Tube worms that first colonized the 1998 lava flow at Nascent vent have now grown to over 1 meter long. In previous years, there were marked differences between the biological communities at different hydrothermal vent sites. This year there are still differences, probably mainly due to vent fluid chemistry, but those differences are becoming less pronounced as new species continue to colonize and spread on the new lava flow. Some new species are taking advantage of the cooler vent temperatures that we are finding this year. On the other hand, the microbiologists on board have found that the Marker 33 vent still has large numbers of hyperthermophiles (microbes that thrive at up to 90 degrees C), even though the temperature measured at the vent has decreased to 34 C this year from 78 C last year. Obviously, there is still plenty of hotter habitat for these microbes below the seafloor.

By late afternoon, ROPOS was back down for dive 550 to extend our Imagenex sonar survey southward along the 1998 eruption site.