John Lehrter, Ph.D.

Bio

Dr. John Lehrter is an Associate Professor in the Department of Marine Sciences at the University of South Alabama and a Senior Marine Scientist at the Dauphin Island Sea Lab. Prior to joining the faculty at USA and DISL in August 2016, Dr. Lehrter was a Research Ecologist with the EPA Office of Research and Development. His research focuses on understanding the biogeochemical cycling of nutrients, organic matter, and oxygen in coastal systems and how these cycles are related to water quality issues such as eutrophication, hypoxia, coastal acidification, and water clarity.

The research is largely aimed at solving complex coastal resource management issues through applications of field and lab studies, satellite oceanography, and numerical ecosystem modeling.

Dr. Lehrter has served on local and national science committees and has won numerous awards for applying science to decision-making activities. He received his Ph.D. in Biology from the University of Alabama and post-doctoral training at the EPA Gulf Ecology Division.

Research Interest

My research focuses on eutrophication, hypoxia, and the biogeochemical cycling of carbon, oxygen, and nutrients in aquatic and marine ecosystems. Specifically, I aim to understand these processes in the context of anthropogenic changes occurring at local, regional, and global scales.

For a complete list publications, please visit Lehrter's Google Scholar site.

Multiple Stressor Impacts to Coastal Ecosystems

Estuaries and coastal ecosystems located at the land-sea interface are among the most highly productive systems on Earth and due their proximity to land are also among the most susceptible to human activities. Therefore, the impacts to these systems are of great societal concern.  Work in our lab focuses on land-use change, nutrient pollution, eutrophication, and hypoxia as primary stressors.  We have hypothesized that these stressors along with a myriad of other stressors such as, ocean acidification, increasing sea surface temperatures, alterations in watershed hydrology, and harvesting of natural resources have combined to impact habitats and their supported flora and fauna.  Our research aims to disentangle and quantify how these stressors manifest both individually and cumulatively in coastal systems, and to predict how the systems may change following management or restoration activities.

Selected publications: 

Le C, Lehrter JC, Schaeffer B, Hu C, MacIntyre H, Hagy JD, Beddick DL. 2015. Relation between inherent optical properties and land use and land cover across Gulf Coast estuaries. Limnology and Oceanography 60:920-933.

Cai W-J,  Hu X, Huang W-J, Murrell MC, Lehrter JC, Lohrenz SE, Chou W-C, Zhai W, Hollibaugh JT, Wang Y, Zhao P, Guo X,  Gunderson K, Dai M, Gong G-C. 2011. Acidification of subsurface coastal waters enhanced by eutrophication. Nature Geoscience 4:766-770.

Oliver LM, Lehrter JC, Fisher WS. 2011. Relating landscape development intensity to coral reef condition in the watersheds of St. Croix, US Virgin Islands. Marine Ecology Progress Series 427:293-302.

Lehrter JC. 2008. Regulation of eutrophication susceptibility in oligohaline regions of a northern Gulf of Mexico estuary, Mobile Bay, Alabama. Marine Pollution Bulletin 56:1446-1460.

Coastal Biogeochemistry and Modeling

To understand coastal ecosystems, it is necessary to quantify the budgets, i.e. the stocks and rates of change, of important elements such as carbon, oxygen, nitrogen, and phosphorus. Our observational studies seek to quantify and predict how these material budgets are impacted by anthropogenic stressors such as land-use change, increased nutrient loading, and climate change. Often, though, it is not possible to isolate how individual or cumulative stress affects an ecosystem through observation alone.  In such cases, we employ numerical ecosystem models to tease apart the complexity that cannot be observed directly. Ecosystem models are also useful for data synthesis and identification of knowledge gaps in our understanding of specific processes, which can lead to new hypotheses about how marine systems are organized and operate. We have developed and applied models ranging from coastal watershed hydrologic and nutrient exports models to coastal three-dimensional hydrodynamic and biogeochemical models to understand and predict how local and global anthropogenic perturbations impact coastal systems. Our present work includes testing and inter-comparison of hypoxia models and development of new biogeochemical models to incorporate current scientific understanding of underlying processes such as controls on phytoplankton community dynamics and the fate of their produced organic matter in the water-column and benthos.

Selected publications:

Lehrter JC, Ko DS, Lowe L, Penta B. Predicted effects of climate change on northern Gulf of Mexico hypoxia. In: Justic D, Rose KA, Hetland RD, Fennel K (eds.). Modeling Coastal Hypoxia: Numerical simulations of Patterns, Controls, and Effect of Dissolved Oxygen Dynamics. Springer, New York (Accepted).

Lehrter JC, Ko DS, Murrell MC, Hagy JD, Schaeffer BA, Greene RM, Gould RW, and Penta B. 2013. Nutrient distributions, transport pathways, and fate on the inner margin of a river-dominated continental shelf. Journal of Geophysical Research: Oceans 118:1-17.

Lehrter JC, Beddick DL, Jr., Devereux R., Yates DF, Murrell MC. 2012. Sediment-water fluxes of dissolved inorganic carbon, O2, nutrients, and N2 from the hypoxic region of the Louisiana continental shelf. Biogeochemistry 109:233-252.

Lehrter JC, Cebrian J. 2010. Uncertainty propagation in an ecosystem nutrient budget. Ecological Applications 20:508-524.

Ocean Color Remote Sensing

There has been a revolution over the past decade in the use of satellite ocean color data to better understand spatial and temporal dynamics of marine systems.  Current satellites provide global, spatially synoptic, coastal data on a daily frequency. Our work revolves around developing new algorithms to retrieve water quality data from satellites in optically complex coastal systems and in the application of these data to develop water quality time-series that can be analyzed to determine the main factors, human vs natural, that drive variability in water quality. 

Selected publications:

Le C, Lehrter JC, Schaeffer BA, Hu C, Murrell MC, Hagy JD, Greene RM, Beck M. 2016. Bio-optical water quality dynamics observed from MERIS in Pensacola Bay, Florida. Estuarine, Coastal and Shelf Science, doi: 10.1016/j.ecss.2016.02.003.

Le C, Lehrter JC, Hu C, Obenour D. 2016. Satellite-based empirical models linking river plume dynamics with hypoxic area and volume. Geophysical Research Letters, doi: 10.1002/2015GL067521.

Barnes BB, Hu C, Schaeffer BA, Lee Z, Palandro DA, Lehrter JC. 2013. MODIS-derived spatiotemporal water clarity patterns in optically shallow Florida Keys water: A new approach to remove bottom contamination. Remote Sensing of Environment 134:377-391.

Schaeffer BA, Hagy JD, Conmy RN, Lehrter JC, Stumpf R. 2012. An approach for developing nutrient-related numeric water quality criteria for coastal waters using SeaWiFS satellite remote sensing data. Environmental Science and Technology 46:916-922.

Projects

Publications

• 2021

  Coogan*, J., B. Dzwonkowski, J. Lehrter, K. Park and R. Collini. Observations of dissolved oxygen and physical drivers in a shallow highly stratified estuary, Estuarine, Coastal and Shelf Science. Estuarine, Coastal and Shelf Science. doi.org/10.1016/j.ecss.2021.107482.

• 2020

  Pauer, J.J., W. Melendez, T.J. Feist, J.C. Lehrter, B. Rashleigh, L.L. Lowe, and R.M. Greene. The impact of alternative nutrient kinetics and computational grid size on model predicted primary production and hypoxic area in the northern Gulf of Mexico. Environmental Modelling & Software. 126(104661. doi.org/10.1016/j.envsoft.2020.104661.

• Jarvis, B.M., J.C. Lehrter, L. Lowe, J.D. Hagy, Y. Wan, M.C. Murrell, D.S. Ko, B. Penta, and R.W. Gould. Modeling Spatiotemporal Patterns of Ecosystem Metabolism and Organic Carbon Dynamics Affecting Hypoxia on the Louisiana Continental Shelf. Journal of Geophysical Research: Oceans. 125(e2019JC015630). doi.org/10.1029/2019JC015630.

• 2019

  Le, C., Y. Gao, W-J. Cai, J. Lehrter, Y. Bai, and Z-P. Jiang. Estimating summer sea surface pCO2 on a river-dominated continental shelf using a satellite-based semi-mechanistic model. Remote Sensing of Environment, 225, 115-126.

• Alvaro, L., J. Lehrter, and M. Fung . Spatial patterns of particulate organic carbon concentrations and isotopic signatures across a salinity gradient in a river dominated estuary. Gulf and Caribbean Research. (in press).

• Jiang, Z-P., W-J. Cai, J. Lehrter, B. Chen, Z. Ouyang, C. Le, B. Roberts, N. Hussain, M. Scaboo, J. Zhang, and Y. Xu. Spring net community production and its coupling with the CO2 dynamics in the surface water of the northern Gulf of Mexico. Biogeosciences. 16, 3507-3525.

• Devereux, R., J. Lehrter, G. Cicchetti, D. L. B. Beddick Jr, D. F. Yates, B.M. Jarvis, J. Aukamp, and M. Hoglund. Spatially variable bioturbation and physical mixing drive the sedimentary biogeochemical seascape in the Louisiana continental shelf hypoxic zone. Biogeochemistry, 143, 151-169.

• Coogan, J., B. Dzwonkowski, and J. Lehrter. Effects of coastal upwelling and downwelling on hydrographic variability and dissolved oxygen in Mobile Bay. Journal of Geophysical Research, 124(2), 791-806. doi.org/10.1029/2018JC014592

• 2018

  Laurent, A., K. Fennel, D.S. Ko, and J. Lehrter. Climate Change Projected to Exacerbate Impacts of Coastal Eutrophication in the Northern Gulf of Mexico Journal of Geophysical Research: Oceans 123 (5), 3408 -3426. doi.org/10.1002/2017JC013583.

• 2017.

  Lehrter, J.C., D. S. Ko, L. L. Lowe, and B. Penta. Predicted Effects of Climate Change on Northern Gulf of Mexico Hypoxia Modeling Coastal Hypoxia, Pages 173-214.

• Le, C., J. C. Lehrter, C. Hu, H. MacIntyre, and M. W. Beck. Satellite observation of particulate organic carbon dynamics on the Louisiana continental shelf. Journal of Geophysical Research: Oceans, Volume 122, Issue 1, Pages 555-569.

• Conmy, R.N., B. A. Schaeffer, J. Schubauer-Berigan, J. Aukamp, A. Duffy, J. C. Lehrter, and R.M. Greene. Characterizing light attenuation within Northwest Florida Estuaries: implications for RESTORE Act water quality monitoring. Marine Pollution Bulletin, Volume 114, Issue 2, Pages 995-1006.

• Chen, Y., J. Cebrian, J.Lehrter, B. Christiaen, J. Stutes, and J. Goff. Storms do not alter long-term watershed development influences on coastal water quality Marine Pollution Bulletin 122: 207-216

  

• 2016.

  Le, C., J. C. Lehrter, C. Hu, and D. R. Obenour.. Satellite‐based empirical models linking river plume dynamics with hypoxic area and volume. Geophysical Research Letters, Volume 43, Issue 6, Pages 2693-2699.

• Pauer, J.J., T. J. Feist, A. M. Anstead, P. A. DePetro, W. Melendez, J. C. Lehrter, M. C. Murrell, X. Zhang, and D. S. Ko. A modeling study examining the impact of nutrient boundaries on primary production on the Louisiana continental shelf. Ecological Modelling, Volume 328, Pages 136-147.

• Laurent, A., K. Fennel, R. Wilson, J.C. Lehrter, and R. Devereux.. Parameterization of biogeochemical sediment-water fluxes using in situ measurements and a diagenetic model. Biogeosciences. Volume 13, Issue 1, Pages 77.

• Ko, D.S., R. W. Gould, B. Penta, J. C. Lehrter. Impact of satellite remote sensing data on simulations of coastal circulation and hypoxia on the Louisiana Continental Shelf. Remote Sensing, Volume 8, Issue 5, Pages 435.

• Fennel, K., A. Laurent, R. Hetland, D. Justić, D. D. Ko, J. C. Lehrter, M. Murrell, L. Wang, L. Yu, and W. Zhang. Effects of model physics on hypoxia simulations for the northern Gulf of Mexico: A model intercomparison. Journal of Geophysical Research: Oceans, Volume 121, Issue 8, Pages 5731-5750.

• Le, C., J. C. Lehrter, B. A. Schaeffer, C. Hu, M. C. Murrell, J. D. Hagy, R. M. Greene, and M. Beck. Bio-optical water quality dynamics observed from MERIS in Pensacola Bay, Florida. Estuarine, Coastal and Shelf Science, Volume 173, Pages 26-38.

• Feist, T. J., J. J. Pauer, W. Melendez, J. C. Lehrter, P. A. DePetro, K. R. Rygwelski, D. S. Ko, and R. G. Kreis, Jr. Modeling the relative importance of nutrient and carbon loads, boundary fluxes, and sediment fluxes on Gulf of Mexico hypoxia. Environmental science & technology. Volume 50, Issue 16. Pages 8713-8721.

• Christiaen, B., J. Lehrter, J. Goff, J. Cebrian. Functional implications of changes in seagrass species composition in two shallow coastal lagoons. Mar Ecol Prog Ser Vol. 557: 111-121

  

• 2015

  Le, C., J. C. Lehrter, C. Hu, B. Schaeffer, H. MacIntyre, J. D. Hagy, and D. L. Beddick. Relation between inherent optical properties and land use and land cover across Gulf Coast estuaries. Limnology and Oceanography, Volume 60, Issue 3, Pages 920-933.

• Fry, B., D. Justić, P. Riekenberg, E. M. Swenson, R. E. Turner, L. Wang, L. Pride, N. N. Rabalais, J. C. Kurtz, J. C. Lehrter, M. C. Murrell, E. H. Shadwick, and B. Boyd. Carbon dynamics on the Louisiana continental shelf and cross-shelf feeding of hypoxia. Estuaries and coasts, Volume 38, Issue 3, Pages 703-721.

• Devereux, R., J. C. Lehrter, D. L. Beddick, D. F. Yates, and B. M. Jarvis. Manganese, iron, and sulfur cycling in Louisiana continental shelf sediments. Continental Shelf Research, Volume 99, Pages 46-56.

• Yu, L., K. Fennel, A. Laurent, M. C. Murrell, and J. C. Lehrter. Numerical analysis of the primary processes controlling oxygen dynamics on the Louisiana shelf. Biogeosciences, 12, 2063-2076.

• Grigas, D., J. Lehrter, J. Cebrian, Y. Chen, B. Ehmen & M. Woodrey.. Effects of Stormwater Pipe Size and Rainfall on Sediment and Nutrients Delivered to a Coastal Bayou. Water Environment Research 87: 796-804

  

• 2014.

  Le, C., J. C. Lehrter, C. Hu, M. C. Murrell, and L. Qi. Spatiotemporal chlorophyll‐a dynamics on the Louisiana continental shelf derived from a dual satellite imagery algorithm. Journal of Geophysical Research: Oceans, Volume 119, Issue 11, Pages 7449-7462.

• Lehrter, J.C., B. Fry, and M. C. Murrell. Microphytobenthos production potential and contribution to bottom layer oxygen dynamics on the inner Louisiana continental shelf. Bulletin of Marine Science, Volume 90, Issue 3, Pages 765-780.

• Hill, B.H., C. M. Elonen, L. E. Anderson, and J. C. Lehrter. Microbial respiration and ecoenzyme activity in sediments from the Gulf of Mexico hypoxic zone. Aquatic Microbial Ecology, Volume 72, Issue 2, Pages 105-116.

• Barnes, B. B., C. Hu, J. P. Cannizzaro, S. E. Craig, P. Hallock, D. L. Jones, J. C. Lehrter, N. Melo, B. A. Schaeffer, and R. Zepp. Estimation of diffuse attenuation of ultraviolet light in optically shallow Florida Keys waters from MODIS measurements. Remote Sensing of Environment, Volume 140, Pages 519-532.

• Pauer, J.J., P. A. DePetro, A. M. Anstead, and J.C. Lehrter.. Application of a one-dimensional model to explore the drivers and lability of carbon in the northern Gulf of Mexico. Ecological Modelling, Volume 294, Pages 59-70.

• 2013

  Barnes, B.B., C. Hu, B.A. Schaeffer, Z. Lee, D.A. Palandro, and J.C. Lehrter. MODIS-derived spatiotemporal water clarity patterns in optically shallow Florida Keys waters: A new approach to remove bottom contamination. Remote Sensing of Environment, Volume 134, Pages 377-391.

• Murrell, M.C., R. S. Stanley, J. C. Lehrter, and J. D. Hagy. Plankton community respiration, net ecosystem metabolism, and oxygen dynamics on the Louisiana continental shelf: Implications for hypoxia. Continental Shelf Research, Volume 52, Pages 27-38.

• Genthner, F.J., D.T. Marcovich, and J. C. Lehrter.. Estimating Rates of Denitrification Enzyme Activity in Wetland Soils with Direct Simultaneous Quantification of Nitrogen and Nitrous Oxide by Membrane Inlet Mass Spectrometry. Microbial & Biochemical Technology, Volume 5, Issue 4, Pages 95-101.

• Lehrter, J. C., D. S. Ko, M. C. Murrell, J. D. Hagy, B. A. Schaeffer, R. M. Greene, R. W. Gould, and B. Penta. Nutrient distributions, transports, and budgets on the inner margin of a river‐dominated continental shelf. Journal of Geophysical Research: Oceans, Volume 118, Issue 10, Pages 4822–4838.

• Pauer, J.J., T.J. Feist, W. Melendez, X. Zhang, and J.C. Lehrter. Stormwater Runoff Loadings To Coastal Bayous Under A Gradient Of Watershed Urbanization, North Central Gulf of Mexico. World Environmental and Water Resources Congress 2013: Showcasing the Future, Pages 350-366.

• Grigas, D., J. Cebrian, B. Ehmen, M. Woodrey, T. Strange, W. Underwood, J. Lehrter and Y. Chen. Stormwater runoff loadings to coastal bayous under a gradient of watershed urbanization, North Central Gulf of Mexico. Proceedings of the World Environmental and Water Resources Congress 2013: 350 -366.

  

• 2012

  Lehrter, J.C., D.L. Beddick, R. Devereux, D. F. Yates, and M.C. Murrell. Sediment-water fluxes of dissolved inorganic carbon, O2, nutrients, and N2 from the hypoxic region of the Louisiana continental shelf. Biogeochemistry, Volume 109, Issue 1–3, pp 233–252.

• Schaeffer, B.A., J. D. Hagy, R.N. Conmy, J.C. Lehrter, and R.P. Stumpf.. An approach to developing numeric water quality criteria for coastal waters using the SeaWiFS satellite data record. Environmental Science & Technology, 46 (2), pp 916–922.

• 2011

  Murrell, M.C. and J.C. Lehrter.. Sediment and lower water column oxygen consumption in the seasonally hypoxic region of the Louisiana continental shelf. Estuaries and Coasts, Volume 34, Issue 5, pp 912–924.

• Schaeffer, B.A., G. A. Sinclair, J. C. Lehrter, M. C. Murrell, J. C. Kurtz, R. W. Gould, and D. F. Yates. An analysis of diffuse light attenuation in the northern Gulf of Mexico hypoxic zone using the SeaWiFS satellite data record. Remote Sensing of Environment, Volume 115, Issue 12, Pages 3748-3757.

• Cai, W.J., X. Hu, W. J. Huang, M. C. Murrell, J. C. Lehrter, S. E. Lohrenz, W. C. Chou, W. Zhai, J. T. Hollibaugh, Y. Wang, P. Zhao, X. Guo, K. Gundersen, M. Dai, and G. C. Gong.. Acidification of subsurface coastal waters enhanced by eutrophication. Nature Geoscience 4, 766-770.

• Oliver, L.M., J. C. Lehrter, and W.S. Fisher. Relating landscape development intensity to coral reef condition in the watersheds of St. Croix, US Virgin Islands. Marine Ecology Progress Series, Vol. 427, pp. 293-302.

• 2010

  Lehrter, J. C. and J. Cebrian.. Uncertainty propagation in an ecosystem nutrient budget. Ecological Applications 20: 508 -524

  

• 2009

  Greene, R.M., J. C. Lehrter, and D. H. James III.. Multiple regression models for hindcasting and forecasting midsummer hypoxia in the Gulf of Mexico. Ecological Applications, Vol. 19 Issue 5, Pages 1079–1375.

• Lehrter, J.C., M. C. Murrell, and J.C. Kurtz. Interactions between Mississippi River inputs, light, and phytoplankton biomass and phytoplankton production on the Louisiana continental shelf. Continental Shelf Research, Volume 29, Pages 1861-1872.

• Penta B., D. Ko, R. Gould, R. Arnone, R. Greene, J. C. Lehrter, J. Hagy, B. Schaeffer, M. Murrell, J. Kurtz, B. Herchenroder, R. Green, and P. Eldridge. Using coupled models to study the effects of river discharge on biogeochemical cycling and hypoxia in the northern Gulf of Mexico. OCEANS 2009, MTS/IEEE Biloxi-Marine Technology for Our Future: Global and Local Challenges, Pages 1-7.

• Lehrter, J.C., M.C. Murrell, and J.C. Kurtz. Interactions between freshwater input, light, and phytoplankton dynamics on the Louisiana continental shelf. Continental Shelf Research, Volume 29, Issue 15, Pages 1861-1872.

• 2008

  Lehrter, J.C.. Regulation of eutrophication susceptibility in oligohaline regions of a northern Gulf of Mexico estuary, Mobile Bay, Alabama. Marine Pollution Bulletin, Volume 56, Issue 8, Pages 1446-1460.

• 2006

  Lehrter, J.C.. Effects of land use and land cover, stream discharge, and interannual climate on the magnitude and timing of nitrogen, phosphorus, and organic carbon concentrations in three coastal plain watersheds. Water Environment Research, Volume 78, Number 12, pp. 2356-2368(13).

• Hagy, J.D., J.C. Lehrter, and M.C. Murrell.. Effects of hurricane Ivan on water quality in Pensacola Bay, Florida. Estuaries and Coasts, Volume 29, Issue 6, pp 919–925.

• 2005.

  Glibert, P. M., C. J. Madden, E. Dettmann, W. Boynton, C. Heil, W. Nelson, J. C. Lehrter, J. Latimer, D. Flemer, M. Kennish, C. Brown, and S. Bricker. A framework for developing nutrient criteria. Nutrients in Estuaries, Page 43.

  

• 2001

  Carey, A.E., W. B. Lyons, J. C. Bonzongo, and J. C. Lehrter. Nitrogen budget in the Upper Mississippi River watershed. Environmental & Engineering Geoscience, Volume 7, Issue 3, Pages 251-265.

• 1999

  Lehrter, J.C., J.R. Pennock, and G.B. McManus.. Microzooplankton grazing and nitrogen excretion across a surface estuarine-coastal interface. Estuaries and Coasts, Volume 22, Issue 1, pp 113–125.

• Carey, A.E., J. R. Pennock, J. C. Lehrter, W. B. Lyons, W. W. Schroeder, and J. C. Bonzongo.. The role of the Mississippi River in Gulf of Mexico hypoxia. Environmental Institute Publication, 70, 35487-0207.

• 1969

  Lehrter, J.C.. Estuarine ecosystem metabolism and retention of allochthonous nutrient loads in three tidal river estuarine systems.

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