Density-Dependent Effects of Coral Reef Restoration on Herbivory and Community Interactions

Coral reefs are among the most productive ecosystems in the world. Yet, with their recent declines due to disease, climate change, and overfishing, restoration of these habitats is one of the main concerns for ecologists, resource managers, and government organizations. Coral reef restoration aims to promote key ecosystem processes to shift these habitats to their historical state of high coral cover, but few studies have focused on effective ways to promote resilience. In addition, little is known about the impact of restoration on the fish communities. The aim of this study is to understand how the community of herbivorous fishes is affected by the density of coral outplants inside a special protection area located in the Florida Keys National Marine Sanctuary. Grazing rates, number of visits and time spent foraging were compared using video footage of sites previously devoid of corals, and six months after coral restorations had occurred. Coral transplantations did not appear to attract herbivores nor increase grazing rates of fishes. Instead Sparisoma and Acanthurus fishes appear to respond to changes in the environment by modifying their grazing behavior. However, there was an observed increase in visits by Acanthurus species after transplantation for all the sites sampled within the reef. These fishes seemed to prefer low coral cover sites for grazing. This study highlights the importance of examining coral restorations impacts at the community level. Understanding how restoration influences herbivores and other guilds of reef fishes will allow individuals to not only determine if these habitats are returning to their “original” state, but provide more information on the ways these systems cope with changes in the environment.

Quantifying the effects of temperature and concentration on variable-density flow in numerical modeling of groundwater systems: Implications for predictive uncertainty and data collection

Groundwater systems of different densities are often mathematically modeled to understand and predict environmental behavior such as seawater intrusion or submarine groundwater discharge. Additional data collection may be justified if it will cost-effectively aid in reducing the uncertainty of a model's prediction. The collection of salinity, as well as, temperature data could aid in reducing predictive uncertainty in a variable-density model. However, before numerical models can be created, rigorous testing of the modeling code needs to be completed. This research documents the benchmark testing of a new modeling code, SEAWAT Version 4. The benchmark problems include various combinations of density-dependent flow resulting from variations in concentration and temperature. The verified code, SEAWAT, was then applied to two different hydrological analyses to explore the capacity of a variable-density model to guide data collection. ^ The first analysis tested a linear method to guide data collection by quantifying the contribution of different data types and locations toward reducing predictive uncertainty in a nonlinear variable-density flow and transport model. The relative contributions of temperature and concentration measurements, at different locations within a simulated carbonate platform, for predicting movement of the saltwater interface were assessed. Results from the method showed that concentration data had greater worth than temperature data in reducing predictive uncertainty in this case. Results also indicated that a linear method could be used to quantify data worth in a nonlinear model. ^ The second hydrological analysis utilized a model to identify the transient response of the salinity, temperature, age, and amount of submarine groundwater discharge to changes in tidal ocean stage, seasonal temperature variations, and different types of geology. The model was compared to multiple kinds of data to (1) calibrate and verify the model, and (2) explore the potential for the model to be used to guide the collection of data using techniques such as electromagnetic resistivity, thermal imagery, and seepage meters. Results indicated that the model can be used to give insight to submarine groundwater discharge and be used to guide data collection. ^

Evaluating Effects of Everglades Restoration on American Crocodile Populations in South Florida Using a Spatially-Explicit, Stage-Based Population Model

The distribution and abundance of the American crocodile (Crocodylus acutus) in the Florida Everglades is dependent on the timing, amount, and location of freshwater flow. One of the goals of the Comprehensive Everglades Restoration Plan (CERP) is to restore historic freshwater flows to American crocodile habitat throughout the Everglades. To predict the impacts on the crocodile population from planned restoration activities, we created a stage-based spatially explicit crocodile population model that incorporated regional hydrology models and American crocodile research and monitoring data. Growth and survival were influenced by salinity, water depth, and density-dependent interactions. A stage-structured spatial model was used with discrete spatial convolution to direct crocodiles toward attractive sources where conditions were favorable. The model predicted that CERP would have both positive and negative impacts on American crocodile growth, survival, and distribution. Overall, crocodile populations across south Florida were predicted to decrease approximately 3 % with the implementation of CERP compared to future conditions without restoration, but local increases up to 30 % occurred in the Joe Bay area near Taylor Slough, and local decreases up to 30 % occurred in the vicinity of Buttonwood Canal due to changes in salinity and freshwater flows.