MEAD, K.S.: Can Surge Channels Act As Reproductive Refuges For Free-Spawning Invertebrates?

CAN SURGE CHANNELS ACT AS REPRODUCTIVE REFUGES FOR FREE-SPAWNING INVERTEBRATES? Like many marine invertebrate animals, sea urchins reproduce by releasing their eggs and sperm into the water column. Their gametes are therefore often exposed to high levels of turbulence caused by breaking waves. This turbulence rapidly dilutes the gametes. In addition, laboratory experiments have shown that moderate and high levels of shear stress (a measure of turbulence) greatly reduce both fertilization and developmental success in a variety of marine invertebrates. On wave-exposed rocky shores gametes are often swept away as soon as they are released. However, due to their semi-enclosed nature, surge channels may limit gamete dispersion and may protect gametes from the most intense turbulence, thus improving the chances of fertilization. To test this hypothesis, eggs and sperm from the purple sea urchin, Strongylocentrotus purpuratus, were released at different distances from each other in surge channels. Gametes were collected at various time intervals after release and immediately placed in potassium chloride solutions to inhibit further fertilization. Wave heights and water exchange were monitored during the experiments. Surprisingly high fertilization rates were observed, even when gametes were released 3 meters apart.