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03 February 2002 - A view from the top deck

RRS James Clark Ross Diary

Position at 1200: 52° 56.1'S, 037° 11.1'W - 70 miles North of South Georgia
Distance Travelled since Grimsby: 29097 Nautical Miles
Air temperature: 7.7°C; Sea temperature: 5.4°C
Weather : Blue sky and sunshine, South-westerly winds, Force 4, slight sea and low swell......in Antarctic speak, a dingle day!


Current, frequent weather observations reported back to BAS Headquarters in Cambridge is used to plot the ship's current position and recent track. Meteorological data are also available from this page. The callsign of RRS James Clark Ross is ZDLP.


And now, the end is near, and so we face, the final station......!

So here we are into the last week of science before we head back to Stanley. We have spent the last week doing much the same as the previous weeks! Going around and around in squares and boxes.......we never do circles on this ship! (Apart from 'great' ones......navigation term used by salty sailors and the 2nd officer). Occasionally we do manage a straight line but as anybody who has ever been on this ship will know, we don't go in straight lines for long. Some of the people on board who notice this probably more than others are the top predator observers on the monkey island, they just get settled in to a routine of looking in front of the ship and we seem to suddenly turn around! This weeks science bit has been written by them.


View from the 'Top Deck'....

The hardy souls that have inhabited our monkey island for the last month, at last let us in on what they have been up to!
Written by Kees Camphuysen

This biosciences cruise covers a whole range of things from ocean currents, via nutrients and phytoplankton to krill right up to seabirds, seals and whales! This last group is also named the "top-predators" as they occupy the top of the food pyramid. So, what would be the most appropriate place to look at these guys? Right! From the very top of the ship, right above the bridge. Some people call this the monkey-island, but a more appropriate name would be the top-deck. Captain and mates have familiarised themselves meanwhile with an infrequent stampede above their heads if the top-predators team (that has consisted of Kees Camphuysen, Matt Swarbrick and Dafydd Roberts) rushes about in a desperate attempt to relocate and identify some non-co-operative whale that was seen alright, but dived away before the ID could be completed. Between these stampedes, it is supposed to be rather quiet, when the team is looking concentrated into a narrow, 300m wide band ahead and on one side of the ship in their desperate attempts to detect the most inconspicuous of them all: subsurface swimming penguins.

At the top deck, a small hide has been erected. Not so much a hide with a roof and walls around the observers, but three chairs on a pile of pallets behind a windshield, where a GPS, a clock and some other small tools are the instrumentation needed to log the data in an appropriate way. 10x40 binoculars, a range finder and clipboards for recording forms are all that is further necessary to do the job. Quite a contrast with all the advanced equipment needed to measure and log the tiny creatures, water and currents as these have been deployed elsewhere on the ship and were reviewed earlier. The outcome, however, is rather similar: a base file with lat-long positions and areas covered, and a records-file with all the air-breathing animals that were visible within that 300m transect plus those that were there but not in transect.

Most answered question: "What if you count the same bird twice?" Well, you end up with a mistake, isn't that obvious!?! That's exactly why ship-following birds are carefully looked at and why these are kept out of the counts and analyses. But otherwise, just as if the same krill is hit twice by the transducer, you would overestimate the number of birds. A far greater problem, however, not often mentioned by ‘our visitors’ is the birds and whales that are missed! To minimise that problem, a fair amount of concentration is required and precisely for that reason, a rather isolated site with clear visibility, not hindered by glossy windows, out in the open was chosen as an observation point.

The fur seal tracks. Click to enlargeSo, what has been achieved so far? A great deal, really. Perhaps the most important top-predator of them all, as it is a rather heavy animal and also very numerous, is the Antarctic Fur Seal or Kerguelen Fur Seal Arctocephalus gazella. At the time of reporting, we've recorded 19,262 individuals! Well, plus or minus a few hundreds. These guys come in groups and these groups are not easy to count! What is very clear, however, is that they occupy most of South Georgia's shelf and wander far beyond that, and that the shelf break seems to play a key role in the whereabouts of their feeding - at least during daytime. There is a lot more to be said about those seals, but the data should be properly analysed first. A striking result, realising that South Georgia's fur seal population at present amounts to around 2 million, was that the western boundary box that we have studied contained some 220,000-230,000 individuals (see density chart). That is, while South Georgia's shores themselves are literally covered in seals and while the study area is in fact a rather small portion of the shelf area and it's immediate surroundings.


Breaching Southern Right Whale. Click to enlargeWhales have been seen frequently, and that includes sightings of (globally) comparatively rare species such as the Southern Right Whale - Eubalaena australis and Humpback Whale Megaptera novaeangliae. However, South Georgia's waters are in fact in a miserable state nowadays. Some 70 years ago, biologists working in these waters would draw density maps of Blue Whales Balaenoptera musculus and Fin Whales B. physalus just as the ones we produce today for fur seals and seabirds (Kemp & Bennett 1932). But for us, drawing density maps of a few odd sightings, would be a rather stupid and a pointless thing to do. Believe it or not, the larger baleen whales are still commercially extinct. A slight recovery of the stock, for some of the species at best, has by no means brought these animals back into the system to an extent that one would call these majestic creatures at present a significant part of the ecosystem around South Georgia.


Left with the seabirds, the ship is followed constantly by a small cloud of Wandering Albatrosses Diomedea exulans and giant petrels Macronectes spp., taking any opportunity that may develop around the ship to start to feed. In the absence of food, however, some individuals followed the ship for more than 24 hours on end. Other species ignore the ship.

Wandering Albatross. Click to enlarge Wandering Albatross. Click to enlarge A Cape Petrel. Click to enlarge

It is clear that the Macaroni Penguins Eudyptes chrysolophus and Gentoo Penguins Pygoscelis papua are mainly utilising relatively shallow shelf waters, while several petrels and albatrosses roam the seas far beyond our study area. Again, the shelf break is of significance on many occasions, but it is obvious that a few weeks of sailing is just not enough to fully appreciate both the variability and the range of these animals.

Only the future will tell us how well our data matched simultaneous recordings of food abundance and prey availability (determined by factors such as density, depth and prey size). Tens of thousands of lines of coding accumulated into our database files meanwhile and on the basis of this, rather accurate distribution maps of all top-predators north of South Georgia will be produced. Preliminary results show, not surprisingly, that the main krill consumers do concentrate their activities in areas rich in dense krill swarms. Less easy to explain will be why some ‘good areas’ are exploited and others are not. Future analysis will have to focus on opportunities and constraints faced by the predators operating in these waters.
Kemp S. & Bennett A.G. 1932. On the distribution and movements of whales on the South Georgia and South Shetland whaling grounds. Discovery Reports 6: 165-190.

Acknowledgements

  • The map showing densities of Antarctic Fur Seals in study area NW of Bird Island, South Georgia, based on observations during the second BIOMASS programme (24-27 January 2002)
  • Breaching Southern Right Whale Eubalaena glacialis (photo CJ Camphuysen)
  • Wandering Albatross Diomedea exulans in flight (photo CJ Camphuysen)

Drifter buoy update

The latest tracks. Click to enlargeAs you will recall we have been deploying some drifter buoys during the time we have been around here to look at ocean currents. This image shows the latest updated positions of the buoys



Pretty satellite images

Steves baby. Click to enlargeWe have mentioned the weather at the top of the webpage, one of the things we use for keeping an eye on the weather is our Dartcom satellite terminal. This is especially useful for keeping an eye on the ice conditions...but only on a cloudless day! It comes into it's own when trying to spot a way through heavy ice. This image is from yesterday (02/02/02).



Thanks this week....

To Kees Camphuysen for writing the science bit and some of the photos, Alex again for more photos, Jon for images and Steve the R/O for the weather image.


Coming up......

We are currently completing the last of the work to the North of South Georgia, then we will be doing some Swath Bathymetry to the North of Bird Island before heading to the South to deploy two more drifters. Once these are in we are heading in the direction of Stanley doing more Swath.....notice I say 'in the direction of' as it was said earlier, we never go anywhere in a straight line!

Then we are due into Stanley on next Thursday night ready for demobilising on Friday. Next week's update will not have any science as such, it will mainly be some photos that we haven't fitted in yet and .....well who knows!?!