DOI: 10.5061/dryad.vg18q
title: Data from: Local and regional stressors interact to drive a salinization-induced outbreak of predators on oyster reefs

description: Predator outbreaks are predicted to increasingly decimate economically and
 ecologically important prey populations because global climate change and
 food-web modifications frequently facilitate predators and stress prey.
 Natural systems are organized hierarchically, with processes operating at
 multiple scales giving rise to patterns of biodiversity, so predicting and
 managing outbreaks requires a framework that accounts for the effects of
 both local and regional stressors. Here, we used the comparative
 experimental approach to investigate whether the collapse of a nationally
 important oyster fishery in the Gulf of Mexico (Apalachicola Bay, Florida)
 could have been (1) caused proximally by a predator outbreak and (2)
 whether this outbreak was mediated by local- and/or regional-scale forces.
 During the fishery collapse, we paired experiments with monitoring in
 Apalachicola Bay and found elevated water salinity, high abundance of
 predatory snails, and intense oyster mortality due to predation. By
 repeating these experiments over 4 yr, we found that periods of reduced
 water salinity inhibited predation on oysters. To partition the influence
 of local-versus-regional factors on this predator outbreak, we
 simultaneously replicated the paired experiments and monitoring in a
 nearby bay (Ochlockonee Bay) that shares the same regional-scale rainfall
 conditions. Increasing freshwater withdrawals from the watershed that
 drains into Apalachicola Bay have increased salinities in that bay, but
 there have not been similar withdrawals in the Ochlockonee Bay watershed.
 Therefore, Apalachicola Bay experienced a localized anthropogenic stress,
 while both bays experienced regional stress from drought. In Ochlockonee
 Bay, our experiments demonstrated that the river maintained sufficiently
 low salinity to provide ~50% of oyster reefs with a refuge from predation.
 In contrast, salinity-dependent predation in Apalachicola Bay extended up
 to the river mouth. Given the stark differences in upstream water
 withdrawals between these watersheds, it is reasonable to surmise that
 these withdrawals exacerbated the stress of regional drought, created the
 difference in predation between the two bays, and thus may have
 precipitated the oyster fishery collapse. Our study provides empirical
 support for recent theory about the hierarchical organization of
 ecosystems, which predicts that stressors will interact across scales to
 cause localized predator outbreaks.
description: Zip file with all data
 and R codeThis zip file contains
 five folders and an R script. Three of the folders refer to figures in the
 manuscript (e.g., Figure1-2, Figure3, and Figure4). In each of these
 folders, there exist the data used to create the figure and the data
 needed to conduct the underlying statistical analyses. The folder
 "Precipitation_and_Flow" contains the river flow and
 precipitation data, which were analyzed to evaluate if river flow and
 precipitation have changed over time in the watersheds of Apalachicola
 River and Ochlockonee River. The folder "Appendix_S7" contains
 all data needed to reproduce the statistical results presented in Appendix
 S7. The statistical analyses and figures were produced with R-software. As
 a result, this zip file also contains an R-script, which contains the code
 necessary to produce all figures and statistical
 results.Data_and_R_Code.zip