September 17th: REA and Cameras at La Perouse Pinnacle
Written By Dan Suthers September 18, 2004
The Plan of the Day shows a typical day of data gathering, like yesterday: Rapid Ecological Assessment (REA) teams, including Fish, Coral and Algae specialists; Towed Diver Surveys of fish and habitat, and Oceanography work by the Mooring Team. I accompanied the REA team to La Perouse Pinnacle to become familiar with their work and the habitat there. Our boat, HI-1, the fast 10 meter jet boat, was the last to leave. I was so excited about this opportunity that I used the extra time to shave off my mustache (for the first time in over 20 years) so that my mask would not leak.
What makes the water murky? (An exercise for the reader)
we arrived at La Perouse, the water was murky; not the
best conditions for photography but adequate visibility
for the work being undertaken. (For this reason I am
borrowing one of the excellent photographs taken by James
Watt in this region during NOWRAMP 2002.) I suspect that
the guano-covered pinnacle is to blame for the murk,
for two reasons (warning, speculation ahead!): the guano
itself may be washed into the water, reducing visibility,
and (more interestingly), the guano, an excellent fertilizer,
may be responsible for a higher concentration of algae
in the area, which then clouds the water. If I am wrong,
then perhaps wave action is churning up the bottom, or
debris stirred up by waves elsewhere are carried here
by currents. I will discuss these hypotheses with on-board
scientists when they return tonight. However, it might
be an interesting exercise for budding scientists reading
this page to consider: How would
you tell whether either of these hypotheses was right?
What measurements would you need to make or samples to
take? From where and over how long? How would you analyze
the data so obtained and interpret the results with respect
to my hypotheses? I invite you to send
your ideas about how to test the hypotheses, and
I'll post some of them on the web site.
While we have been discussing guano, the scientists have been preparing for their Rapid Ecological Assessment (REA). The REA is conducted along a transect (a line, in both the mathematical and physical senses) laid along the bottom. It is important to gather data from the same transect each year so that data may be compared for trends. The coordinates (longitude and latitude) of the previous year's transect had been recorded. When we arrived we spent several minutes moving the boat around to position it at the same location using Global Positioning System (GPS) before we dropped anchor. High precision GPS, formerly classified by the military, is becoming increasingly important for most field science.
The education team got in the water first to provide the divers with more room to work, and so that I could observe and photograph their operations. The REA is conducted by two teams, one after the other.
First, the fish team swims rapidly along the transect, recording any large fish seen while also laying down a line unrolled from a spool. (Co-chief scientist Randy Kosaki is shown doing this in the picture to the left.) The large fish observations must be done first, because they are more likely to scatter upon the arrival of divers. This is actually done in two ways: divers swimming along the transect record fish 20cm or greater in size in a "belt transect", while a diver swimming off to the side conducts "stationary point counts" of all fish larger than 30cm visible in a 10 meter radius. After these counts are completed, the fish team swims back along the transect line to record fish smaller than 20cm, videotaping and writing down observations on underwater notepads. This process is repeated three times along contiguous lines.
The scientists who study things that don't move very fast, or at all, follow the transect line last. They include the coral, algae, and macro-invertebrate scientists. (Co-chief scientist Peter Vroom is shown examining algae to the right.) Several activities are involved in this work. Like the fish scientists, these scientists videotape, photograph and take notes on the animals and plants they are studying. They may also take samples (only as needed, and for which a permit is required). Precise counts of benthic populations are taken by placing a plastic frame on the bottom, and counting and photographing all the creatures that fall within the square it outlines. (See photo from NOWRAMP 2002.)
a snorkeler, I did not follow the team on the transect
out into deeper water, staying instead near the boat
and pinnacle while they worked. David Liittschwager and
Susan Middleton were also in the water, so we snorkeled
about as I tried my consumer-grade underwater camera:
a Sony Marine Pack containing a well used Cybershot P9.
My wife gave my the marine pack well over a year ago,
but I had not used it much, so I was glad to have the
opportunity. My experience here may be of interest to
readers who have similar cameras. It turns out that the
REA team uses Sony and Olympus consumer grade cameras
(as well as much more expensive ones), so these notes
may also be of interest to budding scientists.
Previously I had had trouble with fogging inside the case, but today this was not an issue. I attribute my success to having packed the camera in the highly air-conditioned dry lab, and also to using the anti-fogging agent Sony supplies. Water temperature is also a factor: for whatever reason, at the Maui location I had previously used the camera, the water at skin-diving depths got rapidly colder as one descended, but here there was no noticeable difference in the shallow reef. Several of the scientists on board suggested using silicon dessicant packs: a good idea for the future, but I did not have any available.
Today the issues were flash and focus. Would my images have better color balance if I used the flash? Was the camera able to auto-focus adequately, given the cloudy water and constant movement?
I took some pictures without flash at first, and then tried to turn it on. Since I can't see up close without glasses I was unable to tell whether the force-flash indicator was on. I ended up taking many pictures of my face as I looked at the camera to see whether it was flashing. (At least I can now send my wife pictures of me without a mustache.) After a while and some help from David, I determined that one must push the flash button twice after turning the camera on. (Note to self: run through these procedures before getting into the water!) In the process, David told me I should not use flash in cloudy water unless I am up close. He was right. When in the shadow of the pinnacle later in the day, I used flash while following two divers at a distance. The images light up the gunk in the water very nicely, obscuring the intended subjects. Therefore I cannot show you the turtle or the two small sharks that we saw, nor can I show you the divers surveying life at the base of the pinnacle and looking through the hole that runs through its base.
The focus question is more difficult to answer. About half way through the dive I started to use manual focus, but this was also when I used flash. Budding scientists should note that whenever possible they should vary one variable at a time: otherwise one cannot tell which variable is responsible for the result! One should also take detailed notes: I am not sure which pictures were taken with or without manual focus, nor at what setting. However, I can offer some conclusions. Familiarity with the camera is important (again, practice before getting in the water!). Fortunately I had memorized the sequence of manual focus settings (infinity, 7 meters, 3 meters, 1 meter, 0.5 meter, Center autofocus, Multi autofocus), and one can see the yellow bar in the focus menu OK even in the water. I know from prior experience that the picture will be taken more quickly (closer to when you press the button) with manual focus. Looking at my actual results, the safest conclusion is that picture will be sharp with manual focus if your guess is correct! That is probably the most important consideration: how predictable will subject distance be? Fish can be uncooperative, especially the little wrasse I chased along the underwater cliff face for a while. Estimations for subjects at a distance need not be as precise: 7 meters was about right for the Ulua (large fish) pictured.
Finishing the REA
When the divers returned, I photographed their work as they examined the reef and took samples of coral and algae. See the images to the right: I may also use some of these pictures in an article on REAs.
Shortly, a new aquatic creature arrived on the scene which was difficult to identify at first. It appeared to be a human in board shorts and with large fins, but carried no air tank and did not surface for air. I watched in utter amazement as co-chief scientist Randy Kosaki swam around leisurely at about a 6 meter depth, taking samples and even swimming through a cave. After what seemed like a few minutes, he did surface; apparently he is (super)human, not fish.
Two divers began to document life along the base of the cliff underwater, and I followed them while one took notes and the other videotaped fish life. We saw two small sharks, who went through the hole in the base of the cliff to escape from the divers to the other side.
When it was time to go, the divers ascended, checking their dive clocks to be sure they did not surface too quickly. As I predicted, a skin diver had to go in to release our anchor: it was well wedged in a gap in the reef.
The evening began with another beautiful sunsent, followed by a long night writing in the dry lab.
Later in the voyage I wrote a detailed article describing the REA protocol.
See this related NOWRAMP 2002 journal entry:
9/12/02 French Frigate Shoals, Day 2, Liquid Sky by Carlos Eyles