greater in some regions due to coastal subsidence, as in the
case of New Jersey and other mid-Atlantic states in the USA.
Rising sea level and coastal inundation will lead to significant loss of some coastal wetlands, eliminating buffer
and rendering coastal communities more vulnerable to
extreme events. Human-induced climate change will also
alter temperature and salinity regimes and the structure
and function of biotic communities in estuaries
(Kennish, 2002). Configurations of estuarine basins will
be modified as they widen and deepen. Shifts will occur
in nutrient and sediment supply as well as freshwater
inputs. Tidal prisms and tidal ranges will change in many
systems. More frequent flooding and inundation of
bayshore areas will pose hazards to vulnerable coastal
communities worldwide (Kennish et al., 2008).
Coastal subsidence
Subsiding coasts result in similar impacts as rising sea
level on estuarine and wetland systems. For example, as
coastal subsidence increases, estuarine shoreline retreats
and land submergence accelerates causing the loss of
fringing wetland habitat. The wet surface area of the estuary expands, together with the basin volume, thereby altering the system bathymetry and configuration. The salinity
regime, circulation, and other physical-chemical characteristics of the estuary can change considerably as well,
which will also affect biotic communities.
The effects of coastal subsidence are becoming more
evident around the world with accelerating population
growth and development in coastal watersheds. Human
activities have contributed greatly to the subsidence problems in some areas via excessive groundwater withdrawal
for domestic and agricultural use and oil and gas extraction. Natural factors, such as subsurface sediment compaction, crustal (tectonic) movements, and sinkhole
formation by karst processes, are more significant in some
regions. In the USA, subsidence has been well chronicled
at Galveston Bay, Texas, due to oil and gas extraction
(Shipley and Kiesling, 1994), along the Louisiana coast
due to sediment compaction (DeLaune and Pezeshki,
1994), and at Chesapeake Bay due to groundwater withdrawal and other factors (Boon et al., 2010).
Significant coastal subsidence has also been
documented in other countries (e.g., Po Delta, Italy, and
Tokyo, Japan) (Kennish et al., 2008). Coastal subsidence
problems will take on added significance during the
twenty-first century, exacerbating those due to eustatic
sea-level rise (Kennish, 2002). Subsidence rates, such as
those noted by Boon et al. (2010) at Chesapeake Bay
(À1.3 to À4.0 mm year), will likely continue unabated
into the future. It will be necessary for coastal decision
makers to carefully consider the management options necessary to reduce their impacts.
Floatables/debris
Marine debris, notably plastics, has become an international problem in estuarine and marine environments.
The use of plastic products has reached an all-time high
in many developed countries; plastic debris has been an
ongoing problem in coastal waters of the USA (Ribic,
1998; Kennish, 2001a). Plastics are particularly damaging
to aquatic environments because they essentially do not
degrade, thereby polluting habitats for many years. They
pose a threat to many organisms, particularly fish, turtles,
birds, and mammals that ingest some of the materials or
become entangled in fishing line, nets, and packing bands.
Some organisms mistake floatables for prey (Shaw and
Day, 1994). The ingestion of plastics and other marine
debris can suffocate the animals or obstruct their digestive
systems, causing death.
Pathogens
Estuaries worldwide are susceptible to the entry of pathogenic microorganisms (i.e., bacteria and viruses) from land
runoff and sewage wastes that pose a risk to human health.
Fecal pollution (i.e., fecal coliform bacteria, enterococci,
and coliphage) and human enteric pathogens and enteroviruses can greatly impair human use of impacted estuarine
and coastal marine waters (Lipp et al., 2001). Faulty septic
systems, sewage treatment plant effluent, and wildlife
wastes often degrade estuarine water quality, which must
be continually monitored. Treated municipal wastewater
and urban stormwater runoff may contain more than
100 enteric pathogens (National Research Council, 1993).
These organisms, which are widely distributed by coastal
storms (Fries et al., 2007), pose a hazard to humans who
swim in contaminated estuarine waters or consume contaminated seafood products.
Parasites, notably helminths and protozoa, are commonly associated with waterborne diseases as well. Helminths linked to untreated sewage in estuarine and other
aquatic systems include hookworms, roundworms, tapeworms, and whipworms. Pathogenic enteric protozoa
derived from sewage contamination can be equally devastating to human health.
Summary
A wide array of anthropogenic factors contributes to estuarine degradation. Chief among these are (1) nutrient loading and eutrophication; (2) sewage and organic wastes;
(3) habitat loss and alteration, shoreline hardening, and
erosion; (4) chemical contaminants; (5) human-induced
sediment/particulate inputs; (6) overfishing; (7) intensive
aquaculture; (8) introduced/invasive species; (9) humanaltered hydrological regimes; (10) climate change;
(11) coastal subsidence; and (12) floatables/debris.
Pathogens coupled to human waste discharges and
wildlife are also significant since they adversely affect
water quality. Anthropogenic stressors can be categorized
into those that degrade water quality and are primarily
chemical and biological in nature (e.g., nutrient enrichment,
chemical contaminants, and pathogens), impact habitat and
are mainly physical factors (e.g., shoreline hardening,
lagoon construction, dredging and dredged-material
ANTHROPOGENIC IMPACTS
33
case of New Jersey and other mid-Atlantic states in the USA.
Rising sea level and coastal inundation will lead to significant loss of some coastal wetlands, eliminating buffer
and rendering coastal communities more vulnerable to
extreme events. Human-induced climate change will also
alter temperature and salinity regimes and the structure
and function of biotic communities in estuaries
(Kennish, 2002). Configurations of estuarine basins will
be modified as they widen and deepen. Shifts will occur
in nutrient and sediment supply as well as freshwater
inputs. Tidal prisms and tidal ranges will change in many
systems. More frequent flooding and inundation of
bayshore areas will pose hazards to vulnerable coastal
communities worldwide (Kennish et al., 2008).
Coastal subsidence
Subsiding coasts result in similar impacts as rising sea
level on estuarine and wetland systems. For example, as
coastal subsidence increases, estuarine shoreline retreats
and land submergence accelerates causing the loss of
fringing wetland habitat. The wet surface area of the estuary expands, together with the basin volume, thereby altering the system bathymetry and configuration. The salinity
regime, circulation, and other physical-chemical characteristics of the estuary can change considerably as well,
which will also affect biotic communities.
The effects of coastal subsidence are becoming more
evident around the world with accelerating population
growth and development in coastal watersheds. Human
activities have contributed greatly to the subsidence problems in some areas via excessive groundwater withdrawal
for domestic and agricultural use and oil and gas extraction. Natural factors, such as subsurface sediment compaction, crustal (tectonic) movements, and sinkhole
formation by karst processes, are more significant in some
regions. In the USA, subsidence has been well chronicled
at Galveston Bay, Texas, due to oil and gas extraction
(Shipley and Kiesling, 1994), along the Louisiana coast
due to sediment compaction (DeLaune and Pezeshki,
1994), and at Chesapeake Bay due to groundwater withdrawal and other factors (Boon et al., 2010).
Significant coastal subsidence has also been
documented in other countries (e.g., Po Delta, Italy, and
Tokyo, Japan) (Kennish et al., 2008). Coastal subsidence
problems will take on added significance during the
twenty-first century, exacerbating those due to eustatic
sea-level rise (Kennish, 2002). Subsidence rates, such as
those noted by Boon et al. (2010) at Chesapeake Bay
(À1.3 to À4.0 mm year), will likely continue unabated
into the future. It will be necessary for coastal decision
makers to carefully consider the management options necessary to reduce their impacts.
Floatables/debris
Marine debris, notably plastics, has become an international problem in estuarine and marine environments.
The use of plastic products has reached an all-time high
in many developed countries; plastic debris has been an
ongoing problem in coastal waters of the USA (Ribic,
1998; Kennish, 2001a). Plastics are particularly damaging
to aquatic environments because they essentially do not
degrade, thereby polluting habitats for many years. They
pose a threat to many organisms, particularly fish, turtles,
birds, and mammals that ingest some of the materials or
become entangled in fishing line, nets, and packing bands.
Some organisms mistake floatables for prey (Shaw and
Day, 1994). The ingestion of plastics and other marine
debris can suffocate the animals or obstruct their digestive
systems, causing death.
Pathogens
Estuaries worldwide are susceptible to the entry of pathogenic microorganisms (i.e., bacteria and viruses) from land
runoff and sewage wastes that pose a risk to human health.
Fecal pollution (i.e., fecal coliform bacteria, enterococci,
and coliphage) and human enteric pathogens and enteroviruses can greatly impair human use of impacted estuarine
and coastal marine waters (Lipp et al., 2001). Faulty septic
systems, sewage treatment plant effluent, and wildlife
wastes often degrade estuarine water quality, which must
be continually monitored. Treated municipal wastewater
and urban stormwater runoff may contain more than
100 enteric pathogens (National Research Council, 1993).
These organisms, which are widely distributed by coastal
storms (Fries et al., 2007), pose a hazard to humans who
swim in contaminated estuarine waters or consume contaminated seafood products.
Parasites, notably helminths and protozoa, are commonly associated with waterborne diseases as well. Helminths linked to untreated sewage in estuarine and other
aquatic systems include hookworms, roundworms, tapeworms, and whipworms. Pathogenic enteric protozoa
derived from sewage contamination can be equally devastating to human health.
Summary
A wide array of anthropogenic factors contributes to estuarine degradation. Chief among these are (1) nutrient loading and eutrophication; (2) sewage and organic wastes;
(3) habitat loss and alteration, shoreline hardening, and
erosion; (4) chemical contaminants; (5) human-induced
sediment/particulate inputs; (6) overfishing; (7) intensive
aquaculture; (8) introduced/invasive species; (9) humanaltered hydrological regimes; (10) climate change;
(11) coastal subsidence; and (12) floatables/debris.
Pathogens coupled to human waste discharges and
wildlife are also significant since they adversely affect
water quality. Anthropogenic stressors can be categorized
into those that degrade water quality and are primarily
chemical and biological in nature (e.g., nutrient enrichment,
chemical contaminants, and pathogens), impact habitat and
are mainly physical factors (e.g., shoreline hardening,
lagoon construction, dredging and dredged-material
ANTHROPOGENIC IMPACTS
33