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Dr.
Kenneth L. Heck, Jr.
Senior Marine Scientist and
Professor, University of South Alabama
Ph.D., 1976, Florida State University
kheck@disl.org
Associate Director Alabama
Center for Estuarine Studies (ACES)
Marineecologylab.disl.org
Plant/animal interactions in seagrass-dominated
ecosystems
Research
Interests:
Efforts focus on ecological studies of seagrasses and seagrass-associated
macrofauna, especially shrimps, crabs and fishes.
Current studies include assessments of seagrass nursery value,
investigations of herbivory, and the direct and indirect effects
of nutrients and predator removal as they influence seagrass
meadows.
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
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 are carrying out both
laboratory and field studies of seagrass-dominated ecosystems
at the population and community levels, and employ a team
approach to problem solving. Our goals are to better understand
the relative importance of physical-chemical and biological
factors as they influence the health of seagrass meadows,
as well as an increased understanding of how such high levels
of plant and animal productivity are sustained in seagrass
ecosystems.
Ongoing
projects include:
Relative Role of Top-down and Bottom-up Effects in Seagrass
Ecosystems
Faculty colleagues, research
associates, graduate students and I 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, Mobile Bay, Alabama,
and the northern Florida Keys 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 a unvegetated system.
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 would otherwise be the case 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:
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
The impacts of increased
piscivorous fish density on herbivore abundance
Habitat Fragmentation
In marine environments, many habitats are comprised of discrete
patches of varying size and geometry. For example, in habitats
dominated by submerged aquatic vegetation (SAV), the SAV bed
is actually more often a mosaic of vegetated patches interspersed
with patches of unvegetated substrate (Larkum and den Hartog
1989; Robbins and Bell 1994; Bell et al 1995). While SAV cover
may approach 100% in some areas, numerous natural disturbances
such as wave energy and episodic storms prevent continuous
SAV coverage of the substrate (reviewed by Fonseca et al.
1998).
In addition, human-induced SAV habitat loss has increased
dramatically in recent decades, with activities such as dredging,
eutrophication, disease and damage from boating being major
factors (Onuf 1994; Duarte 1995; Sargent et al 1995). Because
SAV habitats are critical "nursery habitats" for
numerous commercially and recreationally important species,
(Orth et al. 1984, Heck et al 1997 and Fonseca et al. 1998)
we must asses the potential impacts, as well as the overall
susceptibility, of these habitats to an increasing number
of anthropogenic disruptions. In addition, we need to gain
an understanding how SAV habitat fragmentation influences
the productivity of SAV-associated fisheries and delineate
among large-scale negative effects which may be taking place
on populations of economically and ecologically valuable species.
Specifically, the objectives of this project are to 1) evaluate
the effects of SAV bed size, shape and degree of isolation
on the composition, abundance and secondary production of
decapod crustaceans and fishes and 2) develop an understanding
of the potential impacts of SAV fragmentation on the biological
functioning of associated SAV fauna.
Selected
Publications:
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. Proc. of the Blue Crab
Mortality Symposium. Pgs. 18-27.
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 enriched and large predator removal on seagrass
nursery habitats: an experimental assessment. Limnology and
Oceanography, In Press.
Valentine,
J. R. and K. L. Heck, Jr.June 20, 2007y: evidence for the continual grazing
of marine grasses. Marine Ecology Progress Series 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:
Effects of nutrient enrichment and
food web alteration on nearshore ecosystems. EPA - $188,000.
Period Covered: 1997 - 2000. PI's: Heck, Pennock and Valentine.
Fisheries-induced
changes in the structure and function of shallow water nursery
habitats: an experimental assessment. EPA (ACES) - $261,000.
period Covered: 1999 - 2001. PI's: Heck, Valentine, Cowan
and DeVries.
Trophic
cascades and spatial subsidies in a coral reef ecosystem:
a field test using "not take" areas in the Florida
Keys National Marine Sanctuary. NURC - $40,000. Period Covered:
2000 - 2001. PI's: Valentine and Heck.
Evaluation
of the nursery role of wetlands and seagrasses for better
conservation and management. National Center for Ecological
Analysis and Synthesis - $88,000. period Covered: 1999 - 20001.
PI's: Beck and Heck.
Shelter bottlenecks and
self-regulation in blue crab populations: assessing the roles
of nursery habitats and juvenile interactions for shelter
dependent organisms. EPA (ACES). $64,000. Period Covered:
2000- 2002. PI's : Heck and Moksnes.
Predicting seagrass survival in nutrient enriched waters:
toward a new view of an existing
paradigm. EPA (ACES). $105,000. Period Covered: 2001- 2002.
PI's: Heck, Valentine and Pennock.
Shelter bottlenecks and
self-regulation in blue crab populations: assessing the roles
of nursery habitats and juvenile interactions for shelter
dependent organisms. EPA (ACES). $64,000. Period Covered:
2000- 2002. PI's : Heck and Moksnes.
Predicting seagrass survival in nutrient enriched waters:
toward a new view of an existing
paradigm. EPA (ACES). $105,000. Period Covered: 2001- 2002.
PI's: Heck, Valentine and Pennock.
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. Mellon Foundation. $180,000.
Period Covered: 2001- 2003. Heck, Valentine and Beck.
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. NOAA (MARFIN)
$183,000. Period Covered: 2001-2003. Heck and Valentine.
Post-doctoral
Fellow
Per Moksnes (January 2001 - December
2002)
Research Associate
Patricia Spitzer
M.S., Marine Science 1997. University of South Alabama. Thesis
Title: "The Effects of Vegetation
Density on the relative growth rates and foraging behavior
of juvenile pinfish, Lagodon
rhomboides, in Big Lagoon Florida"
B.S. Ecology & Evolutionary Biology. 1994 University of
West Florida
Current Graduate Students
Stacey Harter, M.S. Candidate
Thesis Title: "Growth rates of juvenile pinfish (Lagodon
rhomboides): effects of
habitat and predation risk"
B.S. Biology 1999. Florida State University
Deborah Kilbane, M.S. Candidate
Thesis Title: "Intra-year class cannibalism in early
juvenile blue crabs (Calinectes sapidus)"
B.A. Biology 2000. Wittenberg University
Meg Goecker, M.S. Candidate
Thesis Title: "The effects of nitrogen content of turtlegrass,
Thalassiastestudinum, on the rates of
herbivory by the bucktooth parrotfish, Sparisoma radians."
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