lives there? How fast do things grow and how much do they move around? Where does the food come from that is supporting the community? Where do the young come from? Are there any ongoing impacts?

It is paramount that decisions regarding the placement and degree of MPAs are based upon such fundamental ecological knowledge, and you would be surprised just how little is known about these processes on a small scale around our coasts. So, to support management recommendations and decisions that will have a high likelihood of success, it is essential that the Government funds fundamental ecological research in our coastal seas.

Earlier I said that I was concerned about scientists being considered as stakeholders in these regional forums. These concerns are due to the fact that when it comes to deciding upon management recommendations, scientists will effectively have one 14th of the vote.

I am concerned that such a small influence will lead to expert scientific advice getting diluted. Ask any scientist that has witnessed or been involved in the process of the creation of an MPA: “was it big enough?” And they will invariably say “NO!” Because more often than not during the consultation and negotiation process, the size of the desirable MPA gets whittled down to a fraction of it’s former self.

The question to these scientists then becomes: “Do you think it will still work?” And that is where many scientists will have doubts. I strongly believe that whilst public consultation is very valuable and necessary, scientific knowledge and advice must not be diluted when it comes to making decisions about the future of marine management in New Zealand.

We are entering exciting times with respect to the marine environment. One hopes that in years to come, all New Zealanders will be able to take a short trip to their local marine reserve, and explore an intact and healthy marine ecosystem.

For this vision to become a reality, scientists need to get involved in their local communities and communicate science effectively, so that the public will begin to appreciate that science is definitely something to value, not fear.

Otago Harbour in a red frenzy Rebecca McLeod Jan 18

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Otago Harbour has been bursting with life this summer due to a population explosion of crab larvae, called Munida gregaria. The shoaling animals have attracted thousands of seabirds to the harbour since November, and the feeding frenzy looks set to continue for a few more months. The assault on Munida is not only aerial – fishes, seals and sealions are also following the shoals from beneath. Outgoing tides are leaving Munida stranded on the shore, again offering an easy feast for birds such as red-billed and southern black-backed gulls, pied oystercatchers and spotted shags. Human residents of the harbour may not be quite as excited however as the stranded Munida are creating a stench like no other and the birds are painting the town red. Literally.

As these "post larvae" mature they go from swimming a the surface to sitting on the seafloor

As these "post larvae" mature they go from swimming at the surface to sitting on the seafloor. Photo courtesy of Tomas Bird and the New Zealand Marine Studies Centre

Munida larvae are common off the coast of Otago in spring and early summer, and this summer have moved into the harbour en masse where they will mature and settle to the sea floor. There they may live for 2-3 years, possibly migrating to deeper offshore habitats – that is if they are not feasted upon first.

This summer’s Munida explosion is likely to bring hundreds of tonnes of food into Otago Harbour. And this is by no means unusual. Records from the Portobello Marine Laboratory, going back to the 1950’s show that large Munida aggregations in the harbour used to occur most years, although were quite variable and did not appear once every four or five years. However, this is the first time since 1999 that there has been a significant Munida event in the harbour. The cause of this long absence is up for debate.

The New Zealand Marine Studies Centre at Portobello currently has thousands of Munida on display. Get in quick though – they are sharing their tank with some rather hungry fish…

The display at the New Zealand Marine Studies Centre, Dunedin. Photo courtesy of Tomas Bird.

The display at the New Zealand Marine Studies Centre, Dunedin. Photo courtesy of Tomas Bird.

How resilient are coral reefs to tsunamis? Rebecca McLeod Nov 24

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The September 29th tsunami waves left widespread destruction across the Pacific nations of Samoa, American Samoa and Tonga, evidenced by devastated villages, and multiple fatalities and injuries. But what about the natural environment? Was there paralleled damage under the sea, on the coral reefs that fringe these islands? Not only is this question of interest from an ecological perspective, but also from a social perspective: communities rely heavily upon these reefs for food, tourism and social wellbeing. As these communities begin to rebuild, and eventually encourage tourists to come back, the state of the coral reefs could be a factor in a tourism market that relies heavily on water-based activities.

The potential for damage to coral reefs following major storm surges and tsunamis is two-fold: the initial force of the waves hitting the reef, and the subsequent delivery of huge amounts of sediment and debris onto the reef as the wave retreats and during rainfall in the following weeks.

Using field tests, scientists at the ARC Centre for Excellence in Coral Reef Studies have demonstrated that the shape of the coral influences how vulnerable it is to damage by large waves. For example, table-topped corals (those with a broad top and attached to the reef by a stalk) are more prone to being overturned by a large wave than those that are mounded or branched. Location matters too, with corals on the front and crest of the reef where the waves break being more prone to damage by large waves than those situated on the top and back sides of the reef.

Arguably the greatest tsunami-associated threat to corals is posed by sediment and debris that is carried from the land as the waves retreat. Sediment can smother and even bury corals, leading to suffocation of the coral polyps. Extensive mechanical damage and scouring can result from debris such as building materials, machinery and cars getting pounded onto the reef.

Initial surveys of coral reefs along the west coast of Thailand following the Boxing Day tsunami in 2004 recorded mass destruction of corals. However, despite these initial concerns, repeat surveys in the following months found that the damage, although severe in small patches, was generally not as bad as first feared. This anomaly was due to much of the coral initially recorded as dead having in fact recovered. On the Island of Banda Aceh at the northern tip of Sumatara, scientists were in a unique position of being able to make before and after comparisons of reef health, as they had surveyed the reefs prior to the tsunami. The research team, led by Dr Andrew Baird at the ARC Centre for Excellence in Coral Reef Studies reported a remarkable resilience of coral communities to the tsunami waves. The damage observed was considerably less than that caused by destructive fishing practices (e.g. dynamite fishing) and coral harvesting, and was also considered to be significantly less than that resulting from hurricanes, due to differences in the distribution of wave energy in the water column.

I am not aware of any similar surveys being carried out in areas affected by the most recent tsunami (if you know of any please tell me!), but these experiences from the 2004 tsunami seem to suggest that the long-term impacts of the tsunami waves on coral reefs may not be all that bad. It seems plausible that those reefs in good health prior to the tsunami may experience a faster recovery than those already suffering from bleaching, grazing crown of thorns starfish, or destructive fishing practises.

One step closer to harvesting kelp Rebecca McLeod Nov 09

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On Friday the Fisheries Minister Phil Heatley announced that giant kelp (Macrocystis pyrifera) will be introduced to the Quota Management System (QMS). This decision marks the first step of a process to “manage” the species, which forms extensive forests around much of New Zealand’s coastline. The second step will involve the setting of a Total Allowable Catch limit for the species. I posted a few weeks ago about the scientific arguments against kelp harvesting (“Is it wise to ‘mow’ our kelp forests?”), where kelp specialists Drs Chris Hepburn and Nick Shears gave their responses to the proposal to enter kelp into the QMS.

The Ministry received 26 submissions from stakeholders, most representing large organizations such as the NZ Marine Sciences Society (270+ scientists), the NZ Recreational Fishing Council and multiple iwi. In very general terms, the submissions from those in the fishing industry supported the introduction of the species to the QMS. And the majority of submissions from scientists, environmental and other groups were in agreement with them – perhaps not a huge surprise given that the alternative to QMS introduction was the creation of an open-access fishery! Where these two sides differed in opinion was in size of the future Total Allowable Catch. Industry argued for “a sustainable level”. Nearly everyone else argued that with a complete lack of scientific information, the only guaranteed sustainable level is zero. And the masses raise a very valid point – after all, the overall objective of the QMS is to help ensure the sustainable utilisation of fisheries resources…

Could kelp harvesters like this soon be working along our coasts? Image: http://w3.shorecrest.org

Could kelp harvesters like this soon be working along our coasts? Image: http://w3.shorecrest.org

The Ministry will begin a process of stakeholder consultation early next year before setting Total Allowable Catch limits for attached giant kelp in fisheries management areas 3 (East Coast of the South Island) and 4 (extending out to the Chatham Islands). It will be a very interesting process to observe – given the lack of biomass estimates, location-specific growth rates and knowledge about the ability of kelp to recover from canopy removal, it is difficult to imagine just how the Ministry will go about calculating a “sustainable level of harvest”.

10% by 2010? Yeah Right! Rebecca McLeod Oct 20

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In 2005 an ambitious goal was set by the then Ministers of Conservation and Fisheries – 10% of the marine environment around New Zealand would be under some form of protection by 2010. This announcement was met with much celebration by marine scientists and environmentalists throughout the country and the wheels were set in motion to take a regional approach to marine protection. Going off the recent success of the implementation of a network of marine reserves in Fiordland, the Department of Conservation and the Ministry of Fisheries put together a structure under which local groups of stakeholders would propose networks of marine protected areas in their region. These networks would encompass a variety of habitat types (such as estuarine, offshore reefs, soft sediment etc.) and protection measures (marine reserves, zones with specific fishing restrictions etc.). But despite this initial flurry of activity, the Government has been unnervingly quiet on this issue of late. I am aware of two regional proposals – for the sub-Antarctic Islands, and for the West Coast of the South Island – that are currently at the public consultation stage, but yet to be put forward to the Government. Whilst the fact that these proposals are undergoing consultation is evidence that things are happening at a regional level, I am skeptical that the final proposals will move through parliamentary channels in a timely manner. As we race towards 2010, I am left with considerable doubt as to the ability, or will, of the Government to meet the target of 10% by 2010.

Takeoff to Scott Base Rebecca McLeod Sep 29

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The summer season is about to get underway at Scott Base, Antarctica – if all went to plan, the first flight carrying base and field staff left earlier today. Scientists will follow in the coming weeks. This time last year I was counting down the days until I left for the ice with a group of scientists from Otago University and the States. One of the things that blew me away about doing science in Antarctica was the massive logistic operation undertaken by Antarctica New Zealand. Every year they undertake to get everyone down there (and back of course), keep them fed and warm and happy AND make it easy and safe to do science. This was a field trip like no other.

We got to the Antarctic Centre in Christchurch the day before our flight and set about getting assigned all of our clothing and supplies. Antarctic New Zealand has an incredible collection of gear that they fit you out in before you get onboard – you could turn up in Christchurch in your shorts and flip-flops and it wouldn’t be a problem. We had to don full Antarctic kit before getting on the plane, despite the temperature being well into the twenties. It was difficult to believe that 5 hours time we would be getting off the plane and walking onto a frozen sea. Excitement caused time to slow, but eventually the time came for us to get aboard the C17 Globemaster, strap ourselves in, and put on our earmuffs. Just being inside one of these huge planes was a new experience for me. It was a noisy and incredibly long 5 hours, and most people passed the time on their laptops, or snoozing. I spent my time mostly staring out of a tiny window.

The C17 Globemaster, on the ground at Christchurch Airport

The C17 Globemaster, on the ground at Christchurch Airport

Inside the C17

Inside the C17

Of course, the flights only depart for the ice if the weather forecast is looking good. But 5 hours is a long time in polar weather terms. It isn’t uncommon for a flight to get all the way down there, and then turn back for NZ without touching the ice. After months of excitement containing, (and having eaten all the contents of my lunch bag) I thought I would probably burst if that happened… But after an incredibly smooth landing, it was announced that we were indeed on the ground in Antarctica, and so we stepped out into the white. I won’t try and describe that, as there is no way of doing it without having to revert to a long list of clichés. But I think that rather disproportionate smile sums it up quite nicely (that’s me under all those clothes by the way…)

My first steps onto the Antarctic continent

My first steps onto the Antarctic continent

Scott Base is an incredible place, run by a truly remarkable group of people. And life there is strangely normal. It wasn’t long before I found myself looking at the thermometer on the wall and saying “ohhh lovely, it’s minus 18 today!”. And a typical night in the lab would end with a 2 am visit to the lounge where I would sip a cup of tea and gaze out at the sun low over the mountains in the distance.

Scott Base

Scott Base

Before we could get out there and get stuck into our work, we had to do a field training course. This was where we were taken out for a night of camping and training about how to keep warm, keep fed, keep sheltered, keep from falling through the sea ice, keep smiling, and for us women, how to wee standing up… ahhh the wonders of modern technology.

Being from Dunedin, I thought I was well acclimatized to cold. It wasn’t until I went to take out my contacts and the solution was frozen, then went to put on some solid chap stick, and crunch on a few sultanas, that it really started to dawn on me. It was seriously cold. Beyond the limits of my imagination. The thing is though, it never really felt that cold, because the clothing and sleeping bags we had been given were just so good.

Our camp at the base of Mount Erebus

Our camp at the base of Mount Erebus

Following the field course, we were ready to start preparing for our fieldwork. Our requirements were a little unusual in that we had a dive team with us, and we wanted to dive at five different sites. Underneath 2-3 metres of sea ice… But even that proved to be no problem for the logistics and field team. We were given a vehicle, loads of gear, directions to our first dive hut, and a pile of chocolate that my dreams are made of. And off we went.

"Roads" are marked and checked regularly by field staff from Scott and McMurdo Bases

"Roads" are marked and checked regularly by field staff from Scott and McMurdo Bases

At each dive site a stonking little diesel fire inside the dive hut made it seriously cozy. In the floor of the hut was a hole that had been melted through the 3 metres of ice. A beautiful icy blue emanated from the hole and the water was so clear that you could see the animals on the seafloor 15 metres below.

Our dive site at Razorback Island

Our dive site at Razorback Island

The dive holes were made either with a large drill (the quick option) or a heated coil that melted through 2-3 metres of ice in a couple of days. Each dive site also had a safety hole – a backup for a scenario such as a Weddell seal popping up in the main hole. They can get quite territorial when they find an ice hole, and you aren’t really in a position to negotiate with these 400 kilo creatures…

Within hours of a dive hole being made, we would be visited by Weddell Seals

Within hours of a dive hole being made, we would be visited by Weddell Seals

Diving underneath sea ice obviously has its challenges. Firstly, to state the obvious, it’s bloody freezing! The water is a pretty constant -1.8°C, which is about as cold as seawater can get before it starts to freeze. Divers wear thermal undergarments, and then have dry-suit on top – so only your lips are exposed to the water, and once they are numb, they don’t hurt a bit… until you get out and they start to thaw that is. The cold water also leads to ice building up around the connection between the tank and the regulators and this can cause the air to “free-flow” out of the mouth piece. So an extra set of regulators is attached to the tank as a backup in case that happens. The second thing to consider is that you have a ceiling of ice overhead, and the only way out is through the hole where you came in. As a precaution, each diver is tied to a rope, and the other end is manned by a support person in the hut. The idea is that divers can communicate with the surface by a series of pulls on the rope… although in reality, the rope tends to ger caught around the ladder and things on the bottom, and whipped around in the current, and be nothing more than a comfort to the diver that should they get into trouble our backup diver would know where to find them (being at the end of the rope…).

It takes a lot of gear to ice dive...

It takes a lot of gear to ice dive...

Our mission was to collect a range of different animals from coastal habitats, upon which I would spend the next many months performing chemical analyses. I am getting close to done with that (finally!), but that is a story for another time. Over the years there has been a fair bit of marine research carried out in the Ross Sea, with a focus being on what animals live there and how on Earth they manage to cope with living in an incredibly cold, and for much of the year, an incredibly dark place. It is only in the past few years that the science has begun to include projects that question how whole communities of these animals function – where does all the food come from?, who eats who?, how much do animals move around in their lifetime?, and so on. Of course, with the global climate changing so rapidly, the race is on for us to understand these kinds of interactions better so that we might begin to predict how things might change in a warming Ross Sea.

Sea ice surrounds Razorback Island. You can just see our dive site above the island.

Sea ice surrounds Razorback Island. You can just see our dive site above the island.

Life on top of the ice is a pretty black and white kind of world… unlike at the edge of the ice, it isn’t often that you see many signs of life on the southern end of Ross Island in the spring. But just underneath all of that ice, is a booming community of huge biomass and amazing colour.

A tangled pile of sea stars and Nemertean worms feast upon a seal poo

A tangled pile of sea stars and Nemertean worms feast upon a seal poo

The animals are incredibly well-adapted to a life surrounded by ice. These fish have anti-freeze compounds in their blood.

The animals are incredibly well-adapted to a life surrounded by ice. These fish have anti-freeze compounds in their blood.

A typical day of work included 3 dives to collect the animals, and then we would take them (and the tired hungry divers) back to Scott Base. The divers would head off to get fed and warmed, and we would begin work in the lab. The lab set up was perfect for the kind of work we were doing – there is an excellent system of tanks that have running seawater pumped up from under the ice.

Inside the Summer Lab at Scott Base

Inside the Summer Lab at Scott Base

These animals were collected from 15 m depth at Cape Armitage. Note the Pycnogonids (dinner plate-sized sea spiders)

These animals were collected from 15 m depth at Cape Armitage. Note the Pycnogonids (dinner plate-sized sea spiders)

That’s all for now – I hope to bring you research stories from Antarctica as the season progresses.

Dissolving marine life Rebecca McLeod Sep 26

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Four years ago I went to a Marine Science Conference where a few scientists were talking about the idea of acidification of the oceans. That is how recently we have become aware of this issue that is going to lead to massive changes in the marine ecosystem, should atmospheric carbon dioxide levels continue to rise. The absorption of carbon dioxide into seawater, has the the effect of making seawater more acidic. And that has serious consequences for marine life that has carbonate skeletons (think corals, zooplankton, molluscs, bony fishes…), and also for animals that need these species to survive (like animals that live amongst corals, or feed upon those with carbonate skeletons). Seawater chemistry is changing rapidly, and scientists are predicting massive consequences to marine life within the next 20 years. This film has just been released by the US Natural Resources Defense Council, and I think EVERYBODY should see it. It has the credibility of some leading marine scientists, some amazing footage, and some incredibly sobering truths about how human activity is impacting marine life. A must see.

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Is it wise to ‘mow’ our kelp forests??? Rebecca McLeod Sep 24

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Submissions closed on Monday the 21st for a proposal by the Ministry of Fisheries to enter giant kelp (Macrocystis pyrifera) into the Quota Management System. There is demand for giant kelp on the international market, and at least one Canterbury-based business is keen to develop a harvest of live kelp in the near future. On first thoughts, this might seem like a great idea – the kelp can be used for so many things: pharmaceuticals, food products, fertilizers, feed for aquaculture and farm animals… the possible applications appear to be limited only by the imagination.

However, as the story unfolded on Campbell Live on Monday night , it became clear that there are two sides that are clashing over the potential for kelp to be commercially harvested. One side comprises fishermen, scientists and environmentalists who are concerned that harvesting could lead to a loss of kelp forests and the multitude of species that live amongst them. The other side seems to be made up of a small group of entrepreneurs, who can see only benefits when it comes to kelp harvesting. Financial benefits. This is an unusual situation: it isn’t often that environmentalists and fishermen are united in their views. I feel that it is time to inject some science to the debate, to gauge whether the concerns of the objectors are legitimate.

There are currently two MFish proposals that are undergoing public consultation. In the North Island, it has been proposed that drift kelp (that which is floating unattached, or stranded on beaches) be allowed to be collected from all beaches by commercial operators under permit. Whilst such collection certainly has the potential for ecological impact, it is the other proposal that is attracting the most attention from marine scientists – the entry of live growing giant kelp into the Quota Management System, effectively opening the door to commercial harvesting of kelp forests.

Macrocystis kelp growing up through murky water towards the light

Macrocystis kelp growing up through murky water towards the light

In other countries, kelp forests are cut to one metre below the surface either by hand, or using ships equipped with cutting blades. It might seem appropriate then for the practise to be likened to mowing the lawns. Supporters of kelp harvesting here say that giant kelp grows one metre a day, therefore harvesting it will be totally sustainable. But Dr. Chris Hepburn, a marine botanist at Otago University, believes that growth at that rate, in New Zealand at least, is a myth. Despite many years researching Macrocystis growth around the South Island, and publishing on the topic1, he has never come across the original source of that figure, nor measured growth rates anything like it. It is quite likely that the one metre per day figure is an exaggerated value from research in California, where expansive forests are harvested. “Frond elongation rates of 2-10 cm per day are typical for Macrocystis, while maximal growth rates of 40 cm a day may be possible when a kelp frond first grows up through the water column under perfect conditions. Frond rates really have little relevance to how Macrocystis will respond to harvesting – if you chop the top of a frond it stops growing. It’s the rate that a kelp individual can produce new fronds that matters from a harvest recovery perspective.”

Throughout the MFish proposal, references are made to the operation in California, with a suggestion that it provides a model upon which to base any future harvesting here. But is it wise to make comparisons between New Zealand and Californian kelp forests in this way? Dr Nick Shears is a marine ecologist who has recently returned to work in New Zealand from California. Having expertise in kelp forest ecology2, he is in an ideal position to make comparisons between the two. “The giant kelp forests off California are world renowned for their size and productivity – forests span for miles along the coast, grow to depths of 30 m, and individual plants grow up to 60 m in length. In comparison, New Zealand kelp forests are a fraction of the size, the plants grow slower, are smaller and are less dense”. Dr Shears believes that given the differing sizes of kelp forests in California and New Zealand it is difficult to envisage a viable and ecologically sustainable fishery for kelp in New Zealand.

Kelp forests are highly productive, in that they provide a food source and a habitat for a diverse range of marine species, including many fish and invertebrates that form the basis of large commercial, recreational and cultural fisheries. For example, it is thought that crayfish are closely associated with kelp both as adults, and as juveniles, as larvae recruit into the canopy of the forest, and then make their way down the fronds to the seafloor. Blue cod, moki, trumpeter, paua, kina, and greenbone also inhabit kelp forests. Dr Hepburn says that this provision of habitat for other species is a key difference between giant kelp and every other marine species managed under the Quota Management System. “To harvest a habitat is very shortsighted. Imagine a fishery is supported by a coral reef – does it make sense to allow someone to come in and remove the coral for commercial use and risk the fishery? Harvesting Macrocystis risks high value fisheries and ecosystem services provided by the kelp for an unproven product. At this stage it’s a no-brainer – Macrocystis is worth more in the water than spread over paddocks as fertilser, and we simply don’t know enough about how kelp forests will respond to harvesting.”

A multitude of animals live on and among the forest habitat that giant kelp provides

A multitude of animals live on and among the forest habitat that giant kelp provides

Despite the Californian kelp forests having a century-long history of harvesting, questions are now being raised as to the sustainability of the practise. The annual takes reported by the California Department of Fish and Game have regularly exceeded 150,000 tonnes, but have dropped to less than 5,000 tonnes per year since 2006. This sudden decline reflects the major harvester ceasing operation due to a lack of economic viability, which is caused by competition from exporters in Mexico and China. The exit of this harvester from the market will probably be of much relief to environmentalists in the region, who have observed a dramatic reduction in the extent of kelp forests over the last 35 years3. Scientists from the Scripps Institution of Oceanography have identified many environmental pressures that could be causing this decline, including changes in currents linked to the El Niño – Southern Oscillation, increased abundances of sea urchins due to overfishing of their predators, sedimentation, pollution and kelp harvesting. When it comes to kelp forest health, teasing apart the importance of these different factors is proving to be an incredibly difficult task3. One thing is for sure, kelp forests are under pressure, and they are threatened in many places around the globe. In Tasmania, a more than 50% decline in extent of giant kelp over the past 60 years has prompted the State Government to consider listing Macrocystis kelp forests as an endangered habitat type. They are already listed alongside the Great Barrier Reef as a Special Marine Area. Whether kelp has suffered similar declines in New Zealand has not been monitored by scientists, although there is anecdotal evidence of kelp forest loss in the Otago region.

Back in New Zealand, Dr Hepburn has many concerns about what might happen if you harvest kelp. Unlike California, the East Coast of the South Island has a lot of sediment in the water, which acts to limit the amount of sunlight reaching kelp, and frequent storms act to resuspend the sediment into the water column. The growth of Macrocystis kelp is limited by the amount of sunlight1, meaning that in times when there is a lot of sediment in the water, such as following rainfall or a storm, kelp growth rates slow. “My concern is that were a harvesting event to coincide with a period of high sediment load in the water, the kelp would not receive enough light to promote regeneration and the forest would therefore be at risk of dying off.” There is also the issue of the invasive kelp Undaria. This highly opportunistic species may take advantage of a temporary reduction in giant kelp, and out-compete the species. Such a shift in kelp assemblages, would not necessarily correct itself over time. There are a lot of uncertainties about how kelp, and the species associated with the forest habitat it creates, will respond to harvesting, yet surprisingly little research that could help to address these concerns. The only relevant study was conducted in Akaroa Harbour – a wave sheltered environment that is very different from the exposed coastlines along the extent of the proposed harvesting areas. To progress with harvesting along the East Coast of the South Island appears to be incredibly risky, particularly when the size of associated fisheries are considered. Is it wise to risk the multi-million dollar blue cod and crayfish fisheries, for a market that is yet to be tested?

Many prominent marine scientists have voiced their concerns with the Ministry of Fisheries about the current proposal, along with fishermen, environmental groups and iwi. This large, diverse group of objectors is at odds with one small group of supporters, whom stand to benefit financially from a positive outcome. It will certainly be interesting to see the outcome of this process of public consultation – will the Ministry listen to the voices and experience of the opposition and consider the lack of scientific testing of the sustainability of kelp harvesting when they make their decision? Furthermore will the Ministry adhere to their own management objectives – to protect and maintain habitats that are significant for fisheries? It certainly seems to me that there is a lot at stake.

References

1. Hepburn CD, Holborow JD, Wing SR, Frew RD, Hurd CL (2007) Exposure to waves enhances the growth rate and nitrogen status of the giant kelp Macrocystis pyrifera. Marine Ecology Progress Series 339:99-108

2. Salomon AK, Shears NT, Langlois TJ, Babcock RC (2008) Cascading effects of fishing can alter carbon flow through a temperate coastal ecosystem. Ecological Applications 18(8): 1874-1887

3. Dayton PK, Tegner MJ, Edwards PB, Riser KL (1998) Sliding baselines, ghosts, and reduced expectations in kelp forest communities