Friday, 31 October 2008
Small is beautiful (well ... sometimes)
While to date, much of the cruise blog has dealt with all things BIG, lets not forget about the small creatures of the ocean. Because of their small size, it is easy to forget about the zooplankton. Yet, in the oceans, it is these small animals that convert photosynthetic biomass into the animal biomass that ultimately feeds and sustains all of the larger predators. Without the zooplankton, most of the larger fish, whales and sea-birds could not survive!
Below are shown some of the strange and alien-looking creatures that are being picked up in our samples. (left: amphipod releasing egg; right: copepod; bottom left: ctenophore; bottom center: pelagic polycheate; bottom right: salp).
At the moment, zooplankton samples are being collected both by multi-nets (which can sample at different depths) and by Bongo (which collects larger amounts of zooplankton, but from the whole water column). Samples are being used to determine community composition, the geographical and depth distribution of different species as well as for stable isotope studies that investigate the importance of different zooplankton taxa as a food source for fish and squid.
In addition to being an important food source, zooplankton also harbor the juvenile stages of many commercially and ecologically important fish species. These are called the ichthyoplankton. During the life-cycle of most fish, it is the early juvenile stages that are most at risk from their environment. Due to their small size, the ichthyoplankton are at the mercy of the currents and individual larvae cannot protect themselves against predators. This is why the majority of fish die when they are very young (often >99%). It is frequently the success or failure of this planktonic life-stage that determines the potential success of adult fish stocks.
(left: fish larvae; center: fish larva; right: cephalopod larva)
text and images by: Sven Kaehler
Monday, 27 October 2008
If its Monday .. we must be heading east ...again!!
So what are we doing and where are we?
We are slowly moving northwards towards the gap between the Nazareth and the Saya de Malha Bank (see a previous blog). The last 2 weeks have seen us sailing back and forward and forward and back along acoustic lines, which have been set up to study the fish stocks over the plateau as well as improve our knowledge of the seafloor in this region. It’s pretty amazing to see the seafloor rise from 3000 m to 50 m in about 8 miles! Think of climbing Table Mountain from Cape Town centre and then triple the distance up!!.
As we move northwards we have been measuring sea surface temperatures and you can see from the map on the right that there is a gradual increase from 24 to 26° C with distance north. Dotted along the plateau are sampling stations where we collect bottles of water for oxygen, salinity, nutrient, chlorophyll and zooplankton concentrations from top to bottom...in some places this takes minutes because the seafloor is only 30 m deep!.
..and last week we started receiving data from the drifters thrown in at the start of the cruise. The 2 southern drifters certainly seem to be in pole position! travelling over 50 cm per second westwards we suspect that they have been caught up in a strong current channelled by the gap to the north of Mauritius.
The other 2 drifters on the east side of the plateau were only deployed at the end of last week and we think that they will move south rather than over the plateau.. and that’s an interesting fact because it suggests that the Mascarene Plateau acts as a huge barrier to all surrounding flow. This certainly raises questions on whether the ecosystem varies between the deep ocean and the plateau and how water masses may differ from one region to another. ..hopefully by next week we will have some more data to prove or disprove various theories.. .. so keep posted and we’ll soon update the blog on our progress north!
Saturday, 25 October 2008
Cures from the Deep: The Search for New Pharmaceuticals from Deep Water Western Indian Ocean Marine Sponges.
The search for new chemical entities with exploitable medicinal prop
erties is the cornerstone of modern drug discovery. Traditionally, these new chemical entities have been procured from several sources including the vast natural product reservoirs characteristic of terrestrial and marine ecosystems. Many marine organisms (invertebrates e.g. sponges; algae and micro-organisms) produce natural products (biomolecules) as chemical defence agents against predation or in a chemically mediated response to, inter alia, inter-species competition for limited resources (e.g. space on a reef or nutrients) and intra-species communication (e.g. larval settling cues). Surprisingly, many of these marine natural products also possess medicinal properties and internationally several marine derived chemical compounds are currently in development as new anti-cancer and anti-inflammatory drugs.
The coastline of southern Africa, and the deeper waters off its shores, sustains a unique diversity of endemic marine fauna and flora that can offer rich rewards for marine natural products chemists in search of novel bioactive marine natural products with medicinal properties. For the last fifteen years Professor Mike Davies-Coleman’s marine natural products research group at Rhodes University has been systematically searching for new marine natural products, with medicinal potential, from the marine invertebrates occurring off the coast of South Africa, Mozambique and Marion Island in the
Southern Ocean. While the southern African inshore benthic communities are reasonably accessible with the aid of SCUBA, accessing offshore deepwater invertebrate communities is logistically problematic, and the marine sponge material collected as part of the Macarene Leg of the ASCLME cruise will be crucial in enhancing our knowledge of Western Indian Ocean marine biomolecular diversity.
The Rhodes University research group is part of an international collaboration wor
king together to discover possible new marine medicines and has strong research links to the National Cancer Institute in the USA and marine natural product research groups in the USA, Canada, Australia and New Zealand. Marine sponge material collected during this ASCLME cruise will be screened for natural products that are able to either kill oesophageal cancer cells or activate enzymes that halt the onset of arthritis and osteoporosis. The Eastern Cape Province of South Africa has the highest reported incidence of oesophageal and cervical cancer in South Africa and the identification of marine natural products exhibiting cytotoxicity towards the former cancer is an important component of marine drug discovery efforts at Rhodes University.
Text by Professor Mike Davies-Coleman
Images by Kim Bernard
Saturday, 18 October 2008
Tropical storm approaching
A tropical depression has been evolving in the vicinity of Diego Garcia over the past week. The non-frontal synoptic scale low-pressure system definitely has some indications of cyclonic wind circulation as can be seen in the adjacent synoptic chart and satellite image courtesy of the Mauritius Meteorological Service. Winds circulate clockwise around low-pressure and cyclonic systems in the southern hemisphere. Gusts associated with tropical depressions are generally less than 90 km per hour whereas in a true tropical cyclone winds can range from 150 to over 300 km per hour. The red cross in the satellite image indicates our approximate position and we expect to receive the full force of the storm tomorrow evening followed by two days of strong winds and heavy showers. We will spend some time tomorrow battening down the hatches and ensuring that all the equipment in the labs is securely fastened! If physically possible I will add some photos of the cyclone and the Dr Fridtjof Nansen weathering the storm!
Friday, 17 October 2008
Barbeque on the high seas
From 14-15 October we were sampling stations in the vicinity of the Cargados Carajos Shoals
(see adjacent Google Earth Image). The shoals consist of 16 small islands (and some 34 cays) and are classified as a dependency of Mauritius. The shoals used to be a volcanic island that over time eroded until it became submerged and a coral atoll was left behind. The length of the Mascarene Plateau cruise and the lack of any port calls over the five week period will place strain on both scientists and crew. It was therefore decided at the start of the cruise that we will have two barbeque (braai) parties at locations where we could safely anchor the ship to rest and recuperate. The Cargados Carajos Shoals presented just such an opportunity and it was decided, after completing the last station, to anchor off Coco Island (île aux Cocos at 16°50'S, 59°30'E).
We anchored in 30 m of water and immediately started the fires. In the bottom left image Tom and Bjorn are busy grilling T-bone steaks, fillet steaks, spareribs & chicken. Supper was an "al fresco" affair on the trawl deck. The food was excellent and the evening gave everyone a chance to mingle and get to know one another better!. The night ended with some of the scientists and crew strutting their stuff to the sounds of the Norwegian Oompapa band followed by rhthymic dancing and ethnic knee jerking to the sounds of the Swahili Melaika Marumba band. For those not keen to shake their stuff a fishing group had assembled on the back deck hoping to catch more samples.
Thursday, 16 October 2008
The demersal trawling programme is producing some very colourful fishes of fascinating variety. We caught 38 species in our first half-hour trawl and the total is now up to nearly 130 species. Five of our bottom trawls so far have been in about 20-30 m depth and the species found at this depth are now becoming very familiar to us, so sorting is becoming quicker and easier. I was able to name all of the fish in this morning’s sample in a very short time. Smith’s Sea Fishes is proving an excellent guide to identify these fishes even though we are well away from the sea area covered by this famous book. This illustrates the role of the Agulhas current in spreading these species down the south east African coast.
Before I left Grahamstown, Eric Anderson, SAIAB’s expert on deeper water fishes, told me that the deeper waters around the Mascarene Plateau were very poorly explored and that many species caught in waters around 300 m deep are likely to be new. I’m not sure how true that comment will prove to be, but I’m certainly having difficulty identifying some apparently common large species from deeper water trawls in 200 m and 300 m. I’m still searching the literature and thus won’t put pictures of these on the web yet to ask for help, but may do so before the end of the cruise.
Among the more interesting species landed was a black snoek, Thyrsitoides marleyi
not far short of 2 m long, held up in the photo by Jackie Hill, and also a sawshark, Pliotrema warreni
, whose toothy snout became so entangled in the netting that it had to be cut free. Other common fishes are a variety of trigger fishes, fusiliers, butterfly fishes and other tropical reef fishes. The opening of the codend at the end of each trawl continues to be eagerly anticipated, to see what new species spill out on to the deck
Image captions (top to bottom): A collection of fishes from the trawl awaiting sampling of muscle tissue for genetic analysis; Balistoides conspicillum; Lactoria fornasini; Apolemichthys trimaculatus; Sargocentron spiniferum; A very colourful mantis shrimp trawled from 50 m depth; (bottom left): Jackie holding a large black snoek trawled at 300 m depth; and (bottom middle): A sawshark, Pliotrema warreni, caught at 200 m depth.
Text and images by Denis Tweddle & Oddgeir Alvheim
Wednesday, 15 October 2008
What are we doing here?
A little bit about the Mascarene Plateau
The Mascarene Plateau, in the Southwestern Indian Ocean, is about 2200 km in
length, running from the Seychelles Bank at 4°S to the island of Mauritius at
20°S. As you can see on the left its oriented roughly north–south similar to a crescent. It is characterised by a series of islands, banks and shoals separated by deeper ridges and channels. The main banks are called the Seychelles Plateau, the Saya de Malha Bank, the Nazareth Bank and the Cargados-Carajos Bank. These are typically 20-100 m deep, coral topped and sometimes break the surface to form small islands – in fact we will anchor off Coco island later today! The Plateau is surrounded by steeply descending slopes so that water depths rapidly increase to 3000-4000 m on either side of the plateau - as you can see from the figure below. The nature of this long fractured plateau is thought to form a barrier to the surrounding ocean circulation. Some of the shoals are more than 250 km wide. The Mascarene Plateau is a rare example of an extensive shallow-shelf sea completely detached from land boundaries and is, except for the Shoals of Capricorn Marine Programme and Darwin Initiative in 2000 – 2001, a largely unexplored marine ecosystem.
The red line in the picture above relates to the bathymetry figure on your left which shows the steep rise associated with the Mascarene Plateau. We think that the flow moves up onto the plateau in the east bringing with it (up and over the plateau) an increase in nutrients.
So what do we hope to see?
The most northerly part of the study area is under the influence of the northeast
monsoon from December to February, but during the remainder of the year the whole area is under the influence of the Southeast Trades and the South Equatorial Current (SEC). Recent studies in this area suggest that the shallow Mascarene Plateau acts as a barrier to the predominantly westward zonal flow of the SEC causing it to split into a number of tributaries, which then become channelled through the deep gaps separating the shoals. This creates some interesting questions as to the effect this channeling has on the plateau's ecosystem.
The figure left shows the position of the banks and the velocity of the surface circulation. What we can see really clearly here is how these deep gaps influence the surface circulation as the flow associated with the South Equatorial Current is channelled through each gap...Key Questions and a cruise track!
1. What is the influence of the South Equatorial Current on the waters and ecosystem over the Mascarene Plateau?
2. In what way is the flow of the South Equatorial Current affected by the gaps in the Mascarene Plateau?
3. Is the Mascarene Plateau characterised by an increased diversity in habitats and biota?
4. What are the main components in the Mascarene Plateau pelagic ecosystem, its distribution and abundance?
5. What are the biodiversity of the pelagic ecosystem, and the main fauna of the demersal fish community?
6. Can the Mascarene Plateau be considered a Large Marine Ecosystem on its own?
....and that’s what we are doing here.. to answer the questions we are deploying a network of CTD stations, multinet stations, bongos and demersal trawls similar to what you see in the track above....
Keep posted for some answers!
posted by Isabelle Ansorge - here at 59°S, 16°30' E
Monday, 13 October 2008
Drifting around in the Indian Ocean
Late last week we deployed two drifters at 18.20S, 59.01E. The drifters were deployed in the deep channel north of Mauritius. A number of oceanographers have suggested that a strong current flows from east to west through this channel. Looking at a schematic of the general circulation of this region, you can see that the current flowing westwards is in fact a major tributary of the South Equatorial Current (SEC), which eventually on its travels passes to the north of Madagascar.
This survey is providing us with a wealth of hydrographic data it’s only a snap shot and what happens downstream of the survey or 2 months after the survey has been completed is not known. So drifters give us that missing information. Once deployed they drift with the surface current collecting data such as temperature, current speed and direction, air temperature, air pressure and relay the information back to satellite.
For many years, ocean currents have been estimated by how they carry objects. For example, sailors measured the speed of their ship through the water using the ship log. They measured their absolute position by celestial navigation (in the good old days, pre-GPS!). The difference between the absolute speed and the speed through the water gave the speed of the currents. Very strong currents, such as the Agulhas Current made a big difference in how long it takes to travel. More recently, researchers began tracking objects while they were drifting. This tracking was first done visually either from a coastline or anchored ship, then using radio, and most recently using satellites. During the 1970s, when satellite tracking became possible, many competing drifter designs were proposed, built and deployed in various studies around the world.
How does a drifter work?
The modern drifter is a high-tech version of the "message in a bottle". It consists of a surface buoy and a subsurface drogue attached by a long, thin tether.
The buoy measures temperature and other properties, and has a transmitter to send the data to passing satellites. The drogue dominates the total area of the instrument and extends 20 m below the sea surface. Here is a picture of a drifter in a cold clockwise eddy in the southern ocean. You can see how the drifter rotates round and round in the eddy!!
Drifters basically have a surface float and attached to that a long holey sock known as a drogue. The surface float is on average 40 cm in diameter. It contains: batteries; a transmitter, which relays all the information on a 6-hourly basis to satellite; a thermistor to measure sea surface temperature; a barometer to measure atmospheric pressure, wind speed and direction, as well as a GPS to measure position and the time taken for the drifter to move from one position to another – this way you can measure the surface current speed and direction.
The drogue is centered at 15 meters beneath the surface to “anchor” it to the surface – this prevents strong winds from pushing the drifter around. The outer surface of the drogue is made of nylon cloth. Throughout the drogue, rigid rings support the drogue's cylindrical shape. The drogue is a "holey-sock": each drogue section contains two opposing holes, which allow water to flush through and prevent the drogue from getting “wound up” in strong surface currents.
Once deployed, a drifter lives an average of 400 days before ceasing transmission. Occasionally, drifters are picked up by fishermen or lose their drogue and run aground.
Deploying a drifter
Drifters weigh about 25 kg each. Before deployment, the drogue and tether are bound with paper tape which dissolves in the water, and the tether is sometimes wrapped around a water-soluble cardboard tube to protect it from kinking.
The drifter is deployed by throwing it from the stern of a vessel, preferably from the lowest deck and within 10 m of the sea surface. After deployment, it may take up to an hour for the paper tape to dissolve and trapped air bubbles to be released, so that the drogue sinks to the target depth (15 m).Does my bum look BIG in this?
How much do they cost
Drifters range in price depending on the number of sensors you have. On average you can expect t pay about $2500 per drifter.
Keep posted for more cruise stories!
by Isabelle Ansorge
Saturday, 11 October 2008
The second cruise of the 2008 ASCLME expedition started with a bang on 4 October 2008 following the successful local launch of the ASCLME Project in Port Louis the previous evening. James took some good photos of the event and these will soon be added to the blog. The Mauritian Cruise was largely an oceanographic survey (physical, chemical and biological) along 8 transects perpendicular to Mauritius (see adjacent completed survey track). Due to time constraints the first transect was sampled on the way in from Madagascar and the last two lines to the north (7 & 8) were sampled during the first two days of the Mascarene Plateau Cruise. Due to limited survey time and almost no visible acoustic registrations only one pelagic blind trawl haul was carried out. The only fish species caught were some lantern fishes (Myctophidae) and a few juvenile barracudas (Sphyraenidae), tobies (Lagocephalus) and flounders (Bothidae). Overall, a total of 47 stations were sampled in little more than 5 days, which is more environmental stations than will be sampled during the current 43 day Mascarene Plateau Cruise!! The short survey period and two crew changes in between placed severe strain on the few scientists that had already found their sea-legs or were not prone to sea-sickness. Despite a lack of sleep and the loss of the bongo early on in the cruise, the Mauritian Survey was succesfully completed as planned and the scientists and crew of the Nansen should be congratulated on a job very well done!
On the way back to Port Louis, after completing line 6, we passed close by the ancient basaltic volcanic cone of Gunner's Quoin Island (also known as Coin de Mire seen in the photo above). We docked for the second time in Port Louis (attractive harbour & waterfront shown in the adjacent image) on 7 October and after a crew change on the 8th departed again to complete the last two lines of the Mauritius Survey and continue on with the Mascarene Plateau Survey. It is expected that no land will be sighted for the next five weeks! More on the eventful first day of the Mascarene Plateau Cruise tomorrow.
Saturday, 04 October 2008
Bye bye Bongo
This morning, I received an SMS from Tommy Bornman who is currently on the Nansen
(I left the ship last night after the function; the ship sailed to start the second part of the cruise, a survey around Mauritius, early this morning) to say that the wire that was connected to the Bongo nets snapped whilst the vessel was in around about 1,000m of water off Mauritius. I believe
it was accidentally lifted up too high on the winch, which caused the break EDIT
: I have been corrected - the SMS correspondence I had with someone aboard was evidently incorrect - apparently it was corroded winch cable which caused the loss of the bongo
. There is another bongo net frame on board, but I'm not sure there are spare flowmeters for it; there was a third one in the bongo supply box but it didn't really spin very well. I guess we'll have to expedite some spares from somewhere! There are codends on the vessel which could be adapted too. Whether there are spare nets of the right mesh size though, I'm not sure. There were several in the box, so hopefully, things will be OK. Bongos seem to be quite fragile, or maybe it's just this expedition being overly harsh on them.
I hope Tommy will keep you all informed about what is going on aboard the Nansen
and continue updating this blog. If anyone else aboard the vessel would like to contribute to the Blog, please send me an email (Tommy has the address) and I will add you to the system.
I am currently using a hotel PC as the hotel's wireless internet seems to be down. I've also apparently left my flash stick on the vessel, so can't carry across the images from the big function last night. I will make a retro-active post as soon as I can.
Friday, 03 October 2008
We just had a quick group photograph with many of the delegates from the meeting I mentioned in the last post. Unfortunately, not everyone is in the group photo.
David Vousden, the Project Director of the ASCLME Project and Magnus Ngoile, the Policy and Governance Coordinator for the ASCLME Project had to go and meet with one of the Ministers of Mauritius for a in-depth briefing on the project, which is a fantastic opportunity for us. I, of course, am behind the camera!
This is a full-resolution image, so it is around a 1.87 megabyte download to get the whole image if you click on it. This may take some time if you are on a slow connection; once the picture loads in your browser, right click on it and save it to your computer. If anyone has a problem getting this image, I can provide a resized, lower resolution image - let me know
Thursday, 02 October 2008
I'm currently sitting in a large gathering of projects involved in the marine environment from all around the region, not only the three partner projects in the ASCLME Programme (ASCLME
), but also a diverse range of other projects.
A large problem with managing transboundary resources is that there are not only many countries involved - itself a major challenge - but also many projects involved. All of them are doing excellent work within the region, but sometimes the communication and cooperation between the projects isn't all it could be. Essentially, what we'd all like to do is work together, so that we don't end up duplicating our efforts and so that we can effectively share our knowledge and results, and perhaps work more closely together where particular focus areas overlap. People have been talking about this for years, but we've never quite managed to get this level of collaboration really going.
For these reasons, we are hosting a pioneering 3 day Regional Project Coordination Forum here in Mauritius, at the Hotel La Plantation, a few minutes north of Port Louis. A dedicated meeting to really introduce the projects to each other and then, perhaps more importantly, spend time talking about joint aims, coordination and how to work together, is exactly what we need - and has, as far as we know, not been done in the region previously.
For the last three days, the ASCLME Project has been discussing coordination with its closest partners, with a particular emphasis on cruise coordination, data and information, capacity building and communication; I haven't had a chance to discuss with my colleagues yet how those meetings went, but I think they probably went very well.
The present meeting, however, has a broader vision. Today's meeting is designed to allow projects to briefly introduce themselves and outline their aims and activities. I don't have a full list, but some of the projects either present or represented include the IRD
from France, ACEP
and their projects SWIOFC
and EAF-Nansen, GOOS-Africa
/TRIO, Indian Ocean Commission
, GEF-WIO Marine Highway Development and Coastal and Marine Contamination Prevention Project, International Knowledge Management
, and several other projects whose names I unfortunately do not have in front of me.
I'll go around with a camera later and post some pictures. (Edit: I have added a few pictures).
Wednesday, 01 October 2008
En route to the last station
Well, we're finally en route
to the last station, just outside Port St. Louis Harbour, we're getting a lovely view of the mountains of Mauritius from here. After that, it's straight into the harbour, then time to clear the customs and immigration formalities. And after that, well, we're getting off the ship and going out! Sigbjørn has declared this evening a "welfare dinner", where everyone goes and eats together on shore.
I think everyone is pretty keen to get off and stand somewhere where you don't get thrown off balance every few minutes, where things stay put where you put them, and you don't have to think every moment "Hmm, if I leave this here, will it break?". Not to mention seeing something other than endless blue ocean, that whilst lovely for a while, does eventually get trying - but it makes you realise how badly named this planet is. We call it "Earth", yet over 2/3rd of it is ocean - and a much bigger fraction of the total biosphere. It's strange to note that humans have seen more of the dark side of the moon than the deep oceans. More of even Mars or some of the more distant planets. We still have a lot to learn out here!
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