LAUSR

The interactions between habitat fragmentation and other stressors are considered a key knowledge gap. This work tested the hypotheses that mercury enhances the effects of fragmentation by (i) reducing the cumulative daily movement of organisms, (ii) shifting their foraging behavior, and (iii) altering the vertical movement of the marsh periwinkle (Littoraria Irrorata) in a field experiment. Random walk simulations were used to access how changes in movement affects the search efficiency of organisms in the long term. Eighteen 1.5 m2 plots were constructed in a salt marsh where landscapes characteristics were manipulated to reach three different levels of habitat cover. Daily movement of twelve marked control and mercury exposed snails were measured in each plot. Bayesian models were used to analyze the data and evidence ratios (ER) were used to test the hypotheses. Results shows that the effects of fragmentation were consistent in both control and exposed treatments, with an increase in the cumulative displacement of organisms. However, mercury significantly reduced the movement of organisms in all levels of fragmentation, shifting their foraging behavior (ER > 1000). Exposed snails were more likely to be found inactive in comparison to the control treatment (ER > 1000). Fragmentation also reduced the vertical movement of organisms in both treatments. In contrast, mercury increased the vertical movement of organisms (ER > 1000). The search efficiency of organisms also increased in highly fragmentated landscape suggesting that changes in foraging behavior is likely due to reduced resources and consequently increase in foraging effort. This work shows that mercury exposure can enhance the effects of habitat fragmentation by changing organisms' movement, foraging behavior and their search efficiency. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2022;00:0-0. © 2022 SETAC.