No abstract

Urbanization influences a range of factors related to stream health, including the hydrologic regime, water quality, and riparian conditions that lead to negative effects on terrestrial and aquatic ecosystems. However, impacts on freshwater decapods from urbanization of tropical streams have not been reported. We hypothesized that changes in decapod communities in watersheds with different levels of urbanization are related to changes in physical stream habitats caused by different land uses and their effects on water discharge. The impacts of land use on the physico-chemical characteristics of streams and freshwater decapod communities were evaluated in three watersheds characterized by low, moderate and highintensities of urbanization in Puerto Rico. For the low and moderately developed urban watersheds, decapod species richness ranged from 10 to 11 species; the highly urbanized watershed only had 4 species. Macrobrachium faustinum and Xiphocaris elongata were the most ubiquitously species and were found in all watersheds. Multivariable analysis of physical characteristics and densities of the decapod families resulted in one axis that explained 80 % of the total variation among the watersheds and was correlated with stream discharge. The effect of discharge is likely a result of frequent high flows that sustain habitats with high concentrations of dissolved oxygen and low concentrations of pollutants. An increase in physicochemical parameters were observed from the LUW to the HUW. These results indicate that the decapod communities were most likely influenced by land use and environmental conditions that affected erosional aspects related to water discharge and water quality in the highly impacted watersheds.

An updated checklist of the freshwater decapod species of Puerto Rico is presented based on records of shrimp and crab species whose presence has been confirmed in Puerto Rico as a result of extensive field collections, examination of carcinological collections, literature review, and personal communications from researchers. The freshwater decapods fauna of Puerto Rico consists of 18 species of shrimps belonging to eight genera and three families, and one species of crab belonging to the family Pseudothelphusidae.

Global climate change predictions include decreased precipitation and more frequent droughts in many world regions. In the aseasonal wet tropics, predicting potential impacts is particularly challenging because droughts are rare and therefore poorly understood. In 2015, the Caribbean islands experienced the most severe drought within the past 5 decades. Here, we use this extreme event as an opportunity to assess how tropical stream ecosystems draining the Luquillo Experimental Forest (LEF) in Puerto Rico respond to severe drought. During 2015, precipitation was 45% lower than the long-term (1975-2016) average for the LEF, resulting in a 54% reduction in stream discharge. After 5 mo of declining discharge (April-August 2015), one branch of our focal study stream system became a series of isolated pools and a few riffle-type runs, while the other branch had greatly reduced flow between its pools. Concentrated biotic activity within pools resulted in elevated and highly-variable nutrient (5.1-12.1 lg PO 4 32-P/L; 12.9-57.2 lg NH 4 1-N/L; 80.0-160.0 lg NO 3 2-N/L) and specific conductance (95-114 lS/cm) levels among pools. However, the algal standing crop was 14Â lower than the previous 15-y average despite increases in nutrient levels, reflecting intense grazing pressure of insect and shrimp consumers, potentially due to decreased pool volume. Higher nutrient levels in stream pools did increase biofilm productivity, and at the peak of the drought daily fluctuations in dissolved oxygen ranged from ∼1.0 to 6.5 mg/L. Significantly-higher riparian inputs of organic matter (7.6Â the longterm average) occurred during a 15-d period in May. The drought caused a general increase in macroinvertebrate density, with collector-gatherers and some grazer taxa increasing significantly at the peak of the drought, but taxonomic richness did not change. Omnivorous shrimp abundance increased slightly in response to decreased stream flow in one branch of our focal stream. Our study highlights the marked effects of severe droughts on neotropical streams in the wet tropics, with large effects on basal resources and consequent changes in trophic dynamics. Ultimately, our findings underline the need for a whole-ecosystem perspective to understand how streams respond to increased frequencies of extreme events associated with climate change.

This chapter provides an overview of the species diversity and conservation status of the freshwater decapods in Central America and the Caribbean islands that date back to the late 1800s in both areas. The majority of the early studies were on taxonomy but our knowledge of freshwater decapod ecology (especially of freshwater shrimps from some Caribbean islands) has increased substantially over the last four decades. Currently, 86 species of freshwater decapods are known from Central America and the Caribbean. Here the decapod fauna comprises two families of primary freshwater crabs (Pseudothelphusidae and Trichodactylidae), three families of freshwater shrimps (Atyidae, Palaemonidae and Xiphocarididae), and one family of crayfish (Cambaridae). Several species have been introduced to this region for aquaculture and have now established wild populations. We also provide a list of Central American and Caribbean freshwater decapods that host parasites. To date, the conservation status of 43 % of all freshwater decapods in the region has been assessed using the IUCN Red List protocols; 5 % of these species are endangered or Critically Endangered, and two species (Cambarellus alvarezi and C. chihuahuae) are likely extinct. Cuba is the country with the most Vulnerable species (7 spp.), while Bermuda (2 spp.) and