Beam Reach

Orca echos and diatom blooms

Thursday 05/22/08
Snug Harbor to Snug Harbor

This morning we got a voice message letting us know that the whales were spotted at Hein Bank at about 8:00 AM. After an invigorating breakfast of scrambled eggs and toast, with a dash of onions and peppers, we set off to go south from Snug to catch up with the whales.

While we were busy beginning to deploy the Echosounder to get some bathymetric data around Lime Kiln, the leaders of the pod got to us first, so we began a scramble to deploy our hydrophones. Unfortunately, the CRT gave us some difficulty, so we spent some time cleaning out the phantom box, and testing different flow noise sources of the hydrophone and by going at different speeds. Eventually solving the problem, we were back on track to re-deploy and gather some data! We began to log Echosounder data as we recorded hydrophone data.

We had a very exciting first session right in the main shipping lane, with one whale breaching twice in a row off our portside stern, proceeding later with more breaches and tail slaps. We were quite astonished. After the spectacular show, the whales seemed to mellow out, and began to slowly travel/rest north along the west side.

At about 1:30 in the afternoon we decided we would tilt the Echosounder 90 degrees in order to try to ensonify a whale and see what a 200 kHz whale echo looks like. With much luck and Scott’s excellent angling abilities, we were able to track a group of whales at ranges of up to 170 meters.

Meanwhile, during this macroorganism action we also had some very exciting microorganism action. Robin and Lindsay used two 20-micron plankton tow nets to collect diatoms off of Lime Kiln. They filtered the water they collected in the homemade single-use coffee press and looked at the remaining diatoms left on the filter paper under the microscope. We found that there was a single species bloom, which is unusual because the samples Robin has taken at the labs have contained many species.

Afterwards we began to record some more hydrophone data, following the resting whales until they reached Boundary Pass, where they began to vocalize and regroup from their scattered positions (we estimated about 9 whales in the group). It was a very interesting display of tail slaps and pectoral slaps, with the whales getting silent as a large ship passed through the scene.

To avoid the growing flood, we made our way back to Snug Harbor (while flying a kite along the way), dropping off the lovely Robin. We ended the evening with some sunset dingy lessons from our wind blown Capt’n Mike.

Double breach video

One of the Beam Reach students, Ryan Spragg, captured this double breach on video today:

It’s a notable clip in part because we were towing 4 hydrophones at the time, one of which is calibrated and sensitive up to about 50kHz. Another student, Lindsay Delp, will use the recorded underwater sounds of the breaches to compute the source levels (after she determines the ranges from the calibrated hydrophone to the percussive sounds).If she succeeds, this could be the first time that the “loudness” of such magnificent breaches is determined. The measurement may help us decide whether breaches (and other percussive behaviors like tail lobs and pectoral fin slaps) have a communicative function or not.

The first spring Beam Reach program is nearing completion. Don’t miss learning about how loud breaches are — along with other interesting recent findings — at the final presentations at Friday Harbor labs this June, 7, 2008. If you can’t make it in person, final papers and talks will be available at the students’ home page — http://beamreach.org/081