Brooks, W. Randy

The main objective of this research was to analyze how well my proposed Foundation Species Interaction model explained the benthic communities found on red mangrove (Rhizophora mangle) prop roots. This research investigated the connections between the primary foundation species (mangroves), the dominant secondary foundations species (oysters, sponges, and barnacles), and the resulting biodiversity in order to understand the temporal and spatial variability of the ecosystems at different community levels. Chapter 1 was dedicated to explaining my change in ecological theory, the Foundation Species Interaction model. The interactions included in the model between the foundations species that were examined were the mutualistic (+, +), commensal (+, 0), and parasitic (+, -) interactions. Chapter 2 focused on exploration of the mangrove ecosystem in Southeast Florida and establishing where the secondary foundation species and prop root epibionts where found along the latitudinal gradient. The survey investigated the connections between mangroves, the dominant secondary foundations species (e.g. oysters, sponges, and barnacles), and the resulting biodiversity to understand the temporal and spatial variability of the ecosystems at different community levels. Chapter 3 was dedicated to testing the Foundation Species Interaction model’s ability to predict the biodiversity along the latitudinal gradient of the survey. The difference in mangrove prop root communities were largely explained by where the communities laid along the latitudinal gradient and by secondary foundation species presence. The shift from one foundation species to another had sizable effects on biodiversity. Chapter 4 combined the Foundation Species Interaction model with the established predation hypothesis and tested their abilities to explain biodiversity along the latitudinal gradient. This allowed for shifts in community structure to be examined for top-down and bottom-up influences. Predation effects changed along the latitudinal gradient, as the predation effects changed so did the effects of each of the individual foundation species.

Theoretically, sympatric species must partition resources or space to allow for coexistence. Determining empirically the specific resources each species exploits and species’ interactions (e.g., intra- and interspecific competition) can sometimes be challenging, thus the data are relatively sparse for certain taxa. This paucity of data exists for octopuses. Therefore, I chose to study niches of two sympatric octopuses (Octopus vulgaris and Macrotritopus defilippi) in an intracoastal habitat. Specifically, I assessed (1) spatial distribution of octopus home or “den” space, (2) habitat association, (3) octopus abundance, (4) foraging activity periods, (5) diet, and (6) associated substrates and behaviors used during foraging events. Octopus den locations were marked by GPS to quantify spatial patterns of both species and their spatial relationship to each other. Habitat associations were measured by quantifying photoquadrats of den and surrounding habitats. For foraging activity periods, a video camera was placed near an octopus den for 24-h observation to determine when each octopus species leaves/returns from foraging. Underwater video recording was used to determine associated foraging substrates and behaviors for both species. Prey remains from octopus’ dens and video recordings indicating prey consumption were used to determine diets of the two octopus species. Video recordings from the 24-h camera and foraging behavior events also provided observations of intra- and interspecific interactions. Results revealed that the two species are interspersed throughout the shallow Florida lagoon and are both abundant during the spring months (March, April, May). Although both species are interspersed throughout the lagoon, their den and surrounding habitat association differed. O. vulgaris was associated with hard bottom and M. defilippi was associated with soft bottom, thus they may not compete strongly for habitats. Each species used different foraging strategies and different primary prey, which may also lessen competition and facilitate coexistence. O. vulgaris had peak foraging activity during night hours, foraged mostly on hard bottom and mainly consumed bivalves while M. defilippi had peak foraging activity during day hours, foraged mostly on soft bottom and mainly consumed crustaceans. Octopuses also had species-specific foraging behaviors, with O. vulgaris using parachute attack and M. defilippi using flounder swimming and tripod stance. Additional intra- and interspecific interactions were video recorded and included: fishes following octopuses, predation attempts, agonistic encounters, cannibalism, and tactile communication. This study identified ecological and behavioral components that may facilitate coexistence of these sympatric species, provided insight into cephalopod niches and ecology, and provided baseline conservation requirements for sand-dwelling cephalopods, both of which may be using this site as a mating and nursery habitat.

Ecological components such as availability of resources, physical make-up of the
environment, and biotic interactions amongst and between species are factors that determine
habitat selection and coexistence of organisms within a community. A stable coexistence of
species within a community is possible if the limited resources are partitioned to be speciesspecific.
However, sympatric species are expected to exploit similar resources. Two species of
octopus Octopus vulargis and Macrotritopus defilippi with similar ecological requirements
coexist at an intra-coastal habitat. The ecological phenomena of coexistence of species can be
quantified by measuring the ecological components of the niche. The objective of this study is to
identify the components that facilitate coexistence. The ecological components being examined
include: general habitat location, habitat heterogeneity, foraging and feeding times and locations,
and biotic interactions. Global Positioning System will be used to determine the general location
of the octopus species den. The importance of habitat heterogeneity will be addressed by looking
at substrate make-up of the different species dens. Foraging and feeding times and locations will
be recorded to determine any temporal or spatial influence on species coexistence. Field
observations and laboratory habitat selection experiments will be conducted to determine what
habitat each species selects in the presence and absence of the other species. Our studies will
allow identifying ecological components that facilitate coexistence of sympatric species, provide
insight to cephalopod ecology, and conservation at a heterogeneous environment, which is of
importance to maintain marine biodiversity and ecotourism in south Florida.

Agricultural sites have been acquired under the Comprehensive Everglades Restoration
Plan (CERP) for the creation of water storage areas. Copper desorption and toxicity to
the Florida apple snail (Pomacea paludosa) were investigated using soils from these
sites. Copper concentrations in II soils ranged from 5 to 234 mg/kg Cu dw, and when
flooded, resulted in overlying water Cu concentrations from 9 to 308 11g/L Cu. Juvenile
apple snails exposed to three flooded soils had high mortality and decreased growth
within 9 to 16 days in two ofthe three soils examined. To assess Cu toxicity to the apple snail at various life stages and water quality
parameters, 96 hour acute toxicity studies were conducted. Copper was more toxic to
juvenile than adult apple snails. Copper toxicity increased as pH decreased and
decreased as DOC increased. Hardness had no effect on Cu toxicity to the apple snail.
Copper toxicity was a function of organism age, DOC and pH.
Copper accumulation by juvenile and adult apple snails was determined for multiple
exposure pathways. For 28 days, juvenile snails were exposed to aqueous Cu and adult
snails were exposed to Cu contaminated soil, water and food. Whole body Cu in juvenile
snails increased with time. The mean Cu bioconcentration factor (BCF) for juvenile
snails was 1493. For adult snails, the dietary exposure pathway resulted in the highest
bioaccumulation factor (BAF). Most Cu accumulated in soft tissue.
During a chronic aqueous exposure, apple snails exposed to 8-16 flg /L Cu for 9 months
had high Cu accumulation and significantly reduced clutch production (8-16 flg /L) and
egg hatching (16 flg/L ). Chronic Cu exposure initially decreased growth in juvenile
snails, but growth rebounded by adulthood and snails appeared to acclimate to chronic Cu
exposure.
When apple snails with high tissue Cu were fed to redear sunfish (Lepomis microlophus)
Cu transfer was minimal, suggesting that the risk of trophic transfer (bioaccumulation) of
Cu from the snail to redear sunfish is low and that biomagnification is unlikely. It is
uncertain if other apple snail predators would be at risk for dietary Cu transfer.

Niche partitioning mechanisms may be used by
closely related, sympatric species to reduce competition.
We examine two dimensions of niche partitioning
(diet and temporal) amongst the common
octopus (Octopus vulgaris) and the Atlantic longarm
octopus (Macrotritopus defilippi), which spatially
overlap in a South Florida intracoastal habitat. SCUBA
is used to collect octopus prey remains and gather
supplemental feeding images to determine diets
of each species. A 24h octopus monitoring camera
records foraging activity times for each species. The
common octopus consumes bivalves (49%), gastropods
(32%) and crustaceans (19%), and forages
at dawn, dusk, and nocturnal hours. The Atlantic
longarm octopus consumes crustaceans (89%) and
bivalves (11%), and forages during diurnal hours. Results
suggest there is diet overlap between species
and octopuses use temporal partitioning. This study
provides additional findings to cephalopod niche
partitioning literature, novel information on the ecology
of the Atlantic longarm octopus, and conservation
requirements for sand-dwelling species.

The pinnotherid Tunicotheres moseri (Rathbun, 1918) is a common symbiont
with various solitary ascidians throughout its reported range of Jamaica, Venezuela, and
West Florida. Cues affecting host use and host recognition in the West Florida population
were the focus ofthis study. T. moseri responded to conspecific and host generated
chemical cues in the water column. Although host generated chemical cues were
recognized by T. moseri, tactile cues triggered much stronger responses to host ascidians.
Results of conditioning trials suggest that T. moseri is a generalist in host use and accepts
novel host species after conditioning with Molgula occidentalis and Phallusia nigra.
However, T. moseri prefers S. plicata after conditioning with novel host species. The
results of this study suggest that any genetic divergence existing between geographically
disjunct populations of T. moseri are probably due to limited dispersal potential rather
than population specific host fidelity and host use characteristics.

The ecosystem created by pelagic Sargassum is important in the life histories of a
number of economically and ecologically important associated organisms. Fishes play a
vital role in this food web and nutrient flow within these systems, but it is unknown how
they locate these floating habitats. This study examined the role of natural chemical cues
from Sargassum patches and the synthetic chemical Dimethylsulfonionpropionate
(DMSP) for an associated fish, the planehead filefish (Stephanolepis hispidus) and a
control fish species not associated with Sargassum, the masked goby (Coryphopterus
personatus). Choice trials with a Y-maze apparatus determined that S. hispidus
responded significantly to chemical cues from Sargassum while C. personatus did not.
DMSP cues did not result in any significant behavioral responses for either fish.
Demonstrating that S. hispidus can respond to chemical cues from Sargassum helps
further our understanding of this unique floating algal reef and how fishes may locate it.

Masking or decorator crabs, conceal themselves partially through camouflage, by
selecting or indiscriminately attaching materials from their environment to their
exoskeleton. Functional aspects of decorating behavior and morphology in this group
have not been documented. Using Microphrys bicornutus as a model species, this
dissertation demonstrates clearly that decorating is an advantageous phenotype that has
evolved to serve several functions. Decorating is a complex behavior that begins when a crab approaches an algal substrate and results in the attachment of algae to hooked setae on the exoskeleton. Once decorated, crabs remain motionless on the substrate until disturbed or until another behavior is initiated. This was confirmed for M. bicornutus, as crabs spent a significant
amount of time feeding, remaining motionless, picking, and walking when compared to
decorating. Crabs displayed agonistic behaviors during encounters with conspecifics conspecifics. These included both active aggressive behavior and display behavior.
Crabs showed a decrease in motility during these encounters, helping maintain dispersed
distributions, thereby decreasing intrsapecific encounters in the field. Trials were done to determine the effect of conspecifics, predators and feeding preferences on algal utilization. M. bicornutus showed a significant decrease in the amount of algae used for decoration in the highest density trials (i.e., 4 and 8 crabs). Agonistic displays and aggressive behavior between these crabs likely affected the time available for decorating. Decorated crabs isolated from an algal substrate were more likely to survive in the presence of either of two sympatric fish predators. Thus, being protected by the algal decoration on their exoskeletons. Trials also showed a parallel between algal consumption and algal materials used for decoration. In addition to its protective function, algae used by M. bicornutus for decoration simultaneously serve as
short term food supplies for the crabs. Eleven morphologically complex structures were identified and mapped on the exoskeleton. Hooked setae were the primary structures used to attach algae to the crab’s body. Ten additional setal structures were present, including two novel types of setae. On the basis of location and morphological variation exhibited among these latter structures, a primary sensory function may be inferred.

Bleaching of reef corals and other cnidarians symbiotic with zooxanthellae can be attributed to the stress response of the host, algae or both. To determine if zooxanthellae are involved in the bleaching process, I infected a single strain of sea anemone, Aiptasia pallida with zooxanthellae from different hosts. I measured expulsion of the algae from the host during 24-hour incubations at 25, 32 and 34C, as well as photosynthetic rates at these temperatures. Photosynthesis and expulsion of zooxanthellae were inversely and directly proportional to elevated temperatures, respectively. Photosynthesis and expulsion of zooxanthellae isolated from Condylactis gigantea showed the greatest sensitivity to elevated temperature when compared to other zooxanthellae tested. These results suggest that zooxanthellae have a function in the bleaching process and that this function may be related to their photosynthetic response. Thus, the differential tolerance of zooxanthellae to stress could partly explain the spatial variability characteristic of coral-bleaching episodes.

Colonization of infauna in a newly constructed mangrove environment at Spanish River Park, Boca Raton, Florida was studied for six months following initial site preparation. Monthly core samples for benthic invertebrates were collected from December 1994 to June 1995. Sampling stations were chosen randomly each month in three zones along two transects across a tidal channel: upper mangrove, lower mangrove, and mangrove/Spartina. Fiddler crab burrows were counted within randomly placed square meter quadrats in each zone. Rapid succession over short-term indicated the constructed environment would eventually become an established, functional mangrove community. Natural infaunal colonization began immediately, and a total of 26 species was collected during the study period. The most abundant species were microdrile oligochaetes, capitellid polychaetes, and dipteran larvae. Fiddler crab holes were first encountered in April 1995 and reached a maximum in June of 42 burrows per m^2. No significant zonation (p > 0.05) was found in the most abundant species, average infaunal density, or fiddler crab holes. Samples from two reference sites showed similar faunas, with the organisms found in adjacent channel areas an influencing factor on species diversity and density.