Abstract
Environmental productivity and biodiversity are two intricately linked concepts in the field of ecology, with a plethora of productivity driven mechanisms creating a large variety of biodiversity patterns. One commonly observed pattern is a unimodal curve with biodiversity peaking at intermediate levels of productivity. While unimodal relationships are by no means universal, biodiversity declines at high productivity levels (eutrophication) raises serious concerns. Anthropogenic nutrient inputs have increased global environmental productivity, leading to widespread eutrophication of waterbodies. One habitat that may be particularly vulnerable to anthropogenic eutrophication are California vernal pools. These ephemeral waterbodies provide habitat to numerous invertebrate taxa, many which are federally threatened or endangered endemic species. The presence of these species, combined with the proximity of many vernal pools to agricultural development, may be threatened by anthropogenic nutrient inputs. In order to investigate the impact of nutrient inputs on California vernal pool invertebrates, experimental mesocosms were setup in the California State University, Sacramento arboretum. Mesocosms were inoculated with vernal pool soil and divided into five nutrient treatments. Water quality and biotic parameters were taken over an 18-week period to quantify changes to water quality and biotic conditions over a typical vernal pool hydroperiod. Results were then analyzed via repeated measures ANOVA, MANOVA, PERMANOVA, and SIMPER, alongside Pearson correlations and Principal Components Analysis. Overall results indicated that nutrient inputs increased mesocosm turbidity, chlorophyll-a and phosphorus levels, in addition to causing more extreme shifts in dissolved oxygen and pH. However, while nutrient enrichment increased abundances of small crustacean taxa, there were no significant effects on large branchiopod abundances, insect abundances, or taxa richness. In short, anthropogenic nutrient inputs alone did not have large impacts on vernal pool invertebrate communities, with taxa richness and large branchiopods of conservation concern remaining unaffected by eutrophication. Nevertheless, while these findings improve our understanding of how eutrophication affects ephemeral wetlands and organisms reliant on them, questions remain over how nutrient impacts may interact with other associated human activities, as well as multi-year impacts of eutrophication on California vernal pools.