The “tsunami break:” impact of the Great East Japan Earthquake and the accompanying tsunamis on the shell growth of the invasive clam-eating snail Laguncula pulchella
The Great East Japan Earthquake and accompanying tsunamis occurred on 11 March 2011, causing huge damage to marine organisms. The invasive naticid gastropod Laguncula pulchella (Euspira fortunei), which was introduced with the imported clam Ruditapes philippinarum from China and Korea, survived the earthquake. The “growth break line” observed on the shell surface in over 90% of the individuals collected in Matsushima Bay and Matsukawa-ura Lagoon after the tsunamis was examined by scanning electron microscopy. Each shell presented three layers before and three after the growth break. However, the fracture surface consisted of five layers—two prismatic and three crossed lamellar—around the growth break line. This suggests that shell formation temporarily ceased following the tsunamis and that the five-layered shell may have developed in response to the stress caused by the tsunamis. The newly formed middle layer became thinner after the “tsunami break,” which may be the result of a rapid change in the mineralization process, including rapid shell growth and/or repair. These results suggest that the damage to and forcible removal of habitats by the tsunamis was stressful for L. pulchella. A decrease in or the cessation of shell formation after a tsunami may be a common phenomenon in mollusks that inhabit tidal flats.
Impact of the Great East Japan Earthquake on Polycyclic Aromatic Hydrocarbons in Sediments on the Coast of Matsushima Bay, Northern Japan
Abstract We investigated the concentration, composition, and distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from the Matsushima Bay area (Miyagi Prefecture, Japan) in 2013—an area that experienced significant destruction in the Great East Japan Earthquake and tsunamis of March 2011—using gas chromatography–mass spectrometry (GC-MS). Their PAH concentration and composition were compared with those of sediment samples collected in Tokyo Bay, which had not suffered similar impacts from the tsunamis. The PAH composition in the sediment collected in the Matsushima Bay area was dominated by phenanthrene, fluoranthene, and pyrene. These data suggest that the PAHs in the sediment are a result of combustion, and that oil pollution is now a negligible source of these pollutants in this area. The lowest total PAH concentration (84 μg/kg dry) was found in the outer area of the bay near Miyato-jima Island, an area permitting high-volume inflow and outflow from the open sea. The highest concentration (15,548 μg/kg dry) was at a former fishing harbor, located in the innermost area of the bay. The large difference in PAH concentrations between sites in Matsushima Bay may be attributable to particle redeposition after sediment disturbance by the tsunamis.
Remotely-Piloted Helicopter Citrus Yield Map Estimation
A remotely-piloted Gas Xcell mini-helicopter with GPS, wireless Ethernet, and a machinevision system was flown over orange trees to take overhead images. The individual tree images were processed to estimate the number of orange pixels in the images. The fruit yield of individualtrees at harvest a month later had an r-squared value of 0.373 with the number of orange pixels onthe irrigated tree images. While it was demonstrated that a remotely-piloted mini-helicopter could beused to acquire useful overhead images of citrus trees, substantial further research is needed toimprove the accuracy of estimates of individual tree yields or health.