||Caulerpa sertularioides SG Gmelin Howe, 1905
||Green Feather Alga
The green feather alga,
Caulerpa sertularioides, is among approximately 35 species
and varieties of Caulerpa found in the Caribbean and western
Atlantic Oceans (Littler & Littler 2000). The alga obtains its
name from the feather-like fronds rising from a common stolon. Each
frond is upright, branched and light to dark green in color (Littler
& Littler 2000, Littler et al. 2008, Taylor 1979).
Branchlets are opposite, cylindrical and needle-shaped with upcurved
or straight apices or tips that are bluntly pointed. Each branchlet,
measuring 180-330 µm in diameter and 3-11 mm long, is connected
to a central, cylindrical axis measuring 1.0-1.5 mm in diameter.
These axes connect each frond to a creeping stolon, 2.0-2.5 mm in
diameter and up to 2 m long. Stolons branch to slender points and
rhizoids stem from the ventral or bottom surface of each stolon
to hold the alga to the substrate.
Potentially Misidentified Species
contains two additional varieties, C. sertularioides f. farlowii
and C. sertularioides f. longiseta. The range of
f. farlowii overlaps with the original variety described
above. However, it is more commonly found on reef flats, rocks and
coral fragments (Littler & Littler 2000). Further distinction
can be made by examining the branchlets of f. farlowii, which
are at least twice as thick, crowded and radially arranged on each
frond. The range of the remaining variety, f. longiseta,
is most likely confined to the Greater and Lesser Antilles. Although
similar in appearance to C. sertularioides, this form is
characterized by branching fronds. Three other similar species occur
in Florida waters: C. ashmeadii, C. mexicana and
C. taxifolia. The branchlets and fronds of C. ashmeadii
are usually much larger than those of C. sertularioides,
and are often club-shaped. Branchlets of both C. mexicana
and C. taxifolia are broader and flattened.
HABITAT AND DISTRIBUTION
The range of C. sertularioides extends from North Carolina
to Florida, Bermuda, Bahamas, Greater and Lesser Antilles (Rodríguez-Prieto
et al. 1999), Gulf of Mexico, throughout the Caribbean
(Littler & Littler 2000, Littler et al. 2008) and in
the southern Atlantic Ocean to Brazil (Taylor 1979). The species
also occurs in many locations worldwide, including: the Great Barrier
Reef in Australia (Benzie et al. 1997), Papua New Guinea
(Coppejans & Meinesz 1988), Philippines (Meñez &
Calumpong 1982), Palau (Santoso et al. 2004), and along
the northern Pacific coast of Mexico (Scrosati 2001). In addition,
C. sertularioides is considered to be an invasive alga
along the northern Pacific coast of Costa Rica, where it is spreading
rapidly over coral reefs (Fernández & Cortés 2005).
The green feather alga is mostly found in coastal and estuarine
environments, growing in sandy areas, seagrass beds or on mangrove
prop roots (Littler et al. 2008). It is commonly a shallow-water
species, occurring to 10 m deep, although sparse individuals have
been dredged from depths of up to 110 m (Taylor 1979).
This green alga occurs throughout the Indian River Lagoon, often
carpeting the lagoon bottom, jetties and seawalls (Littler et
al. 2008). Fronds can be found attached to the prop roots of
the red mangrove, Rhizophora mangle,
and scattered among seagrass beds.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Information concerning the lifespan and age of C. sertularioides
is limited, and growth may vary with water temperature, light and
nutrient availability, salinity and other factors. As mentioned
above, stolons of the green feather alga can reach up to 2 m in
length. To form algal mats, they often overlap and entwine with
other stolons. Fronds originating from the stolons can grow up to
20 cm high and 2 cm wide (Littler & Littler 2000).
Abundance of C. sertularioides can vary depending on environmental
conditions and other factors. Single stolons supporting a few fronds
can be found in between seagrass blades, on rocks and shells, and
attached to mangrove prop roots. However, carpets of the alga can
grow as large as several square meters in certain habitats.
Like most other macroalgae, C. sertularioides can reproduce
sexually or asexually. Asexual reproduction occurs via fragmentation
of the parent plant. These pieces of the original alga can drift
through the water column before settling and starting a new population.
Sexual reproduction occurs by the release of both male and female
gametes. While details on the specific reproductive strategies for
C. sertularioides are lacking, studies on other Caulerpa
species have shown that entire reproductive events may last no longer
than 36 hours. Algae become fertile, release gametes during spawning
events that occur around sunrise, and die after discharging all
cellular contents into the water column (Clifton 1997).
Although information on
the temperature tolerance for C. sertularioides is lacking,
the current tropical and subtropical range of the species suggests
that it thrives best in warm waters.
The green feather alga
is found in a wide range of salinities in tropical and subtropical
estuaries, and coastally on coral reefs. However, this species is
a marine alga, and mortality most likely occurs in salinities lower
than those in which populations naturally occur.
Like other macroalgae,
C. sertularioides is autotrophic, obtaining energy through
photosynthesis. As a photosynthetic organism, it is most commonly
found in shallow waters with high light intensities. In the Indian
River Lagoon, the photosynthetic rates associated with these light
levels are elevated when compared to other species of Caulerpa
(Gacia et al. 1996). Although optimum light and temperature
values likely exist for each species, some studies suggest that
C. sertularioides and other macroalgae have the ability
to adapt to a wide range of environmental conditions (Gacia et
Many marine organisms
may find C. sertularioides unpalatable due to the presence
of chemical compounds within the alga. However, gut contents and
feeding observations have uncovered a few predators of the species,
including: the green sea turtle, Chelonia
mydas (López-Mendilaharsu et al. 2003);
the lettuce slug, Elysia crispata; and the sea slug, Elysia
diomedea (Trench et al. 1972). One sea slug, Oxynoe
panamensis, feeds exclusively of C. sertularioides
by puncturing the alga and sucking up the cellular contents, including
whole chloroplasts (Lewin 1970).
Benefit to the IRL
With its well developed fronds and carpet-like
growth pattern, C. sertularioides can provide habitat structure
for a variety of fishes and invertebrates in the IRL. Algal cover
can act as a refuge from predators and create a nursery habitat
that provides juvenile organisms with food sources. In one example,
aquaculture studies in Mexico on the yellowleg shrimp, Panaeus
californiensis, show that the growth and survival of the crustacean
increased significantly in the presence of C. sertularioides
(Porchas Cornejo et al. 1999).
In addition to being grazed
upon by the predators listed above, C. sertularioides is
an edible crop consumed by humans in some parts of the world. In
the Philippines, the alga is used for dietary and medicinal purposes
(Trono 1998). As a food source, C. sertularioides may provide
important anti-oxidants. In fact, studies on the extracts from populations
in Palau showed the highest anti-oxidant activity of any alga examined
(Santoso et al. 2004). The green feather alga has also
been sold, along with other macroalgae, to aquarium hobbyists in
retail shops and via internet sites throughout the United States
and overseas (Stam et al. 2006). Though little information
is available on the negative impacts of C. sertularioides,
similar species of Caulerpa can carpet reefs and reduce
coral cover, especially species that have invaded new ranges.
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from the Great Barrier Reef, Australia. J. Phycol. 33:
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over coral reef communities in Culebra Bay, North Pacific of Costa
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Report by: LH
Sweat, Smithsonian Marine Station at Fort Pierce
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Page last updated: 21 June 2009