Abstract. Partial pressure of CO 2 (pCO 2 ) in surface water and vertical profiles of the carbonate system parameters were measured during austral summer in the Indian sector of the Southern Ocean (64-67 • S, 32-58 • E) in January 2006 to understand the CO 2 dynamics of seawater in the seasonal ice zone. Surface-water pCO 2 ranged from 275 to 400 µatm, and longitudinal variations reflected the dominant influence of water temperature and dilution by sea ice meltwater between 32 and 40 • E and biological productivity between 40 and 58 • E. Using carbonate system data from the temperature minimum layer (−1.9 • C < T < −1.5 • C, 34.2 < S < 34.5), we examined the winter-to-summer evolution of surface-water pCO 2 and the factors affecting it. Our results indicate that pCO 2 increased by as much as 32 µatm, resulting mainly from the increase in water temperature. At the same time as changes in sea ice concentration and surface-water pCO 2 , the air-sea CO 2 flux, which consists of the exchange of CO 2 between sea ice and atmosphere, changed from −1.1 to +0.9 mmol C m −2 day −1 between winter and summer. These results suggest that, for the atmosphere, the seasonal ice zone acts as a CO 2 sink in winter and a temporary CO 2 source in summer immediately after the retreat of sea ice. Subsequent biological productivity likely decreases surface-water pCO 2 and the air-sea CO 2 flux becomes negative, such that in summer the study area is again a CO 2 sink with respect to the atmosphere.

Acoustic telemetry and microchemical analysis of otolith strontium-calcium ratios were used to evaluate how exotic brown trout Salmo trutta have responded to Japanese riverine environments of south-western Hokkaido by observing their migratory patterns. The existence of anadromous S. trutta was also verified. Most S. trutta caught in rivers for otolith analysis were freshwater residents (95·6%), whereas those caught in the sea were mainly smolts (91·3%), which had just migrated from rivers during spring. Anadromous S. trutta (n = 6) were captured in rivers and in the sea, confirming the existence of mature pre- and post-spawning fish. According to telemetry results, both mature and immature S. trutta used the river in winter, and their estimated sea-run timings showed individual differences. Through the combination of these two methods, migratory patterns on various spatio-temporal scales were observed. This first documentation of the presence of both male and female anadromous S. trutta in the same region within Japan indicated the risk of further colonization of exotic S. trutta via oceanic migration.

Abstract. Partial pressure of CO2 (pCO2) in surface water and vertical profiles of the aqueous carbonate system were measured during austral summer in the Indian sector of the Southern Ocean (64–67° S, 32–58° E) in January~2006 to understand the CO2 dynamics of seawater in the seasonal ice zone. Surface-water pCO2 ranged from 275 to 400 μatm, and longitudinal variations reflected the dominant influence of water temperature and dilution by sea-ice meltwater between 32° and 40° E and biological productivity between 40° and 58° E. Using carbonate system data from the temperature minimum layer, we examined the winter-to-summer evolution of surface-water pCO2 and the factors affecting it. Our results indicate that pCO2 increased by as much as 32 μatm, resulting mainly from the increase in water temperature. In synchrony with changes in sea ice concentration and surface-water pCO2, air–sea CO2 flux with considering the exchange of CO2 between sea ice and atmosphere, changed from −1.1 to +0.9 mmol C m−2 day−1 between winter and summer. These results suggest that for the atmosphere, the seasonal ice zone acts as a CO2 sink in winter and a CO2 source in summer immediately after ice melt. Subsequent biological productivity likely decreases surface-water pCO2 and air–sea CO2 flux becomes negative, such that in summer the study area is a CO2 sink with respect to the atmosphere.

No abstract

Pacific white-sided dolphin (PWS) Lagenorhynchus obliquidens is the most common cetacean species found in the Tsugaru Strait, Japan. This paper estimates the population of PWS migrated in the strait. The sighting records were collected from the sighting survey in the strait between 2004 and 2010. The PWS population was estimated by using the line transect method for two periods; March to July and May, which is responds to the migration season and mostly observed season. From the limitation of the number of data, the all data from 2004 to 2010 were pooled and estimated the average population. In for March to June, the average estimated population was 4,482 (CV=0.192) and effective strip width was 111.75m. In May the total estimated population of PWS was 9,592 (CV=0.251) and effective strip width was 109.45m. Comparing to the result of the previously reported studies, it was suggested that part of PWS at the coast of both Sea of Japan and Pacific migrate to Tsugaru Strait and most of them use different routes.