Tag: Jan Hodder

Water Flux in a Mangrove Forest

Presenter: Katalin Plummer

Co-Presenters: Alyssa Bjorkquist

Faculty Mentor: Richard Emlet, Jan Hodder

Presentation Type: Poster 48

Primary Research Area: Science

Major: Marine Biology, Spanish

Water flux plays an important role in structuring and maintaining biodiversity in aquatic environments, such as tropical mangrove forests where lower water flux could reduce organic carbon outflow so that critical nutrients are more available for regulating organismal trophic processes. In the present study, we used two dissolution methods to estimate water flux at two mangrove sites within Bocas del Toro, Panama. We investigated how water flux differs with respect to mobility of a substratum (mobile versus stationary) as well as its position within a mangrove forest (exterior versus interior). We also examined organic carbon content of the sediment of each site in relation to water flux activity to ascertain the existence of a correlation between water flux and nutrient cycling in these environments.

Water flux differed significantly between sites for both the long-term and short-term (p < 0.001, both) dissolution trials. Additionally, we found a significant difference in sediment carbon content between sites (p < 0.01). While the two sites differed significantly from one another overall, these results do not suggest that water flux alone significantly affects marine community composition within a mangrove forest. We speculate that outside abiotic or geographic factors also influence physical conditions of these communities. Studying the intersection of biological and physical factors within mangrove forests may inform future research and conservation efforts pertaining to these environmentally sensitive habitats.

Ontogenetic Shifts in Resource Use And Behavior in the Striped Parrotfish, Scarus Iseri, on a Patch Reef in Bocas Del Toro, Panama

Presenter(s): Haley Faringer − Environmental Science

Co Presenter(s): Rulon Hardy, Christina Ellison

Faculty Mentor(s): Richard Emlet, Jan Hodder

Poster 60

Research Area: Natural/Physical Science, Marine Biology, Ecology

Scarus iseri, the striped parrotfish, is among the most abundant parrotfish on Caribbean coral reefs. As grazing herbivores, they shape community structure by transmitting primary production up the food chain, regulating algal biomass, and facilitating benthic settlers in the process of removing patches of algae. S. iseri are protogynous hermaphrodites with 3 life stages (juvenile, initial and terminal) identifiable in the field. Our study investigates differences in range size, habitat utilization, and behavior between the juvenile and terminal phases. Through this research, we hoped to gain a better understanding of how these fish utilize their habitat as they grow, and how resources are partitioned among members of a population.

Our research was conducted at House Reef, near the Smithsonian’s Tropical Research Institute in Bocas del Toro, Panama. We followed 6 focal individuals of each life stage for a 15-minute period to establish their range. These parameters were chosen due to time constraints of the study period. We only had 4 days to complete the research, including data analysis, and wanted to maximize both the amount of time we followed each fish, and the number of replicates for each life stage. The numbers we chose reflect a compromise between these two variables. Using survey flags and transect-tape, we calculated the area of each range and drew a map of its shape.

Before conducting surveys in the field, we constructed an ethogram, or a table of observed behaviors for the fish. Then for 5 minutes of the 15-minute period we observed and recorded behaviors of the fish according to our ethogram. This allowed us to gain insight about feeding frequency, substrate used for feeding (e.g. sediment, sponge, sand, etc.), the proportion of each type of substrate used, and social behavior within a population.

Our results suggest that range size increases with more advanced life stage. Time allocations for feeding and non-feeding behaviors are similar between the two stages and both life stages utilize the same substrate types for feeding, in similar proportions. Juveniles frequently form groups, while terminal phase individuals are often found alone.

Because Scarus iseri is so prominent in the Caribbean Ocean, it has an increased ability to transfer nutrients through trophic levels. Not only is it important to understand how resource utilization within this species is affected by life stage, but how this resource utilization affects nutrient levels and habitat availability for other species on reefs of the Caribbean Ocean. With the recognition of variable social behaviors and range sizes between juveniles and terminal adults, we hope to better understand the nature of these fish’s relationship with each other and other stakeholders on the reef. The data collected is important because it can be used to inform the management of marine protected areas aimed at preserving this important group of fish.