In collaboration with Drs. Gina Wimp and Danny Lewis (Georgetown University), we are investigating how nutrient subsidies affect foodweb dynamics within salt marsh communities.
Natural wetlands are increasingly threatened by nutrient pollution. We are studying the contrasting effects of a short-term increase in nutrient availability (pulse) versus a long-term increase in nutrients (press) on the productivity of the dominant cordgrass, Spartina alterniflora, and the extended consequences for species interactions and food-web structure (Murphy et al. 2012). Conservation of coastal wetlands, particularly salt marshes, is a major concern because they play a critical role in the ecology and geology of wave-protected shorelines and are the nursery grounds for commercial fish and shellfish. The treatments that we have imposed are specifically designed to mimic nutrient-runoff from agricultural fields and golf courses in order to understand how variable nutrient regimes influence community structure over time. Remarkably, the effects of contrasting nutrient-input regimes on food-web structure in native habitats remain poorly understood in terrestrial systems, despite the increasing fraction of landscapes affected by nutrient runoff from agriculture and development. We have found that nutrient enrichment and increasing primary production have significant effects on arthropod species composition, particularly higher trophic levels (Wimp et al. 2010).
We are also investigating how generalist predators change their feeding habits seasonally based on prey availability. We found that spider hunting mode (web-building vs. hunting) influences the extent to which spider species use prey from grazing and epigeic (soil surface detritus/microbe/algae consumers) food webs (Wimp et al. 2013). Furthermore, we found that for hunting spiders, ontogenetic changes in body size affects whether they primarily feed on the grazing or epigeic food web (Murphy et al., 2020). Our results have important implications for how the strength of top-down trophic cascades may vary temporally and we are just beginning to test how these effects may interact with nutrient enrichment.
Relevant Publications
Rippel, T. M.*, A. L. DeCandia, J. Tomasula*, C. L. McIntosh, S. M. Murphy, and G. M. Wimp. 2023. Detritivores and exogenous nitrogen influence litter microbial communities in coastal salt marshes. Marine Ecology Progress Series 716: 17-29.
Tomasula, J.*, B. Maguire**, T. M. Rippel*, E. Lopez, S. Perez, A. Arab, S. M. Murphy, and G. M. Wimp. 2023. Conditions for collapse: chronic nutrient enrichment increases native insect density linked to salt marsh dieback. Biological Conservation 278: 109882.
Rippel, T. M.*, J. Tomasula*, B. Maguire**, S. M. Murphy, and G. M. Wimp. 2022. Dominant detritivores mediate the impact of nitrogen on litter decomposition in salt marshes. Oecologia 200: 479-490.
Rippel, T. M., J. Tomasula, S. M. Murphy# and G. M. Wimp#. 2021. Global change in marine coastal habitats impacts insect populations and communities. Current Opinion in Insect Science 47:1-6.
Wimp, G. M., D. Lewis¶ and S. M. Murphy. 2021. Prey identity but not prey quality affects spider performance. Current Research in Insect Science 1: 100013.
Wimp, G. M. and S. M. Murphy. 2021. Disentangling the effects of primary productivity and host plant traits on arthropod communities. Functional Ecology 35(3): 564-565.
Murphy, S. M., D. Lewisª, and G. M. Wimp. 2020. Predator population size structure alters consumption of prey from epigeic and grazing foodwebs. Oecologia 192: 791-799.
Wimp, G. M., D. Lewisª and S. M. Murphy. 2019. Impacts of nutrient subsidies on salt marsh arthropod food webs: a latitudinal survey. Frontiers in Ecology and Evolution 7:350.
Wimp, G. M., S. M. Murphy, D. Lewis, M. R. Douglas*, R. Ambikapathi**, L’A. Van-Tull**, C. Gratton and R. F. Denno. 2013. Predator hunting mode influences patterns of prey use from grazing and epigeic food webs. Oecologia 171: 505-515.
Murphy, S. M., G. M. Wimp, D. Lewis and R. F. Denno. 2012. Nutrient presses and pulses differentially impact plants, herbivores, detritivores and their natural enemies. PLoS One 7(8): e43929.
Wimp, G. M., S. M. Murphy, Finke, D. L., A. F. Huberty and R. F. Denno. 2010. Increased primary production shifts the structure and composition of a terrestrial arthropod community. Ecology 91(11): 3303-3311.
Natural wetlands are increasingly threatened by nutrient pollution. We are studying the contrasting effects of a short-term increase in nutrient availability (pulse) versus a long-term increase in nutrients (press) on the productivity of the dominant cordgrass, Spartina alterniflora, and the extended consequences for species interactions and food-web structure (Murphy et al. 2012). Conservation of coastal wetlands, particularly salt marshes, is a major concern because they play a critical role in the ecology and geology of wave-protected shorelines and are the nursery grounds for commercial fish and shellfish. The treatments that we have imposed are specifically designed to mimic nutrient-runoff from agricultural fields and golf courses in order to understand how variable nutrient regimes influence community structure over time. Remarkably, the effects of contrasting nutrient-input regimes on food-web structure in native habitats remain poorly understood in terrestrial systems, despite the increasing fraction of landscapes affected by nutrient runoff from agriculture and development. We have found that nutrient enrichment and increasing primary production have significant effects on arthropod species composition, particularly higher trophic levels (Wimp et al. 2010).
We are also investigating how generalist predators change their feeding habits seasonally based on prey availability. We found that spider hunting mode (web-building vs. hunting) influences the extent to which spider species use prey from grazing and epigeic (soil surface detritus/microbe/algae consumers) food webs (Wimp et al. 2013). Furthermore, we found that for hunting spiders, ontogenetic changes in body size affects whether they primarily feed on the grazing or epigeic food web (Murphy et al., 2020). Our results have important implications for how the strength of top-down trophic cascades may vary temporally and we are just beginning to test how these effects may interact with nutrient enrichment.
Relevant Publications
Rippel, T. M.*, A. L. DeCandia, J. Tomasula*, C. L. McIntosh, S. M. Murphy, and G. M. Wimp. 2023. Detritivores and exogenous nitrogen influence litter microbial communities in coastal salt marshes. Marine Ecology Progress Series 716: 17-29.
Tomasula, J.*, B. Maguire**, T. M. Rippel*, E. Lopez, S. Perez, A. Arab, S. M. Murphy, and G. M. Wimp. 2023. Conditions for collapse: chronic nutrient enrichment increases native insect density linked to salt marsh dieback. Biological Conservation 278: 109882.
Rippel, T. M.*, J. Tomasula*, B. Maguire**, S. M. Murphy, and G. M. Wimp. 2022. Dominant detritivores mediate the impact of nitrogen on litter decomposition in salt marshes. Oecologia 200: 479-490.
Rippel, T. M., J. Tomasula, S. M. Murphy# and G. M. Wimp#. 2021. Global change in marine coastal habitats impacts insect populations and communities. Current Opinion in Insect Science 47:1-6.
Wimp, G. M., D. Lewis¶ and S. M. Murphy. 2021. Prey identity but not prey quality affects spider performance. Current Research in Insect Science 1: 100013.
Wimp, G. M. and S. M. Murphy. 2021. Disentangling the effects of primary productivity and host plant traits on arthropod communities. Functional Ecology 35(3): 564-565.
Murphy, S. M., D. Lewisª, and G. M. Wimp. 2020. Predator population size structure alters consumption of prey from epigeic and grazing foodwebs. Oecologia 192: 791-799.
Wimp, G. M., D. Lewisª and S. M. Murphy. 2019. Impacts of nutrient subsidies on salt marsh arthropod food webs: a latitudinal survey. Frontiers in Ecology and Evolution 7:350.
Wimp, G. M., S. M. Murphy, D. Lewis, M. R. Douglas*, R. Ambikapathi**, L’A. Van-Tull**, C. Gratton and R. F. Denno. 2013. Predator hunting mode influences patterns of prey use from grazing and epigeic food webs. Oecologia 171: 505-515.
Murphy, S. M., G. M. Wimp, D. Lewis and R. F. Denno. 2012. Nutrient presses and pulses differentially impact plants, herbivores, detritivores and their natural enemies. PLoS One 7(8): e43929.
Wimp, G. M., S. M. Murphy, Finke, D. L., A. F. Huberty and R. F. Denno. 2010. Increased primary production shifts the structure and composition of a terrestrial arthropod community. Ecology 91(11): 3303-3311.