Morphological Response of Bolivina Lowmani to Sediment Composition and Organic Matter: Applying Geometric Morphometrics for Potential Bio-Monitoring

It is well established that sediment composition plays an important role in shaping the community of benthic foraminifera (e.g., species richness). To our knowledge, there is little information about morphometric variations in benthic foraminifera in relation to sediment composition and organic matter content. However, given their sensitivity to these environmental variables, variations in size (width and height of the test) and shape (form of the test) of the foraminifera could provide information about potential disturbances, serving as an index of anthropogenic pressure for coastal ecosystems. In this study, we used geometric morphometrics to compare the average size and shape of a common species, Bolivina lowmani, among islets in La Parguera, Puerto Rico. We hypothesized that the average size and shape of B. lowmani will be different among islets. We further hypothesize that there will be a concomitant morphometric gradient of B. lowmani with sediment particle size and organic matter content. After a random sampling approach, we found that size regressed as a function of mud content and shape variations regressed as a function of organic matter content. Therefore, sediment composition could be a factor affecting foraminiferal growth rates highlighting that the morphometrics of benthic foraminifera could be added to the list of potential indexes that could be used to track current environmental degradation in coastal habitats. Furthermore, our data validate the sensitivity of foraminifera and their usefulness as indicators of environmental hazards.