Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Oceanography and Coastal Sciences

First Advisor

Donald M. Baltz


The ecology of fishes and macroinvertebrates inhabiting shallow seagrass beds was studied at Bahia La Graciosa, located in Amatique Bay in the Caribbean coast of Guatemala. The study area included extensive turtle grass, Thalassia testudinum, meadows over muddy substrate, whereas a more exposed shoreline also supported turtle grass meadows over sandy substrates outside the bay. A total of 166 samples were collected across two seasons and habitat types in three sampling trips to the area with a cylindrical drop sampler. Diversity and abundance of fishes and macroinvertebrates inhabiting seagrass and adjacent bare-sand sites were described to assess the relative importance of seagrasses as nurseries. Utilization of seagrass meadows by fishes and decapod crustaceans was also described for exposed (beach) and protected (bay) habitat types. Seagrass fish and decapod crustacean community structure was compared between beach and bay habitat types during rainy and dry season months. Total crustacean and fish densities, species diversity, and evenness were several times higher in seagrass beds compared to bare-sand substrates, with no significant differences in gastropod densities between habitats. The majority of the fishes collected on seagrass were juveniles, supporting the hypothesis that seagrass is an important nursery habitat. When comparing beach and bay habitat sites, total fish and decapod crustacean densities were similar, but densities of individual species differed significantly between habitat types. Over half of the species were present in both seasons and almost half of the species were present in both habitat types; however, significant interactions were detected between season and habitat for densities of the most abundant species. Significant differences in fish and decapod crustacean community structures were detected with analyses of similarities between habitat types, but the same analyses between seasons were significant only for fishes. An analysis of complex ecological gradients revealed that the highest variability was related, in decreasing order, to seagrass abundance, habitat type, and seasonal variables.