suspended matter in the water column, supporting the holothuroids, whereas
ophiuroids had been affected by the loss of natural refuges.
Zamorano and Leyte-Morales (2005b) worked in La Entrega and assessed
population densities at two depth ranges (0–6 m and 6–12 m) of four echinoid
species: E. thouarsii, E. vanbrunti, T. roseus and D. mexicanum. Density of the
four populations varied considerably with the highest densities in the deep zone.
Total abundance of sea urchins, including shallow and deep samples, did not vary
significantly over time. However, the abundance per depth range was different
over time for all species except for E. thouarsii. The authors established that the
reef at La Entrega was undergoing an advanced state of erosion that could favor an
increase in sea urchin abundance and therefore an increase in bioerosion activity.
Rios-Jara et al. (2008) described the specific composition of echinoderms from
Isla Isabel National Park, in the central Mexican Pacific, on rocky and sandy
substrates in subtidal areas to 19 m depth. The most important species according to
the biological value index were D. mexicanum, T. roseus, P. unifascialis, Pharia
pyramidatus, Ophicoma alexandri, Holothuria lubrica, Isostichopus fuscus and
E. thouarsii. They established these species showed more affinity to the Gulf of
California than to the central-south Pacific region.
Lopez-Uriarte et al. (2009) described the specific composition and community
structure of the macrobenthic invertebrates from Bahia de Chamela, Jalisco, using
quadrants along transects of 50 m length. Echinoderms showed the highest species
richness, and the abundance and number of species were related to the heterogeneity
of the substrate, which was characterized by stable mixed substrates including
rocks, medium sized sand and scattered coral colonies. These kinds of substrates
provide shelter in their cavities and crevices, and surfaces for the attachment of
sessile species.
Zamorano and Leyte-Morales (2009) described and characterized the community of echinoderms associated with coral reefs in Zihuatanejo and Acapulco,
Guerrero during the rainy and dry seasons. The authors proposed the mean values
obtained for diversity in the 13 study sites are low compared to the maximum
possible diversity, due to the dominance of the sea urchin D. mexicanum and the
sea star P. unifascialis. These species, T. roseus and Hesperocidaris asteriscus
were the most frequent and predominant species. Compared to other sites of the
Eastern Tropical Pacific, densities were considered low. However, they did not
find statistically significant differences in the densities of D. mexicanum between
localities, depths, and seasons, although in some localities, the sea urchin densities
increased considerably during the rainy season. The results also showed that, in
localities close to Acapulco, Guerrero, a heavily visited touristic place, the
diversity of echinoderms was lower and the abundance of D. mexicanum was
higher.
2 The Echinoderms of Mexico
31
ophiuroids had been affected by the loss of natural refuges.
Zamorano and Leyte-Morales (2005b) worked in La Entrega and assessed
population densities at two depth ranges (0–6 m and 6–12 m) of four echinoid
species: E. thouarsii, E. vanbrunti, T. roseus and D. mexicanum. Density of the
four populations varied considerably with the highest densities in the deep zone.
Total abundance of sea urchins, including shallow and deep samples, did not vary
significantly over time. However, the abundance per depth range was different
over time for all species except for E. thouarsii. The authors established that the
reef at La Entrega was undergoing an advanced state of erosion that could favor an
increase in sea urchin abundance and therefore an increase in bioerosion activity.
Rios-Jara et al. (2008) described the specific composition of echinoderms from
Isla Isabel National Park, in the central Mexican Pacific, on rocky and sandy
substrates in subtidal areas to 19 m depth. The most important species according to
the biological value index were D. mexicanum, T. roseus, P. unifascialis, Pharia
pyramidatus, Ophicoma alexandri, Holothuria lubrica, Isostichopus fuscus and
E. thouarsii. They established these species showed more affinity to the Gulf of
California than to the central-south Pacific region.
Lopez-Uriarte et al. (2009) described the specific composition and community
structure of the macrobenthic invertebrates from Bahia de Chamela, Jalisco, using
quadrants along transects of 50 m length. Echinoderms showed the highest species
richness, and the abundance and number of species were related to the heterogeneity
of the substrate, which was characterized by stable mixed substrates including
rocks, medium sized sand and scattered coral colonies. These kinds of substrates
provide shelter in their cavities and crevices, and surfaces for the attachment of
sessile species.
Zamorano and Leyte-Morales (2009) described and characterized the community of echinoderms associated with coral reefs in Zihuatanejo and Acapulco,
Guerrero during the rainy and dry seasons. The authors proposed the mean values
obtained for diversity in the 13 study sites are low compared to the maximum
possible diversity, due to the dominance of the sea urchin D. mexicanum and the
sea star P. unifascialis. These species, T. roseus and Hesperocidaris asteriscus
were the most frequent and predominant species. Compared to other sites of the
Eastern Tropical Pacific, densities were considered low. However, they did not
find statistically significant differences in the densities of D. mexicanum between
localities, depths, and seasons, although in some localities, the sea urchin densities
increased considerably during the rainy season. The results also showed that, in
localities close to Acapulco, Guerrero, a heavily visited touristic place, the
diversity of echinoderms was lower and the abundance of D. mexicanum was
higher.
2 The Echinoderms of Mexico
31