Surveying the pristine seas of the Pacific Ocean

Mobilising for the expedition

After nearly two days of travelling via Paris and Vancouver I finally arrived in Papeete, Tahiti to join the ship, Offshore Solution. The vessel is more usually employed in the oil industry so the crew are excited to have the opportunity to get involved in a National Geographic expedition.

I get to meet up with a good friend of mine, the explorer and National Geographic Pristine Seas Expedition Leader, Paul Rose. After catching up on some much needed sleep, Paul and I help load the expedition cargo onto the ship while waiting for the rest of the team to arrive.

A huge amount of cargo was loaded including the diving air compressors,

recompression chamber, six Zodiac inflatable boats and about 60 Pelican cases for the media team. A National Geographic documentary will be filmed of the expedition, so we have media teams for both surface and underwater filming.

Over the next few days the rest of the expedition team join the ship including Enric Sala, the Executive Director of National Geographic Pristine Seas.

The 22-person team is international, with members from the USA, Spain, Australia and the UK. After 3 days of loading the ship and checking equipment we depart for our first research site Flint Island in Kiribati.

The adventure begins...

Science plan

The aim of the National Geographic Pristine Seas programme is to identify the most pristine areas left in the ocean and persuade governments to protect them as the remaining examples of what our seas used to look like. In turn, these areas will be important as biodiversity and genetic reservoirs as increasing proportions of the sea are hopefully protected. Once pristine, or near-pristine areas are identified, expeditions are planned to investigate the biodiversity and gauge the value in protecting the area.

The data collected on the expeditions is used to support the government, in whose jurisdiction the area lies, to provide robust marine protection, or if they are reluctant to provide protection, to try and persuade them! To date, the Pristine Seas programme has played a part of, or led the creation of 23 Marine Protected Areas totalling over 6 million square kilometres.

Each expedition allows a snapshot of the biodiversity in the area using a variety of methods including; deep sea drop cameras, mesopelagic (40-100m) baited cameras, pelagic baited cameras, fish and benthic surveys, eDNA water sampling, foraminifera sediment sampling and terrestrial plant and animal surveys.

In addition, on this expedition we are also carrying out coral coring to look at the effect of the exceptionally warm 2015/16 season which caused widespread coral bleaching in the Pacific and coral photogrammetry mosaics to look at coral growth and succession post the 2015/16 event. We are also shark tagging to look at reef shark movements and installing a network of Aqualink buoys to measure water temperature, wave height and direction.

Together, this data will help give us a good oversight of the reef and associated pelagic diversity and the potential resilience of the reef to recover from warm water events. The Southern Lines are of particular interest to the Pristine Seas programme, as their first expedition was run to these islands in 2009 and there is additional data available from the Scripps Institution of Oceanography in 2013 and 2017, thereby providing a detailed time series of the condition of these remote reefs. Ecological theory suggests that more pristine reefs should be more resilient to warming events due to a full suite of species being present.

The plan with this expedition is to test this hypothesis after the 2015/16 bleaching event.

Flint Island

We have arrived at Flint Island! Pretty much everyone was up at dawn to watch our arrival at 0500. The island is around 400nm north west of Tahiti and very remote. Flint is only about 2.5miles long and 0.5miles wide, so pretty small. The island is surrounded by a fringing reef and covered with native vegetation and coconut palms that were planted for copra in the 1880s. Landing is very difficult and it took three attempts to land our terrestrial biologist through the surf. The only way to get Mike ashore was to swim him in with his gear.

As soon as the landing was complete we deployed the pelagic baited cameras and deep water drop cameras, before commencing diving operations. We have five Zodiac inflatables aboard so boating operations are pretty busy. We prepare and load our diving gear into the inflatables on the deck, before they are craned into the water and we climb in via a pilot ladder.

The island is spectacular against the deep blue sea. I really hadn’t expected the island’s terrestrial flora to be so dense. Pretty much the whole island is covered by dense vegetation right down to the white coral sand beaches. The only reason the vegetation can survive is the nutrient rich guano provided by the frigate birds, brown boobies and terns.

The diving is incredible. I have carried out maybe 200-250 dives prior to this expedition in tropical waters and on just six dives on this trip I have seen many more sharks than I have ever seen previously. The water is teeming with life. As the island is almost never dived, the fish are not scared of divers, so they approach much closer than normal. In a few dives I have seen black tip reef sharks, grey sharks, many green turtles and one manta ray as well as amazing corals and pristine fish populations.

Diving is very busy underwater and I have been working with the photomosaic team creating large scale 10x10m photo mosaics consisting of thousands of high resolution overlapping images fed through a model that creates a highly accurate 3D model of the coral. Each photomosaic is created at a fixed reference point on the reef that has previously been surveyed, so with repeated mosaics it is possible to track individual coral growth and any species changes over time. Each mosaic takes around 70 minutes to carry out, from setting up and stripping the site to taking thousands of images with a stereo camera system, on fixed survey lines. The diver taking the images swims up and down the 10x10m grid in a process the team call mowing the lawn and you can see why!

In the time when I am not helping set up the photomosaic grid, I am collecting water samples for eDNA both on the surface and the seabed. The DNA is released from marine organisms as mucus, faeces, gametes etc and can be analysed to identify the species. The water samples will be analysed back in the lab ashore and will help improve our knowledge of the reef’s biodiversity.

An important part of this expedition is to install Aqualink moorings at the remote coral islands we are visiting. These moorings when installed will provide water temperature data at two depths, as well as wave height and direction. This data is critical in helping understanding the environmental stresses these reefs are exposed to. Fitting the moorings is quite complicated and yesterday Paul Rose and I installed the first mooring on the leeward side of Flint at 20m. It was a fairly tricky operation as we had to find a site, lower the 90kg anchor weight and position it in the position we had selected with a lift bag. The installation was successful and the buoy is now operational and providing data.

Vostock Island

So after an amazing three days at Flint, we steam 86nm to the NNW to Vostock Island. Vostock is tiny, only 0.7 x 0.6km. The land area away from the beaches is pristine Pisonia forest. Unlike other islands in the Line Islands group, this island was never mined for guano and coconut palms were never planted, as the island was too small to be commercially viable. It has the most pristine native vegetation of just about any Pacific island.

We are now into the rhythm of the science programme and boats are away for diving at 0830. By this time we have already got Mike ashore to carry out the terrestrial biology surveys including vegetation mapping using a drone. The diving is even better than Flint. Many more sharks accompany us on most dives and the fish biodiversity is considerably higher than Flint.

The corals have been hit hard by the 2015/16 warming event but are re-growing well and there are some spectacular areas of Montipora corals carpeting large areas of the seabed.

Boating conditions are challenging next to the reef with the large swell increasing in size at it approaches the reef before breaking spectacularly. The top of the survey sites we are working in are only about 6m deep, so we are working very near the reef top and have to exit and enter the Zodiacs quickly to avoid the boat and divers being washed onto the reef.

As I was getting back into the boat on one of the last dives I felt a searing pain in my hand and spotted the float of a Pacific Man ‘O’ War, Physalia physalis, on the surface. Luckily we were not too far from the ship and the Zodiac skipper dropped me back to see our paramedic.

I haven’t been stung before by a Man ‘O’ War although I have been stung by plenty of normal jellyfish. It is much more painful and I don’t recommend it! Luckily after the afternoon off diving I was back in the water the next day.

The daily routine onboard Offshore Solution

0600 – I usually get up, make a cup of tea and start dealing with work emails that have come in overnight.

0700 – Breakfast in the galley. After which we are usually preparing equipment for the forthcoming dives.

0800-1230 – Two 70-80 minute dives at depths of up to 18m with an hour surface interval. Most days I am working with Brian Zglizinkski and Stuart Sandin from Scripps helping carry out 10 x 10m photomosaics of the coral and collecting water samples for eDNA. On most dives, after we have set up the work site, I usually have around 20 minutes to take photographs to illustrate the work we and others are carrying out.

1300-1400 – Back to the ship for lunch.

1500-1700 – Afternoon single dive, again generally on the photomosaic project unless I am working with Paul Rose installing one of the Aqualink oceanographic buoys.

1800 – Dinner, after which people often sit around talking for a while or head to their cabins to work up the day’s data. I usually catch up on any more urgent University tasks I have to complete. We don’t have a bar on board but National Geographic kindly bought some beer and wine. Paul Rose, the Expedition Leader, usually gives a quick update and brief for the following day’s operations during dinner.

2100 – Bed most nights as most people are pretty worn out by the amount of diving!

One evening we watched the National Geographic documentary of the Pristine Seas previous visit to the Southern Lines Islands in 2009. It was the programme’s first research expedition and it was interesting to discuss how much it has evolved after a further 30 expeditions and how much work there is still to do with another 39 expeditions planned over the next nine years.

The island on the international dateline - Millennium

Since joining the expedition, those on board who were on the 2009 National Geographic Pristine Seas expedition have been describing Millennium as the most spectacular of the Southern Line Islands, with talk of pristine reefs and huge numbers of top predators, especially sharks. Millennium Island, situated on the international dateline, only has a land area of 1.45 square miles but consists of 20 islets surrounding a shallow lagoon. The central lagoon is six miles long and at most a mile wide. The land is covered with a mix of planted coconut palms and natural Pisonia forest, thousands of birds nest on the atoll including brown and red footed boobies and several species of terns. It is a remarkable place and quite different to the other two islands we have visited.

We spent the first three days working at established survey sites around the island to help understand how the 2015/16 warming event has impacted on fish, coral and invertebrate community structures. At some sites this will be the third set of data to be collected since 2009 so provides a reasonable time series. We start off working on the leeward side of the island as conditions on the windward side of the atoll are unworkable. Unfortunately, due to the constant winds we never manage to work any of the windward sites.

Conditions are pretty much continually challenging working on the reef edge, with large ground swells and breaking waves. All operations need to be carried out with a good reserve of safety, as the nearest help is two days away by ship and we are well out of the range of any helicopter support in an emergency. If we have any problems we have no choice but to deal with them ourselves. For this reason we are carrying both a paramedic, Dave McAloney, and a diving recompression chamber. Many of our team are trained as advanced first aiders and chamber operators.

On day four at Millennium we finally make it into the lagoon where we have a range of diving survey tasks to carry out, including the installation of an Aqualink oceanographic buoy. The lagoon is spectacular, azure waters surrounded by surprisingly verdant islands and golden beaches. The lagoon is criss-crossed by many shallow reefs of Acropora coral that in places reach the surface and make traversing the lagoon slow and painstaking, with the boat having to be walked through some shallow areas. When the lagoon was visited in 2009, the lagoon floor was dominated by vast numbers of Tridacna clams, almost unheard of on most tropical islands where the clams are heavily exploited for food. Tragically the lagoon floor is now littered with the empty shells of these beautiful animals which did not survive the warming event, along with much of the coral. Thankfully small numbers of clams were still spotted alive both inside and outside the lagoon and in time these will hopefully recolonise the lagoon in numbers. The lost corals are being replaced by the fast growing coral Acropora which now dominates the lagoon.

Shark numbers on Millennium are extremely high and I have seen large numbers of sharks on nearly every dive, especially at the Northern and Southern tips of the island where currents are highest which in turn attracts high predator densities. We have seen very large numbers of black tip and white tip reef sharks and in particular grey reef sharks, often over a dozen on a dive. The sharks are quite inquisitive of the divers and will come fairly close, but I have not felt threatened at any point. It is amazing to be in a situation where predators such as snappers, jacks and sharks show no fear of humans, usually they keep their distance. We have also regularly seen pacific manta rays, eagle rays, giant Napoleon wrasse some nearly 1.5m long and incredible fish densities, it often feels like swimming in fish soup and a huge contrast to other tropical areas I have dived.

Return to Papeete and demobilisation

So after sailing just over 1,000 nautical miles and visiting three pristine tropical islands, the expedition is over and we have returned to Papeete.

In 12 days working on science stations, we have carried out 372 dives, counted over 250,000 fish of 190 species on underwater visual census transects, assessed coral and algal species cover, completed 2700m2 of coral photo-mosaics, and taken 50 coral cores. We have also found what is almost certainly a new coral species, taken extensive water samples for eDNA, deployed 13 deep-sea drop cameras, 95 pelagic BRUVs and deployed four oceanographic Aqualink buoys.

In addition, we have shot 16TB of film for a documentary about the expedition and taken thousands of still images for a National Geographic magazine article.

A huge amount of work will now be required to work up the data and compare the results with the previously collected 2009 dataset. But what is clear is that unlike some reefs that have been severely impacted by major bleaching events, the reefs of the Southern Lines Islands – although certainly impacted by the 2015/16 warming event – are still some of the most pristine in the Pacific and clearly recovering. The interesting challenge will be to understand why even after a much more severe warming event than the Great Barrier Reef – a reef severely