progressed, populations of the native bivalve prey,
Nutricola, decreased dramatically. At the same time,
a previously introduced but rare bivalve (Gemma gemma)
underwent a population explosion and spread, an example
of what he termed “invasional meltdown.”
Trophic cascades
Trophic cascades occur when predators in a food web suppress the abundance and/or alter traits (e.g., behavior) of
their prey, thereby releasing the lower trophic level from
predation (discussed above), and then this change affects
the next lowest trophic level. For example, if the abundance of piscivorous fish increases, the abundance of their
prey, zooplanktivorous fish, should decrease. This should
be followed by an increase in abundance of large zooplankton since their predators have become scarce, and
the large numbers of zooplankton should cause phytoplankton to decrease. A cascade in southern US salt
marshes was noted by Silliman and Bertness (2002) who
found that blue crab (Callinectes sapidus) predation on
periwinkle snails (Littorina saxatilis) regulated the snail
population size. Without the blue crab predators, the
populations of periwinkles increased so much that their
grazing on marsh grass could destroy the salt marsh,
converting it into a mudflat. This trophic cascade
suggested that overharvesting of blue crabs could be an
important factor contributing to the die-off of salt marshes
across the southeastern United States. Another example of
a cascade is a study by Nifong and Silliman (2013)
who focused on the next trophic level – the role of alligators (top predators) in southern US salt marshes. In
mesocosms (large experimental tanks with many species
present), they found that alligators reduced the abundance
of blue crabs and induced behavioral changes, causing the
crabs to decrease their own foraging activity and spend
more time in a refuge. The effects of reduced crab abundance and reduced feeding behavior translated into
increased survival of snails and mussels within the marsh
mesocosms. Trophic cascades may also be important for
understanding the effects of removing top predators from
food webs, as humans have done in many places through
fishing activities.
Summary
Predator–prey relationships are among the most important
ones in ecosystems. They play major roles in structuring
ecosystems and involve behavior, morphology, and evolution. They can be studied by manipulating ecosystems or
observing changes in populations of native species following an invasion of a new species into an ecosystem.
Bibliography
Freeman, A., 2007. Specificity of induced defenses in Mytilus edulis
and asymmetrical predator deterrence. Marine Ecology Progress
Series, 334, 145–153.
Grosholz, E. D., 2005. Recent biological invasion may hasten
invasional meltdown by accelerating historical introductions.
Proceedings of the National Academy of Sciences, 102,
1088–1091.
Leonard, G. H., Bertness, M. D., and Yund, P. O., 1999. Crab predation, waterborne cues, and inducible defenses in the blue mussel,
Mytilus edulis. Ecology, 80, 1–14.
Nifong, J. C., and Silliman, B. R., 2013. Impacts of a large-bodied,
apex predator (Alligator mississippiensis Daudin 1801) on salt
marsh food webs. Journal of Experimental Marine Biology
and Ecology, 440, 185–191.
Paine, R. T., 1974. Intertidal community structure: experimental
studies on the relationship between a dominant competitor and
its principal predator. Oecologia, 15, 93–120.
Silliman, B. R., and Bertness, M. D., 2002. A trophic cascade regulates salt marsh primary production. Proceedings of the National
Academy of Sciences, 99, 10500–10505.
Smith, L. D., 2004. Biogeographic differences in claw size and performance in an introduced crab predator Carcinus maenas.
Marine Ecology Progress Series, 276, 209–222.
Trussell, G., and Smith, L. D., 2000. Induced defenses in response
to an invading crab predator: an explanation of historical and
geographic phenotypic change. Proceedings of the National
Academy of Sciences, 97, 2123–2127.
PUBLIC TRUST RIGHTS
Julien Victor Monnot
1 and J. Javier Diez
2
1
Civil Engineering: Land & Urban Management and
Environment, Escuela de Caminos, Canales y Puertos,
Universidad Politécnica de Madrid, Madrid, Spain
2
Research Group on Marine, Coastal and Port
Environment and Other Sensitive Areas, Department of
Land and Urban Planning and Environment,
Universidad Politécnica de Madrid, Madrid, Spain
Definition
Coastal public trust rights include an indeterminate and
evolving set of faculties grounded in the principle of free
access to the coast. Primary coastal public trust rights
that include pedestrian access, navigation, swimming,
hunting, and fishing arose under the Roman Digest and
have remained ever since. After recreational uses adjoined
these customary faculties in the second half of the twentieth century, the latest coastal acts bear yet a third generation that incorporates education and research. According
to the North Carolina General Statutes (1982), public trust
rights are “those rights held in trust by the State for the use
and benefit of the people of the State in common. They are
established by common law [and] include, but are not limited to, the right to navigate, swim, hunt, fish, and enjoy all
recreational activities in the watercourses of the State and
the right to freely use and enjoy the State’s ocean and
estuarine beaches and public access to the beaches.”
Defense of public trust rights
The defense of public uses constitutes one major objective
in coastal law. For such purposes, conventional and
national instruments provide many different devices,
PUBLIC TRUST RIGHTS
499
Nutricola, decreased dramatically. At the same time,
a previously introduced but rare bivalve (Gemma gemma)
underwent a population explosion and spread, an example
of what he termed “invasional meltdown.”
Trophic cascades
Trophic cascades occur when predators in a food web suppress the abundance and/or alter traits (e.g., behavior) of
their prey, thereby releasing the lower trophic level from
predation (discussed above), and then this change affects
the next lowest trophic level. For example, if the abundance of piscivorous fish increases, the abundance of their
prey, zooplanktivorous fish, should decrease. This should
be followed by an increase in abundance of large zooplankton since their predators have become scarce, and
the large numbers of zooplankton should cause phytoplankton to decrease. A cascade in southern US salt
marshes was noted by Silliman and Bertness (2002) who
found that blue crab (Callinectes sapidus) predation on
periwinkle snails (Littorina saxatilis) regulated the snail
population size. Without the blue crab predators, the
populations of periwinkles increased so much that their
grazing on marsh grass could destroy the salt marsh,
converting it into a mudflat. This trophic cascade
suggested that overharvesting of blue crabs could be an
important factor contributing to the die-off of salt marshes
across the southeastern United States. Another example of
a cascade is a study by Nifong and Silliman (2013)
who focused on the next trophic level – the role of alligators (top predators) in southern US salt marshes. In
mesocosms (large experimental tanks with many species
present), they found that alligators reduced the abundance
of blue crabs and induced behavioral changes, causing the
crabs to decrease their own foraging activity and spend
more time in a refuge. The effects of reduced crab abundance and reduced feeding behavior translated into
increased survival of snails and mussels within the marsh
mesocosms. Trophic cascades may also be important for
understanding the effects of removing top predators from
food webs, as humans have done in many places through
fishing activities.
Summary
Predator–prey relationships are among the most important
ones in ecosystems. They play major roles in structuring
ecosystems and involve behavior, morphology, and evolution. They can be studied by manipulating ecosystems or
observing changes in populations of native species following an invasion of a new species into an ecosystem.
Bibliography
Freeman, A., 2007. Specificity of induced defenses in Mytilus edulis
and asymmetrical predator deterrence. Marine Ecology Progress
Series, 334, 145–153.
Grosholz, E. D., 2005. Recent biological invasion may hasten
invasional meltdown by accelerating historical introductions.
Proceedings of the National Academy of Sciences, 102,
1088–1091.
Leonard, G. H., Bertness, M. D., and Yund, P. O., 1999. Crab predation, waterborne cues, and inducible defenses in the blue mussel,
Mytilus edulis. Ecology, 80, 1–14.
Nifong, J. C., and Silliman, B. R., 2013. Impacts of a large-bodied,
apex predator (Alligator mississippiensis Daudin 1801) on salt
marsh food webs. Journal of Experimental Marine Biology
and Ecology, 440, 185–191.
Paine, R. T., 1974. Intertidal community structure: experimental
studies on the relationship between a dominant competitor and
its principal predator. Oecologia, 15, 93–120.
Silliman, B. R., and Bertness, M. D., 2002. A trophic cascade regulates salt marsh primary production. Proceedings of the National
Academy of Sciences, 99, 10500–10505.
Smith, L. D., 2004. Biogeographic differences in claw size and performance in an introduced crab predator Carcinus maenas.
Marine Ecology Progress Series, 276, 209–222.
Trussell, G., and Smith, L. D., 2000. Induced defenses in response
to an invading crab predator: an explanation of historical and
geographic phenotypic change. Proceedings of the National
Academy of Sciences, 97, 2123–2127.
PUBLIC TRUST RIGHTS
Julien Victor Monnot
1 and J. Javier Diez
2
1
Civil Engineering: Land & Urban Management and
Environment, Escuela de Caminos, Canales y Puertos,
Universidad Politécnica de Madrid, Madrid, Spain
2
Research Group on Marine, Coastal and Port
Environment and Other Sensitive Areas, Department of
Land and Urban Planning and Environment,
Universidad Politécnica de Madrid, Madrid, Spain
Definition
Coastal public trust rights include an indeterminate and
evolving set of faculties grounded in the principle of free
access to the coast. Primary coastal public trust rights
that include pedestrian access, navigation, swimming,
hunting, and fishing arose under the Roman Digest and
have remained ever since. After recreational uses adjoined
these customary faculties in the second half of the twentieth century, the latest coastal acts bear yet a third generation that incorporates education and research. According
to the North Carolina General Statutes (1982), public trust
rights are “those rights held in trust by the State for the use
and benefit of the people of the State in common. They are
established by common law [and] include, but are not limited to, the right to navigate, swim, hunt, fish, and enjoy all
recreational activities in the watercourses of the State and
the right to freely use and enjoy the State’s ocean and
estuarine beaches and public access to the beaches.”
Defense of public trust rights
The defense of public uses constitutes one major objective
in coastal law. For such purposes, conventional and
national instruments provide many different devices,
PUBLIC TRUST RIGHTS
499