roselike (ῥ odeiοB) and stone (lίyοϚ). A rhodolith
could be monospecific or multispecific, that is, if it consists of one or more than one coralline algal species.
A rhodolith is developed around a nucleus of a rock,
coral, shell, or any other element which serves as
substrate for their development, but they also are found
without any material in the center, usually consisting of
a number of concentric thallus layers. Rhodoliths have
a wide variety of growth forms ranging from fruticose
to lumpy, and they are discoid or irregular shaped averaging approximately 6 cm in diameter (Foster, 2001).
Rhodoliths are slow growing and can be long lived
(>100 years), being resilient to varying environmental
disturbances (Bosence, 1983b). They form a high-Mg
calcite skeleton with periodic growth bands. Recent geochemical studies on coralline algae have focused on
sea-surface temperature (SST) secular changes and have
revealed a strong relationship with the variations of the
Mg/Ca ratio in the algal skeleton at a monthly or
biweekly resolution (Kamenos et al., 2008, 2009). They
can form extensive beds, typically 30–100 % cover or
more with layers over the seafloor, mostly in coarse clean
gravels and sands or muddy mixed sediments. They
can occur either on the open coast or in tide-swept
channels of marine inlets. Rhodolith beds represent the
transition between rocky and sandy areas (Foster, 2001)
in which they may be mixed with kelp/fucalean forest
or with seagrasses, but they can also cover extensive
areas alone.
Rhodolith/maerl beds have been found worldwide,
from low to high latitudes, at different depths, ranging
from the intertidal down to 286 m (see review in Foster,
2001). Rhodoliths provide a stable, three-dimensional
habitat onto which a wide variety of species can attach,
including other algae, commercial species such as clams
and scallops, and true corals. Although rhodoliths are
resilient to a variety of environmental disturbances, they
can be severely impacted by harvesting of commercial
species (Steller et al., 2003), ocean acidification, or global
warming (Martin and Gattuso, 2009).
Rhodoliths are a common feature of modern and
ancient carbonate shelves worldwide (Nelson, 2009).
Rhodolith communities contribute significantly to the
global calcium carbonate budget (Amado-Filho et al.,
2012), and fossil rhodoliths are commonly used to
obtain paleoecologic and paleoclimatic information
(Kamenos et al., 2008; Kamenos et al., 2009). More
recently, the geological nomenclature indicates that the fossil counterparts of living rhodolith beds include a suite of
terms such as rhodolith facies, coralline algal facies,
rhodolith rudstone and floatstone, oncolithic rudstone,
rhodolith pavements (¼ densely packed rhodolith
rudstone), coralline algal nodule limestone, maerl pavement, red algal clast rudstone, and coralline branch rudstone
and floatstone. Under the right conditions, rhodoliths can be
the main carbonate sediment producers, often forming
extensive deposits of beaches or sand dunes. They have
an excellent fossil record since the Early Cretaceous
(Aguirre et al., 2000).
Bibliography
Aguirre, J., Riding, R., and Braga, J. C., 2000. Diversity of coralline
red algae: origination and extinction patterns from Early
Cretaceous to Pleistocene. Paleobiology, 26, 651–667.
Amado-Filho, G. M., Moura, R. L., Bastos, A. C., Salgado, L. T.,
and Sumida, P. Y., 2012. Rhodolith beds are major CaCO 3
bio-factories in the tropical South West Atlantic. PLoS ONE,
7(4), e35171.
Bosence, D. W. J., 1983a. The occurrence and ecology of recent
rhodoliths – a review. In Peryt, T. M. (ed.), Coated Grains.
Berlin: Springer, pp. 225–242.
Bosence, D. W. J., 1983b. Coralline algal reef frameworks. Journal
of the Geological Society of London, 140, 365–376.
Foster, M. S., 2001. Rhodoliths: between rocks and soft places.
Journal of Phycology, 37, 659–667.
Kamenos, N., Cusack, M., and Moore, P. G., 2008. Coralline algae
are global palaeothermometers with bi-weekly resolution.
Geochimica et Cosmochimica Acta, 72, 771–779.
Kamenos, N. A., Cusack, M., Huthwelker, T., Lagarde, P., and
Scheibling, R. E., 2009. Mg-lattice associations in red
coralline algae. Geochimica et Cosmochimica Acta, 73,
1901–1907.
Martin, S., and Gattuso, J., 2009. Response of Mediterranean
coralline algae to ocean acidification and elevated temperature.
Global Change Biology, 15, 2089–2100.
Nelson, W. A., 2009. Calcified macroalgae – critical to coastal
ecosystems and vulnerable to change: a review. Marine and
Freshwater Research, 60, 787–801.
Steller, D., Riosmena-Rodriguez, R., Foster, M. S., and Roberts, C. A.,
2003. Species assemblages associated with Mexican rhodolith
beds: the importance of rhodolith structure. Aquatic Conservation –
Marine and Freshwater Ecosystems, 13, S5–S20.
Cross-references
Macroalgae
RIA
J. Javier Diez
1 and Efren M. Veiga
2
1
Research Group on Marine, Coastal and Port
Environment and Other Sensitive Areas, Department of
Land and Urban Planning and Environment, Universidad
Politécnica de Madrid, Madrid, Spain
2
Civil Engineering: Land & Urban Management and
Environment, Universidad Politécnica de Madrid,
Escuela de Caminos, Canales y Puertos, Madrid, Spain
Synonyms
Flooded river valley
RIA
505
could be monospecific or multispecific, that is, if it consists of one or more than one coralline algal species.
A rhodolith is developed around a nucleus of a rock,
coral, shell, or any other element which serves as
substrate for their development, but they also are found
without any material in the center, usually consisting of
a number of concentric thallus layers. Rhodoliths have
a wide variety of growth forms ranging from fruticose
to lumpy, and they are discoid or irregular shaped averaging approximately 6 cm in diameter (Foster, 2001).
Rhodoliths are slow growing and can be long lived
(>100 years), being resilient to varying environmental
disturbances (Bosence, 1983b). They form a high-Mg
calcite skeleton with periodic growth bands. Recent geochemical studies on coralline algae have focused on
sea-surface temperature (SST) secular changes and have
revealed a strong relationship with the variations of the
Mg/Ca ratio in the algal skeleton at a monthly or
biweekly resolution (Kamenos et al., 2008, 2009). They
can form extensive beds, typically 30–100 % cover or
more with layers over the seafloor, mostly in coarse clean
gravels and sands or muddy mixed sediments. They
can occur either on the open coast or in tide-swept
channels of marine inlets. Rhodolith beds represent the
transition between rocky and sandy areas (Foster, 2001)
in which they may be mixed with kelp/fucalean forest
or with seagrasses, but they can also cover extensive
areas alone.
Rhodolith/maerl beds have been found worldwide,
from low to high latitudes, at different depths, ranging
from the intertidal down to 286 m (see review in Foster,
2001). Rhodoliths provide a stable, three-dimensional
habitat onto which a wide variety of species can attach,
including other algae, commercial species such as clams
and scallops, and true corals. Although rhodoliths are
resilient to a variety of environmental disturbances, they
can be severely impacted by harvesting of commercial
species (Steller et al., 2003), ocean acidification, or global
warming (Martin and Gattuso, 2009).
Rhodoliths are a common feature of modern and
ancient carbonate shelves worldwide (Nelson, 2009).
Rhodolith communities contribute significantly to the
global calcium carbonate budget (Amado-Filho et al.,
2012), and fossil rhodoliths are commonly used to
obtain paleoecologic and paleoclimatic information
(Kamenos et al., 2008; Kamenos et al., 2009). More
recently, the geological nomenclature indicates that the fossil counterparts of living rhodolith beds include a suite of
terms such as rhodolith facies, coralline algal facies,
rhodolith rudstone and floatstone, oncolithic rudstone,
rhodolith pavements (¼ densely packed rhodolith
rudstone), coralline algal nodule limestone, maerl pavement, red algal clast rudstone, and coralline branch rudstone
and floatstone. Under the right conditions, rhodoliths can be
the main carbonate sediment producers, often forming
extensive deposits of beaches or sand dunes. They have
an excellent fossil record since the Early Cretaceous
(Aguirre et al., 2000).
Bibliography
Aguirre, J., Riding, R., and Braga, J. C., 2000. Diversity of coralline
red algae: origination and extinction patterns from Early
Cretaceous to Pleistocene. Paleobiology, 26, 651–667.
Amado-Filho, G. M., Moura, R. L., Bastos, A. C., Salgado, L. T.,
and Sumida, P. Y., 2012. Rhodolith beds are major CaCO 3
bio-factories in the tropical South West Atlantic. PLoS ONE,
7(4), e35171.
Bosence, D. W. J., 1983a. The occurrence and ecology of recent
rhodoliths – a review. In Peryt, T. M. (ed.), Coated Grains.
Berlin: Springer, pp. 225–242.
Bosence, D. W. J., 1983b. Coralline algal reef frameworks. Journal
of the Geological Society of London, 140, 365–376.
Foster, M. S., 2001. Rhodoliths: between rocks and soft places.
Journal of Phycology, 37, 659–667.
Kamenos, N., Cusack, M., and Moore, P. G., 2008. Coralline algae
are global palaeothermometers with bi-weekly resolution.
Geochimica et Cosmochimica Acta, 72, 771–779.
Kamenos, N. A., Cusack, M., Huthwelker, T., Lagarde, P., and
Scheibling, R. E., 2009. Mg-lattice associations in red
coralline algae. Geochimica et Cosmochimica Acta, 73,
1901–1907.
Martin, S., and Gattuso, J., 2009. Response of Mediterranean
coralline algae to ocean acidification and elevated temperature.
Global Change Biology, 15, 2089–2100.
Nelson, W. A., 2009. Calcified macroalgae – critical to coastal
ecosystems and vulnerable to change: a review. Marine and
Freshwater Research, 60, 787–801.
Steller, D., Riosmena-Rodriguez, R., Foster, M. S., and Roberts, C. A.,
2003. Species assemblages associated with Mexican rhodolith
beds: the importance of rhodolith structure. Aquatic Conservation –
Marine and Freshwater Ecosystems, 13, S5–S20.
Cross-references
Macroalgae
RIA
J. Javier Diez
1 and Efren M. Veiga
2
1
Research Group on Marine, Coastal and Port
Environment and Other Sensitive Areas, Department of
Land and Urban Planning and Environment, Universidad
Politécnica de Madrid, Madrid, Spain
2
Civil Engineering: Land & Urban Management and
Environment, Universidad Politécnica de Madrid,
Escuela de Caminos, Canales y Puertos, Madrid, Spain
Synonyms
Flooded river valley
RIA
505