A preliminary survey of the inland aquatic macroinvertebrate biodiversity of St. Thomas, US Virgin Islands

The use of quantitative invertebrate community indices to monitor inland water quality is widespread. However, this approach is rare for the Caribbean, where the dominant animal groups are substantially different from those in continental waters and surface water availability is strongly influenced by seasonality. For the United States Virgin Islands, these limitations are amplified by a general lack of biodiversity data on non-marine aquatic environments. To begin bridging this knowledge gap, we surveyed 41 inland aquatic sites on the island of St. Thomas and adjacent Water Island and Saba Island. Samples were obtained from lotic and lentic habitats, phytotelmata, rural and urban areas, and natural and anthropogenic settings. Out of 118 taxa across 591 records, 46% were first records for the islands sampled, with 23.4% of these being new to the US Virgin Islands territory. Shrimps and snails dominated lotic environments taxonomically, whereas insects dominated lentic environments and phytotelmata. Two confirmed undescribed species were encountered, but this is likely underestimated given the large number of juveniles encountered for some insect groups and the need for a taxonomic revision of multiple genera. The most common and widespread species was the invasive snail Melanoides tuberculata. When sampling periods or multiple samples from the same site were compared, only a 36-42% similarity was found, suggesting a much higher biodiversity than currently appreciated for these seasonally fluctuating habitats. Deep knowledge of inland aquatic biodiversity is necessary to establish baselines to assess watershed health and develop management and conservation plans in the US Virgin Islands, which in turn may be applied to other Caribbean islands.

Automated summary

The study surveyed 41 inland aquatic sites in the US Virgin Islands and found a high level of biodiversity, with many first records and some undescribed species. The results suggest that the inland water habitats have much higher biodiversity than currently appreciated. Deep knowledge of inland aquatic biodiversity is crucial for assessing watershed health, developing management and conservation plans in the region.