by Rhonwyn Wilkinson.
One of the really exciting things about diving is that you never know what you will see when you drop beneath the surface. A few days ago, we were waiting at the dive shop for our surface interval between dives to be completed. Clement, one of the marine biology researchers from Hong Kong University using Tioman Dive Centre as their research base ran past us heading into the surf with his snorkel equipment. “Mass sea urchin spawning!” he yelled as he disappeared. We looked at each other with curiosity, then kitted up and headed into the water for a practice survey of the house reef. We soon noticed what Clement was referring to. The diadema sea urchins were on the move! Diademas everywhere were congregating into great masses, they were climbing to the top of the highest available point be it rock, coral head or each other! Once there, at some humanly imperceptible signal, the first urchin started to spawn, spewing its gametes into the water column. The others followed suit, creating a cloud of gametes so thick it almost obscured the urchins themselves. Gradually the water cleared as the presumably fertilized gametes were whisked away by the currents. We felt lucky to have witnessed such an amazing event!
The next evening I was to be treated again. Snorkelling off the rocks a little off the house reef at Tioman Dive Centre I came upon a lone cushion star getting ready to spawn. Being a hermaphrodite, it can produce both egg and sperm. It had crawled to the highest point on the largest coral head in the area and began discharging it’s gametes into the sea and into the waiting mouths of numerous small fish who noticed the event!
We usually dive twice per day with our Blue Ventures Malaysia program. I can’t wait to see what tomorrows dive will reveal!