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ABSTRACT ObjectiveThe objective of this study was to quantify the effects of temperature, hydrology, and body size on the diet and energy requirements of a generalist predator, Common Snook Centropomus undecimalis (hereafter, “snook”), to gain a better understanding of predator–prey dynamics in the wake of global change. We first ask how temperature, hydrology, and body size influence the occurrence of fish, invertebrates, and empty stomachs in the diet of snook. Next, we model the energetic requirements of snook as a function of body size and temperature. Last, we use predation simulations to test how changes in prey quality, together with snook energy requirements, interact to shape prey demand. MethodsThis study used long-term empirical diet information for snook that were collected from the Shark River, Everglades National Park, alongside models of consumer energetic needs and predation simulations. We used a set of generalized linear models to determine the relationships between snook diet and a suite of predictor variables representing hydrology, temperature, and body size. Models of consumer energetic requirements were used to better understand the total daily caloric needs of snook across a range of temperature and body sizes relative to the available energy in the fish and invertebrate prey that were collected from the system. Last, we conducted predation simulations to highlight the effects of variable diet scenarios on the foraging behaviors that are required to meet the total daily energetic requirements of snook at various temperatures and body sizes. ResultsSnook were observed consuming less fish, coupled with an increased likelihood of empty stomachs, at higher temperatures. Reliance on invertebrate taxa increased at high marsh stages. In addition to marsh stage, smaller-bodied individuals were more likely to consume invertebrates. The predation simulations revealed that snook that consumed invertebrate-dominated diets required greater prey biomass as well as an increased number of individual prey items to meet their daily energetic requirements relative to fish that consumed diets that contain fish. However, if snook maintained even a small proportion of fish in their diet, it substantially reduced the number and biomass of prey needed to meet their energetic requirements. ConclusionsOur predation simulations indicated that snook should select for high-quality fish prey as temperatures warm. However, the empirical data revealed a decrease in the probability of high-quality fish prey in the diets of snook. Furthermore, the empirical diet data showed that low-quality invertebrate prey were more likely to be seen in the diets of snook at high water levels. As temperatures increase and hydrology becomes increasingly variable because of global change, snook will likely need to consume larger quantities of lower quality prey (i.e., compensatory foraging) or disperse to forage in more optimal habitats. These results highlight the dynamic interplay between environmental conditions and consumer energetic needs for shaping the foraging ecology of a generalist predator. 

The Atlantic goliath grouper (Epinephelus itajara) is the largest grouper species in the Atlantic and exhibits high site fidelity and limited range of movement. By 1990, the goliath grouper population in US waters had declined approximately 95% relative to unfished levels, leading to a harvest ban in 1990. Since then, the south Florida population has grown but the magnitude of recovery remains unknown due to uncertainties about life history characteristics. However, despite these unknowns, the state of Florida approved a limited recreational harvest of goliath grouper. In 2021, fine-scale habitat use of three juvenile goliath grouper was investigated using acoustic telemetry and a positioning solver. All three individuals exhibited high site fidelity as well as a diel habitat use pattern, utilizing seagrass habitat during the night and mangrove habitat during the day. Fine-scale acoustic telemetry provides insight into not only habitat use, but broader habitat preferences as well. This study illustrates the need to consider deep seagrass-dominated channels lined with red mangroves when protecting juvenile goliath grouper populations within Florida Bay, especially as the population is opened to harvest. 

Abstract Macrophyte foundation species provide both habitat structure and primary production, and loss of these habitats can alter species interactions and lead to changes in energy flow in food webs. Extensive seagrass meadows in Florida Bay have recently experienced a widespread loss of seagrass habitat due to a Thalassia testudinum mass mortality event in 2015 associated with prolonged hypersalinity and bottom-water anoxia. Using stable isotope analysis paired with Bayesian mixing models, we investigated the basal resource use of seven species of seagrass-associated consumers across Florida Bay in areas affected by the 2015 seagrass die-off. Three years after the die-off, basal resource use did not differ for species collected inside and outside the die-off affected areas. Instead, consumers showed seasonal patterns in basal resource use with seagrass the most important in the wet season (58%), while epiphytes were the most important in the dry season (44%). Additionally, intraspecific spatial variability in resource use was lower in the wet season compared to the dry season. We were unable to detect a legacy effect of a major disturbance on the basal resource use of the most common seagrass-associated consumers in Florida Bay. 

Seagrasses are threatened worldwide due to anthropogenic and natural disturbances disrupting the multiple feedbacks needed to maintain these ecosystems. If the disturbance is severe enough, seagrass systems may undergo a regime shift to a degraded system state that is resistant to recovery. In Florida Bay, Florida, United States, two recent, large-scale disturbances (a drought-induced seagrass die-off in 2015 and Hurricane Irma in 2017) have caused 8,777 ha of seagrass beds to degrade into a turbid, unvegetated state, causing a large sediment plume. Using satellite imagery digitization and long-term seagrass cover data, we investigate the expansion of this sediment plume between 2008 and 2020 and the potential interaction of this sediment plume with seagrass recovery in two focal basins in Florida Bay affected by the die-off, Johnson and Rankin. The average size of the sediment plume increased by 37% due to the die-off and Hurricane Irma, increasing from an average of 163.5 km 2 before the disturbances to an average of 223.5 km 2 . The expansion of the plume was basin-specific, expanding into Johnson after the 2015 seagrass die-off with expansive and long-lasting effects, but only expanding into Rankin after Hurricane Irma with less severe and short-term effects. Furthermore, the sediment plume was negatively correlated with seagrass cover in Johnson, but held no relationship with seagrass cover in Rankin. Thus, different disturbances can act upon seagrass ecosystems at varying scales with varying consequences. This study illustrates the advantage of combining satellite imagery with field data to monitor disturbances as well as highlights the importance of investigating disturbances of seagrass ecosystems at various scales to comprehend seagrass resilience in the context of future extreme events.