Mission Blog: October 17, 2009
A Great Day On The Water
By Jason Helyer, Scientist, Diver
Large Kahala swimming amongst the divers on the northern forereef at Kure. (Photo: Jason Helyer)
We left Midway after a great day on the water and everyone was excited to get back to Kure Atoll before making our way back south. But with a northwest swell building, the veterans of the cruise were predicting the next couple of days to be a little bumpy and more typical for a "Rock-tober" cruise, a well deserved nickname for expeditions to the NWHI during the month of October.
Sure enough, while diving at a depth of 95 feet the next morning, we could feel the power of the swell as we hovered above the reef one moment, only to find ourselves several meters down the reef one second later... and then back at our initial location shortly after. For some survey methods like fish surveys, the "surge" associated with a large swell is not a major hindrance to data collection, as both the diver and the fish move roughly the same distance with each swell. However, for divers surveying the benthos it makes for a hard day of work, as we have only a fraction of a second to identify and measure a coral or algae between our three meter swings along our survey area.
Lucky for us, the swell did not stick around long, and by the third day, calm seas had returned. When the seas are calm, diving at Kure Atoll can be spectacular, allowing us to study the world's most northern coral atoll! Due to the relatively cold water associated with Kure's northern latitude which slows the growth of corals, the atoll is considered to be at its Darwin Point - a point where the growth or accretion of a coral reef equals the rate at which it erodes.
Safety stop at Kure Atoll. (Photo: Jason Helyer)
Still, the reefs at Kure are thriving with branching cauliflower coral of the genus Pocillopora, and encrusting lobe coral, Porites lobata covering the spur and groove formations which dominate the atoll's forereef habitat. The topographic relief of the spurs provides great habitat for a number of fish species and while surveying, divers were greeted by a number of friendly visitors including a group of Hawaiian Grouper Hapu'upu'u, and two large amberjacks or Kahala estimated at over four feet! As we ascended, a group of Galapagos sharks which were lurking around our dive site quickly surrounded us making for a great photo opportunity while we conducted our safety stop at fifteen feet.