The Role of Habitat in Bivalve Predator-Prey Interactions

EPA Grant Number: F13F11064
Title: The Role of Habitat in Bivalve Predator-Prey Interactions
Investigators: Glaspie, Cassandra Nicole
Institution: Virginia Institute of Marine Science
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2014 through September 1, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Fellowship - Marine Sciences , Academic Fellowships

Objective:

This project addresses the indirect effects of nutrient pollution on the Chesapeake Bay estuary, investigates a possible feedback loop that may lead to worsening effects of nutrient pollution and results in the creation of a model that can be parameterized and used to understand the effects of nutrient pollution in many systems worldwide. The specific objective of this study is to quantify the shift in functional response of blue crabs on bivalves due to a shift in habitat structural complexity.

Approach:

Individuals of the soft-shell clam (Mya arenaria, thin-shelled deep infaunal) and hard clams (Mercenaria mercenaria, armored shallow infaunal) will be exposed to blue crab predation in a mesocosm experiment conducted at the Seawater Research Laboratory at the Virginia Institute of Marine Science. Mesocosms will be assigned one of four substrate treatments: sand, sand/seagrass, sand/oyster shell, and sand/shell hash. After 48 hours, the contents of all mesocosms will be collected, and the remaining bivalves (as well as any broken shells) will be counted. In addition, an infrared-sensitive video system will be used on two replicates from each treatment to estimate search time (amount of time spent foraging), encounter rat, and handling time (amount of time a blue crab spends handling and consuming a bivalve). Lotka-Volterra predator-prey models will be parameterized using the data from the mesocosm trials, and the resultant model will be used to examine the effect of habitat loss on the persistence and distribution of crabs and bivalves in the Chesapeake Bay.

Expected Results:

Blue crabs have a type II hyperbolic functional response when feeding on armored clams and the attack rate is a function of habitat. Blue crabs have a type III sigmoidal functional response when feeding on thin-shelled burrowing bivalves and the attack rate is a function of habitat. Handling time will be significantly greater for armored species than for avoidance species and will not be influenced by the presence of complex habitat. Encounter rate will be significantly greater for armored species, and the presence of complex habitats will significantly decrease encounter rate for avoidance species. Burrowing bivalves will continue to persist under scenarios of habitat loss, but at much lower densities. Armored bivalves will not be affected by scenarios of habitat loss that are likely to occur in the Chesapeake Bay.

Potential to Further Environmental/Human Health Protection

This project will advance the current state of knowledge about important environmental issues, namely nutrient pollution and resultant seagrass habitat loss. Very few studies examine the mechanisms behind predator-prey interactions, and this study is particularly timely because it quantifies a shift in the functional response of benthic predators due to changes that are very likely to happen in nutrient-polluted systems. Understanding of the effects of changes in handling time and attack rate on predator-prey interactions is essential to predict what effects global change will have on marine communities and ecosystem services.

Supplemental Keywords:

habitat use and loss, nutrients, seagrass

Progress and Final Reports:

  • 2015
  • Final