DIVE DRY WITH DR. BILL # 615: I WANT TO TAKE YOU HIGHER
I first drafted this column over a year ago after one of my night dives in the summer of 2013. On that night dive I once again encountered one of my favorite behaviors... mating. No, I didn't finally locate my lovely mermaid and this column will probably not titillate my readers too much! The surge was causing the giant kelp to sway back-and-forth (last year we had some), not to mention round and round. Such conditions make filming difficult, but like the postman I'll brave rain, sleet, snow and ice to deliver the very best underwater footage and tales I can to my viewers and readers. Oh, wait... the post office here on Catalina doesn't deliver!
I happened to look up into the kelp forest to see if any of the spawning worms had braved the elements to procreate. Not many... most were home in their "kelp beds" on a stormy night. But I caught a glimpse of red among the greenish-brown kelp blades that caused neurons to fire all the way to my "beautiful mind" (with apologies to Russell Crowe)! It had to be another southern kelp crab (Taliepus nuttallii) doing one of the two primary functions of any species... munching or mating. There is always the chance that it was up there defending its life by avoiding the hungry morays and octopus down on the reef. And, of course, mating is a time of potential vulnerability so it is always best to practice "safe sex" away from predators.
My buoyancy was perfect for the position of the crab and as I approached the swaying kelp I could see four claws. Hmm, no self-respecting southern kelp crab would possess four claws even though it might constitute a strong evolutionary advantage for feeding... that is unless the radiation from the Fukushima nuclear plant had made its way into our waters and caused a gross mutation. Upon closer inspection I could see that there were two crabs, each with two claws... and they were locked in a tight embrace. I found it hard to choose whether to title this column "Love Lift Us Up Where We Belong" or "I Want to Take You Higher."
Somehow I was synchronized with the kelp that was whipping around in the surge and managed to film these two in their loving embrace while in mid-water. Eventually the water motion was too great for them and they tumbled out of the forest onto the reef, still locked together. I guess these crabs weren't familiar with the Kama Sutra since they employed what we humans refer to as the missionary position, unusual in my experience for this species. I continued to film them until the lovely lady wrenched free from the male's "tender" embrace and hightailed it for the hills... er, nooks and crannies in the reef.
Now, more than a year later, I'm reflecting on the differences between what I saw last summer and this past one. My readers are well aware that our giant kelp (Macrocystis) forests are gone for a while thanks to the warm water, low nutrient levels, strong hurricane surge and the dominance of the non-native Asian seaweed caused in part by the disappearance of the kelp. No way I could look up into the kelp on my night dives... it just isn't there! What little is left is lying on the bottom.
In previous years I've also seen the southern kelp crabs wandering about the rocky reef feeding on the various seaweeds they find there, including occasional blades of giant kelp. I'd often see half a dozen or more on a single dive. Over the last few months I think I've seen only one or two of these crabs and not a single sign of mating. To paraphrase Peter, Paul & Mary (yes, I'm stuck in the 60s)... "Where have all the kelp crabs gone?" Good question... and I have no answer to offer.
So many things are different this year if your eye is trained to see the changes. I spent tens of thousands of greenbacks for my three college degrees that certify I'm a marine biologist, so I'd better be able to see them! And, of course, my long experience diving the island's waters gives me a better perspective to judge changes (if I can only remember what I saw way back then... or even last night for that matter). Someone who has not dived our waters for decades may not realize (in Bob Dylan's words) "the times they are a'changing."
I've written extensively on the new critters that enter the island's ocean during warm water episodes. However, to get the complete picture of the changes, one must also look at what isn't here this year. For some species the warm water has undoubtedly driven them deeper into cooler regions where temperatures are more to their liking. Others may have discovered that with the decimation of the giant kelp forests, there is no longer a readily available source of munchies. Either they select another menu item, or the lack of food causes a good portion of the population to die off.
It is hard to believe that we are already into December and I still dive my thin 3/2mm wetsuit. It is sufficient to keep me warm for one long dive. I relish the fact that I don't have to squeeze into my thick 7mm wetsuit to observe what is going on in our dive park. There are some changes that are really nice! However, as night time air temperatures drop well below our water temperature, I'm starting to research trips to the tropics in the near future! Hmmm... Palau? The Red Sea? The Cayman Islands? Zanzibar? Hawaii?
© 2014 Dr. Bill Bushing. For the entire archived set of over 600 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Southern kelp crabs doing "the wild thing" up in the forest