The acorn barnacle Perforatus perforatus is a common European species that is distributed from southwest England to the Mediterranean and the northwest coast of Africa. Here, we present the first record of invasion of P. perforatus in Japan. This species was found in September, 2012, at a high density on a buoy in Toga Bay in Akita Prefecture, northwest Honshu. It was identified based on the morphological characteristics of the shell and opercular valves, and by molecular analysis using a 300 bp nucleotide sequence of the mitochondrial 12S rRNA. Additionally, a detection and quantification method for P. perforatus using species-specific primer sets for quantitative real-time polymerase chain reaction was developed. Using this method, it was possible to identify and quantify the planktonic nauplius larvae of this alien species.

To investigate environmental factors affecting the species composition of benthic diatoms, surveys of the surface sediment and overlying water were conducted at three intertidal flats in Tokyo Bay: Marine Park, Edogawa, and Kasai. Species were identified by light microscopy and classified into two growth form types: gliding and adhesive. In total, 67 taxa were identified. Seasonal variations of dominant growth forms differed between the intertidal flats; dominant species were Catenula adhaerens, Cocconeis sp. 1, and Fallacia sp. (adhesive type) on the Marine Park; Fallacia forcipata (gliding type) on the Edogawa; and Amphora copulata, A. laevissima (adhesive type), Gyrosigma fasciola, and Navicula cf. mollis (gliding type) on the Kasai. Cluster analysis based on the similarity of major species differentiated the three sites, while the Kasai cluster was further subdivided by season. Redundancy analysis revealed that (1) the correlative environmental factors differed between growth forms and only the gliding type was positively related to mud content, and (2) diatom species composition on the Kasai was related to salinity. These results indicate that tide and wave disturbance and also salinity strongly affect benthic diatom species composition in Tokyo Bay.

Recently, the golden mussel Limnoperna fortunei, an alien species, has invaded the Tenryu, Yahagi and Toyo rivers in Central Japan. This has raised concerns about the impact it may have on hydraulic power generation facilities. We investigated the period of occurrence and attachment of its planktonic larvae, and their growth. The purpose was to understand the current status of their distribution and consequently develop control methods. The results indicate a clear correlation between water temperature and the period of occurrence of planktonic larvae and the growth of this species.

The mussel (Mytilus galloprovincialis) is an important seafood species and is cultivated in many countries. It is also considered a major fouling organism because it colonizes artificial structures causing economic problems. Many studies have demonstrated that M. galloprovincialis larval settlement is influenced by various substrata, i.e., macroalgae, conspecifics and biofilms. This review summarizes the roles of substrata on the larval settlement, with reference to the involvement of chemical cue(s). Literature on M. edulis larval settlement is also included. Larvae of M. galloprovincialis settle on specific filamentous algae in response to chemical cue(s), and not to the algal morphology or associated organisms. Evidence of the gregariousness in this species has also been demonstrated in the laboratory. Biofilms strongly induce the larval settlement and their activities are modulated by immersion periods and months (seasons). Bacteria in biofilms are directly involved in the induction of larval settlement and the viability of bacteria is a requirement for the production of chemical cue(s). Evidence also suggests that two chemical cues derived from bacteria, i.e., waterborne and surface-bound cues, act synergistically on the larval settlement. Further research on the identification of chemical cues is necessary to clarify the mechanism of mussel larval settlement.