Fantastic voyage to the South China Sea

Early in the morning of June 17, 1998 three of us (Dr. Marietta De Leon, Ms. Hannah Mirabueno of PhiVolcs and myself) boarded the German research vessel R/V Sonne in the port of Jurong, Singapore.

With luggage laden with Lucky Me noodles, Sunflower crackers and champoy (comfort food in case we get seasick), we excitedly walked the plank and up the stairs into our assigned cabins.

The next three and a half week cruise was not a pleasure trip a la Love Boat (although we did get to eat rabbit meat) but was a serious research expedition involving mud — lots of mud.

This research cruise is part of a cooperative program between the University of Hamburg, Germany, the Philippine Institute of Volcanology and Seismology (PhiVolcs) and U.P. NIGS.

There are three main research problems that are being addressed. The first study investigates the effects of El Nino and the Southeast Asian monsoon system on the particle production and sedimentation in eastern South China Sea.

This involves deploying and recovering funnel-shaped sampling instruments called sediment traps. These collection devices together with flotation buoys and electronic release and signal packages are strung on metal chains and fixed to the sea bottom with metal weights.

It is really an exciting sight to see the colorful yellow buoys bob up to the surface after being under 2000–3000 meters water depth for more than a year!

Actually, the sediment traps that we recovered during this cruise were deployed in November-December 1996 during Sonne cruise 114, which had Drs. Militante-Matias, De Leon, Listanco and Catane as participants.

So, you might ask: “why do I have to look at the particle flux in the China Sea and expend so much time and resources doing it?”

The oceans are a major sink for carbon dioxide, 50 times more than the atmosphere. This means that small changes in the carbon cycle in the oceans have large effects in the atmosphere.

This has implications on our understanding of the issue of global climate change. It has been shown in previous studies, that the oceans take up as much as 1/3 of the carbon dioxide that man produces on Earth.

To be able to understand the ocean carbon cycle therefore, one has to be able to quantify how much carbon goes into and out of the ocean system and understand the movement of the carbon within the water column. This is where the sediment traps get in the picture.

Interestingly, one of the major sinks for carbon in the ocean is calcareous organisms (coccoliths and foraminifera) which is why we were really keen on joining the cruise.

The South China Sea is a good place to study particle flux variability because climate in this region is strongly influenced by the monsoons. This makes the South China Sea particularly sensitive to climate change. Also, the monsoons create a strong seasonal signal in primary production.

Aside from the sediment traps, work on most of the 55 stations involved sampling the sea bottom using a box corer and a multi-corer.

A box core sample enables us to observe depositional features and benthic organisms on the surface of a 0.5 x 0.5 x 05-meter piece of seafloor.

On many occasions we would find living tube-like benthic foraminifera, xenophyrophores, deep-sea sponges along with pteropod shells and numerous crustacean and worm burrow in situ on the core surface.

We were surprised to see in one of the stations close to Manila Bay numerous burnt wood and bamboo twigs in the box core. These were probably brought down from the slope during a storm event.

The multi-corer is composed of 12 cylinders, each 0.5 meter long and 10 cm in diameter. This covers more surface area for sampling than the box core.

In both corers, the thicknesses of the 1991 Pinatubo ash were measured and mapped to reconstruct its extent within South China Sea.

The layers above and below the Pinatubo ash horizon were also studied by the micropaleontologists onboard for signs of recolonization of benthic foraminifera.

The micropaleontologists who were mostly from the University of Kiel, Germany observed that different community of opportunistic group of bottom-dwelling creatures have decided to take advantage of the habitat “vacated” by their cousins.

In a couple of stations, a CTD water sampler was also deployed to measure physical properties in the water column.

Life onboard R/V Sonne for those 23 days involved 12-hour shifts in the geology laboratory… and that means WORK!

What was really difficult was trying to stay awake during the early morning hours while waiting for the cores to come up from the depths of the South China Sea.

But once the cores come up, work starts to pile in.

Our clothes are covered with mud as we stain samples, siphon off sea water, slice the cores, carry them around, describe them and try to pack them as best as we can so that they can get to NIGS as undisturbed as possible.

Packing the cores became creative near the end of the cruise when we realized we were running out of the peanut Styrofoam packing material.

One of the scientists had the idea of using empty soda and beer cans that we had in the trash bins to pack the tops of the cores in order to keep them in place.

And so, we did just that. So, don’t be alarmed when strong beer odors emanate from the NIGS Micropaleontology Lab. in the next few months — we’re just doing science.



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