Kenneth L. Heck, Jr.

Senior Marine Scientist
Chair of University Programs, DISL
Professor, University of South Alabama 
Assistant Director, Alabama Center for Estuarine Studies (ACES)

Ph.D., 1976, Florida State University

Email
 

Research Interests

Seagrass ecosystems serve as essential nursery areas for a wide variety of species in coastal waters, including many economically important finfish and shellfish. They are also among the most productive environments known, and support abundances of animals that are frequently 10 to 100 times those of nearby unvegetated bottoms. During the past two decades there have been unprecedented declines in seagrass ecosystems along the Atlantic, Gulf and Pacific coastlines. Despite the recognized importance of seagrasses, the critical environmental factors limiting the seagrasses meadows are poorly understood, as are the biological interactions that directly and indirectly affect the health of seagrass ecosystems.  We employ a team approach to problem solving and are carrying out both laboratory and field studies of seagrass-dominated ecosystems at the population and community levels. Our goals are to better understand the relative importance of physico-chemical and biological factors as they influence the health of seagrass meadows and to obtain an increased understanding of how such high levels of plant and animal productivity are sustained in seagrass ecosystems. A selection of ongoing projects includes:

Relative Role of Top-down and Bottom-up Effects in Seagrass Ecosystems
We are conducting field tests of the interacting effects of large predator reductions and nutrient additions at a biologically relevant scale in marine systems. We expect these studies, being carried out in St. Joseph Bay, Florida, Perdido Bay, Florida, and Mobile Bay, Alabama to provide fresh insight into how to maintain the "health" of seagrass ecosystems. Specifically, we expect to gain a better understanding of the degree to which "top down" and "bottom up" factors influence the structure of seagrass beds in coastal waters, and the factors that might promote a shift from a seagrass-dominated system to an unvegetated bottom. Because nutrient enrichment and overfishing are occurring at an advancing rate along the Gulf coast, and indeed throughout the world, it is urgent that we understand the direct and indirect consequences of altering large predator abundance and concomitantly increasing nutrient supply. 

Trophic Cascades and Spatial Subsidies in a Coral Reef Ecosystem: A Field-test using "No take" Areas in the Florida Keys National Marine Sanctuary
It has been known since the 1960's that feeding in nearby vegetated (seagrass) habitats can subsidize coral reef consumers and may allow them to be more abundant than if they were supported solely by in situ productivity. To date, most of what we know about the flow of energy within coral reefs comes from locations that have experienced heavy fishing pressure. Since fishing has been intense for centuries in most coastal areas, it is difficult to know what natural unharvested systems might have been like. In this study, we will determine the impact of the removal of large fish predators from coral reef food webs, by quantifying the amount of trophic transfer from nearby seagrass foraging grounds on both no take and unprotected reefs. Our specific objectives are to determine: 1) the effects of the projected increases in large piscivorous fish density and biomass within no-take reserves on the rates at which production in adjoining seagrass habitats is consumed by reef associated marine herbivores and 2) the impacts of increased piscivorous fish density on herbivore abundance.

Effect of Herbivory on Seagrasses
This work is aimed at understanding the effects of herbivory on seagrasses at spatial scales varying from individual clones to entire seagrass landscapes. Studies focus on sea urchin and parrotfish grazing and its consequences for the dominant species in Florida seagrass ecosystems, turtlegrass (Thalassia testudinum). We are investigating how varying levels of grazing influence turtlegrass productivity, shoot production, above- and belowground standing crop and flowering intensity, and the conditions under which urchin grazing might be expected to lead to complete loss of seagrasses. Work to date indicates a highly significant, and under-appreciated, impact of urchin herbivory on seagrasses, which ranges from beneficial (through stimulation of shoot and flower production) to devastating, depending on intensity and season. 

Heck, K. L. Jr. and J. F. Valentine.  2007.  The primacy of top-down effects in shallow benthic systems.  Estuaries and Coasts 30:371-381. PDF of Publication©

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.  2007.  Food web interactions along seagrass-coral reef boundaries: effects of piscivore reductions on cross-habitat energy exchange.  Mar. Ecol. Prog. Ser. 333:37-50.  PDF of Publication©

Vanderklift, M. A., J. How, T. Wernberg, L. D. MacArthur, K. L. Heck, Jr. and J. F. Valentine.  2007.  Proximity to reef influences density of small predatory fishes, while type of seagrass influences intensity of their predation on crabs.  Mar. Ecol. Prog. Series 340:235-243.  PDF of Publication©

Heck, K. L. Jr. and R. J. Orth.  (In press).  Predation in seagrass meadows. In: A. Larkum, R. J. Orth and C. Duarte (Eds.), Seagrasses: Biology, Ecology and their Conservation. Kluwer, Amsterdam.  

Valentine, J. F. and K. L. Heck, Jr. (In press). Perspective review of the impacts of overfishing on coral reef food web linkages. Coral Reefs.

M. E. Goecker, K. L. Heck, Jr. and J. F. Valentine. 2005. Effects of nitrogen concentrations in turtlegrass, Thalassia testudinum, on consumption by the bucktooth parrotfish, Sparisoma radians. Mar. Ecol. Prog. Ser. 286:239-248.

Ibarra-Obando, S., K. L. Heck, Jr. and P. M. Spitzer.  2004. Effects of simultaneous changes in light, nutrients, and herbivory levels on the structure and function of a subtropical turtlegrass meadow.  J. Exp. Mar. Biol. Ecol. 301:193-224.

Heck, K. L. Jr., R. J. Orth and C. G. Hays.  2003. Critical evaluation of the nursery role hypothesis for seagrass meadows. Mar. Ecol. Prog. Ser. 253:123-136.  

Beck, M. W., K. L. Heck, Jr., K. W. Able, D. L. Childers, D. B. Eggleston, B. M. Gillanders, B. S. Halpern, C. G. Hays, K. Hoshino, T. J. Minello, R. J. Orth, P. F. Sheridan and M. P. Weinstein. 2003. The role of nearshore ecosystems as fish and shellfish nurseries.  Issues in Ecology, Number 11.  Ecological Society of America, Washington, D.C. 12pp. (available at: http://www.esa.org/sbi/sbi_issues/).

Spitzer, P. M., K. L. Heck, Jr. and J. F. Valentine.  2003. Then and now: a comparison of patterns in blue crab post-larval abundance and post-settlement mortality during the early and late 1990s in the Mobile Bay system.  Bull. Mar. Sci. 72:435-452.

Heck, K. L. Jr., L. D. Coen and D. M. Wilson. 2002. Growth of northern (Merceneria mercenaria (L.)) and Southern (M. campechensis (Gmelin)) quahogs: influence of seagrasses and latitude. J. Shellfish Res. 21:635-642.

Able, K. W., M. P. Fahay, K. L. Heck, Jr., C. T. Roman, M. A. Lazzari and S. C. Kaiser. 2002. Seasonal distribution and abundance of fishes and decapod crustaceans in a Cape Cod estuary. Northeastern Naturalist 9:285-302.

Orth, R. J., K. L. Heck, Jr. and D. J. Tunbridge. 2002. Predation on seeds of the seagrass Posidonia australis in Western Australia.  Mar. Ecol. Prog. Ser. 244:81-88.

Bologna, P. A. X. and K. L. Heck, Jr.  2002. Impact of habitat edges on density and secondary production of seagrass-associated fauna. Estuaries 25:1033-1044.

Kirsh, K. D., J. F. Valentine and K. L. Heck, Jr. 2002. Parrotfish grazing in turtlegrass Thalassia testudinum: evidence for the importance of seagrass consumption in food web dynamics of the Florida keys national Marine Sanctuary. Mar. Ecol. Prog. Ser. 227:71-85.

Williams, S. W. and K. L. Heck, Jr.  2001. 'Seagrass Communities'.  Pp. 317-337 In: M. Bertness, S. Gaines and M. Hay  (Eds.), Marine Community Ecology.  Sinauer Press, Sunderland, Mass.

Valentine, J. F., K. L. Heck, Jr., K. K. Kirsch and D. Webb. 2001. The role of leaf nitrogen content in determining turtlegrass (Thalassia testudinum) grazing by a generalist herbivore in the northeastern Gulf of Mexico. J. Exp. Mar. Biol. Ecol. 258:65-86. 

Peterson, B. J. and K. L. Heck, Jr.  2001.  Interactions between suspension feeding bivalves and seagrass assemblages - a facultative mutualism.  Mar. Ecol. Prog. Ser. 213:143-155.

Aronson, R. B., K. L. Heck, Jr. and J. F. Valentine. 2001.  Measuring predation with tethering experiments. Mar. Ecol. Prog. Ser. 214:311-312.  

Beck, M. W., K. L. Heck, Jr., K. W. Able, D. L. Childers, D. B. Eggleston, B. M. Gillanders, B. Halpern, C. G. Hays, K. Hoshino, T. J. Minello, R. J. Orth, P. F. Sheridan and M. P. Weinstein.  2001. The identification, conservation and management of estuarine and marine nurseries for fish and invertebrates. Bioscience 51:633-641. 

Heck, K. L., Jr., L. D. Coen and S. G. Morgan. 2001. Pre- and post-settlement factors as determinants of juvenile blue crab abundance: results from the north-central Gulf of Mexico. Mar. Ecol. Prog. Ser. 222:163-176.

Heck, K. L., Jr., and P. M. Spitzer.  2001. Post settlement mortality of juvenile blue crabs: patterns and processes. Pp. 18-27, Proceedings of the Blue Crab Mortality Symposium. 

Spitzer, P. M., K. L. Heck, Jr. and J. Mattila. 2000. The effects of vegetation density on the relative growth rates of juvenile pinfish, Lagodon rhomboides, in Big Lagoon, Florida. J. Exp. Mar. Biol. Ecol. 244:67-86.

Heck, K. L., Jr., J. R. Pennock, J. F. Valentine, L. D. Coen and S. S. Sklenar.  2000.  Effects of nutrient enrichment and large predator removal on seagrass nursery habitats: an experimental assessment. Biol. Mar. Medit. 7:220-222

Valentine, J. R. and K. L. Heck, Jr. 1999. Seagrass herbivory: evidence for the continual grazing of marine grasses. Mar. Ecol. Prog. Ser. 176:291-302.

Bologna, P. A. X. and K. L. Heck, Jr. 1999. Macrofaunal associations with seagrass epiphytes: relative importance of trophic and structural characteristics. J. Exp. Mar. Biol. Ecol. 242:21-39.

Peterson, B. J. and K. L. Heck, Jr.  1999. The potential for suspension feeding bivalves to increase seagrass productivity. J. Exp. Mar. Biol. Ecol. 240:32-52.

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

Bologna, P. A. X. and K. L. Heck, Jr. 1999. Differential predation and growth rates of bay scallops within a seagrass habitat.  J. Exp. Mar. Biol. Ecol. 239:299-314.

Selected Current Research Grants 

Alabama Center for Estuarine Studies, US EPA - Predicting seagrass survival in nutrient enriched waters: toward a new view of an existing paradigm.  (With John F. Valentine and Patricia M. Spitzer)

Alabama Center for Estuarine Studies, US EPA - The Role of Habitat Fragmentation on the Structure and Function of Seagrass Ecosystems in the Northern Gulf of Mexico.   (With Matthew W. Johnson)

US Department of Commerce - Quantifying fisheries benefits of oyster reef restoration in Mobile Bay. (With Sean P. Powers)

US Department of Commerce - Ecosystem services provided by oyster reefs: An experimental assessment.  (With Just Cebrian and Sean P. Powers)

Nature Conservancy/ Mellon Foundation - 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.  (With John F. Valentine and Michael Beck)

NOAA 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.  (With John F. Valentine)