Archive for October of 2006

Dusk and Night Dive at Breakwater

October 14, 2006
Today (2006/10/14) we; Julie, Glenn and I; dove breakwater at dusk and then at night. We were hoping to see the shift in active animal species between day (diurnal animals) and night (nocturnal animals). So dive planning involved finding out when the sun was predicted to set (predicted time was 6:33pm), the phase of the moon (we had less than last quarter) and then counting backwards from sunset for a half hour serface interval (6:00pm), and subtract about 40 minutes for our first dive (5:20pm entry time). We arrived at 4:00pm with overcast skies. We parked on the breakwater (lot 2) where we suit up for our dusk (crepuscular) dive.

Our dusk dive started when we walked into the ocean at around 5:00pm followed by a 10 minute surface swim to our drop point. We all brought our lights for this dive. Glenn had bought a new housing for his digital camera to give it a try. We decended with our lights on and came to rest in 30 feet of water. It was still too bright underwater to see the bioluminescence so we swam off on our heading of 70°. Glenn captured some nice pictures and videos while on this dive. During the dive we saw the nearly ubiquitous Pachycerianthus fimbriatus, there was very little Macrocystis sp. or other types of alga, of course there was Calliarthron sp. (red coralline alga), there was only one or two Phalacrocorax pelagicus (pelagic cormorant), Cryptochiton stelleri were found on the rocks of the breakwater, Citharichthys sp. (Sanddab), many Paralabrax clathratus (kelp bass), Cymatogaster aggregata (shiner surfperch), and another fish I could not identify. The unknown fish was 5-6" long, only 3/4-1" wide at the head and swam like an eel. We surfaced about 5:45 and swam back to shore. We were back on shore about 6:00. [Max. Depth 46 feet for 34 minutes]

Our nocturnal dive started with us walking in at 6:30pm and swimming out along the breakwater for 10 minutes. At this point it was dark enough to see a small amount of bioluminescence while on the surface thanks to the cloud/fog covering the moon and stars. We dropped down into 30 feet of water again and gathered together. We switched off our lights and waved our hands through the water to see the faint blue (some people see a faint green or white color) bioluminescence of the zooplankton. Afterwards, we switched our lights back on and swam on the same heading as the first dive (70°). We quickly ran into another group underwater. They were heading in the opposite direction which meant we were going to be swimming through all of the junk they stirred up--it knocked our flashlight vis down in half. The junk settled out of the water quickly and we found ourselves near the breakwater. There were fish hanging near motionless in the water column like stars. When we shone our lights near them, they swam for cover. On the seafloor between the Pachycerianthus fimbriatus was many clusters of tiny ball-bearings reflecting a copper color. On closer examination the ball-bearings turned out to be the eyes of Neotrypaea californiensis (Bay ghost shrimp). During this dive, I believe I was mistaken when I thought I saw a Holocentrus sp. (squirrelfish) belonging to the Holocentridae family. It was more likely a Sebastes spp. (Rockfish) belonging to the Scorpaenidae family. [Surface interval of 40 minutes, Max. Depth 49 feet for 34 minutes]