Marine Sciences Programs Faculty Research news and Events Contact Us Links Home USA Home



Dr. John F. Valentine
Senior Marine Scientist & Associate Professor
Dauphin Island Sea Lab & University of South Alabama 

Research Interests

My current research interests examine the role of biotic processes, and human perturbations, in controlling the flow of energy among trophic levels both within and between marine habitats, with emphasis on submerged vegetated habitats. This research is being conducted in diverse locations ranging from the lower reaches of the Mobile Bay Delta to the Marine Protected Areas of the northern Florida Keys.

Much of the emphasis of this work is on 1) experimental assessments of grazing intensity in seagrass habitats, 2) responses of seagrasses to this grazing, and 3) the role of omnivory in controlling trophic cascades in marine systems. Newly funded work will examine 1) the degree to which marine production can subsidize the diets adult freshwater piscivorous fishes in oligohaline vegetated habitats in the northern Gulf of Mexico, 2) the relative value of infaunal functional groups to demersal fish growth, also in the northern Gulf of Mexico and 3) the indirect effects of the removal of large predatory fishes on the base of seagrass food webs in the Florida Keys. Finally, one planned project will be to investigate the degree to which seagrass detritus can subsidize the productivity of macroinvertebrates in nearby unvegetated habitats.

The overall significance of this research lies in its attempt to understand the processes that control the distribution and productivity of submerged vegetated habitats throughout the western Atlantic Ocean. Because of the widespread occurrence of these habitats, the extraordinary productivity and richness of their associated biota, an understanding of the factors controlling their distribution and the degree to which they subsidize the productivity of nearby less productive habitats is essential to our understanding of how the overall productivity of nearshore waters is determined. 

Selected Publications

Fioravanti. G. and J. F. Valentine.  In press.  Impacts of reef architecture and fishing on food webs in back reef environments of the upper Florida Keys national marine sanctuary.  Florida Scientist.

Goecker, M., J. Valentine and S. Sklenar.  In press.  Declining waterfowl populations of the Mobile-Tensaw Delta and the effects of exotic submerged aquatic vegetation.  Gulf of Mexico Science.

Heck, K. L., J. F. Valentine, J. R. Pennock, G. Chaplin and P. M. Spitzer.  In press. How herbivores can mediate the effects of nutrient enrichment on seagrass meadows: unexpected results of a field experiment.  Marine Ecology Progress Series.

Valentine, J. F., K. L. Heck, M. Dardeau and H. Burch.  In press.  Ecosystem-based management of Mobile Bay, Alabama.  In: The Gulf of Mexico: Its Origins, Waters, Biota & Human Impacts. Volume V: The Gulf of Mexico: Ecosystem-Based Management. J. Day and A. Yanez-Arancibia (Eds.). Texas A & M University Press.

Valentine, J. F. K. L. Heck, Jr., D. Blackmon, M. E. Goecker, J. Christian,
R. M. Kroutil, K. D. Kirsch, B. J. Peterson, M. Beck and M. A. Vanderklift In press.  Food web interactions along seagrass-coral reef boundaries: An experimental test of the impacts of piscivore reductions on cross-habitat energy exchange using the marine protected areas of the Florida Keys National Marine Sanctuary.  Marine Ecology Progress Series.  

Valentine, J. F. and J. E. Duffy. In press. The central role of grazing in seagrass ecosystems. In: "Seagrasses: Biology, Ecology and Conservation," A. W. D. Larkum, R. J. Orth & C. M. Duarte (Eds.). Springer.

Heck, K. L. and J. F. Valentine.  2006.  Plant - Herbivore interactions in seagrass meadows.  Journal of Experimental Marine Biology and Ecology 330:420-436.

Goecker, M. E., K. L. Heck, Jr. and J. F. Valentine.  2005.  Effects of nitrogen content in turtlegrass, Thalassia testudinum, on consumption by the bucktooth parrotfish, Sparisoma radians.  Marine Ecology Progress Series 286:239-248.

Valentine, J. F. and K. L. Heck, Jr.  2005.  Interaction strength at the coral reef-seagrass interface: has overfishing diminished the importance of seagrass habitat production for coral reef food webs?  Coral Reefs 24:209–213.

Valentine, J. F., E. F. Blythe, S. Madhavan and T. Sherman.  2004.  Turtlegrass responses (Thalassia testudinum) to leaf defoliation in a subtropical seagrass meadow: field tests of the impact of simulated herbivory on seagrass nitrogen assimilation and translocation.  Aquatic Botany 79:235-255. 

Spitzer, P., K. L. Heck, Jr. and J. F. Valentine.  2003.  Then and now: A comparison of blue crab research during the early and late 1990's in the Mobile Bay system.  Bulletin of Marine Science 72:435-452.

Valentine, J. F., K. L. Heck Jr. and A.M. Cinkovich.  2003.  Impacts of seagrass food webs on marine ecosystems: a need for a broader perspective.  Bulletin of Marine Science 71:1361–1368.

Kirsch, K. D., J. F. Valentine and K. L. Heck Jr.  2002.  Seagrass consumption by herbivorous fish: an underestimated trophic pathway in Florida Keys national marine sanctuary.  Marine Ecology Progress Series 227:71-85.

Valentine, J. F.
 and K. L. Heck, Jr. 2001. The role of leaf nitrogen content in determining turtlegrass (Thalassia testudinum) grazing: field and laboratory tests with a generalized herbivore. Journal of Experimental Marine Biology and Ecology 258:65-86.

Valentine, J. F.
, K. L. Heck, Jr., K. D. Kirsch and D. Webb. 2000. Seagrass herbivory in the turtlegrass habitats of the Florida Keys. Marine Ecology Progress Series 200:213-228. 

Valentine J. F., 
K. L. Heck, Jr. and K.D. Kirsch. 2000. The importance of the grazing pathway in seagrass food webs: a changing paradigm. Biologia Marina Mediterranea 7: 290-293.

Heck, K. L. Jr., J. R. Pennock, J. F. Valentine, L. D. Coen and S. A. Sklenar. 2000. Effects of nutrient enrichment and overfishing on seagrass ecosystems: an experimental assessment. Biologia Marina Mediterranea 7: 220-222

Heck, K. L., J. R. Pennock, J. F. Valentine, L. D. Coen and S. Sklenar. 2000. Effects of nutrient enrichment and large predator removal on seagrass nursery habitats: an experimental assessment.  Limnology and Oceanography 45: 1041-1057.

Rose, C. D., W. S. Sharp, W. J. Kenworthy, J. H. Hunt, W. G. Lyons, E. J. Prager, J. F. Valentine, M. O. Hall, P. Whitfield and J. W. Fourqurean. 1999. Sea urchin overgrazing of a large seagrass bed in outer Florida Bay. Marine Ecology Progress Series 190: 211-222.

Mattila, J., G. Chaplin, M. R. Eilers, K. L. Heck, Jr., J. P. O'Neal and J. F. Valentine. 1999. Spatial and diurnal distribution of invertebrate and fish fauna of a Zostera marina bed and nearby unvegetated sediments in Damariscotta River, Maine (USA). Netherlands Journal Sea Research 41:321-332.

Valentine, J. F. and K. L. Heck, Jr. 1999. Seagrass herbivory: evidence for the continued grazing of marine grasses. Marine Ecology Progress Series 176:291-302.

Valentine, J. F., K. L. Heck, Jr., J. Busby and D. Webb. 1997. Experimental evidence that herbivory increases shoot density and productivity in a subtropical turtlegrass (Thalassia testudinum) meadow. Oecologia 112:193-200.

Valentine, J. F., K. L. Heck, Jr., P. Harper and M. Beck. 1994. An experimental examination of the role of bioturbation in the maintenance of seagrass sand flat patch mosaics. Journal of Experimental Marine Biology and Ecology 178:181-192.

Valentine, J. F. and K. L. Heck, Jr.  1993.  Mussels in seagrass meadows: their influence on macroinvertebrate abundance, and production and macrophyte biomass in the northern Gulf of Mexico. Marine Ecology Progress Series 96:63-74.

Valentine, J. F. and K. L. Heck, Jr. 1991. The role of sea urchin grazing in regulating seagrass meadow size. Journal of Experimental Marine Biology and Ecology 154:215-230.

Selected Current Research Grants 

MARFIN. Marine reserve effectiveness in restoring coastal food webs: an experimental test using special
protection areas and an ecological reserve in the Florida Keys National Marine Sanctuary. 2001-2003.

Andrew Mellon Foundation - Ecosystem Research Program. Human-induced changes in the cross-habitat flow of energy in a subtropical marine ecosystem: experimental assessments using newly created marine reserves in the Florida Keys. 2001-2002. Co-Principal Investigator with K. L. Heck and M. Beck.

Alabama Center for Estuarine Studies. Food web interactions, spatial subsidies and the flow of energy between the Mobile Bay Delta and offshore waters: A SGER proposal to the Alabama Center for Estuarine Studies. 1999-2000. Co-Principal Investigator with T. Sherman, J. Cowan and S. Madhavan.

NOAA-NURP. Trophic cascades and spatial subsidies in a coral reef ecosystem: a field test using no take areas in the Florida Keys National Marine Sanctuary. Funded. 2000-2001. Co-Principal Investigator with K. L. Heck.

Alabama Center for Estuarine Studies. Effects of variation in river discharge and wind driven resuspension on the potential for regulating human-induced impacts on the Mobile Bay ecosystems.1999-2002. Co-Principal Investigator with J. Cowan and M. Graham. 

Alabama Center for Estuarine Studies. Fisheries induced changes in the structure and function of shallow water nursery habitats: an experimental assessment. Co-Principal Investigator with K. Heck, J. Cowan and D. DeVries. 

EPA. Effects of nutrient enrichment and large predator removal on seagrass nursery habitats: an experimental assessment. 1997-2000. Co-Principal Investigator with K. L. Heck and J. Pennock.


Current Graduate Students Former Graduate Students Technicians

Charlie Martin
Riikka Puntila
LaTina Steele 
Leslie Baggett
Theresa Berrell
Derrick Blackmon
Fennel Blythe
Glen Chaplin
Julie Christian
Geremea Fioravanti
Kevin Kirsch
Ryan Kroutil

Susan Sklenar 





University of South Alabama - Mobile Alabama 36688-0002 / 1 (251) 460-6101
For questions or comments Contact Us
Last date changed: June 20, 2012 4:04 PM