Colón-Molina, Dimaris

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    Changes in shoreline and the relation between diversity of shell-mollusks and sand texture on beaches of the west coast of Puerto Rico
    (2018) Colón-Molina, Dimaris; Santos-Flores, Carlos J.; College of Arts and Sciences - Sciences; Ramírez-Martínez, Wilson R.; Mayer-Arzuaga, Robert; Acosta-Martínez, Jaime; Department of Biology; Ramírez-Durand, Lillian
    The effects of shoreline changes on coastal habitats, such as loss of faunal biodiversity, remain as central topics of marine ecological research. Thus, we determined shoreline changes (erosion or deposition) at selected beaches based on aerial photographs and using ENVI Remote sensing program. It is known that the distribution of marine invertebrates in the beaches is partly directed by the composition of the substrates; however, relationships between sand texture and mollusk diversity had not been assessed yet in the beaches of Puerto Rico. Therefore, we set transects on two occasions in four beaches on the western coast of Puerto Rico: Balneario Tres Hermanos (Añasco), Córcega (Rincón), El Combate (Cabo Rojo) and El Maní (Mayagüez), to determine patterns of abundance and species richness of shell-mollusks. Our hypothesis was that the patterns of abundance and species richness for gastropods and bivalves (death or alive species; since based on collected shells) varied significantly among the selected beaches, and mollusk diversity was somehow related to sand textural attributes, such as sorting and particle grain size. A total of 133 taxa were collected and identified, at least to family-level. These organisms comprised 56 and 83 species of bivalves and 30 families and 50 species of gastropods. Every locality showed a distinctive mollusk fauna. The bivalve Donax denticulatus was found at all selected beaches and in both samplings. Gastropod Echinolittorina ziczac found only at Córcega, Rincón, and El Maní, Mayagüez, where it exhibited aggregated spatial dispersion. ANOVA and Tukey tests indicated that significant differences in mollusk diversity (richness and abundance) between beaches were related to the following factors: the number of transects, the study site (beach per se), zones (sand versus aquatic), and samplings (I, II). Changes in the Shannon Wiener Index values suggested changes in diversity at these beaches over a short period of time (between both samplings). According to Jaccard Index values, the species compositions in the samples from differente beaches had low similarities among them. A granulometric analysis showed that the sands of the selected beaches ranged from fine to coarse, with coarse sands dominating during both samplings. In general, PCA analyses showed that increased sorting of the sand was not associated to diversity of mollusks. This study will serve as a baseline for future studies on the monitoring and conservation of biodiversity of shell-mollusks found at the Caribbean sandy beaches.