Loss of seagrass ecosystems is accelerating globally, making large-scale restoration efforts more important than ever. Successful restoration and the return of ecosystem services provided by these habitats give reasons to be optimistic. Our research focuses on the largest seagrass restoration in the world: a 36 km2 restoration of eelgrass (Zostera marina) in the Virginia Coast Reserve coastal bays. Long-term data collected over the last 20 years gives us a unique opportunity to study both the mechanisms and feedbacks of restoration and the resilience of seagrass meadows, especially to marine heatwaves that are increasingly in frequency and duration.
Positive feedbacks enhance ecosystem state change
• Trajectories of seagrass restoration are non-linear (McGlathery et al. 2012)
• A positive feedback of the seagrass canopy on sediment stabilization improves light availability and enhances habitat suitability for seagrass growth (Carr et al. 2010, 2012a,b, 2016; Hansen & Reidenbach 2012, 2013; Reidenbach & Timmerman 2019)
• Restoration by seeds promotes genetic diversity and population structure, especially where barriers to natural recruitment exist (Reynolds et al. 2012a,b, 2013)
Restoration reinstates ecosystem services
• Key ecosystem services are reinstated within a decade of restoration by seeding and are enhanced by genetic diversity (McGlathery et al. 2012, Reynolds et al. 2012, Orth et al. in review)
• Primary productivity measured by aquatic eddy covariance is enhanced 10-25 fold in seagrass meadows compared to unvegetated sediments (Hume et al. 2011, Rheuban et al. 2014a,b)
• Seagrass restoration reestablishes the coastal nitrogen filter through enhanced nitrogen burial (10x) and denitrification (4x) (Aoki & McGlathery 2017, 2018, Aoki et al. 2019)
• Carbon sequestration in plant biomass and burial in sediments at the meadow scale is on par with natural meadows (Greiner et al. 2013, Oreska et al. 2017a, Berger et al. 2020)
Resilience to ocean warming varies both spatially and temporally
• Seagrass meadows recovered in some regions within 3 years from a heatwave-induced die-off
• High temperatures caused a shift in trophic status from balanced to net heterotrophy during the die-off to net autotrophy as the meadow recovered (Berger et al. 2020)
• Water depth modulates rates of recovery following a marine heatwave (Aoki et al. 2020)
• Aquatic eddy covariance measurements suggest seagrass will not be ‘winners’ in more acidic warmer oceans (Berg et al. 2019)
Connectivity is central to carbon and sediment dynamics
• Up to half the carbon buried in seagrass sediments comes from adjacent ecosystems (Greiner et al. 2016, Oreska et al. 2017b)
• Seagrass meadows reduce sediment fluxes and wave energy at the salt marsh edge (Carr et al. 2018)
• Long-term aquatic eddy covariance measurements (11 years) suggest that carbon burial matches net external carbon inputs to the seagrass meadow (Berger et al. 2020)
Oreska, M.P.J., K.J. McGlathery, L. Aoki, P. Berg, A. Berger. 2020. Net greenhouse gas benefits of the Virginia eelgrass (Zostera marina) restoration: a seagrass blue carbon case study. Nature Scientific Reports. https://doi.org/10.1038/s41598-020-64094-1
Berger, A., P. Berg, K. McGlathery, M.L. Delgard. 2020. Long-term trends in seagrass metabolism measured by eddy covariance. Limnology and Oceanography. doi: 10.1002/lno.11397 Aoki, L, K.J. McGlathery, P.L. Wiberg, and A. Al-Haj. 2020. Depth affects seagrass resilience to a marine heat-wave. Estuaries and Coasts. https://doi.org/10.1007/s12237-019-00685-0.
Aoki, L., K.J. McGlathery, and M.P.J. Oreska. 2019. Seagrass restoration reestablishes the coastal nitrogen filter. Limnology and Oceanography. DOI 10.1002/lno.11241
Berg, P., M. L. Delgard, M.L., P. Polsenaere, K.J. McGlathery, S.C. Doney, and A.C. Berger. 2019. Dynamics of benthic metabolism, O2, and pCO2 in a temperate seagrass meadow. Limnology and Oceanography. https://doi.org/10.1002/lno.11236.
Oreska, M. P. J., K. J. McGlathery, R. J. Orth, and D. J. Wilcox. 2019. Seagrass mapping: A survey of recent seagrass distribution literature. In: L. Windham-Myers, S. Crooks, and T. Troxler (eds.). A Blue Carbon Primer: The State of Coastal Wetland Carbon Science, Policy, and Practice. CRC Press, Boca Raton, FL.
Reidenbach, M.A. and R. Timmerman. 2019. Interactive effects of seagrass and the microphytobenthos on sediment suspension within shallow coastal bays. Estuaries and Coasts. https://doi.org/10.1007/s12237-019-00627-w
Carr, J., G. Mariotti, S. Fagherazzi, K. McGlathery, and P. Wiberg. 2018. Exploring the impacts of seagrass on coupled marsh-tidal flat morphodynamics. Frontiers in Environmental Science, 03 September 2018 | https://doi.org/10.3389/fenvs.2018.00092
Aoki, L., and K. J. McGlathery. 2018. Restoration enhances denitrification and DNRA in subsurface sediments of Zostera marina seagrass meadows. Marine Ecology Progress Series. Vol. 602: 87–102. https://doi.org/10.3354/meps12678
Aoki, L., and K.J. McGlathery. 2017. Push-pull incubation method reveals the importance of denitrification and DNRA in seagrass root zone. Limnology and Oceanography Methods. DOI 10.1002/lom3.10197
Oreska, M.P.J., K.J. McGlathery, J.H. Porter, M. Bost, and B.A. McKee. 2017a. Seagrass blue carbon accumulation at the meadow-scale. PLOS ONE. DOI 10.1371/journal.pone.0176630
Oreska, M. J. P., K. McGlathery, G. Wilkinson, M. Bost, and B. McKee. 2017b. Allochthonous carbon contributions to seagrass bed blue carbon. Limnology and Oceanography. DOI 10.1002/lno.10718
Reynolds, P., J. Stachowicz, K. Hovel, C. Bostrom, K. Boyer, M. Cusson, J. Eklof, F. Engel, A. Engelen, B. Ericksson, J. Fodrie, J. Griffin, P. Jorgensen, C. Hereu, M. Hori, T. Hanley, M. Ivanov, C. Kruschel, K.-S. Lee, K. McGlathery, P. O. Moksnes, M. Nakoaka, F. Nash, M. O’Connor, N. O’Connor, R. Orth, F. Rossi, J. Reusink, E. Sotka, R. Unsworth, M. Whalen, and J. E. Duffy. 2017. Latitude, temperature regime and habitat complexity predict predation pressure in eelgrass across the Northern Hemisphere. Ecology. DOI 10.1002/ecy.2064
Reynolds, L.K., M. Waycott, K. J. McGlathery, R.J. Orth. 2016. Ecosystem services returned through restoration. Restoration Ecology. DOI: 10.1111/rec.12360
Carr, J. A., P. D’Odorico, K. J. McGlathery and P. L. Wiberg. 2016. Spatially explicit feedbacks between seagrass meadows, sediment and light: habitat suitability for seagrass growth. Advances in Water Research.doi:10.1016/j.advwatres.2015.09.001.
Rheuban, J. E., P. Berg, and K. J. McGlathery. 2014a. Seasonal oxygen metabolism in restored Zostera marina meadows measured by eddy correlation. Marine Ecology Progress Series 507: 1-13. doi: 10.3354/meps10843.
Rheuban, J. E., P. Berg, and K. J. McGlathery. 2014b. Ecosystem metabolism along a colonization gradient of eelgrass (Zostera marina L.) measured by eddy correlation. Limnology and Oceanography. 59(4): 1376-1387. doi: 10.4319/lo.2014.59.4.1376
Reynolds, L. K., M. Waycott, and K. J. McGlathery. 2013.Restoration recovers population structure and landscape genetic connectivity in a dispersal-limited ecosystem. Journal of Ecology 101: 1288-1297, doi: 10.1111/1365-2745.12116.
Greiner, J. T., K. J. McGlathery, J. Gunnell, and B. A. McKee. 2013. Seagrass restoration enhances “blue carbon” sequestration in coastal waters. PLoS ONE 8(8): e72469. doi:10.1371/journal.pone.0072469
Hansen, J.C.R. and M.A. Reidenbach. 2013. Seasonal growth and senescence of a Zostera marina seagrass meadow alters wave-dominated flow and sediment suspension within a coastal bay. Estuaries and Coasts., 36, 1099–1114
Cole, L. W. and K. J. McGlathery. 2012. Dinitrogen fluxes from restored seagrass meadows. Marine Ecology Progress Series 448: 235-246.
Carr, J., P. D’Odorico, K. J. McGlathery, and P. L. Wiberg. 2012a. Modeling the effects of climate change on seagrass, the stability and bistability of seagrass meadows. Marine Ecology Progress Series 448: 289-301.
Carr, J. A., P. D’Odorico, K. J. McGlathery, and P. L. Wiberg. 2012b. Stability and resilience of seagrass meadows to seasonal and interannual dynamics and environmental stress. Journal of Geophysical Research VOL. 117, G01007, DOI:10.1029/2011JG001744
McGlathery, K. J., L. Reynolds, L. W. Cole, R. J. Orth, and A. Schwarzchild. 2012. Recovery trajectories during state change from bare sediment to eelgrass dominance. Marine Ecology Progress Series 448: 290-221.
Reynolds L., M. Waycott, K. J. McGlathery, R. J. Orth, and J. C. Zieman. 2012. Eelgrass restoration by seed maintains genetic diversity: case study from a coastal bay system. Marine Ecology Progress Series 448: 223-233.
Reynolds, L.K., K.J. McGlathery, and M. Waycott. 2012. Genetic diversity enhances restoration success by augmenting ecosystem services. PLoS ONE 7(6): e38397. doi:10.1371/journal.pone.0038397.
Lawson, S. E., K. J. McGlathery, and P. L. Wiberg. 2012. Enhancement of sediment suspension and nutrient flux by benthic macrophytes at low biomass. Marine Ecology Progress Series 448: 259-270.
Hansen, J.C.R. and M.A. Reidenbach. 2012. Wave and tidally driven flows within Zostera marina seagrass beds and their impact on sediment suspension. Marine Ecology Progress Series, 448, 271–287.
Hume, A., P. Berg, and K. J. McGlathery. 2011. Dissolved oxygen fluxes and ecosystem metabolism in an eelgrass (Zostera marina) meadow measured with the eddy correlation technique. Limnology & Oceanography 56: 86-96.
Carr, J., P. D’Odorico, K. J. McGlathery, and P. Wiberg. 2010. Stability and bistability of seagrass ecosystems in shallow coastal lagoons: Role of feedbacks with sediment suspension and light availability. Journal of Geophysical Research – Biogeosciences, Vol 115, G03011, doi:10.1029/2009JG001103.