A distinctive new species of the genus Polyonyx Stimpson, 1858 (Crustacea: Decapoda: Anomura: Porcellanidae) from Okinawa, southwestern Japan

The new porcellanid crab Polyonyx deezi n. sp. is described on the basis of two specimens from Okinawa Island, Ryukyu Islands, southwestern Japan. The new species belongs to the P. sinensis group and may be closest to P. socialis Werding & Hiller, 2019 in the comparatively broad proportions of the carpi of the chelipeds and meri of the ambulatory legs. However, P. deezi n. sp. is immediately distinguished from all other congeners by the median branchial margins of the carapace being bluntly angular and produced laterally and the dorsal surfaces of the carapace and chelipeds with distinct protuberances. The occurrence of P. deezi n. sp. from coral reefs may be unusual in species of the P. sinensis group because many of the known species have been recorded from estuaries or coastal embayments. An identification key to the Indo-West Pacific species of the Polyonyx sinensis group is provided.

Models to predict total phosphorus concentrations in coastal embayments of eastern Georgian Bay, Lake Huron

Several coastal embayments of eastern Georgian Bay show signs of water-quality impairment thought to be caused by human activities. Here, we evaluate the ability of the Lakeshore Capacity Model (LCM), developed for Precambrian Shield lakes, to assess the impact of cottage development on the trophic status of ten Georgian Bay embayments. The LCM could only be applied to eight embayments due to the large size and complexity of two watersheds and produced unacceptably high estimates of mean seasonal total phosphorus concentrations ([TP]; i.e., exceeded 20% of measured values for five of eight embayments); accuracy of [TP] estimates could not be improved by accounting for internal phosphorus loading. We developed an additional model, the Anthro-Geomorphic Model (AGM), which uses building density and basin morphometry as variables. Estimates of [TP] for the AGM were within 20% of measured values for all sites. Compared with other aquatic systems, coastal embayments of Georgian Bay have significantly higher chlorophyll a concentrations per unit [TP]; we suggest that the TP–chlorophyll relationship presented in this study be used to estimate productivity in these systems.