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DipFIP

Degree and Structure of cryptic diversity in morphotaxa of planktonic Foraminifera of the Indo-Pacific warm pool

 

The CTD is being deployed by the Crew of RV Sonne...

...while the CTD sensor data can be monitored in real time from the lab.

The Fluorospectrometer is used to measure chlorophyll a concentrations in the water obtained from the CTD rosette.

Cruise Narrative

Having embarked the ship in Wellington on 3.3.2013 at noon, the scientific party used the rest of the day to mobilise equipment and install the laboratories. On Monday 4.3.2013 at 10:30 local time, with fair weather and calm sea, the ship has left the harbour of Wellington heading NW for the Tasman Sea. Although the weather remained good, heavier swell was encountered in the night. In the morning of 5.3.2013, the edge of the Zealandia shelf has been crossed and the first station was taken over the continental slope in the Tasman Sea. The sampling programme, which will be with small modifications repeated at every station, consisted of a CTD cast to 1000 m, followed by two plankton net hauls to 700 m and 100 m, with standard sampling intervals. Both the ship CTD and our plankton net are working fine, although a tear in one of the nets has been discovered. The fluorescence probe yielded a dataset which appears unlikely to be correct. The CTD cast revealed a shallow mixed layer of about 40 m and a low population density of foraminifera, showing a typical temperate assemblage. Heavy swell continued whilst the ship was heading North.
The second station was taken close to the northernmost tip of New Zealand in the morning on 6.3.2013, yielding a rich temperate assemblage of planktonic foraminifera. At this station and all following stations, it was decided to sample with the CTD only the top 800 m of the water column. A third plankton net haul to 700 m was taken to cover the entire water column and test the filtration apparatus for use with parallel samples. The EEZ of New Zealand was crossed on 7.3.2013 at 6 am local time, the EEZ of New Caledonia has been reached on 8.3.2013 at 4 pm local time. Three stations were taken on the way, always at the same time of the day. The CTD data indicated subtropical conditions with thermally mixed layer reaching to 100 m, followed by a shallow and thick thermocline.
On 8.3.2013 the weather report showed a tropical storm north of New Caledonia, which was predicted to develop slowly towards the south. The associated winds and swell were considered too high to continue in the planned direction and the cruise track has been modified to pass further east.

The Multinet is armed for deployment....

...deployed...

...and the obtained samples are being retrieved.

The last station in the EEZ of New Caledonia has been taken on 9.3.2013 and the next two days were spent by transiting the EEZ of Vanuatu, where no stations were taken due to lacking permission. In the wake of the large tropical storm, the weather deteriorated with heavy swell, clouds and rain.
The EEZ of the Solomon Islands has been reached on 12.3.2013 and the first station in the morning on that day revealed a water column structure indicative of a complex equatorial circulation system, including strong subsurface salinity maximum and a steep thermocline suggestive of up doming of deep waters. After five unsuccessful attempts, it was decided not to deploy the fluorescence probe in the water any more but to confront it with water from CTD-Rosette bottles instead. In the afternoon, the Duff Islands have been sighted. The last station in the EEZ of the Salomon Islands was taken on 13.3.2013, including one additional net haul to 700 m for filtration. The thermal mixed layer reaches almost to 200 m, the topmost 20 m harbour a particularly rich population of planktonic foraminifera. After a brief spell on high seas, the modified cruise track took us through the EEZ of Papua New Guinea on 14.3.2013, where no station could be taken due to lacking permission.
The cruise continued heading northwest, the sea has calmed and the clouds lifted in the afternoon. The next station was taken on 15.3.2013 at 10:30 local time as soon as the EEZ of Papua New Guinea was abandoned. On 16.3.2013 at 2 am local time, the Equator was crossed. Operating between high seas and the EEZ of Micronesia, the ship follows a straight track heading away from the equatorial waters above the Ontong Java Plateau towards the subtropical waters of the deep Philippine Sea. No station was taken on 16.3.2013, because the net haul from the previous day was too rich and its processing took another day.
The next three stations were taken between 17.3.2013 and 19.3.2013, all still recording the complex equatorial circulation system. On 19.3.2013, a third net haul for filtration was taken. The samples were so rich that on 20.3.2013 only a CTD has been deployed and the counting and picking of foraminifera continued the entire day. The Island arch of the South Marianas has been crossed in the night to 21.3.2013 and the next station was taken in the morning, now in the deep, cooler and oligotrophic waters of the Philippine Sea. The assemblage of foraminifera was still tropical, with lower density, but conspicuously deeper penetration in the water column, which displayed the lowest phytoplankton pigment concentration measured so far. The weather turned cloudy again, with slightly higher swell.

One sample of each deep Multinet deployment is being filtered...

...but most samples are being picked under the binocular...

...which means that all planktic foraminifera are extracted manually with a brush.

Heading NNW for our final destination, the last three stations were taken in international waters, before reaching the EEZ of the Philippines on 24.3.2013. The three stations revealed a typical subtropical water layering with a thick mixed layer and a clearly developed oxygen minimum. At all three stations, three net hauls have been taken, with one 700 m haul per station being used entirely for filtration. The clouds have broken again on 21.3.2013 and good weather with moderate swell has accompanied the ship on its way to Taiwan.
The last two days of the cruise the ship steamed through the EEZ of the Philippines and Taiwan, where no permissions were available. The transit has been used to demobilise equipment and consolidate cruise data. The ship has reached the port of Kaohsiung, Taiwan, on 27.3.2013 at 4 pm local time. The demobilisation was completed on 28.3.2013 and the first part of the scientific party disembarked the ship. On 29.3.2013, samples for genetic studies have been handed over to courier for transport on dry ice back to Bremen and the remaining scientists disembarked the ship at 1 pm local time, marking the end of the expedition SO226-3.

The full cruise report is available via the University of Bremen online library and
the PANGAEA database (cruise report and oceanographic data)

Some of the species recovered from the samples:

Globigerinoides sacculifer

Hastigerina pelagica
Note the spines and bubble capsule.

Globigerinoides conglobatus

Hastigerina pelagica feeding on a Artemia nauplia in culture aboard the ship.
Note the transport of body tissue from the nauplia along the spine in direction of the foraminifera shell.