Multiple dimensions of biodiversity within and across producer and consumer guilds in the food web affect an ecosystem’s functionality and stability. Tropical and subtropical aquatic ecosystems, which are extremely diverse, have received much less attention than terrestrial ecosystems in regards to the effects of biodiversity on ecosystem functioning. We conducted a field experiment that tested for effects of macrophyte functional diversity on diversity and stability of associated fish assemblages in floodplain lakes of the Upper Paraná River floodplain, Brazil. Three levels of macrophyte functional diversity were maintained through time in five floodplain lakes and response variables included various components of fish taxonomic and functional diversity and stability. Components of functional diversity of fish assemblages were quantified using a suite of ecomorphological traits that relate to foraging and habitat use. Response variables primarily distinguished macrophyte treatments from the control. Macrophyte treatments had, on average, double the number of species and total abundance than the control treatment, but only limited effects on stability. The high diversity treatment was essentially nested within the low diversity for assemblage structure and had similar or even slightly lower levels of species richness and abundance in most cases. Gymnotiformes and young-of-year were diverse and relatively abundant in …

The 2010 Deepwater Horizon (DWH) oil spill resulted in a large release of polycyclic aromatic hydrocarbons (PAH) into the Gulf of Mexico. PAH can interact with ultraviolet radiation (UV) resulting in increased toxicity, particularly to early lifestage organisms. The goal of this research was to determine the sensitivity of fiddler crab larvae (Uca longisignalis) to photo-induced toxicity following exposure to Deepwater Horizon spill oil in support of the DWH Natural Resource Damage Assessment. Five replicate dishes each containing 20 larvae, were exposed to one of three UV treatments (10%, 50%, and 100% ambient natural sunlight) and one of five dilutions of water accommodated fractions of two naturally weathered source oils. A dose dependent effect of PAH and UV on larval mortality was observed. Mortality was markedly higher in PAH treatments that included co-exposure to more intense UV light. PAH treatments under low intensity sunlight had relatively high survival. These data demonstrate the importance of considering combined effects of non-chemical (i.e. UV exposure) and chemical stressors and the potential for photo-induced effects after exposure to PAH following the Deepwater Horizon spill.