the main drivers (Eslami-Andargoli et al., 2009) and wetland topography providing the opportunity for connection.
Classes of connectivity
Classes of connectivity include both narrow and broad
interfaces and also constrained and diffuse connections
(Beger et al., 2010a; Beger et al., 2010b). The two categories especially relevant to estuaries are the broad interface
and diffuse connection types. The broad interface category
in estuaries has a mixing of fresh- and saline water and so
is associated with organisms that require brackish conditions, that is, their habitats experience the effects of both
sea- and freshwater. The diffuse connection category in
estuaries is variable with both fresh and saline components
that are spatially disjunct but which nevertheless facilitate
connectivity for organisms that spend different parts of the
life cycle in contrasting habitats – needing saline or freshwater at specific stages.
Threatening processes: natural and
anthropogenic
Natural processes that can threaten estuarine connectivity
include climate changes such as increasing extreme events
that can, over a short time frame, destroy fringing mangroves in tropical estuaries and tall grasslands in temperate
ones. Sea-level change is also likely to affect estuarine
connectivity, changing the patterns of interaction between
fresh- and saline waters and thereby having critical
impacts on aquatic biota including vegetation.
Human activities can interrupt connectivity. For example, constructing barriers, dams, and hydroelectric
schemes impacts organisms that depend on connections
between saline and freshwater habitats. Examples include
the effects of barriers on marine-spawned fish in South
Africa (Wasserman et al., 2011) and on fish biota throughout a temperate system in Australia (Rolls, 2011), the
impact of impoundments on estuaries in Australia
(Sheaves et al., 2007b), and the impacts of hydropower
developments in Vietnam (Sheaves et al., 2008). These
are all point sources of interruption. There are also the
more diffuse effects of development that can change, for
example, surface hydrology, sediment and nutrient supply
and which can affect both the broad interface extent and
the diffuse pattern of salinity types, with ongoing impacts
on dependent organisms.
Summary
Estuarine connectivity facilitates biogeographic, ecological, and evolutionary processes within and among estuarine systems and between estuarine systems and their
upstream fluvial and terrestrial ecosystems and their
downstream marine ones.
Estuarine connectivity is crucial to sustaining ecosystems but vulnerable to threatening processes of natural
or anthropogenic origin at a variety of scales.
Bibliography
Abrantes, K. G., and Sheaves, M., 2010. Importance of freshwater
flow in terrestrial-aquatic energetic connectivity in intermittently
connected estuaries of tropical Australia. Marine Biology, 157,
2071–2086.
Beger, M., Grantham, H. S., Pressey, R. L., Wilson, K. A.,
Peterson, E. L., Dorfman, D., Mumby, P. J., Lourival, R.,
Brumbaugh, D. R., and Possingham, H. P., 2010a. Conservation
planning for connectivity across marine, freshwater and terrestrial
realms. Biological Conservation, 143, 565–575.
Beger, M., Linke, S., Watts, M., Game, E., Treml, E., Ball, I., and
Possingham, H. P., 2010b. Incorporating asymmetric connectivity into spatial decision making for conservation. Conservation
Letters, 3, 359–368.
Bradbury, I. R., Campana, S. E., and Bentzen, P., 2008. Low genetic
connectivity in an estuarine fish with pelagic larvae. Canadian
Journal of Fisheries and Aquatic Sciences, 65, 147–158.
Connolly, R. M., Hindell, J. S., and Gorman, D., 2005. Seagrass and
epiphytic algae support nutrition of a fisheries species, Sillago
schomburgkii, in adjacent intertidal habitats. Marine Ecology
Progress Series, 286, 69–79.
Davis, B., Johnston, R., Baker, R., and Sheaves, M., 2012. Fish
utilization of wetland nurseries with complex hydrological
connectivity. Plos One, 7(11), e49107. doi:10.1371/journal.
pone.0049107.
Eslami-Andargoli, L., Dale, P. E. R., Sipe, N., and Chaseling, J.,
2009. Mangrove expansion and rainfall patterns in Moreton
Bay, Southeast Queensland, Australia, Australia. Estuarine and
Coastal Shelf Science, 85, 292–298.
Gale, E., Pattiaratchi, C., and Ranasinghe, R., 2006. Vertical mixing
processes in intermittently closed and open lakes and lagoons,
and the dissolved oxygen response. Estuarine and Coastal Shelf
Science, 69, 205–216.
McLusky, D. S., and Elliott, M., 2004. The Estuarine Ecosystem:
Ecology, Threats and Management. New York: Oxford University Press.
Meynecke, J. O., Poole, G. C., Werry, J., and Lee, S. Y., 2008.
Use of PIT tag and underwater video recording in assessing
estuarine fish movement in a high intertidal mangrove and salt
marsh creek. Estuarine and Coastal Shelf Science, 79,
168–178.
Minello, T. J., Able, K. W., Weinstein, M. P., and Hays, C. G., 2003.
Salt marshes as nurseries for nekton: testing hypotheses on density, growth and survival through meta-analysis. Marine Ecology
Progress Series, 246, 39–59.
Rolls, R. J., 2011. The role of life-history and location of barriers to
migration in the spatial distribution and conservation of fish
assemblages in a coastal river system. Biological Conservation,
144, 339–349.
Sheaves, M., Abrantes, K., and Johnston, R., 2007a. Nursery
ground value of an endangered wetland to juvenile shrimps. Wetlands Ecology and Management, 15, 311–327.
Sheaves, M., Johnston, R., Molony, B., and Shepard, G., 2007b.
The effect of impoundments on the structure and function of fish
fauna in a highly regulated dry tropics estuary. Estuaries and
Coasts, 30, 507–517.
Sheaves, M., Duc, N. H., and Khoa, N. X., 2008. Ecological attributes of a tropical river basin vulnerable to the impacts of clustered hydropower developments. Marine and Freshwater
Research, 59, 971–986.
Wasserman, R. J., Weyl, O. L. F., and Strydom, N. A., 2011. The
effects of instream barriers on the distribution of migratory
marine-spawned fishes in the lower reaches of the Sundays
River, South Africa. Water SA, 37, 495–504.
Wolanski, E., 1995. Transport of sediment in mangrove swamps.
Hydrobiologia, 295, 31–42.
ESTUARINE CONNECTIVITY
259
Classes of connectivity
Classes of connectivity include both narrow and broad
interfaces and also constrained and diffuse connections
(Beger et al., 2010a; Beger et al., 2010b). The two categories especially relevant to estuaries are the broad interface
and diffuse connection types. The broad interface category
in estuaries has a mixing of fresh- and saline water and so
is associated with organisms that require brackish conditions, that is, their habitats experience the effects of both
sea- and freshwater. The diffuse connection category in
estuaries is variable with both fresh and saline components
that are spatially disjunct but which nevertheless facilitate
connectivity for organisms that spend different parts of the
life cycle in contrasting habitats – needing saline or freshwater at specific stages.
Threatening processes: natural and
anthropogenic
Natural processes that can threaten estuarine connectivity
include climate changes such as increasing extreme events
that can, over a short time frame, destroy fringing mangroves in tropical estuaries and tall grasslands in temperate
ones. Sea-level change is also likely to affect estuarine
connectivity, changing the patterns of interaction between
fresh- and saline waters and thereby having critical
impacts on aquatic biota including vegetation.
Human activities can interrupt connectivity. For example, constructing barriers, dams, and hydroelectric
schemes impacts organisms that depend on connections
between saline and freshwater habitats. Examples include
the effects of barriers on marine-spawned fish in South
Africa (Wasserman et al., 2011) and on fish biota throughout a temperate system in Australia (Rolls, 2011), the
impact of impoundments on estuaries in Australia
(Sheaves et al., 2007b), and the impacts of hydropower
developments in Vietnam (Sheaves et al., 2008). These
are all point sources of interruption. There are also the
more diffuse effects of development that can change, for
example, surface hydrology, sediment and nutrient supply
and which can affect both the broad interface extent and
the diffuse pattern of salinity types, with ongoing impacts
on dependent organisms.
Summary
Estuarine connectivity facilitates biogeographic, ecological, and evolutionary processes within and among estuarine systems and between estuarine systems and their
upstream fluvial and terrestrial ecosystems and their
downstream marine ones.
Estuarine connectivity is crucial to sustaining ecosystems but vulnerable to threatening processes of natural
or anthropogenic origin at a variety of scales.
Bibliography
Abrantes, K. G., and Sheaves, M., 2010. Importance of freshwater
flow in terrestrial-aquatic energetic connectivity in intermittently
connected estuaries of tropical Australia. Marine Biology, 157,
2071–2086.
Beger, M., Grantham, H. S., Pressey, R. L., Wilson, K. A.,
Peterson, E. L., Dorfman, D., Mumby, P. J., Lourival, R.,
Brumbaugh, D. R., and Possingham, H. P., 2010a. Conservation
planning for connectivity across marine, freshwater and terrestrial
realms. Biological Conservation, 143, 565–575.
Beger, M., Linke, S., Watts, M., Game, E., Treml, E., Ball, I., and
Possingham, H. P., 2010b. Incorporating asymmetric connectivity into spatial decision making for conservation. Conservation
Letters, 3, 359–368.
Bradbury, I. R., Campana, S. E., and Bentzen, P., 2008. Low genetic
connectivity in an estuarine fish with pelagic larvae. Canadian
Journal of Fisheries and Aquatic Sciences, 65, 147–158.
Connolly, R. M., Hindell, J. S., and Gorman, D., 2005. Seagrass and
epiphytic algae support nutrition of a fisheries species, Sillago
schomburgkii, in adjacent intertidal habitats. Marine Ecology
Progress Series, 286, 69–79.
Davis, B., Johnston, R., Baker, R., and Sheaves, M., 2012. Fish
utilization of wetland nurseries with complex hydrological
connectivity. Plos One, 7(11), e49107. doi:10.1371/journal.
pone.0049107.
Eslami-Andargoli, L., Dale, P. E. R., Sipe, N., and Chaseling, J.,
2009. Mangrove expansion and rainfall patterns in Moreton
Bay, Southeast Queensland, Australia, Australia. Estuarine and
Coastal Shelf Science, 85, 292–298.
Gale, E., Pattiaratchi, C., and Ranasinghe, R., 2006. Vertical mixing
processes in intermittently closed and open lakes and lagoons,
and the dissolved oxygen response. Estuarine and Coastal Shelf
Science, 69, 205–216.
McLusky, D. S., and Elliott, M., 2004. The Estuarine Ecosystem:
Ecology, Threats and Management. New York: Oxford University Press.
Meynecke, J. O., Poole, G. C., Werry, J., and Lee, S. Y., 2008.
Use of PIT tag and underwater video recording in assessing
estuarine fish movement in a high intertidal mangrove and salt
marsh creek. Estuarine and Coastal Shelf Science, 79,
168–178.
Minello, T. J., Able, K. W., Weinstein, M. P., and Hays, C. G., 2003.
Salt marshes as nurseries for nekton: testing hypotheses on density, growth and survival through meta-analysis. Marine Ecology
Progress Series, 246, 39–59.
Rolls, R. J., 2011. The role of life-history and location of barriers to
migration in the spatial distribution and conservation of fish
assemblages in a coastal river system. Biological Conservation,
144, 339–349.
Sheaves, M., Abrantes, K., and Johnston, R., 2007a. Nursery
ground value of an endangered wetland to juvenile shrimps. Wetlands Ecology and Management, 15, 311–327.
Sheaves, M., Johnston, R., Molony, B., and Shepard, G., 2007b.
The effect of impoundments on the structure and function of fish
fauna in a highly regulated dry tropics estuary. Estuaries and
Coasts, 30, 507–517.
Sheaves, M., Duc, N. H., and Khoa, N. X., 2008. Ecological attributes of a tropical river basin vulnerable to the impacts of clustered hydropower developments. Marine and Freshwater
Research, 59, 971–986.
Wasserman, R. J., Weyl, O. L. F., and Strydom, N. A., 2011. The
effects of instream barriers on the distribution of migratory
marine-spawned fishes in the lower reaches of the Sundays
River, South Africa. Water SA, 37, 495–504.
Wolanski, E., 1995. Transport of sediment in mangrove swamps.
Hydrobiologia, 295, 31–42.
ESTUARINE CONNECTIVITY
259