Climatic forcing of the Southern Ocean deep-sea ecosystem.

The deep-time development of the Southern Ocean's deep-sea ecosystem remains poorly understood, despite being a key region in global ecological, climatological, and oceanographic systems, where deep water forms and biodiversity is unexpectedly high. Here, we present an ∼500,000-year fossil record of the deep-sea Southern Ocean ecosystem in the subantarctic zone. The results indicate that changes in surface productivity and the resulting food supply to the deep sea, driven by eolian dust input and iron fertilization, along with changes in bottom-water temperature influenced by deep-water circulation, have controlled the deep-sea ecosystem in the Southern Ocean on orbital (10-10 years) timescales following the Mid-Brunhes event (MBE), a major climatic transition ∼430,000 years ago.

Cenozoic history of the tropical marine biodiversity hotspot.

The region with the highest marine biodiversity on our planet is known as the Coral Triangle or Indo-Australian Archipelago (IAA). Its enormous biodiversity has long attracted the interest of biologists; however, the detailed evolutionary history of the IAA biodiversity hotspot remains poorly understood. Here we present a high-resolution reconstruction of the Cenozoic diversity history of the IAA by inferring speciation-extinction dynamics using a comprehensive fossil dataset.

Size distribution studies of 137Cs in river water in the Abukuma Riverine system following the Fukushima Dai-ichi Nuclear Power Plant accident.

The occurrence of (137)Cs in size fractionated samples in river water from the Abukuma River system, (the Kuchibuto and Abukuma Rivers, five sampling events for three sites) was studied from June 2011--approximately some three months after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident until December 2012. The total concentration of (137)Cs (mBq/L) in river water was generally high at the upper stream site in the Yamakiya District within the evacuation/off-limits zone. The (137)Cs concentration was about 1Bq/L for the first sampling campaign (June 2011) at all sites, but then decreased substantially to about one-tenth of that by the time of a second sampling campaign (November or December 2011).

Size-dependent distribution of radiocesium in riverbed sediments and its relevance to the migration of radiocesium in river systems after the Fukushima Daiichi Nuclear Power Plant accident.

We investigated the particle size distribution of radiocesium in riverbed sediments after the Fukushima Daiichi Nuclear Power Plant accident. Riverbed sediments were collected in the Abukuma River system in Fukushima and Miyagi Prefectures. The collected sediments were separated into 11 fractions, ranging from granular size (>2000 μm) to clay size (<2 μm) fractions.

Investigation of spatial distribution of radiocesium in a paddy field as a potential sink.

Surface soils, under various land uses, were contaminated by radionuclides that were released by the Fukushima Daiichi Nuclear Power Plant accident. Because paddy fields are one of the main land uses in Japan, we investigated the spatial distribution of radiocesium and the influence of irrigation water in a paddy field during cultivation. Soil core samples collected at a paddy field in Fukushima showed that plowing had disturbed the original depth distribution of radiocesium.