Metabarcoding analysis of trophic sources and linkages in the plankton community of the Kuroshio and neighboring waters.

Trophic sources and pathways supporting early life stages are crucial for survival of forage fishes recruiting around the oligotrophic and unproductive Kuroshio. However, information is limited for the Kuroshio planktonic food web and its trophodynamics because of its high biodiversity. Here, we explore trophic sources and linkages in the Kuroshio plankton community using metabarcoding analysis of gut-content DNA for 22 mesozooplankton groups.

Genetic characteristics of the amphidromous fish Ayu Plecoglossus altivelis altivelis (Osmeriformes: Plecoglossidae) on Yaku-shima Island in Japan, the southernmost population of the subspecies.

The Ayu (Plecoglossus altivelis altivelis) population on Yaku-shima Island, Kagoshima Prefecture, Japan represents the southernmost population of the subspecies and is considered to be facing extinction. We investigated the genetic characteristics of Ayu in the Miyanoura River (MYU) in the northeast of the island and the Kurio River (KRO) in the southwest of the island, using partial sequences of mitochondrial (mt) control region and polymorphic microsatellite (simple sequence repeat: SSR) loci. The mtDNA analysis revealed that the Yaku-shima Island population was significantly differentiated from other Ayu populations; additionally, the MYU and KRO populations were significantly different from each other in terms of mtDNA (pairwise Φ = 0.

Using environmental DNA analyses to assess the occurrence and abundance of the endangered amphidromous fish .

The Ryukyu ayu is an endangered amphidromous fish that inhabits rivers in the Ryukyu Archipelago (Japan). Populations of the species have declined dramatically. Consequently, the Ryukyu ayu has been registered as a natural monument in Japan and monitoring surveys with direct catching are restricted legally.

Spatial, phase, and temporal distributions of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in Tokyo Bay, Japan.

The spatial distribution, partitioning, and time trends of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) were investigated in the water column and bottom sediment of Tokyo Bay, Japan, during 2004-2006. A total of 480 water and 60 sediment samples obtained by regular 20-station samplings ascertained the three-dimensional distributions of these compounds and changes in the seawater structure in the whole bay. The median of volume-based average water-borne concentrations of PFOS and PFOA was 3.

Impaired megabenthic community structure caused by summer hypoxia in a eutrophic coastal bay.

Eutrophication and hypoxia are major problems affecting the health of coastal ecosystems throughout the world. Tokyo Bay, Japan, is a eutrophic coastal area where the abundance of the megabenthic community has been decreasing. To assess factors associated with the impaired biota, seasonal surveys of the megabenthic community and water and sediment quality were conducted in the bay.