摘要：Impacts of the 2011 tsunami disaster were investigated in a shallow brackish lagoon (Gamo Lagoon) in Sendai City, Japan. The tsunami caused drastic changes in lagoon topography, vegetation and sediment characteristics. Muddy sediment was flushed away and the sediment became much sandier. Changes in nutrients and chlorophyll a (chl. a) budgets implied that the lagoon became less eutrophic. Forty-seven macrozoobenthos species and two macroalgal species were nearly extirpated in 2011, while six species including opportunistic polychaetes and amphipods rapidly recovered their population within five months after the tsunami. In 2012 and 2013, some of the species that disappeared, including bivalves, amphipods, decapods and macroalgae, recruited and increased their population sizes. Shorebird populations in Gamo Lagoon and nine other sites in eastern Japan were less affected by the tsunami, since the population size and number of species did not change notably. Compositions of polycyclic aromatic hydrocarbons (PAHs) and normal alkanes (n-alkanes) in lagoon sediment implied petroleum contamination, which was discharged from an oil refinery in Sendai Port although the levels were quite low. A sharp increase in lagoon salinity caused an invasion of stenohaline marine species and limited the growth of the marsh reed Phragmites australis after the tsunami. Therefore lagoon salinity should be regulated to restore the reed-dominated brackish marsh and associated biota of this lagoon. The ongoing construction of huge sea walls is another potential threat to the lagoon ecosystem. Care should be taken to conserve coastal habitats such as tidal flats, salt marshes, sand dunes, as well as their backside landward areas during restoration.
