Many habitats are formed by living organisms that affect the habitats they live in.   Some of these effects are positive, while others are negative.   I’m interested in how these positive and negative interactions create spatial patterns across a seascape.  These dynamics depend on factors such as settlement patterns, mortality, and the strength and direction of the interaction.  My lab studies these dynamics on oyster reefs, coral reefs, and in saltmarshes.  

To address these questions, I use a combination of field and modeling approaches.  For example, in Hamman 2018 (Coral Reefs), I documented the spatial distributions of two corallivorous snails and explored the causes and consequences of those distributions.  In Hamman et al. 2018 (Theoretical Ecology), I led a modeling effort that demonstrated how the configuration of habitat patches (e.g. corals) could generate similar levels of heterogeneity in occupant numbers as variation in habitat quality.  We are currently working on an expansion of this model that includes feedbacks with coral occupants as part of an NSF grant.  

On oyster reefs, we use cages filled with oyster shell to study how the amount and type of shell, its proximity to existing habitat affects the oyster communities that assemble.  We've already published two papers from this work, and are currently working with the St. Mary's Watershed Association on a study that will explore these patterns through a site's restoration that is currently funded by the National Fish and Wildlife Foundation.

In saltmarshes, we largely focus on the relationship between the marsh periwinkle (Littoraria irrorata) and smooth cordgrass (Spartina alterniflora).  Currently, we are working on understanding how the relationship between the snail and the cordgrass affect and are affected by the plant's endophytes.  This work is in collaboration with SMCM faculty Lorena Torres-Martinez and funded by the Maryland Native Plant Society.  

Corals are damaged by predators that create different scars of different sizes, shapes, and spatial patterns. It’s advantageous for the coral to heal quickly, and as a result, neighboring polyps often contribute resources to heal damage.  I’m interested in how corals (and other colonial or modular organisms) respond to different patterns of damage.  For example, if a coral predator creates clustered damage, is that better or worse for scar healing?  Does it affect the health of the colony?  What are the long-term effects of that pattern?  How do environmental factors contribute to healing?

To address these questions, I use a combination of field experiments and stochastic growth models.   Using field surveys and experiments, I’ve demonstrated how scars close to one another heal more slowly than scars far apart, and that these effects can affect the morphology of the coral (Hamman 2019, Oecologia).  At SMCM, students in my lab use corals such as Galaxea fascicularis, to study a variety of questions surrounding coral healing (see list of SMP Projects).  I recently upgraded the setup in my lab to include 4 smaller tanks to serve as mesocosms for additional environmental manipulations and there will continue to be opportunities for students to continue this work as directed research or SMPs.

These projects overlap with my teaching interests.  I'm on the steering committee of the UBE-RCN BioGraphI, which is developing lessons for undergraduate biology classes that combine graphical activities with scientist interviews.  You can check out our website for more!