The ReH(7)(PPh(3))(2)-catalyzed addition of carbonyl compounds to the carbon-nitrogen bond of nitriles proceeds efficiently and selectively to give the corresponding (Z)-enamines, which are important synthetic intermediates. The key step of the reaction is the chemoselective alpha-C-H activation of carbonyl compounds induced by the alpha-heteroatom effect in the presence of nitriles.

Environmental filtering and dispersal limitation are important processes within the metacommunity concept. Non-random species turnover occurs in places where environmental filtering plays the key role in determining local community structure, whereas dispersal limitation causes nested patterns of species assemblages organized by non-random colonization processes. However, factors that modify the relative importance of these processes remain unclear for many ecosystems. We tested whether salinity gradient affect the relative importance of environmental filtering and dispersal limitation for structuring epifaunal and infaunal communities in three lagoons in Hokkaido, Japan, that have different salinity gradients. Specifically, we compared patterns of species diversity and similarity of eelgrass-associated invertebrate assemblages across space. Beta diversity (i.e., species turnover among different sites in each lagoon) was highest in Akkeshi, the lagoon with the salinity gradients.Variation partitioning of similarity components showed that spatial variation in the community assemblage pattern was mostly explained by environmental filtering in Akkeshi, but that it was explained more by species dispersal patterns and the difference in eelgrass biomass and shoot density in Notoro and Saroma, the lagoons without clear salinity gradient. Redundancy analysis showed that spatial variation in community structure was related to salinity and eelgrass biomass in Akkeshi, and to eelgrass aboveground biomass in Notoro and Saroma. Our findings highlight the effects of environmental heterogeneity on beta diversity and community structure and indicate that environmental gradients can be a key factor causing a shift in the relative importance of different metacommunity processes and the role of the foundation species in provisioning habitat. K E Y W O R D Seastern Hokkaido, environmental filtering, epifauna and infauna, metacommunity, salinity gradient.

Coastal fisheries are in decline worldwide, and aquaculture has become an increasingly popular way to meet seafood demand. While finfish aquaculture can have substantial adverse effects on coastal ecosystems due mostly to necessary feed inputs, bivalves graze on natural phytoplankton and are often considered for their positive ecosystem services. We conducted two independent studies to investigate the effects of long-line Crassostrea gigas oyster aquaculture on Zostera marina seagrass beds and associated epibiont communities in Akkeshi-ko estuary, Japan. Results from both studies yielded no evidence of an effect of oyster aquaculture on the morphology, density, or biomass of Z. marina, but significant differences were apparent in the epibiont community. Reference seagrass beds located away from aquaculture had higher seagrass epiphyte loads and higher abundances of amphipods. Conversely, seagrass beds below aquaculture lines had higher sessile polychaete biomass and higher isopod abundances. Our results suggest that the presence of oyster aquaculture may have indirect effects on seagrass by changing epibiont community composition and relative abundances of species. One proposed mechanism is that cultured oysters feed on epiphytic diatoms and epiphyte propagules before they can settle on the seagrass, which reduces epiphyte loads and influences subsequent faunal settlement. If carefully implemented and monitored, long-line oyster aquaculture may be a sustainable option to consider as bivalve aquaculture expands to meet global seafood demand, but further work is needed to fully assess and generalize the community-level effects on seagrass epibionts.

Large-scale analysis along latitude or temperature gradients can be an effective method for exploring the potential roles of light and temperature in controlling seagrass phenology. In this study, we investigated effects of latitude and temperature on seagrass biomass and reproductive seasonality. Zostera japonica is an intertidal seagrass with a wide latitudinal distribution expanding from tropical to temperate zones in its native range in Asia, with an additional non-native distribution in North America. We collated available data on phenological traits (timings of peak biomass or reproduction, durations of biomass growth and reproductive season, and maximum biomass or reproductive ratio) from publications and our own observations. Traits were compared among geographic groups: Asia-tropical, Asia-temperate, and North America-temperate. We further examined relationships between traits and latitude and temperature for 3 population groups: Asian, North American, and all populations. Our analysis revealed significant variation among geographic groups in maximum biomass, peak reproductive timing, and maximum reproductive ratio, but not in other traits. Maximum biomass and peak reproductive timing for Asian and all populations were significantly correlated with latitude and temperature. Maximum biomass was highest at mid-latitudes or intermediate temperatures and decreased toward distribution range limits, and peak reproductive timing occurred later in the year at higher latitudes or cooler sites. North American populations showed shorter growth durations and greater reproductive ratios at higher latitude. Different responses observed for North American populations may reflect effects of introduction. Our study demonstrates potential variation among geographic regions and between native and non-native populations.