1. 1. Mechanisms important to community structure under different ecological and spatial scales in estuarine and rocky intertidal communities.

  1. 2.Invasion, modification, and restoration dynamics of invasive dune and estuarine grasses.

Our work involves using observational and experimental methods to explore the relative importance of local versus regional effects on community structure and function in estuaries and rocky intertidal communities. We are using observations and experiments at sites across the latitudinal range from Washington to Oregon to northern California to understand how variable nutrients and phytoplankton productivity produced by ocean upwelling influence the interactions among dominant community members in both estuaries and rocky intertidal communities.

Here are some selected references for our recent work:

Hessing-Lewis, M.L., S.D. Hacker. 2013. Latitudinal trends in macroalgal blooms and seagrass production in northeast Pacific upwelling-influenced estuaries. Limnology and Oceanography 58: 1103–1112.

Gouhier, T. C., B. A. Menge, S.D. Hacker. 2011. Recruitment facilitation can promote coexistence and buffer population growth in metacommunities. Ecology Letters 14: 1201–1210.

Menge, B.A., S.D. Hacker, T. Freidenburg, J. Lubchenco, R. Craig, G. Rilov, M. Noble, E. Richmond. 2011. Potential impact of climate-related changes is buffered by differential responses to recruitment and interactions. Ecological Monographs 81:493–509.

Moulton O.M., S.D. Hacker. 2011. Congeneric variation in surfgrasses and ocean conditions influence macroinvertebrate community structure. Marine Ecology Progress Series 433:53-63.

Our work also involves exploring how non-native species invade and modify their environment, and the mechanisms involved in restoration, under different contexts or gradients in physical conditions. In particular, we are studying dune grass invasions in Oregon and Washington to understand the mechanisms  involved in creating foredunes, how these modifications affect species diversity and rare endangered species, and  the potential for coastal protection against storms and tsunamis. Two separate congeners (Ammophila arenaria and A. breviligulata)  are simultaneously invading sandy beaches but they appear to have different effects on foredune morphology and species diversity (click here for a dune plant identification guide). For example, Ammophila has been implicated in the decline of a number of endangered plants and the federally listed Snowy plover. We are using observations, experiments, and modeling to understand how the three grass species and sand supply shape foredune morphology and ecology.

Here are some selected references for our recent work:

Zarnetske, P., T. Gouhier, S.D. Hacker, E. Seabloom, V. Bokil. 2013. Indirect effects and facilitation among native and non-native species promote invasion success along an environmental stress gradient. Journal of Ecology doi: 10.1111/1365-2745.12093.

Seabloom, E.W., P. Ruggiero, S.D. Hacker, J. Mull, P.L. Zarnetske. 2013. Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems. Global Change Biology 19:824-832.

Hacker S.D., P. Zarnetske, E. Seabloom, P. Ruggiero, J. Mull, S. Gerrity, C. Jones. 2012. Subtle differences in two non-native congeneric beach grasses significantly affect their colonization, spread, and impact. Oikos 121:138–148.

Zarnetske, P., S.D. Hacker, E.W. Seabloom, P. Ruggiero, J.R. Killian, T.B. Maddux, D. Cox. 2012. Biophysical feedback mediates effects of invasive grasses on coastal dune shape. Ecology 93:1439-1450.

Zarnetske P.L., E.W. Seabloom, S.D. Hacker. 2010. Non-target effects of invasive species management: Beach grass, birds, and bulldozers in coastal dunes. Ecosphere 1: 13.

We have also studied the invasion of estuarine grass, Spartina anglica in Washington. Through a series of experiments, our work has produced results that inform general theories on the ecology of invasions. In particular, we found that invasion, removal, and restoration of these estuarine grasses and the habitats the engineer are highly context dependent. These results have led us to explore in more detail the ecological consequences of removing invaders; we predict that the legacy effects of highly modifying invaders can produce widely varying and alternative restoration outcomes.

Here are some selected references for our recent work:

Hacker S.D., M.N. Dethier. 2009. Differing consequences of removing ecosystem–modifying invaders: significance of impact and community context to restoration potential. Pages 375–385 in: Marine Bioinvasions: Ecology, Conservation and Management Perspectives, Editors: Gil Rilov and Jeffrey Crooks, Springer-Verlag.

Hacker S.D., M.N. Dethier. 2006. Community modification by a grass invader has differing impacts for marine habitats. Oikos 113: 279-286.

Dethier M.N., S.D. Hacker. 2005. Physical factors vs. biotic resistance in controlling the invasion of an estuarine marsh grass. Ecological Applications. 15:1273-1283.

Hacker S.D., D. Heimer, C.E. Hellquist, T.G. Reeder, B. Reeves, T. Riordan, M.N. Dethier. 2001. A marine plant (Spartina anglica) invades widely varying habitats: potential mechanisms of invasion and control. Biological Invasions 3: 211-217.

Finally, we have been studying how disturbance influences the invasive eelgrass, Zostera japonica, in estuaries in Oregon and Washington.

Here are some selected references for our recent work:

Henderson, J. 2013. Direct effects and tradeoffs affect vegetative growth and sexual reproduction in an invasive seagrass experiencing different disturbance regimes. MS Thesis, Oregon State University.

Ruesink J.L., J. Fitzpatrick, B.R., Dumbauld, S.D. Hacker, A.C. Trimble, E.L. Wagner, L.M. Wisehart. 2012. Life history and morphological shifts in an intertidal seagrass following multiple disturbances. Journal of Experimental Marine Biology and Ecology 424-425:25-31.

Ruesink J.L., J-S. Hong, L. Wisehart, S.D. Hacker, B.R. Dumbauld, A.C. Trimble, M. Hessing-Lewis. 2010. Congener comparison of native (Zostera marina) and introduced (Z. japonica) eelgrass at multiple scales within a Pacific Northwest estuary. Biological Invasions 12: 1773–1789.

  1. 3.The protective role of ecosystems in mitigating coastal vulnerability from climate change.

The beach grass project outlined above was the first to explicitly measure the interaction between beach grass invasions and coastal geomorphology on the Pacific coast to determine the role of vegetation in delivering important ecosystem services, including coastal protection and conservation management. The project also included exposure analyses to determine the role of vegetation in creating barriers to extreme waves and sea level rise, both today and under future climate change scenarios. Our work has been inspired by a collaborative project at the National Center for Ecological Analysis and Synthesis that considered the ecosystem services of coastal interface habitats (including dune vegetation) and their usefulness in coastal management. One paper, Barbier et al. (2011), has been ranked first of the top ten publications on marine ecosystem services by a global survey of marine academics and professionals.

Here are some selected references for our recent work:

Seabloom, E.W., P. Ruggiero, S.D. Hacker, J. Mull, P.L. Zarnetske. 2013. Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems. Global Change Biology 19:824-832.

Barbier E., S.D. Hacker, C. Kennedy, E. Koch, B. Silliman, A.D. Stier. 2011. The value of estuarine and coastal ecosystem services. Ecological Monographs 81:169-193.

Granek E., Polasky, S., Barbier, C. Kappel, D. Stoms, D.J. Reed, J. Primavera, E.W. Koch, C. Kennedy, L.A. Cramer, S.D. Hacker, G.M.E. Perillo, S. Aswani, B. Silliman, E. Barbier, E. Wolanski, D. Bael. 2010. Ecosystem services as a common language for coastal ecosystem-based management. Conservation Biology 24: 207-216.

Koch E.W., E.B. Barbier, B. Silliman, G.M.E. Perillo, D.J. Reed, S.D. Hacker, E. Wolanski, J. Primavera, E. Granek, S. Polasky, S. Aswani, L.A. Cramer, D. Stoms, C. Kennedy, D. Bael, C. Kappel. 2009. Nonlinearity in ecosystem services: temporal and spatial variability in coastal protection. Frontiers in Ecology and the Environment 7:29–37.

Barbier E.B., E.W. Koch, B. Silliman, S.D. Hacker, E. Wolanski, J. Primavera, E. Granek, S. Polasky, S. Aswani, L.A. Cramer, D. Stoms, C. Kennedy, D. Bael, C. Kappel, G.M.E. Perillo, D.J. Reed. 2008. Coastal ecosystem-based management with non-linear ecological functions and values. Science 319: 321-323.