Colonies of the Hawaiian gold coral Gerardia sp. (n = 48) were measured, marked and then revisited 1 to 9 yr later to look for evidence of linear growth. The video images showed no change in the proportional size of the coral colonies relative to the marker pots left on the bottom and no change in the pattern of distal branches. Few of the measured delta values exceeded the error of our measurement technique, and the detected change in the sample was statistically indistinguishable from zero. Even though the temperature cycle in the coral beds appears seasonal, these observations indicate that gold coral growth is much slower than growth estimates derived from basal stem ring counts treated as annuli. The period of study was too short to effectively evaluate the validity of life span estimates from radiocarbon studies. The variability in radiocarbon data was assessed with broad sampling (n = 23) across study sites to reveal a mean life span of 950 yr with an overall radial growth of ~41 µm yr

Submarine lava flows on the leeward flank of the Island of Hawai'i, USA, were examined by submersible and remotely operated vehicles to understand the structure and development of deep-water coral communities. Three sites were selected where historically documented lava flows crossed older prehistoric flows, providing 3 pairs of lava substrates of different ages (61/ 400 yr, 134/2000 yr, 143/2330 yr) to compare and contrast with a nearby older coral community (15 000 yr) growing on fossil carbonate. The number of coral taxa, abundance, and colony size increased with substrate age on the 3 historical lava flows and fossil carbonate site, but not on the prehistoric flows. The faster-growing Coralliidae were the dominant taxa forming patches on the peaks of ridged terrain, while the slower-growing Antipatharia and Isididae were less abundant except at the fossil site where the community was dominated by the slowest-growing corals (including Kulamanamana haumeaae). A multivariate analysis of similarity of coral communities on lava flows found site, rather than substrate age, to be a better explanation for why paired flows were ecologically the same despite considerable age differences. The data suggest that hot, turbid, mineral-rich water from the more recent historical lava event re-initialized the community succession of the adjacent prehistoric lava substrate. Coral mortality would be greatest close to the edge of the historical flow with the expectation that survivorship would increase with distance from the impact. The survey transects were too short to detect a significant increase in the total coral community, but an increase was evident for the Coralliidae.

Video from cameras fitted to Hawaiian monk seals showed that seals visited patches of loose mesophotic seafloor rock to flip them and obtain the prey hiding underneath. Diver surveys of rock patches documented 38 species of fish and invertebrates and found 38% of the larger diameter rocks (10-100 cm) flipped with the encrusted live coral and algae side left face down. We developed a set of ‘electric rocks’ (artificial rocks fitted with event loggers) to record the date and time of any movement. We deployed the rocks in multiple clusters on the terraced slope of the seal colony atoll (French Frigate Shoals) close to the beach haulout and at 2 sites further away on the summits of neighboring banks. The goal was to expand temporal monitoring (diurnally and seasonally) of the seal’s use of mesophotic rubble patches without requiring further instrumentation of monk seals. The data from the electric rocks showed patterns consistent with the behavior seen from the seal-mounted video, including rapid rock-to-rock searching and more movements closer to seal haulouts. The electric rocks detected more rock tips on the atoll terrace than on the banks, with higher counts seen during the day at the bank summits. Seasonally, both the terrace and bank detected more movements in summer and fall months consistent with the monk seal’s reproductive pupping and molting season than during the rest of the year, suggesting some seasonal change in the foraging habitat of monk seals.