After a plane strike that made us fear the worst, finally, with a two-day delay, a good part of the scientific team and part of the crew were able to join the rest of the group, which had already been in Tahiti since September 9. On Monday morning, the crew did a covid test to make sure that everyone was negative before embarking; safety is paramount when you go to sea, far from land, for a long period.

The day was long and busy with the unpacking of the equipment that had travelled with the boat from New Caledonia to French Polynesia a few months earlier. Some of the equipment such as the WBAT acoustic instrument and the Hydrobios zooplankton net were flown in from Europe. There was a lot of logistical work involved in preparing this mission.

We then had to assemble the instruments that had been dismantled, put them in the stainless steel structures that protect them, and install all the electronics and cables. The next step was to check all the connections and the proper functioning of the instruments. Storing all the equipment in the wet lab and dry lab remains a challenge, it's a giant Tetris game with a lot of stuff to fit into a small space.

The Alis at the quay in Papeete.

Unpacking the multiple boxes of equipment.

The crew helped us get the big equipment out of the boxes (the Hydrobios for collecting zooplankton on the picture) and to find space to store the empty boxes.

The electronics technicians install the controls for each of the instruments.

We acquired a new WBAT, an acoustic instrument for observing micronekton.

For our second day of mobilisation we have to check the functioning of all the devices and finish the installation of all the equipment. The manipulations follow one another and everything works rather well but the time passes quickly, everyone is busy.

We decide to calibrate the WBAT, so that this acoustic instrument which allows the detection of micronekton can give us good quality standard results. The manoeuvre consists of putting the WBAT in the water at the back of the boat and placing a 3.8cm diameter tungsten ball with a known acoustic signature underneath it. While the WBAT is a piece of technology, we use broomsticks and fishing line to suspend the ball underneath the device and move it around to locate it in the instrument's beam. On the computer screen we can follow the acquisition of the information live. Computer processing of the data allows the calibration to be completed.

During this time, the crew completes the provisioning of the boat because we are leaving in complete autonomy for 3 weeks and we must be able to feed 18 people during this period.

We have the impression that we are close to the end of our day when we realise that a bad manipulation has been made on the TAPS, another acoustic instrument that allows us to observe the zooplankton. It is no longer functional and we will have to open it up to try and reset it. This is a very big job, with no guarantee of success.

Installation of the zooplankton nets.

Launching the WBAT for calibration at the back of the boat in the port of Papeete.

Calibrating the WBAT with broomsticks to move the calibration ball under the instrument.

During the calibration of the WBAT, the data acquisition can be seen in real time.

Loading of the supplies by the crew.

Dismantling the TAPS to try to reset it.

We left the port of Papeete a little after 9:00 am to head for the first station. We rounded Moorea to the south and as soon as we left the shelter of the islands we were embroiled in a relatively large swell. For those of us who are seasick, this is a tough ordeal and more than a few of us went to bed after giving the fish our last meal.

Despite this we started the first station at 2pm and kept on working until midnight. As with any first station, there were a number of glitches that we will have to rectify before the second station. The CTD that gives us the depth on the WBAT acoustic instrument did not work and we had to leave the instrument just under the surface for 40 minutes instead of descending to 500m depth while waiting for the instrument to finish its data acquisition cycle as it should not leave the water during this phase. We almost lost the hydrobios, which is the zooplankton collection net, because one of the attachment points of the instrument broke and it was only suspended by one point. As the sequence of operations was not well established for either the scientists or the sailors, everything took longer and we decided to do only one trawl instead of two at the end of the day. Everyone was also very tired from a long day in very difficult sea conditions.

The scientific team just before departure, from left to right, Christophe, Martine, Valerie, Damien, Laure and Anne.

The Alis leaves the port of Tahiti under a magnificent blue sky that does not give any indication of the state of the very rough sea.

The weather is very difficult with a swell of 2.5-3m and a lot of wind. The instruments and the teams are put to the test. After the first descent of the rosette which carries sensors (light, salinity, oxygen, fluorescence, temperature, depth) and bottles to take samples of sea water at different depths, it is noticed that the electronic cable which carries the instrument and sends it the commands is damaged. We have to cut the cable to remove the damaged part and re-splice it to ensure that the cable does not break during manoeuvres. This is a big job for our electronics engineer, especially in the current conditions with the boat moving around a lot.

Meanwhile we decide to make a zooplankton net descent with 2 nets of 0.2 and 0.1mm mesh. The nets are installed on a metal frame with 2 hoops. The system is weighted so that it can be lowered without being carried away by the currents. We collect zooplankton between 500m depth and the surface. Our objective is to be able to compare the zooplankton caught in each net, i.e. zooplankton larger than 0.2mm and those larger than 0.1mm. This will allow us to calibrate the zooplankton collections between our old campaigns done with 0.2mm nets and our new campaigns done with 0.1mm nets.

The electronic cable having been repaired, we carry out a second rosette descent and then the hydrobios (zooplankton net with 5 layers) and we notice once again that the cable is damaged. The strong swell creates important tensions in the cable with very brutal jerks. We therefore stopped the operations requiring the cable, i.e. we did not lower the WBAT (acoustic instrument for the micronekton), and we carried out a trawl between the surface and 200m depth in which we only recovered a few fish and crustaceans.

Damien, the electronics technician, repairs the electronic cable.

The Bongo, a double zooplankton net.

The meagre catch of the day.

We had hoped that the weather would ease a bit and it seemed to be the case, but as soon as we recovered the first rosette we were disappointed. The recovery of the instrument was very difficult and for the safety of the sailors and the integrity of the instruments we decided not to make the second run. While waiting for the night to come, we prepared the zooplankton bongo net but a hose in the hydraulic system broke. The crew reacted very quickly by stopping the hydraulic pump and getting out the spill kit and the leak was quickly contained with no spillage into the sea. The team of mechanics then mobilised to make a repair as without hydraulics to operate the winches we could not put any instruments in the water.

The repair was quickly made, and we were able to resume the manoeuvres by putting the Hydrobios 5-sheet zooplankton net in the water, then the WBAT. Finally! This is the first WBAT profile of the campaign after the problems at the first two stations.

We were able to do two trawls, one on the surface, between the surface and 200m depth and a second trawl at 500m depth. In the first trawl there was a small shark of less than 30cm that we released alive into the sea.

A small yellowfin tuna was caught on the trolling line and some squid jumped on the deck, we released them back into the water; some of their colleagues were not so lucky as we had squid on the menu for the evening.

Recovery of the rosette, rodeo-style.

The mechanics in action: Victor, Lucas and Yann.

Catch of the surface trawl with a small cookie-cutter shark.

Trolling for tuna.

The night has been very agitated, the weather has worsened again. Everyday life is very difficult and we have a special thought for our cooks, Jacques and Matéo, who every day, whatever the conditions, prepare and serve us food.

We left the waters of French Polynesia and entered the waters of Kiribati, in the Line Islands. On arrival at the station the swell is less difficult than the day before when we had a cross swell, according to Antoine our first mate. And indeed, the manoeuvres are easier and less dangerous for the crew and the instruments.

We had dreamed of a station that would go smoothly after two rosette descents to 250m and then 600m and a zooplankton sampling with the Multinet Hydrobios, unfortunately the electrocarrier cable twisted again because of the jerks and the pounding of the boat. We finally gave up on the idea of doing a WBAT run and ended the day with 2 micronekton trawls at 200 and 500m. The fishing was a little better than the day before and it was nice to see a little more trawl content with some interesting fish and shrimp. The work ends after midnight and the station lasts a total of 8 hours when all goes well.

Jacques and Matéo, our cooks.

Antoine, our first mate at work.

The rosette is back on board, everyone is busy fixing the instrument and taking samples.

Martine takes water samples to measure phytoplankton.

Laure takes water samples to measure oxygen in the water.

Catch of the surface trawl.

A juvenile ribbonfish and a deep-sea fish with a pink photophore on its head.

Today we were hoping to see land as our sampling station was located near an atoll: Caroline Island also called Millennium Island. But being about 15 nautical miles away with a bit of swell, it was impossible to make out this low-lying land outcropping above the water. On the other hand, probably coming from this island, we were visited by some magnificent frigatebirds which accompanied us all day, hovering above the boat. We also saw some boobies and terns later on.

The splice of the electrocarrier cable having been redone this morning, once again, we decided to change the order of the manoeuvres to ensure that we acquired an acoustic profile of the WBAT and to put last the manoeuvre that put the greatest stress on the cable. We therefore do the Multinet Hydrobios zooplankton net last and extra precautions were taken at all stages. The strategy pays off as the plan goes smoothly this time and all the manoeuvres follow each other and the cable seems to have held up well during the day. This is station 5 and it's the first full station we've been able to do; let's hope it continues.

The harvest in the zooplankton nets remains meagre and we hope to see the quantities increase as we approach the equator. Today we had 2 large specimens (20-30cm) in the trawls: a squid in the first and a fish in the second, with a nice diversity of fish and shrimp. We acquired a motion-compensated balance scale to try and weigh the fresh gelatinous organisms, as once frozen and thawed in the lab they lose all their water content and we have no real estimate of their weight. But with a boat that moves a lot, it is still difficult to get good quality data.

We had a visit from frigate birds.

Valérie collects zooplankton.

Micronekton recovery.

Daytime capture at 500m.

Weighing of gelatinous organisms.

After the success of the previous day, we tried to make a complete station +, that is, in addition to the usual set of manipulations (2 rosettes, 1 Multinet Hydrobios for zooplankton, 1 WBAT, 2 trawls), we added the double zooplankton net, the Bongo. Everything went perfectly, it must be said that the weather was a bit better, making it much easier to launch.

The day ended with 2 trawls which brought us once again some strange specimens. The trawl net is made up of different sized meshes, ending in square meshes of 1cm on each side. The trawl net is 55m long and has a theoretical opening of 10x10m, giving an opening area of 100m2. The net is held wide open by two large metal panels that spread the wings of the trawl; these heavy panels make manoeuvring difficult.

Launching the Bongo for zooplankton by Jean and Vincent, the bosco on board and one of the sailors.

Preparation of the WBAT at sunset.

Taking the panels of the trawl net out.

Launching the trawl net.

Recovering the contents of the trawl net's bottom.

A gold fish.

A big mouth fish.

The swell was again felt today, especially during the steaming due north to the new sampling station. With a swell and side waves the boat moves a lot. We have left Kiribati waters and are now in international waters.

Yesterday, during the first trawl, holes were found in the cod end of the trawl net, suggesting that some fish may have escaped from the net. The sailors made a quick repair so that we could carry out the second trawl. This morning it was necessary to restart things and Edwin, one of the sailors took his needle to patch and sew pieces of new net to plug the holes. Laure took the opportunity to be introduced to the sailor's art of repairing fishing nets.

The sailors took advantage of the waiting time when the instruments are in the water to cast fishing lines and they caught a mahi mahi which was immediately taken care of by the kitchen, probably for tomorrow's menu.

We had some trouble with the Multinet Hydrobios for zooplankton and were half an hour behind schedule which did not allow us to do the second deep trawl. But it seems that the zooplankton harvest is much greater than at previous sampling stations, as we are approaching the rich areas at the equator.

Edwin mending the net.

Laure learns to row

The day's fishing.

A larger than usual zooplankton harvest.

Jeff, the commander, makes sure the trawling is going well.

The trawl team (Christophe and Valérie) ready to go.

Today, in spite of the swell and the cross waves, we managed to make another station +.

The contents of the trawl were a little heavier than usual with notably a lot of Pyrosomes which are gelatinous organisms with a rather rigid consistency, and which have a tube shape closed at one end. Just like the llama, the pyrosome has the particularity of spitting on us when we handle it, it expels a small jet of water; Laure was the victim. We suspect that these organisms are the cause of the acoustic signal observed this evening. Indeed, whereas the previous days' acoustic signal showed a denser layer of organisms around 50 metres, this evening this layer was deeper, at around 135 metres with a stronger acoustic signal at 38kHz compared to 70, 120 and 200kHz.

Launching the Bongo zooplankton net into the swell and waves.

Juveniles of two species of ribbonfish whose adults can be several metres long.

A specimen we named Boa fish which has an eye more than half the diameter of its head.

The contents of the trawl with many gelatinous organisms and in particular pyrosomes.

Echogram of the acoustic signal. The acoustic signal is plotted against depth (vertical axis) and time (horizontal axis). Yellow-red colours indicate a higher density of organisms.

On the transit to station 9, at latitude 2°S, we observed on the EK60 echogram, a set of small dense aggregations in the first 150m. The void appearing around these detections in the surface layer (0-~180m) suggests that they are predators (such as tuna or other large predators) feeding on the micronektonic organisms present in the layer, or that there is an avoidance phenomenon of these small organisms in the presence of these aggregations, or a bit of both.

We had high hopes for tonight's trawls, especially the surface trawl as the acoustic layer was very dense. But disappointingly, the trawl content was very thin. There were however many very small fish caught in the mesh of the net but not found in the codend. It is likely that these are the same as the small fish caught in the zooplankton net.

The acoustic signal is plotted as a function of depth (vertical axis, from the surface to 150m) and time (horizontal axis). Yellow-red colours indicate a higher density of organisms. The green-red spots represent large predators and the blue dots smaller organisms that appear to be moving away from predators.

Tiny fish in the zooplankton sample that are too small to be caught in our micronekton net.

Contents of the deep trawl with a beautiful purple jellyfish.

A relaxing interlude in the sun with reading and music until a stronger roll sends a wave flooding over the deck bringing everyone inside, more or less soaked.

Today we arrived at the equator and although the weather was not as bad as the previous days, it was not the calm we had hoped for to cross this imaginary line. We still marked the occasion with a small sign.

Crossing the equator.

We left Tahiti toward the equatorial region where ocean currents have a very peculiar behavior, to the mysterious equatorial line where the water rotating in a sink is said to change direction.

As we sailed to the equator along 150°W, the ocean surface temperature was measured continuously. From 26.5°C in Tahiti, the temperature increased gradually up to 8°S (27.5°C) and decreased again as we moved to the equator with a temperature of 26°C. The maximum temperature was not situated at the equator, counter to intuition.

In fact, that equatorial region of the central and eastern Pacific is named the equatorial upwelling, characterized by cooler temperature centered around the equator. There and off about 1° north and south, ocean currents behave in a very special manner.

Indeed, we encountered a series of currents along the route as seen on Figure 1 with mostly westward flowing currents in the top 400 meters of the ocean reaching at most 0.6 knots with some small alternances of eastward currents in the first 400m. The dominantly westward flowing currents constitute the South Equatorial Currents (SEC). When we reached the 1?S-1?N region, a very narrow and intense band of eastward flowing currents was encountered with currents reaching up to 1 knot in the top 400 meters. This narrow and swift eastward current is called the Equatorial Under Current (EUC).

Figure 1 Left panel: the ocean currents in the first 400 meters of the ocean (red arrows indicate currents towards the west and blue towards the east). Right panel: The ocean surface temperature measured continuously by the thermosalinograph, the instrument on board pumping water from the surface.

When looking at the vertical structure of that Equatorial Under Current, it appears that it is a tube of eastward flow lying just underneath the South Equatorial Currents from about 50 to 150 meter depth and centered slightly south of the equator. Such current also exists in the Atlantic oceans at the equator.

Figure 2. The vertical structure of the east-west (or ‘zonal’, top, in yellow towards the east and in blue towards the west) currents along 150°W.

Today was an off day. The fatigue of the teams and the equipment was felt.

To start with, the weather was once again getting worse, making manoeuvres more difficult. Then, as soon as the rosette was lowered for the first cast, we had problems. When the rosette was at 60m depth, alarms went off in the science centre. We immediately brought the rosette up to find that one of the connectors had taken on water. We had to replace it and an hour later we were able to put the rosette back in the water.

However, due to the heavy swell and the delay we decided not to do the second rosette and to move on to the next operation, the lowering of the WBAT, which went well. During the third operation, while the zooplankton sampler, the Multinet hydrobios, was at a depth of 400m, during the ascent, a fire alarm sounded throughout the boat. Smoke and the smell of burning was spreading outside the boat. It was quickly identified that it was a lifebuoy smoke that had been set off on its own. No repercussions, but a good adrenaline rush for everyone.

So, we continued the manoeuvres and to round off the day, in the first trawl we had an oceanic shark of about 1.5 metre long which was alive and well and which we immediately released. But it had had time to damage the codend by making big holes in the codend and so we only got a few shrimp. There was a lot of repair work to be done on the trawl so we called it a day. Tomorrow is another day.

The meagre harvest of the day.

After yesterday's hard day, we were reassured to see that everything went well today. Except for a glitch on the rosette where we had to remove the faulty light sensor that was preventing commands from being sent to the instrument. After the intervention of our electronics technician, we were able to carry out all the manoeuvres one after the other without any problem, helped by a slightly milder weather than the day before, but far from a dead calm all the same.

We had a particularly good time fishing. On the one hand we caught a mahi mahi with a troll line on the back for cooking and on the other hand with the micronekton trawl for science. We are in rich waters, and thanks to innovations by our captain on the trawl to facilitate the arrival of organisms to the bottom of the trawl, we are fishing better.

Programming the WBAT just before it was launched.

Good surface fishing.

The day's catches were rich in squid and octopus of all kinds.

We also had some magnificent shrimp specimens.

Today we did the last station of the Warmalis2 mission, it was the thirteenth station. We had no problems, everything went well and we ended the day with 2 trawls as the previous days.

However, the last trawl was a bit special as it was trawl number 300 since we started this study in collaboration with IRD and CPS in 2011. These 300 trawls were all carried out on board the Alis and more than 95% were carried out under the direction of Captain Jean-Francois Barazer who despairs a little at the low quantities caught but who is always trying to improve the technique; we thank him for all this.

This one has been christened gronchon fish, a contraction of grumpy and Rochon.

An octopus whose head with its tentacles is at the top of the picture but which at the bottom of the body has 2 large dots (photophores) that look like eyes and 2 fins that look like ears; an octopus with two heads.

Last trawl of the mission, and 300th trawl for our team on board the Alis since 2011. In red helmets the sailors, in yellow helmets the scientists.

After station 13, we changed course, heading southwest to our port of call. We were going to refuel in Kiritimati but logistical complications have forced us to change our plan and we are going a little further, to Apia in Samoa. We have 9-10 days of transit ahead of us. We also changed the day by passing through Kiribati waters and lose Tuesday 27th September in the blink of an eye.

Martine is doing the last manipulation, i.e. the filtration of her bottles to estimate the production of phytoplankton, these microalgae which float in the ocean. She has left her samples from station 13 to grow for 24 hours and it is therefore time to filter them to recover the microalgae on a filter. The filters are kept in the freezer and the measurements will be taken on return to land in the laboratory.

The sailors start to tidy up and clean the equipment. In the absence of manoeuvres there is more time available to fish and to do some exercises such as measuring the position of the boat with the sextant.

Martine makes the last filtrations of the campaign.

2 wahoo taken simultaneously on the 2 trolling lines.

The Kiribati and Brittany flags fly side by side on the Alis mast; a rarely seen combination no doubt.

Antoine, the first mate, takes measurements of the sun's height with a sextant.

We take advantage of the slightly milder weather to put the equipment away, rinse it and grease all the instruments when necessary to prevent them from rusting.

We also take advantage of the day to start analysing the data collected, but it remains difficult with a moving boat.

Cleaning in the lab.

Cleaning the zooplankton nets.

Herbal tea evening.

This morning we are waiting outside Apia, the capital of Samoa. It's good to see land after 3 weeks on the open sea. Apia offers us a mountainous view, with luxuriant vegetation and large buildings on the seafront. After the health services have come by dinghy to check that we have followed the covid protocol (vaccination, negative test at the port of departure and daily temperature check) we are allowed to dock.

The Alis docks between a Chinese longliner and a huge container ship; next to it our boat seems very small and yet we have just travelled 6000km without touching land. Before setting foot on land we still have to wait for the green light from the immigration services who check our papers and stamp our passports.

Finally, we are allowed to get off. However, we still have to stay on board to organise all the equipment for the final transit to Noumea. The wet laboratory is filled with all the equipment boxes. Only the biggest equipment will be left outside as it is not afraid of the weather, even if it is sheltered under tarpaulins or in boxes.

After a last meal on board the boat, we finally go ashore with our luggage. A colleague from the Samoan fisheries department comes to pick us up and drop us off at the hotel. The sailors of the Alis get organised to refuel and food supply and at the end of the afternoon they will leave for another long week of transit to Noumea. We will be waiting for them when they arrive to unload all the equipment and the precious samples that we have collected with great difficulty. The weather has been particularly bad during these 3 weeks, and we have not had much respite so we are quite happy to find stable ground under our feet.

View of Apia on our arrival.

The wet lab is filling up with boxes of equipment.

Some of the equipment scattered on the deck between 2 showers.

The Alis at the dock, in Apia, Samoa, right next to a container ship.

The scientific team had left the boat on October 6 in Apia and we were able to return to Noumea on October 10 by air. During this time, the boat also resumed its route with sea conditions still as difficult as ever with a very strong swell. The Alis arrived at the quay in Noumea this morning, October 14th.

We were happy to see all the crew who were working hard to unload the heavy equipment. We came to retrieve the valuable scientific samples from the freezer to transfer them to the laboratory before the on-board freezers were shut down.

On Monday 17 October we will return to the ship to collect all the scientific equipment, and this will mark the end of the mission at sea. The long phase of sample and data analysis will then begin. But we are already starting to think about the next mission, Warmalis3, which we hope will take place in September-November 2023.

The adventure continues.

Unloading the large equipment with the crane, under a bright sun in Noumea.

The wet lab full of the equipment we will unload on Monday.

Down to the freezers to collect the samples.

We filled an entire chest freezer with all our samples; a lot of work ahead.