Predicting the extent of marine invasions
Characteristics of invading species and the recipient environment have long been identified as two key attributes controlling biological invasion. However, the ability of these factors to predict patterns of invasion may be dependent on adequate time elapsing for species to spread to all potential habitats. In collaboration with Drs. Jeb Byers, Melanie Bishop, Emma Johnston, and James Pringle, I compiled a database of life-history traits, climate data, and current global distributions of invasive marine invertebrates in order to determine the relative importance of history, as well as abiotic and biotic factors in predicting distributions of dominant global marine invaders. Interestingly, our models suggest that invasion history is more important than either life history or environmental variables in determining invader distributions. This database lays the groundwork for targeted species risk assessment of marine invertebrate invasibility with climate change. |
Indirect effects of non-native species on ecosystem services
Non-native species can alter ecosystem functions performed by native species, often by directly displacing influential native species. However, little is known about how ecosystem functions may be modified by trait-mediated indirect effects of non-native species. Working with Jeb Byers in coastal Georgia, I used mesocosm experiments to explore the direct and indirect effects of a non-native crab species on native bivalve water filtration, a critical ecosystem service. Chlorophyll a drawdown by native bivalve filter-feeders was measured with and without the non-native crab, both in the presence and absence of native mud crab predators. The non-native crab did not affect native bivalve water filtration in the absence of predators. However, the presence of the non-native crab rescued water filtration rates for hard-shell clams, which dampen in the presence of mud-crab predators. This work suggests that non-native species can indirectly affect ecosystem services by aiding the performance of native species. |
Habitat complexity and community development
Habitat complexity strongly affects the structure and dynamics of ecological communities, with increased complexity often leading to greater species diversity and abundance. However, habitat complexity changes as communities develop, and some species alter their environment to themselves provide habitat for other species. Working with Drs. Graeme Clark and Emma Johnston, I examined how the importance of basal substrate complexity changes over the course of sessile marine invertebrate community development. In both a temporal and a spatial study, basal complexity affected marine sessile invertebrate community composition in the early stages of community development when resource availability was high. However, effects of complexity diminished through time as the amount of available space (the primary limiting resource) declined. There is likely a bare-space threshold at which structural complexity of the basal substrate is overwhelmed by secondary biotic complexity. |
Community effects of novel aquaculture structures
Intertidal aquaculture of geoduck clams is a rapidly expanding industry in Puget Sound, Washington, yet little is known about the ecological effects of disturbances associated with geoduck aquaculture operations. I worked with Dr. P. Sean McDonald to examine the effects of novel geoduck aquaculture predator exclusion structures on community composition and dietary patterns of migrating intertidal macrofauna. Community composition varied significantly between structured aquaculture and natural sites. Migrating fish caught on aquaculture structures had a more diverse diet relative to natural sites. Differences in stomach fullness between large and small fish on the incoming and outgoing tide at aquaculture sites suggest that small fish may seek refuge in aquaculture structures. |
© Rachel Smith, 2021. All rights reserved.