coastal lagoons, the influx of sediments from land sources
is minimal, and a significant amount of sediment accumulating in various areas of the lagoonal basin is the result of
sediment reworking of the lagoonal floor. This is the case
in Barnegat Bay-Little Egg Harbor, New Jersey (Psuty,
2004; Psuty and Silveira, 2009), as well as many other
temperate coastal lagoons of North America (Oertel,
2005). Coarser sediments generally are found in proximity
to the backbarriers and tidal inlets. These sediments,
which are typically better sorted than those near the mainland, primarily derive from marine and backbarrier
sources via storm surge and overwash events which build
washover fans, and tidal currents through inlets which
build ebb-tidal deltas and other sandy deposits in the
lagoonal basin.
Biotic production
Coastal lagoons are characterized by high levels of biotic
production. This is so because the photic zone extends to
the lagoonal floor in most areas, and they usually receive
considerable amounts of nutrients from the surrounding
watersheds which stimulate primary production. Benthic
algal and seagrass production can exceed phytoplankton
production in coastal lagoons. In addition, there is strong
benthic-pelagic coupling; in coastal lagoons the effects
of biogeochemical cycling, bioturbation, and other interactions between the bottom sediments and the overlying
water column may be far greater than those in deeper estuaries. Nutrients may be recycled many times before
exiting inlets to the coastal ocean due to protracted water
residence times which account for high rates of productivity per unit nutrient input (Kennish and Paerl, 2010b).
The range of annual primary production in coastal
lagoons is large ($50–>500 g C m
À2 year
À1
). Based on
the classification of Nixon (1995), many coastal lagoons
fall within the range of eutrophic conditions (300–500 g
C m
À2
year
À1
) or even exhibit hypereutrophic
conditions (>500 g C m
À2 year
À1
) (Nixon, 1995). The high
primary production in these water bodies, together with the
input of organic matter from adjoining wetlands and
external systems, supports rich faunal communities, with
many species utilizing these environments seasonally.
Benthic macrofaunal productivity in coastal lagoons
amounts to $20–200 g ash-free dry weight m
À2 year
À1
,
with zooplankton productivity being as much as 50 % of this
amount. Nekton productivity in turn ranges from $10 % to
100 % of the zooplankton productivity in these systems
(Alvarez-Borrego, 1994). Coastal lagoons also provide ideal
nursery and feeding habitats for many marine fauna
(Kennish and Paerl, 2010b; Day et al., 2012).
Anthropogenic effects
Coastal lagoons are used for fisheries and aquaculture,
energy production, biotechnology, transportation, shipping, and many other human uses (Pauly and YáñezArancibia, 1994; Kennish and Paerl, 2010b). Watersheds
surrounding coastal lagoons are often heavily populated
and developed because of the great commercial and recreational value of these water bodies, their exceptional
ecosystem services, and the access they afford to coastal
ocean waters. However, altered land use/land cover of
upland areas associated with increasing population growth
and development, together with escalating human activities in the coastal lagoons themselves, has impacted their
structure and function and compromised their ecological
integrity (Kennish and Paerl, 2010b). For example, the
removal of natural vegetation, compaction of soils, and
construction of impervious surfaces promote nutrient runoff into the lagoons, hastening their nutrient enrichment
and eutrophication (Kennish, 1997; Kennish, 2002).
Eutrophication of coastal lagoons and estuaries is on
the increase worldwide (Nixon, 1995; Kennish et al.,
2008; Kennish, 2009; Kennish and Paerl, 2010a), and it
poses the greatest threat to the ecological integrity of these
valuable ecosystems (Kennish and de Jonge, 2011). Eutrophication leads to an array of cascading changes in ecosystem structure and function such as decreased dissolved
oxygen levels, increased microalgal and macroalgal abundance, occurrence of harmful algal blooms (HABs), loss
of seagrass habitat, reduced biodiversity, declining fisheries, imbalanced food webs, altered biogeochemical
cycling, and diminished ecosystem services (Nixon,
1995; Kennish, 1997; Kennish et al., 2008; Kennish and
Paerl, 2010b).
Because of their extreme enclosure and restricted circulation, coastal lagoons are highly susceptible to accumulation of chemical contaminants such as polycyclic aromatic
hydrocarbons, halogenated hydrocarbons, and metals.
Bottom sediments serve as a repository and secondary
pool of these hazardous substances. Volatile organics
and plastics are also a potential threat to organisms
inhabiting these environments. Oil spills are particularly
detrimental. Pathogens delivered to lagoonal systems in
stormwater runoff subsequent to rainfall events frequently
compromise their water quality, although such events are
usually ephemeral.
The shorelines of many coastal lagoons are altered by
housing and bulkhead construction, which interferes with
natural processes and directly impacts habitat. The siting
of marinas along these shorelines, oil and gasoline leakages from fixed installations, sanitation-tank releases from
boats, sewage wastewater discharges, and dredging activities adversely affect lagoonal organisms. Aquaculture
operations can markedly degrade water quality in confined areas. In many systems, organic loading contributes
to elevated BOD levels and significant oxygen depletion
leading to system impairment.
Conclusions
Coastal lagoons are highly productive, enclosed water
bodies that are heavily utilized by humans. They are complex physiographic features susceptible to eutrophication
and other anthropogenic impacts due to their relatively
low freshwater inputs, shallow depths, restricted
142
COASTAL LAGOONS
is minimal, and a significant amount of sediment accumulating in various areas of the lagoonal basin is the result of
sediment reworking of the lagoonal floor. This is the case
in Barnegat Bay-Little Egg Harbor, New Jersey (Psuty,
2004; Psuty and Silveira, 2009), as well as many other
temperate coastal lagoons of North America (Oertel,
2005). Coarser sediments generally are found in proximity
to the backbarriers and tidal inlets. These sediments,
which are typically better sorted than those near the mainland, primarily derive from marine and backbarrier
sources via storm surge and overwash events which build
washover fans, and tidal currents through inlets which
build ebb-tidal deltas and other sandy deposits in the
lagoonal basin.
Biotic production
Coastal lagoons are characterized by high levels of biotic
production. This is so because the photic zone extends to
the lagoonal floor in most areas, and they usually receive
considerable amounts of nutrients from the surrounding
watersheds which stimulate primary production. Benthic
algal and seagrass production can exceed phytoplankton
production in coastal lagoons. In addition, there is strong
benthic-pelagic coupling; in coastal lagoons the effects
of biogeochemical cycling, bioturbation, and other interactions between the bottom sediments and the overlying
water column may be far greater than those in deeper estuaries. Nutrients may be recycled many times before
exiting inlets to the coastal ocean due to protracted water
residence times which account for high rates of productivity per unit nutrient input (Kennish and Paerl, 2010b).
The range of annual primary production in coastal
lagoons is large ($50–>500 g C m
À2 year
À1
). Based on
the classification of Nixon (1995), many coastal lagoons
fall within the range of eutrophic conditions (300–500 g
C m
À2
year
À1
) or even exhibit hypereutrophic
conditions (>500 g C m
À2 year
À1
) (Nixon, 1995). The high
primary production in these water bodies, together with the
input of organic matter from adjoining wetlands and
external systems, supports rich faunal communities, with
many species utilizing these environments seasonally.
Benthic macrofaunal productivity in coastal lagoons
amounts to $20–200 g ash-free dry weight m
À2 year
À1
,
with zooplankton productivity being as much as 50 % of this
amount. Nekton productivity in turn ranges from $10 % to
100 % of the zooplankton productivity in these systems
(Alvarez-Borrego, 1994). Coastal lagoons also provide ideal
nursery and feeding habitats for many marine fauna
(Kennish and Paerl, 2010b; Day et al., 2012).
Anthropogenic effects
Coastal lagoons are used for fisheries and aquaculture,
energy production, biotechnology, transportation, shipping, and many other human uses (Pauly and YáñezArancibia, 1994; Kennish and Paerl, 2010b). Watersheds
surrounding coastal lagoons are often heavily populated
and developed because of the great commercial and recreational value of these water bodies, their exceptional
ecosystem services, and the access they afford to coastal
ocean waters. However, altered land use/land cover of
upland areas associated with increasing population growth
and development, together with escalating human activities in the coastal lagoons themselves, has impacted their
structure and function and compromised their ecological
integrity (Kennish and Paerl, 2010b). For example, the
removal of natural vegetation, compaction of soils, and
construction of impervious surfaces promote nutrient runoff into the lagoons, hastening their nutrient enrichment
and eutrophication (Kennish, 1997; Kennish, 2002).
Eutrophication of coastal lagoons and estuaries is on
the increase worldwide (Nixon, 1995; Kennish et al.,
2008; Kennish, 2009; Kennish and Paerl, 2010a), and it
poses the greatest threat to the ecological integrity of these
valuable ecosystems (Kennish and de Jonge, 2011). Eutrophication leads to an array of cascading changes in ecosystem structure and function such as decreased dissolved
oxygen levels, increased microalgal and macroalgal abundance, occurrence of harmful algal blooms (HABs), loss
of seagrass habitat, reduced biodiversity, declining fisheries, imbalanced food webs, altered biogeochemical
cycling, and diminished ecosystem services (Nixon,
1995; Kennish, 1997; Kennish et al., 2008; Kennish and
Paerl, 2010b).
Because of their extreme enclosure and restricted circulation, coastal lagoons are highly susceptible to accumulation of chemical contaminants such as polycyclic aromatic
hydrocarbons, halogenated hydrocarbons, and metals.
Bottom sediments serve as a repository and secondary
pool of these hazardous substances. Volatile organics
and plastics are also a potential threat to organisms
inhabiting these environments. Oil spills are particularly
detrimental. Pathogens delivered to lagoonal systems in
stormwater runoff subsequent to rainfall events frequently
compromise their water quality, although such events are
usually ephemeral.
The shorelines of many coastal lagoons are altered by
housing and bulkhead construction, which interferes with
natural processes and directly impacts habitat. The siting
of marinas along these shorelines, oil and gasoline leakages from fixed installations, sanitation-tank releases from
boats, sewage wastewater discharges, and dredging activities adversely affect lagoonal organisms. Aquaculture
operations can markedly degrade water quality in confined areas. In many systems, organic loading contributes
to elevated BOD levels and significant oxygen depletion
leading to system impairment.
Conclusions
Coastal lagoons are highly productive, enclosed water
bodies that are heavily utilized by humans. They are complex physiographic features susceptible to eutrophication
and other anthropogenic impacts due to their relatively
low freshwater inputs, shallow depths, restricted
142
COASTAL LAGOONS