Alejandro Granados-Barba

Distribution and diversity of the Syllidae (Annelida: Polychaeta) from the Mexican Gulf of Mexico and Caribbean

The objective of this study was to contribute to the knowledge of the syllids distributed in the eastern coasts of Mexico (Gulf of Mexico and Caribbean) taking into consideration their composition, distribution and diversity. Sampling was done at 77 stations including 49 in soft bottoms (terrigenous and carbonate sediments), and 28 in hard bottoms (coralline substrates) sampled in nine reef zones included in three reef systems (Veracruz, Campeche and Cozumel). In all 2084 individuals were collected (13.5% in soft sediments and 86.4% in coralline areas). Forty-five species were identified: 31 in soft bottoms and 38 in corals, with 21 species common to both types of environments. In soft bottoms, the highest species richness and diversity were found in the Carbonate Zone, while syllids were uncommon in the Terrigenous Zone. In hard bottoms, the highest density, species richness and diversity values were found in the Veracruz Reef System, followed by the Campeche Bank and Cozumel Island Reef Systems. The dominant species in soft bottoms were Haplosyllis spongicola, Exogone lourei, Typosyllis cornuta and T. papillosus, whereas T. alosae, T. corallicola, T. cornuta and H. spongicola dominated in hard bottoms. The importance and success of the syllids in both soft bottoms and reef environments, particularly in those of the Gulf of Mexico is emphasized.

Diversidad y distinción taxonómica de la macrofauna en fondos blandos de la plataforma norte y suroccidental cubana

Diversity of macrofaunal groups in soft bottoms of the northern and southwestern Cuban shelf was assessed using taxonomic indices that depend on community structure, are independent of habitat type and sampling effort, and have a monotonic response to environmental disturbances. Taxa heterogeneity was significantly higher in sandy-muddy with vegetation, sandy with vegetation, and sandy with vegetation on hard bottom substrates. Biotopes diversity showed a gradient from smaller to greater particle size and from absence to presence of vegetation. Average taxonomic distinctness expected in these zones of the Cuban marine shelf is 92.5 with 95% confidence limits between 76.7 and 100. Sites with average taxonomic distinctness lower than 92.5 and outside the estimated confident limits can be considered environmentally deteriorated or favoring diversity of some particular groups. Dominant groups in this benthos fraction are crustaceans and polychaetes, which is consistent with studies in other tropical and temperate regions. These results constitute a baseline for environmental assessment and monitoring of macrofauna in Cuban soft bottoms, as a key component for marine ecosystems functioning.