(i.e., “harmful” effects) for ecosystem structure and function, such as the production of toxins, depression of oxygen levels, severe light attenuation, alterations in food
web structure, and related impacts on aquatic animal
and human health (Moore et al., 2008). Concerns about
the impacts of harmful algae blooms have grown
with increasing evidence that human activities have
increased the frequency, intensity, and magnitude of
blooms (Heisler et al., 2008). Among these concerns
are the potential effects of future changes in climate on
phytoplankton blooms (Moore et al., 2008; Paerl and
Huisman, 2009; Wetz and Yoskowitz, 2013).
Conclusions
The rapidly increasing body of knowledge on the
ecophysiology of phytoplankton blooms and the growing
availability of long-term data sets are providing a better
picture of the factors that control blooms. These
advancements, along with breakthroughs in computing
and monitoring technologies, are providing the framework for the development of predictive models and
effective management strategies.
Bibliography
Burkholder, J. M., Glibert, P. M., and Skeleton, H. M., 2008.
Mixotrophy, a major mode of nutrition for harmful species in
eutrophic waters. Harmful Algae, 8, 77–93.
Heisler, J. P., Clibert, P. M., Burkholder, J. A., Anderson, D. M.,
Cochlan, W., Dennison, W., Dortch, Q., Gobler, C. J., Heil, C.,
Humphries, E., Lewitus, A., Magnien, R., Marshall, H., Sellner,
S., Stockwell, D., Stoecker, D., and Suddleson, M., 2008. Eutrophication and harmful algal blooms: a scientific consensus.
Harmful Algae, 8, 3–13.
Moore, S. K., Trainer, V. L., Mantua, N. J., Parker, M. S., Laws,
E. A., Backer, L. C., and Fleming, L. E., 2008. Impacts of climate variability and future change on harmful algal blooms
and human health. Environmental Health, 7(Supplement 2),
doi:10.1186/1476-069X-7-S2-S4
Paerl, H. W., and Huisman, J., 2009. Climate change: a catalyst for
global expansion of harmful cyanobacterial blooms. Environmental Microbiology Reports, 1, 27–37.
Phlips, E. J., 2002. Eutrophication and algae. In Bitton, G. (ed.),
Encyclopedia of Environmental Microbiology. New York: Wiley.
Reynolds, C. S., 2006. Ecology of Phytoplankton. Cambridge:
Cambridge University Press.
Smayda, T. J., 1997. What is a bloom? A commentary. Limnology
and Oceanography, 42, 1132–1136.
Wetz, M. S., and Yoskowitz, D. W., 2013. An extreme future for
estuaries? Effects of extreme climatic events on estuarine water
quality and ecology. Marine Pollution Bulletin, 69, 7–18.
Cross-references
Algal Blooms
Anoxia, Hypoxia, and Dead Zones
Anthropogenic Impacts
Climate Change
Cyanobacteria
Eutrophication
Food Web/Trophic Dynamics
Macroalgal Blooms
Toxic Blooms
PNEUMATOPHORES
Luzhen Chen
College of the Environment and Ecology, Xiamen
University, Xiamen, China
Definition
Pneumatophores are specialized aerial roots stemming
from a subterranean root system, which enable plants to
utilize air in waterlogged soil habitats.
Description
Mangrove pneumatophores vary in size and morphological
characteristics. The black mangroves (Avicennia spp.) have
pencillike or fingerlike pneumatophores, while those of
Sonneratia species are conical. Pneumatophores are usually
unbranched, but branching may occur when damaged. Typical pneumatophore height is generally less than 30 cm for
Avicennia, less than 20 cm for Laguncularia, and from
30 to 3 m for Sonneratia species. Pneumatophore density
is typically large; for example, a 2–3 m-tall Avicennia
marina tree usually has more than 10,000 pneumatophores.
In Avicennia and Sonneratia genera, the pneumatophores
contain chlorophyll in the subsurface layers and conduct
photosynthesis in chlorophyllous layers under cuticles
(Hovenden and Allaway, 1994; Duke, 2006).
As a kind of aerial roots, pneumatophore function is
closely correlated with structure. Their surface is usually
covered with lenticels, which permit outside air to diffuse
into the spongy aerenchyma tissue. The aerenchyma is not
only the oxygen container but also the oxygen transport
pathway. Air is transported by aerenchyma to other
parts of the plant, especially the underground roots
below the pneumatophores that are tidally inundated. The
pneumatophores are also pathways for carbon dioxide.
Thus, oxygen can be pumped into the pneumatophores,
enabling some mangrove species to survive in waterlogged
conditions, while carbon dioxide, as a by-product of respiration, can be detected outside the pneumatophores
(Scholander et al., 1955; Tomlinson, 1986).
Bibliography
Duke, N., 2006. Australia’s Mangroves: The Authoritative Guide to
Australia’s Mangrove Plants. Brisbane: University of
Queensland.
Hovenden, M. J., and Allaway, W. G., 1994. Horizontal structures
on pneumatophores of Avicennia marina (Fotsk.) Vierh –
a new site of oxygen conductance. Annals of Botany, 73,
377–383.
Scholander, P. F., van Dam, L., and Scholander, S. I., 1955. Gas
exchange in the roots of mangroves. American Journal of
Botany, 42, 92–98.
Tomlinson, P., 1986. The Botany of Mangroves. Cambridge:
Cambridge University Press.
Cross-references
Mangroves
494
PNEUMATOPHORES
web structure, and related impacts on aquatic animal
and human health (Moore et al., 2008). Concerns about
the impacts of harmful algae blooms have grown
with increasing evidence that human activities have
increased the frequency, intensity, and magnitude of
blooms (Heisler et al., 2008). Among these concerns
are the potential effects of future changes in climate on
phytoplankton blooms (Moore et al., 2008; Paerl and
Huisman, 2009; Wetz and Yoskowitz, 2013).
Conclusions
The rapidly increasing body of knowledge on the
ecophysiology of phytoplankton blooms and the growing
availability of long-term data sets are providing a better
picture of the factors that control blooms. These
advancements, along with breakthroughs in computing
and monitoring technologies, are providing the framework for the development of predictive models and
effective management strategies.
Bibliography
Burkholder, J. M., Glibert, P. M., and Skeleton, H. M., 2008.
Mixotrophy, a major mode of nutrition for harmful species in
eutrophic waters. Harmful Algae, 8, 77–93.
Heisler, J. P., Clibert, P. M., Burkholder, J. A., Anderson, D. M.,
Cochlan, W., Dennison, W., Dortch, Q., Gobler, C. J., Heil, C.,
Humphries, E., Lewitus, A., Magnien, R., Marshall, H., Sellner,
S., Stockwell, D., Stoecker, D., and Suddleson, M., 2008. Eutrophication and harmful algal blooms: a scientific consensus.
Harmful Algae, 8, 3–13.
Moore, S. K., Trainer, V. L., Mantua, N. J., Parker, M. S., Laws,
E. A., Backer, L. C., and Fleming, L. E., 2008. Impacts of climate variability and future change on harmful algal blooms
and human health. Environmental Health, 7(Supplement 2),
doi:10.1186/1476-069X-7-S2-S4
Paerl, H. W., and Huisman, J., 2009. Climate change: a catalyst for
global expansion of harmful cyanobacterial blooms. Environmental Microbiology Reports, 1, 27–37.
Phlips, E. J., 2002. Eutrophication and algae. In Bitton, G. (ed.),
Encyclopedia of Environmental Microbiology. New York: Wiley.
Reynolds, C. S., 2006. Ecology of Phytoplankton. Cambridge:
Cambridge University Press.
Smayda, T. J., 1997. What is a bloom? A commentary. Limnology
and Oceanography, 42, 1132–1136.
Wetz, M. S., and Yoskowitz, D. W., 2013. An extreme future for
estuaries? Effects of extreme climatic events on estuarine water
quality and ecology. Marine Pollution Bulletin, 69, 7–18.
Cross-references
Algal Blooms
Anoxia, Hypoxia, and Dead Zones
Anthropogenic Impacts
Climate Change
Cyanobacteria
Eutrophication
Food Web/Trophic Dynamics
Macroalgal Blooms
Toxic Blooms
PNEUMATOPHORES
Luzhen Chen
College of the Environment and Ecology, Xiamen
University, Xiamen, China
Definition
Pneumatophores are specialized aerial roots stemming
from a subterranean root system, which enable plants to
utilize air in waterlogged soil habitats.
Description
Mangrove pneumatophores vary in size and morphological
characteristics. The black mangroves (Avicennia spp.) have
pencillike or fingerlike pneumatophores, while those of
Sonneratia species are conical. Pneumatophores are usually
unbranched, but branching may occur when damaged. Typical pneumatophore height is generally less than 30 cm for
Avicennia, less than 20 cm for Laguncularia, and from
30 to 3 m for Sonneratia species. Pneumatophore density
is typically large; for example, a 2–3 m-tall Avicennia
marina tree usually has more than 10,000 pneumatophores.
In Avicennia and Sonneratia genera, the pneumatophores
contain chlorophyll in the subsurface layers and conduct
photosynthesis in chlorophyllous layers under cuticles
(Hovenden and Allaway, 1994; Duke, 2006).
As a kind of aerial roots, pneumatophore function is
closely correlated with structure. Their surface is usually
covered with lenticels, which permit outside air to diffuse
into the spongy aerenchyma tissue. The aerenchyma is not
only the oxygen container but also the oxygen transport
pathway. Air is transported by aerenchyma to other
parts of the plant, especially the underground roots
below the pneumatophores that are tidally inundated. The
pneumatophores are also pathways for carbon dioxide.
Thus, oxygen can be pumped into the pneumatophores,
enabling some mangrove species to survive in waterlogged
conditions, while carbon dioxide, as a by-product of respiration, can be detected outside the pneumatophores
(Scholander et al., 1955; Tomlinson, 1986).
Bibliography
Duke, N., 2006. Australia’s Mangroves: The Authoritative Guide to
Australia’s Mangrove Plants. Brisbane: University of
Queensland.
Hovenden, M. J., and Allaway, W. G., 1994. Horizontal structures
on pneumatophores of Avicennia marina (Fotsk.) Vierh –
a new site of oxygen conductance. Annals of Botany, 73,
377–383.
Scholander, P. F., van Dam, L., and Scholander, S. I., 1955. Gas
exchange in the roots of mangroves. American Journal of
Botany, 42, 92–98.
Tomlinson, P., 1986. The Botany of Mangroves. Cambridge:
Cambridge University Press.
Cross-references
Mangroves
494
PNEUMATOPHORES