Center for Environmental Studies

The hydrological and topographical variation of wetlands can affect the behavior,
population growth, and local densities of aquatic species, which in turn can drive the
behavior and density dynamics of gleaning predators. Prey availability, primarily
determined by prey density and water depth in wetlands, is an important limiting factor
for nesting wading bird populations, top predators in the south Florida Everglades. The
Everglades is able to support large colonies of nesting wading birds because of the
microtopographic variation in the landscape. Some types of prey concentrate in flat,
shallow sloughs or become trapped in isolated pools as they move down from higher
elevation ridges with receding water levels. Manipulations to the hydrology and
landscape of the Everglades has negatively impacted nesting wading bird populations in
the past, and may continue to be detrimental by allowing flat, shallow sloughs to be
intersected by deep canals, a potential refuge for wading bird prey. In addition, the subtle
elevation differences between the ridge and slough landscape may be an important mechanism for increasing slough crayfish (Procambarus fallax) prey availability for the
most abundant and seemingly depth-sensitive Everglades wading bird, the White Ibis
(Eudocimus albus). I implemented a 2-year experimental study in four replicated manmade
wetlands with controlled water recession rates in order to determine the effects of
proximate deep water (akin to canals) on fish prey concentrations in the sloughs, as water
levels receded similarly to a natural Everglades dry season. I also calculated average
daily wading bird densities with game cameras (Reconyx PC800 Hyperfire) using timelapse
imagery over 60 days to determine when and where wading birds responded to
changing prey concentrations. I completed an additional observational study on White
Ibis and slough crayfish prey from the first year of data (2017). Crayfish make up the
majority of the diet for nesting White Ibis, and literature has suggested crayfish are most
abundant at slough depths much deeper than previously proposed foraging depth
limitations for White Ibis. This study specifically compared recent determinations about
crayfish movement dynamics in the ridge and slough system with White Ibis foraging
behavior and depth limits. Results from the first experimental study suggest that canals
might be an attractive refuge for relatively large prey fishes (> 3 cm SL) in sloughs, but it
is uncertain if the fencing blocked all prey fish movement. The second observational
study determined White Ibis foraging activity was primarily driven by a down-gradient
crayfish flux from ridge to slough, with the majority of foraging activity occurring at
much deeper slough depths than previously suggested water depth limitations for White
Ibis. Results from both of these studies support the importance of preserving the ridgeslough
landscape of the Everglades to sustain high prey availability for wading birds.

Relying on field research to complete the life history for certain fish
species can be inadequate, but laboratory research can be used to fill these
gaps. These gaps exist for Bonefish (Albula spp.), a tropical marine fish and
popular sportfish. In this study, aquaculture techniques were applied to Bonefish
in a captive setting at Harbor Branch Oceanographic Institute (HBOI) and Cape
Eleuthera Institute (CEI) to induce spawning and describe early ontogeny.
Photothermal manipulations and hormone injections were used to induce gonad
maturation and spawning, which was achieved once at CEI and is the first record
of hormone-induced spawning for Bonefish. From that spawn, egg and larval
development were recorded and described through 26 hours and 56 hours
respectively, representing the first record of these early life stages for Bonefish. This work expands upon what is known about Bonefish reproductive biology and
will be useful for management and future captive research.

The Florida manatee (Trichechus manatus latirostris) is native to Florida and the
Indian River Lagoon. Harbor Branch Oceanographic Institute (HBOI) is located in Indian
River Lagoon and is frequently visited by manatees. The Manatee Project was created in
2009 to document and photograph the manatees visiting HBOI. Analyzing photographs
of 146 manatee that visited HBOI showed that a majority of the injuries sustained were
caused by boats. 97% of the manatee had at least one propeller injury and 31% of the
manatee had at least one skeg injury. Other non-boat related injuries seen in the images
included cold stress and entanglement injuries. This study looked at the prevalence of
scar by anatomical region, the cause of injury, and compared injury locations between
male and female manatees.

Gopher tortoises (Gopherus polyphemus) are keystone species mainly due to their burrow construction. Gopher tortoises can also impact the plants around them, but it is rarely quantifiable due to constraints in dispersal studies including time period and seasonality of fruit. The objective of this study was to measure the effect gut-passage has on a native Florida stone-pitted shrub, the cocoplum bush (Chrysobalanus icaco), as well as to attempt to model the relationship between the gopher tortoise and the plant using our unique field site. This study shows that gut-passage has a significant effect on the germination rate of the cocoplum, allowing it to germinate faster than control groups. This study also found that a model involving covariates relating to tortoise movement as a predictor for cocoplum intensity was favored over a homogeneous null model. We believe the pattern of plants is nonrandom and relates to the gopher tortoise’s seed dispersal.

The Gulf of Mexico (GoM) contains a variety oceanographic features including;
the Loop Current, cyclonic/anticyclonic eddies, common water, and the Mississippi River
Plume. The relationship these features have on the community assemblages of Families
Lutjanidae and Serranidae has been of great interest from both biological and economic
standpoints. These families represent some of the most economically important fisheries
in the GoM. Identifying the role these features play in the transportation of larval and
juvenile nearshore species to offshore environments is vital to resource managers. Using
data collected shortly after the Deepwater Horizon Oil Spill via the NOAA Natural
Resource Damage Assessment in 2011 as well as cruises conducted by the Deep Pelagic
Nekton Dynamics of the Gulf of Mexico (DEEPEND) Consortium from 2015-2017, the
faunal composition and abundance of these families were analyzed with respect to
seasonality, oceanographic features, depth distribution, and time.

In the eutrophic waters of the Indian River Lagoon (IRL), decreases in overall
shellfish size have been reported, which may be related to coastal acidification. To
understand the relationship between acidification and eutrophication, water samples from
20 sites spanning the IRL were collected and analyzed for dissolved nutrients and omega
values in spring (dry season) and fall (wet season), 2016-2017. Additionally, three sites
were sampled weekly to observe temporal variability of nutrients and omega values. For
the IRL-Wide sampling, sites with higher dissolved nutrient concentrations showed lower
omega values with significant negative relationships. Both sampling programs showed an
overall positive linear relationship between salinity and omega values. This work
suggests that salinity and dissolved nutrients have implications for acidification in the
IRL and must be considered for future water quality, shellfish and coral reef restoration.

In tropical wetlands, breeding wading birds rely on concentrations of aquatic
fauna during the dry season to meet increased energetic demands. Wetland
microtopography increases aquatic fauna concentration levels. Crocodilians modify the
landscape creating deep-water refugia but their role as a mechanism for aquatic fauna
concentration is unknown. I sampled alligator (Alligator mississippiensis) abundance and
slough microtopography to examine correlation between the two measures. Despite
increased microtopography in high alligator use sloughs, the differences were not
significant. Using an in situ experimental approach, I quantified the magnitude, timing,
and spatial extent of aquatic fauna concentrations within simulated alligator depressions
and the surrounding marsh. Aquatic fauna density and biomass were greater within
simulated depressions, thus enhancing wading bird foraging habitat. Further
understanding the mechanisms creating microtopography, thus enhancing wading bird habitat, is critical to facilitate restoration and prevent declines of wading bird populations
in seasonally pulsed wetlands worldwide.

Little Blue Herons, Snowy Egrets, and Tricolored Herons that nest in the
Everglades have declined sharply over the past decade, due in part to food resource
limitations. Here, I examined the diet of small herons to determine how prey
characteristics affected the fitness of small herons in the highly modified Florida
Everglades. Analysis of these diet differences showed birds nesting in 2017, a
hydrologically dryer-than average year, and a more taxonomically varied diet were
associated with nest success and improved body condition of nestlings. Over half (51%)
of the fish biomass Little Blue Herons consumed were non-native species, compared to
14% and 19% non-native fish biomass consumed by Snowy Egrets and Tricolored
Herons, respectively. Surprisingly, <7% of fish biomass available in the Everglades were
comprised of non-native fish species, suggesting that small herons, and Little Blue
Herons in particular, may be using alternative foraging habitats, to supplement their
dietary needs.

The Deepwater Horizon oil spill in 2010 prompted an enormous survey effort to
assess the under-studied, deep-ocean ecosystems of the Gulf of Mexico. The resulting
samples and datasets afforded a unique opportunity to study the ecology of a poorly
known group of mesopelagic fishes, the barracudinas (Aulopiformes: Paralepididae).
Here we address several important data gaps regarding the ecology of the Paralepididae.
Our results indicate that a majority of barracudina species are efficient at avoiding
research-sized nets, suggesting that their overall abundance has been historically underestimated.
Notable differences in vertical distribution, seasonal abundances of sizes
classes, and diets were observed among the three major sub-groups of the family, with
potential implications to ecosystem-based management of deep-pelagic fisheries. This
thesis is dedicated to all the fish, squids, and shrimps that gave their lives to make these
data and to those that endured the hardship of the Deepwater Horizon oil spill.

Human reliance on the goods and services provided by ecosystems and the global
decline in the health of many of these ecosystems, necessitates ecosystem valuation for the
purposes of decision-making and conservation policy. The literature suggests that conventionally
employed economic valuation methods have been unsuccessful in capturing the full scope of the
benefits ecosystems provide, particularly those benefits that are considered cultural. This
research explores public perceptions of salt marsh value through the use of focus groups in
marsh-adjacent communities in Massachusetts, Virginia, and Georgia. Results suggest that in
case study communities, outdoor experiences in salt marshes inspire serenity in Massachusetts,
shape shore and “marsh” identities in Virginia, and promote stewardship cultivation in Georgia.
Perceived threats to these benefits, such as the threat of residential development, industrial
pollution, and increasing flood risk, together constitute the context for various community
responses related to marsh protection. Results contribute to existing economic valuations.