Map of the second cruise of Nectalis
Day 18-14/12/2011: Arrival in Nouméa
We arrived today at Noumea harbour around 2:30pm. This is the end of a 17 day-trip and everybody is happy to back on land. The work has been intense during this cruise and we all come back to our respective labs with hips of data and samples which will keep us busy for a few months at least. We hope to get together in 2012 to gather all the results and to make a comparison between the 2 cruises. With all the results in hand we might consider follow-up cruises to complete our data. We would like to thank Captain Jean-Francois Barazer and his crew for yet another very successful trip which couldn’t have been done without them.
All the equipment on the deck, ready to be disembarked
A final cup of champagne to celebrate the end of the cruise
Group photo in front of the Amedée lighthouse less than one hour before arrival. We are all wearing the T-shirt that was made for Nectalis to celebrate Francis last cruise onboard the Alis.
The back of the T-shirt
Day 17-13/12/2011: Nec2023
While in transit during the day we worked on the data obtained so far to produce the final report of the cruise. We arrived at the sampling station around 5 pm and we were hoping for a quiet final sampling station but the equipment decided otherwise. We started with the CTD probe and while checking the procedure before the CTD goes down we realised we had lost the configuration of the probe. We had to reload a new configuration before doing the CTD cast, it only induce a 20 minutes delay. Martine then had some problems to filter the water to collect phytoplankton. No other issues and quite successful fishing with the micronekton net to finish the day. As it was the last sampling station for Francis he cut the extremity of the electro-portative cable which is used to cast instruments and also provides power supply. This is a nice souvenir for his last cruise onboard the Alis.
Martine in the wet lab filtering water which has been collected with the bottles at different depth from 180m to the surface
Martine, Christophe and Marc collecting water from the last bottle cast of the cruise.
The trophy Francis will bring back home!
Day 16-12/12/2011: Nec2021 & Nec2022
This morning we conducted our last daytime sampling station. It was located in the channel between Grande Terre and Loyaulty islands, off Maré. The last 2 stations will occur during the night.
Results of the CTD probe which is casted at every sampling station down to 500m depth have been plotted showing temperature, salinity, density and fluorescence profiles. Results are shown for the first 19 sampling stations. We can observe a clear difference between profiles of salinity, temperature and density (which depends on temperature and salinity) before and after 2 Dec which corresponds to sampling station 8. South of station 8, that is stations 1 to 7 (28 Nov to 2 Dec), we were located in the waters with lower temperature, lower salinity and consequently higher density. North of sampling station 8, stations 8 to 19 (2 Dec to 10 Dec) waters are characterised with higher temperature, higher salinity and lower density. The 25°C isotherm is deeper in the northern part of the area. Despite these different vertical structures in waters masses we do not observe large difference in fluorescence which reflects the phytoplankton. The maximum of fluorescence is located around 100m in the whole area sampled. As we continue our route down south we expect encountering colder, saltier and denser waters from station 20.
Vertical profiles from the surface down to 200m at sampling stations 1 to 19 from 28 November to 10 December during Nectalis2. Temp= temperature (red=hot, blue=cold), Salinity (red =saltier, blue =fresher), Sigma Theta= density depending on temperature and salinity (red =denser, blue =less dense), Fluorescence= index of phytoplankton (red =high value, blue =low value).
Ship’s track and position of the stations sampled until the 10th of December during Nectalis2 cruise.
Days 14 & 15 - 10/12/2011 & 11/12/2011: Nec2019 & Nec2020
The afternoon before arriving to sampling station 20 was used to make various repairs. We had some issues on the TAPS as one of the 6 frequencies was blocked on its way back from depth during sampling station 18. It stayed at the same value during sampling station 19 so we decided to open it to check if the electronic circuits were OK. After a thorough inspection nothing abnormal was detected; some electronic contact cleaner was added and we hope it will solve the problem. There is no way to test it before so we will have to wait for the cast during sampling station 20. Other repairs were necessary on the zooplankton net as we discovered 3 more round holes made by the cookie cutter shark in the nets.
Today is Sunday and the cooks made us a special meal: Bougna which is the traditional melanesian dish in New Caledonia. It is usually cooked in the ground, but obviously it was made in a cooking pot; it was composed of chicken, taro root, bananas and sweet potatoes. We really enjoyed it. In the afternoon we could see the coast of Lifou, one of the Loyalties islands.
Zooplankton net repairs
Bougna, traditional Melanesian dish of New Caledonia
Examining the electronic circuits of the TAPS
Day 13-09/12/2011: Nec2017 & Nec2018
Yesterday we conducted 2 sampling station, the first one during the night before dawn and the second one also during the night but after dusk. The work went well with no particular issues. Since the beginning of the cruise we have noted the presence of large quantities of surgeonfish larvae (Acanthuridae) in the trawl catch. It was particularly obvious in last night’s catch. The larvae were caught both close to the surface around 20m depth but also deeper at 100m. We suppose it is the result of a large spawning event by these reef species which probably took place few weeks ago. These larvae are translucent except for a vertical silvery band around the eye. Because we suspected a number of small specimens were going through the cod-end mesh, the captain found a solution to stretch the mesh and sure enough we caught a number of small organisms we were missing before.
All day long during the transit between sampling stations 18 and 19 we have observed unusual detections on the echosounder. They have the particularity of being visible at 120 and 200 kHz frequency while they are not visible on the 38 and 70 kHz. We are not sure of what it could be but it could correspond to jellyfish.
Because we are well on schedule, we decided to add a supplementary sampling station. Discussing with the captain we decided to add this sampling station south of Ile of Pines, 20 nautical miles away from the Antigonia Seamount. It will allow us to sample more in the colder waters of the south.
Echosounder image with the 4 frequencies and signal visible on the 120 and 200 kHz between the surface and 100m depth, but not on the 38 and the 70 kHz. It could correspond to jellyfish signature.
Surgeonfish (Acanthuridae) larvae collected at the surface (on the left of the tray)
New cruise plan with a sampling station added in the south of Ile of Pines
Day 12-08/12/2011: Nec2016 & Huon
Last night sampling station was particularly successful for trawling. We were located west off Huon atoll on the slope and the echosounder detection was strong around 100m depth. We did two tows and we obtained a fair amount of samples with small fish and squids mainly; we also caught 4 cookie-cutter sharks of about 30cm long. We caught these small sharks during Nectalis1 and we suppose they swim with the micronekton waiting for a large predator (tuna, marlin...) feeding on the small fish to attack them and bite a small piece of flesh of the tuna. When tuna longliners land their catch we can often see some of the tuna with a missing round piece of flesh on the flank. In the zooplankton net we found 2 large red shrimp which is quite unusual and we suspect that the round hole of about 2 cm in diameter in one of the nets was made by a cookie-cutter shark trying to eat the shrimp in the net or trying to escape the net (earlier during the cruise we found a cookie-cutter shark in the zooplankton net).
After the sampling station we decided to anchor in front of Huon Island for a break of a few hours as a farewell gift before Francis retires. Nectalis2 is his last cruise onboard the Alis with which he did many cruises during his 30 year long career. Huon is the northernmost piece of land in New Caledonia EEZ and is a very low island 50m wide and about 400m long made of sand with vegetation running on the ground, no trees, no bushes. We took the dingy to go on land and we were welcomed by many birds. We could see eggs on the grounds, chicks of different ages and adults nesting. On the eastern side of the island we meet 5 turtles we were stuck in a pool blocked by the beackrock. There were many tracks on the sand and deep holes were they had been laying their eggs the previous night and they went back to the sea while the tide was too low. We helped one turtle crossing the beackrock and we saw 2 of them managing to reach the ocean. The others were resting in a pool and waiting for high tide, fortunately it was overcast with rain so they would not suffer of the sun. We really enjoyed going on land and having the opportunity to observe the wildlife; thanks to the captain for this stopover. Back onboard the cook had prepared a very special meal to celebrate Francis’s last cruise on the Alis. We left after lunch to reach the next sampling station the following night.
A hole in the zooplankton net probably made by a cookie-cutter shark
30-cm long cookie-cutter sharks caught in the micronekton net
Special cake to celebrate Francis’s last cruise on the Alis
A turtle in a pool waiting for the high tide to come to cross the beachrock on Huon Island
Adult noddi and their eggs laid on the ground
Adult and chick gannet
Two instruments allow measuring ocean currents onboard: the S-ADCP (fixed on the hull) and the L-ADCP casted down to 800m depth at each sampling station. These 2 gears are complementary as S-ADCP measures currents continuously along the track of the ship but only perceives the first 150m in depth. ON the other hand L-ADCP only measures currents at sampling stations but provide information on current structure over 1000m in depth and it is the only way to obtain this data.
First 2 figures below show the structure of currents measure over 1000m in depth by the L-ADCP at each sampling station along the track of the ship. Two types of currents are visible: surface currents which are generally stronger from the surface down to 200m depth. These currents are produced by the wind (Ekman layer is the name of this surface layer influenced by the wind), as well as by density (determined by both temperature and salinity) difference of the water (called geostrophic effect). The other current type, visible on the figure at two stations along our track, influences at least the 1000m depth. These currents are particularly common in the south Pacific and are called “zonal jets” as they are very powerful and homogeneous on the water column and generally go from East to West. These jets are produced by the dispersion of large oceanic currents hitting islands (Fiji, Vanuatu, New Caledonia) such as the south equatorial current coming from the eastern Pacific and crossing the ocean to reach Australian coast.
Just like S-ADCP, L-ADCP measures the difference in frequency of emitted and received signal which hit particles in the water (Doppler effect). We can deduce current speed based on this difference. It also means that we can estimate the quantity of particles in the water according to depth. Depending on the type of ADCP used we can measure particles of various sizes. Our instruments allow us to detect organisms of the size ranging from zooplankton to small fish. On the last figure below high values of amplitude in red indicate high concentrations of organisms while blue areas indicate low concentrations. We can see that maximum abundance of organisms are located in the surface layer (0-100m) and in the deep layer (400-600m). Despite being used primarily for current analysis, these L-ADCP measures are in agreement with net sampling and results of acoustic instruments dedicated to organism detection which demonstrate similar distribution of organisms.
Results of the L-ADCP for the first 9 days of Nectalis2 cruise. First 2 figures show zonal (east-west) and meridian (south-north) current from the surface down to 1000m depth; the 2 zonal jets are shown as large vertical bands in blue and yellow corresponding to a north-westward jet at station 5 on the 29th of November and an eastward jet at station 13 on the 5th of December. Last figure show the amplitude which is an index of the quantity of small organisms in the water with high values in red and low values in blue.
Xavier our chief engineer fixing a new battery on the framework of the 2 L-ADCP (in yellow). One the of L-ADCP looks downward, the second one looks upward. We recently had problems with the L-ADCP and after adding a new battery and changing all the connecting cable, Francis our electronician realised it was the L-ADCP itself which did not work. Fortunately we had a spare one which was installed on the framework and we hope everything works at the next sampling station.
Day 10-06/12/2011: Nec2014 & Nec2015
We had a short transit of 5 hours between sampling station 13 last night and station 14 this morning; only a few hours of rest before this sampling station during which we doubled the work. Indeed we decided to take extra samples of water to examine small zooplankton, so we had to cast the bottles twice. Then we did 2 zooplankton nets to collect extra samples for a colleague of us. We also did a phytoplankton net down to 100m to look at the species composition of phytoplankton cells. Moreover we had a problem with the LADCP which was not recording the data and we suspected there was a problem with the battery. Francis our electonician cleaned the connections and we did a second cast, unfortunately it was still not working. Francis did a more thorough check and we did a third cast of the LADCP after the trawls. Finally some data were obtained, however we decided to add a complementary battery to avoid any further problem, meaning some more work has to be done on the LADCP. This station lasted about 9 hours which is about twice the usual time; next sampling station has been delayed by 3 hours to allow everybody to rest.
We would like to mention the excellent work done by our team in the kitchen: Jacques and Nicolas. Meals are a very important moment on a boat. Work is sometimes difficult and weather condition can make it even more difficult so gathering everybody around the table for a break and good food is always appreciated. We don’t make it easy as sampling station happen sometimes during the meal or some of us have to work when other eat, but the kitchen team keeps smiling and preparing us excellent food and providing great service. Thanks a lot Jacques and Nicolas.
Jacques and Nicolas the team in the kitchen
Lowering down the small net for phytoplankton
Francis and Christophe cleaning and repairing the LADCP
Brown trails of Trichodesmium at the surface of the sea. This picture was taken off Noumea in 2003.
Results of the hull’s ADCP (currents and prey biomass index) and thermosalinograph (temperature and salinity) on Nectalis2 tracks.
Day 9-05/12/2011: Nec2012 & Nec2013
Yesterday we observed at the surface of the sea large brown trails; it was blooms of Trichodesmium. These organisms are cyanobacteria which are bacteria with photosynthetic pigments like algae. All photosynthetic organisms require nitrogen. These bacteria do have the particularity of absorbing atmospheric nitrogen dissolved in the water (diazotrophy process) which exists in large quantities. On the other hand, most of the phytoplanktonic organisms can only absorb nitrogen in nutrients such as ammonium or nitrate which can be in small quantities and limit the development of algae such as in poor areas (oligotrophic areas). Trichodesmium appear in general in hot waters in summer.
First sampling station of the day started at 5:00 this morning. We made all the usual measurements. With the probe we obtained a vertical profile of fluorescence which gives us information on the quantity of phytoplankton in the waters and the depth of its maximum. This morning the maximum was particularly shallow, at 60m depth while on previous sampling stations it was generally around 100-110m depth. Maximum of fluorescence was never observed at the surface during this cruise. Absence of surface enrichment and a clear deep maximum of fluorescence are characteristic of oligotrophic waters, that is poor waters. Preliminary results do not allow explaining variations in maximum depth. It does not seem to be controlled by vertical movement of water masses which is usually the first source of enrichment of the ocean.
Two trawls were conducted at the end of the sampling station. The first tow was deep at 450m and the second one was shallow at 25-30m depth. The second tow was somewhat disappointing as there were only gelatinous organisms. However there was one fish in the net. This small 1.5cm long fish is rarely observed and it raised a lot of interest as it is probably a tuna larvae. A closer look in the lab will allow confirming if it is a tuna larva and we might be able to identify the species.
Fluorescence (indication of quantities of phytoplankton) according to depth at sampling stations 10 (black), 11(blue) and 12 (red) showing the deep maximum characteristic of very poor waters (oligotrophic).
Fish larvae found this morning in the second trawl towed at 30m depth. It might be a tuna larva which measures about 1.5cm.
Day 8-04/12/2011: Nec2011
We continue our route in the northern part of New Caledonia exclusive economic zone sampling station after station. We now navigate in waters with temperature above 28 degrees. Data of the hull’s ADCP which in a current profiler also providing an index of prey biomass and data of the hull’s thermosalinograph providing continuous temperature and salinity have been analysed. We now have more data than in the logbook of the 28 and 29 of November; it allows us to better understand the oceanography of the area. Maps of temperature and salinity clearly show that two waters masses exist. Cold and salty waters are located in the south of the area while hotter and less salty waters are in the north. In-between there is a transition zone with water of intermediate temperature and salinity where the two water masses meet and which are slightly mixed by turbulent currents in this area. Index of prey biomass is coherent with temperature and salinity data with larger quantities of prey in cold and salty waters of the southern area.
Day 7-03/12/2011: Nec2HS1 & Nec2010
Today we crossed the northern part of the large Chesterfield bank to come back toward the Grande Terre of New Caledonia. During Nectalis1 when navigating in this area we observed on the echosounder large quantities of organism on the slope of Chesterfield bank. These organisms were located at 220m depth during the day which was very unusual compared to classic detections found around 500m depth during the day. At the time, the trawl we towed on this detection brought back a species of hachetfish very specific; we did not find its description in the scientific literature which makes us think it might be a new species. Specimens were about 4 to 5 cm long. During Nectalis2 we wanted to check if these detections were still here. This morning when we arrived on the East slope of the bank we found again the detections yet very intense but located a little bit deeper around 300m. We lowered down the trawl and yet the hatchet fish were caught. The content of the trawl was monospecific. Specimens were smaller, 1-2 cm long, but quantity caught was larger than during Nectalis1. We still need to conduct research in the scientific literature and we need to contact specialists to confirm or not if this species is new; if this is the case we probably collected enough specimens to describe thoroughly this species.
Echosounder signal on the East slope of the Chesterfield bank showing classic structures of organisms located deeper than 500m and just below the surface during the day. Note the unusual structures of high density around 300m depth.
Valerie Allain and the catch of the day
Catch of the day sorted. On the left, large quantities of the hatchetfish Polyipnus sp. which species name could not be determined.
Days 5/6-01/12/2011-02/12/2011: Nec2007 & Nec2008 & Nec2009
During our cruise we are studying zooplankton which is composed of small organisms such as crustaceans. Krill found in Antarctica on which whales are feeding is a zooplankton organism. Zooplankton is feeding on phytoplankton and bacteria and is then located at the second level of the food web. The area we are sampling during Nectalis is located in a very poor region and the samples we have been collecting so far show small quantities of zooplankton. However sampling station 7 was richer than any other sampling station. As for all other stations the surface layer (0-100m) is the richest). We also examined zooplankton using the TAPS (Tracor Acoustic Profiler Sensor), an acoustic profiler we cast at 200m depth. TAPS provide information on vertical distribution of zooplankton by size class. We can compare these distributions to environmental parameters such as fluorescence (index of phytoplankton) or temperature.
Results of the TAPS showing distribution according to depth (from 0 to -200m) of small, medium and large zooplankton during day and night sampling station. At the same time fluorescence and temperature are shown. Fluorescence is a proxy of phytoplankton on which zooplankton is feeding (particularly the small zooplankton). Small zooplankton is distributed at the surface, medium-size zooplankton is located above the maximum of fluorescence and large zooplankton is at the same level as maximum of fluorescence during the day and above during the night.
Marc Pagano using High Tech equipment to transfer zooplankton in jars.
Some reef fish larvae caught offshore: a 1 cm butterflyfish (Chaetodontidae) on the top left, boxfish (Ostraciidae) on the bottom right
Zooplankton organisms: small crustaceans.
Day 4 -30/11/2011: Sampling station Nec2006
This is the second night in a row that we have problems of entanglement on the trawl. Captain thinks we were going too fast, more than 3.5 knots and when slowing down to turn on the winch to bring back the trawl, the doors came close to each other and get tangled. However the situation was slightly different than yesterday because at the time we had only 120m long of cable outboard while last night 600m long of cable was out as we were targeting detection at 90m depth. By the time all the cable was wind up the trawl had plenty of time to roll over. It took the crew about 2hours and a half this times to bring back the trawl and the doors; the work was not facilitated by a 20 knots wind and rough seas. Cables were repaired the following day. Catch of the trawl was not large but was mainly composed of squids including 2 large specimens.
Jonathan, one of the crew members, splicing a cable
Edwin, Féfé and Steve working on the other cable
Squids caught during last night trawl with 2 purple squid Stenoteuthis oualaniensis of about 20 cm long.
Day 3 -29/11/2011: Sampling stations Nec2004 & Nec2005
Today we carried out our last sampling station off the west coast of New Caledonia Grande Terre. We started at dawn and in about 5 hours we conducted a current profiler (LADCP) cast at 800m, a temperature/salinity/depth profiler cast at 500m with 9 bottles collecting water for chemical and phytoplankton analyses, a zooplankton net cast at 600m, a zooplankton acoustic profiler (TAPS) cast at 200m and finally 2 trawls at 490 and 30m depth. In the second trawl close to the surface we caught some reef fish larvae which grow offshore before coming back to settle on the reefs. We left the sampling station around midday to go to the West towards the Lansdowne bank where we will conduct the next station above 1000m depth bottom. We will then cross the bank which shallower depth is about 40m depth. We started analysing the data recorded continuously by the instruments mounted on the hull; particularly we do have some data on prey quantities and currents.
A 4 cm filefish (Monacanthidae).
A 3 cm soldierfish (Priacanthidae).
The hull mounted current profiler (SADCP) allows calculating a biomass index of prey and the direction and strength of the currents. Data presented here are a mean over the 100 first meters and for biomass index the day-night effect has been removed. The first graph indicates that quantities of prey are larger in the southern part where the waters are colder (see logbook 28/11/2011). Current data clearly show the current named Alis going towards the south-east in opposition to the dominant trade winds, however some oscillations are observed
Last night sampling station (Nec2005) has been hectic. We started the work with trawling and we targeted detection observed close to the surface at 25m depth. When we lowered the trawl in the water with noted on the echosounder screen that the detection came even closer to the surface. When trying to move up the trawl to catch these organisms, the captain quickly realised there was a problem. Depth and mouth opening probes of the trawl indicated the gear had a very strange behaviour. Cable was wind up we realised that the 2 heavy metallic doors which allow maintaining the mouth of the trawl wide open became tangled. We had a similar problem on the last trawl tow during Nectalis1. The crew reacted very quickly and managed to disentangle the cable and bring back the trawl onboard. We conducted a second trawl and the rest of the experiments. The following day the cables were shortened to remove the twisted end. Congratulations to the crew who were very efficient and very fast to deal with the incident.
One of the doors is onboard (on the right on the picture); the other door is dragged in the water at the back. We can see the twisted cable been disentangled.
The 2 doors are now onboard; trawl cables have also twisted and need to be disentangled.
Day 2 - 28/11/2011: Sampling station Nec2002 and Nec2003
After two days we have already completed 3 sampling stations. Indeed we added a new sampling station mid-way through sampling stations 1 and 2. Before departing we checked the most recent temperature maps provided by the satellite and we observed a front separating cold waters in the south from warmer waters in the north. The front was located around 21°S and because in our original plan we only had few stations in the south, we decided to add another station. We successively sampled the 3 first stations with 6 hours of work at each station and 6 hours of transit between stations. We recorded sea surface temperature difference of 2 degrees between the stations going from24.3 to 26.3 degrees indicating we crossed the front. Station 3 was conducted during daytime when micronekton is at depth. We had to send the trawl down to 500m depth to hope and catch some specimens. Harvest was not very big but at this depth there is always a chance to bring back some weird fishes
Salinity (left) and temperature (right) along the ship’s track. Contrast is clear between the southern area characterised by salty (yellow-green) and cold (blue) waters and the northern area characterised by fresher (blue) and warmer (red) waters.
Content of the trawl towed at 500m depth, at station 3.
Same after sorting by groups: jelly-like organisms, shrimps and crustaceans, squids, hachetfish (silver), mix of deep fish, some reef fish (limefish and pufferfish) and leptocephali larvae (eel, moray eel larvae...).
A strange fish barreleyes (Opisthoproctidae) caught at 500m depth. It is about 4 cm long et has a transparent snout.
Day 1 - 27/11/2011: Sampling station Nec2001
Just before our departure on Sunday morning, Jean-Michel Boré from the communication department at IRD came to make a video interview of Francis Gallois who is participating to his last cruise onboard the Alis. After a few shots we left the harbour at 8:15. With relatively good weather condition in the lagoon, we took the opportunity to conduct security exercise: get dressed with the safety suit which that is quickly transformed into a sauna. As planned we arrived around 12:00 at sampling station Nec2001. During this first station we conducted all the experiments planned: CTD, LADCP, TAPS, zooplankton net and 2 tows of micronekton net. As usual during a first sampling station, a number of small incidents took place: a missing shackle, inversed cable, systems that used to work on land that do not work anymore at sea, etc… It took us 7 hours instead of the planned 6 hours to complete our experiments which all went well. Crew and scientists are becoming familiar again with the work.
Jean-Michel Bore interviewing Francis Gallois just before the departure of Nectalis2 cruise
Security exercise for Marc Pagano and Christophe Menkes