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Eutrophication Impacts on Salt
Marshes Natural Metal Remediation
Isabel Caçador and Bernardo Duarte
B. Duarte () · I. Caçador
Center of Oceanography, Faculty of Sciences, University of Lisbon,
Campo Grande, 1749–016, Lisbon, Portugal
e-mail: baduarte@fc.ul.pt
Abstract
Salt marshes are a very important part of the estuarine ecosystem, with an important role
within the biogeochemical cycles, being areas of high primary production, which also contribute importantly as shoreline stabilizers. Besides, periodical tidal flooding of salt marshes also causes the transport of significant quantities of pollutants, which tend to accumulate in the marsh ecosystem. Therefore, salt marshes are considered to be important sinks
namely of heavy metals. Their important role has been recently admitted by the inclusion
of these ecosystems in the European Water Framework Directive (WFD). Multiple services
of wetlands and its value are already well known, such as excess contaminant and nutrient
removal. Nitrogen concentrations in salt marsh sediments have been increasing, mostly
owing to the anthropogenic activities increase in the estuarine surrounding areas. This leads
to an increase in the halophyte biomass and an apparent reduction in the phytoremediation capacity. Although eutrophication processes apparently reduce the natural remediation
capacity of the marsh toward the estuary, it also allows an increase in the potential sink
capacity and a reduction of the contaminated detritus export into the estuarine system and
into the food web.
Keywords
Eutrophication · Halophyte · Phytoremediation · Salt marshes
11.1 Salt Marshes: Valuable Ecosystem
Services Providers
Salt marshes have great ecological value, in terms of nutrient
regeneration, primary production, habitat for wildlife, and as
shoreline stabilizers. Periodic tidal flooding of salt marshes
provides large quantities of pollutants to the marsh ecosystem. Thus, salt marshes are considered to be important sinks
for pollutants (Caçador et al. 1993, 1996, 2007; Davy 2000;
Prange and Dennison 2000). Salt marshes are natural sites
for deposition of heavy metals in estuarine systems (Caçador
et al. 1993, 2009; Doyle and Otte 1997; Williams et al. 1994;
Duarte et al. 2010). When located near polluted areas, these
ecosystems receive large amounts of pollutants from industrial and urban wastes that either drift downstream within
the river flow or are the direct result of waste dumping from
nearby industrial and urban areas (Caçador et al. 2009).
When metals enter salt marshes they spread along with the
tides and periodic floods and interact with soil and the biotic
community (Suntornvongsagul et al. 2007). Most salt marsh
plants accumulate large amounts of metals in their aerial and
below ground organs (Caçador et al. 2000). Among these are
the most common plants of southern European salt marshes:
Sarcocorniafruticosa, S. perennis, Halimioneportulacoides
and Spartinamaritima. Their ability to phytostabilize those
contaminants in the rhizosediment is an important aspect of
self-remediative processes and biogeochemistry in this ecoA. A. Ansari, S. S. Gill (eds.), Eutrophication: Causes, Consequences and Control,
DOI 10.1007/978-94-007-7814-6_11, © Springer Science+Business Media Dordrecht 2014
11
Eutrophication Impacts on Salt
Marshes Natural Metal Remediation
Isabel Caçador and Bernardo Duarte
B. Duarte () · I. Caçador
Center of Oceanography, Faculty of Sciences, University of Lisbon,
Campo Grande, 1749–016, Lisbon, Portugal
e-mail: baduarte@fc.ul.pt
Abstract
Salt marshes are a very important part of the estuarine ecosystem, with an important role
within the biogeochemical cycles, being areas of high primary production, which also contribute importantly as shoreline stabilizers. Besides, periodical tidal flooding of salt marshes also causes the transport of significant quantities of pollutants, which tend to accumulate in the marsh ecosystem. Therefore, salt marshes are considered to be important sinks
namely of heavy metals. Their important role has been recently admitted by the inclusion
of these ecosystems in the European Water Framework Directive (WFD). Multiple services
of wetlands and its value are already well known, such as excess contaminant and nutrient
removal. Nitrogen concentrations in salt marsh sediments have been increasing, mostly
owing to the anthropogenic activities increase in the estuarine surrounding areas. This leads
to an increase in the halophyte biomass and an apparent reduction in the phytoremediation capacity. Although eutrophication processes apparently reduce the natural remediation
capacity of the marsh toward the estuary, it also allows an increase in the potential sink
capacity and a reduction of the contaminated detritus export into the estuarine system and
into the food web.
Keywords
Eutrophication · Halophyte · Phytoremediation · Salt marshes
11.1 Salt Marshes: Valuable Ecosystem
Services Providers
Salt marshes have great ecological value, in terms of nutrient
regeneration, primary production, habitat for wildlife, and as
shoreline stabilizers. Periodic tidal flooding of salt marshes
provides large quantities of pollutants to the marsh ecosystem. Thus, salt marshes are considered to be important sinks
for pollutants (Caçador et al. 1993, 1996, 2007; Davy 2000;
Prange and Dennison 2000). Salt marshes are natural sites
for deposition of heavy metals in estuarine systems (Caçador
et al. 1993, 2009; Doyle and Otte 1997; Williams et al. 1994;
Duarte et al. 2010). When located near polluted areas, these
ecosystems receive large amounts of pollutants from industrial and urban wastes that either drift downstream within
the river flow or are the direct result of waste dumping from
nearby industrial and urban areas (Caçador et al. 2009).
When metals enter salt marshes they spread along with the
tides and periodic floods and interact with soil and the biotic
community (Suntornvongsagul et al. 2007). Most salt marsh
plants accumulate large amounts of metals in their aerial and
below ground organs (Caçador et al. 2000). Among these are
the most common plants of southern European salt marshes:
Sarcocorniafruticosa, S. perennis, Halimioneportulacoides
and Spartinamaritima. Their ability to phytostabilize those
contaminants in the rhizosediment is an important aspect of
self-remediative processes and biogeochemistry in this ecoA. A. Ansari, S. S. Gill (eds.), Eutrophication: Causes, Consequences and Control,
DOI 10.1007/978-94-007-7814-6_11, © Springer Science+Business Media Dordrecht 2014