Marine Biodiversity in the Caribbean: Regional Estimates and Distribution Patterns

This paper provides an analysis of the distribution patterns of marine biodiversity and summarizes the major activities of the Census of Marine Life program in the Caribbean region. The coastal Caribbean region is a large marine ecosystem (LME) characterized by coral reefs, mangroves, and seagrasses, but including other environments, such as sandy beaches and rocky shores. These tropical ecosystems incorporate a high diversity of associated flora and fauna, and the nations that border the Caribbean collectively encompass a major global marine biodiversity hot spot. We analyze the state of knowledge of marine biodiversity based on the geographic distribution of georeferenced species records and regional taxonomic lists. A total of 12,046 marine species are reported in this paper for the Caribbean region. These include representatives from 31 animal phyla, two plant phyla, one group of Chromista, and three groups of Protoctista. Sampling effort has been greatest in shallow, nearshore waters, where there is relatively good coverage of species records; offshore and deep environments have been less studied. Additionally, we found that the currently accepted classification of marine ecoregions of the Caribbean did not apply for the benthic distributions of five relatively well known taxonomic groups. Coastal species richness tends to concentrate along the Antillean arc (Cuba to the southernmost Antilles) and the northern coast of South America (Venezuela – Colombia), while no pattern can be observed in the deep sea with the available data. Several factors make it impossible to determine the extent to which these distribution patterns accurately reflect the true situation for marine biodiversity in general: (1) highly localized concentrations of collecting effort and a lack of collecting in many areas and ecosystems, (2) high variability among collecting methods, (3) limited taxonomic expertise for many groups, and (4) differing levels of activity in the study of different taxa

Crystallinity and microchemistry of Nassarius reticulatus (Caenogastropoda) statoliths: Towards their structure stability and homogeneity

Gastropod statoliths are spherical biocarbonates formed during their lifespan. The stability and homogeneity of these structures' mineral matrix was characterised along their radiuses, using Nassarius reticulatus as a model. Generally, they were proved to be bimineralic. Two of the three CaCO3 crystalline polymorphs occurring in biocarbonates - aragonite and calcite - coexist along statolith radiuses, aragonite being unequivocally the most abundant phase. The presence of a diffuse organic matrix was also perceived by the detection of a weak Raman band between 2800 and 3000cm-1 consistently observed along radiuses. Beyond the apparent stability and homogeneity, different crystalline orientations were disclosed by Raman spectroscopy. A change in the intensity pattern of the features related to the lattice and bending modes of aragonite between different radiuses give new insights for a possible spherulitic-like growth of these structures. As expected from the relative homogeneity of both mineral and organic signals, there was no pattern on the distribution of Ca, O, Na and S along radiuses. However, a higher concentration of Sr occurs in growth rings (known as winter tags), corroborating the already described negative correlation between the concentration of this element in statoliths and temperature. Despite the apparent stability and homogeneity of the matrix during its lifespan, the periodic distribution of Sr potentially influences a dissimilar incorporation of trace elements in increments and growth rings. Since gastropod statolith elemental fingerprinting was recently suggested as a new tool to monitor marine environmental changes, the pressing need for further studies on the incorporation of traces in these structures is highlighted

Detection of periodic Sr Ca-1 cycles along gastropod statoliths allows the accurate estimation of age

Gastropods retain less obvious periodic growth marks on calcified structures than individuals in other groups (e.g. bivalves, cephalopods, fish), a fact that has hampered age estimation in this Class. Nevertheless, a model of age estimation for the gastropod Nassarius reticulatus is possible based on the annual growth rings deposited in statoliths during the winter. These spherical aragonitic carbonate structures are located inside the statocysts and contain a characteristic microstructural pattern of concentric rings. However, this pattern can be biased by the formation of nonperiodic disturbance rings (DRs). In Aveiro (NW Portugal), an increased frequency of DRs was reported in statoliths of specimens inhabiting the Ria de Aveiro lagoon (a highly dynamic environment), when compared with specimens collected from the relatively environmentally stable adjacent offshore area. One approach to resolve annual growth in organically precipitated carbonates is to find a chemical signature within the microstructure that faithfully records changes in seasonal environmental parameters. In this contribution, we have analysed the Sr Ca−1 variation along statolith sections by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy to resolve seasonal cycles of temperature, allowing the identification of annual growth rings. Combining this information with size–frequency distributions of shell height, we found strong evidence that the rings chemically labelled with 88Sr 48Ca−1 peaks are formed annually during the cold season. Hence, LAICPMS allows not only the detection of visible rings but also the distinction between rings formed at low temperatures (i.e. a periodic seasonal signature) and those of disturbance (not characterised by increased 88Sr 48Ca−1). There is also clear evidence that the 88Sr 48Ca−1 peaks become less conspicuous from the nucleus to the statolith edge, leading to a loss of discriminatory power for the identification of older age rings. Nevertheless, this new method allows the accurate age estimation of N. reticulatus specimens and is liable to be applied in a wide range of gastropods after specific validation