This study is the first detailed investigation of microplastics (MPs) ranging from 20 µm to 5 mm in surface waters of coral reef ecosystems of the coast of Cuba. A total of 72 samples were collected from 22 stations during the scientific cruise "BOJEO CUBA 2024". The post-sampling treatment was based on enzymatic digestion of organic matter and subsequent analysis of the MPs using laser direct infrared (LDIR) Chemical Imaging Spectroscopy. A total of 2,616 MPs and 11 types of polymers have been identified, with a significant composition of Polypropylene accounting for 27% of the total, followed by Polyethylene (25%), Polytetrafluoroethylene (12 %), Polyurethane (11 %), and Polyethylene terephthalate (10 %). From a size perspective, 94 % of these MPs were smaller than 300 microns, indicating a significant presence of very small particles. Total number concentrations ranged from 11 to 176 microplastic particles per Liter, with an average of 75 MP L⁻¹ and a standard deviation of 41 MP L⁻¹. The spatial analysis clustered the selected sampling sites into three groups based on the abundance and polymer composition, reflecting varying levels of MP pollution and potential sources across the island.

Microplastic contamination in coral reef environments is increasingly recognized as a global concern; however, the extent to which polymer composition can resolve contamination sources and transport processes remains poorly understood. In this study, we assessed the abundance, composition, and diversity of microplastics (< 300 µm) across multiple reef systems in the Cuban archipelago using high-resolution spectroscopic analysis. Microplastic abundance varied substantially among sites, with a median concentration of 66 particles L⁻¹ (IQR: 45–115 particles L⁻¹), ranging from 8 to 218 particles L⁻¹. A total of 11 polymer types were identified, with polyethylene (PE), polypropylene (PP), and polyamide (PA) dominating the assemblages and accounting for approximately 77% of detected particles. While these polymers were consistently observed across all sites, indicating a pervasive regional background signal, highly impacted reefs exhibited more complex polymer profiles, including the enrichment of polyurethane (PU), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC), reflecting localized anthropogenic inputs. Multivariate analysis revealed distinct compositional groupings associated with different contamination regimes. Notably, some sites exhibited elevated microplastic abundances while remaining dominated by common polymers, indicating a decoupling between contamination levels and source-specific signatures. This pattern suggests that regional transport and mixing processes, including circulation through the Caribbean basin and the Yucatán Channel, play a major role in shaping microplastic distributions in reef environments. These findings demonstrate that polymer composition provides critical information beyond abundance alone, enabling the differentiation between source-driven contamination and transport-driven accumulation. The integration of polymer-specific analysis with abundance and diversity metrics offers a robust framework for improving source apportionment and informing monitoring and management strategies in coral reef systems.

Blue carbon ecosystems are important carbon sinks that sequester large amounts of organic carbon in soils over time scales ranging from decades to millennia, offering high potential for climate change mitigation and adaptation strategies. Cuba is considered as one of the world's blue carbon hotspots due to its extensive and well-preserved mangrove and seagrass habitats, as well as the high carbon densities found in its soils. However, quantitative assessments of organic carbon inventories and accumulation rates are still lacking. This study aimed to evaluate organic carbon stocks and sequestration rates through the evaluation of sediment profiles in seagrasses, mangroves and marshes in the Ciénaga de Zapata wetland and the Gulf of Batabanó, representative areas of these marine-coastal ecosystems in Cuba. Organic carbon content and dating by 210Pb and 137Cs were determined in the sediment profiles. Organic carbon stocks were highest in mangrove soils dominated by Avicennia germinans (mean value of 1014 ± 70 MgC/ha), compared to those dominated by Rhizophora mangle (mean value of 110 ± 3 MgC/ha), marsh soils (mean value of 179 ± 48 MgC/ha), and seagrass soils (mean value of 198 ± 62 MgC/ha). Sequestration rates were also generally higher in mangrove (mean value of 172 ± 132 g Corg m-2 yr-1) than in marshes (mean value of 33,8 ± 1,2 g Corg m-2 yr-1) and seagrasses (mean value of 26,5 ± 13,3 g Corg m-2 yr-1). This study represents a pioneering effort in Cuba, providing essential data on organic carbon stocks and sequestration rates within blue carbon ecosystems. Such information is critical for guiding future research, enhancing management and conservation strategies, and supporting regional climate change mitigation efforts.

Microplastic contamination in coral reef environments is increasingly recognized as a global concern; however, the extent to which polymer composition can help distinguish contamination sources and transport-related processes remains poorly understood. In this study, we assessed the abundance, composition, and diversity of microplastics (20–300 µm) across multiple reef systems in the Cuban archipelago using high-resolution Laser Direct Infrared (LDIR) spectroscopic analysis. Microplastic abundance varied substantially among sites, with a median concentration of 66 particles L⁻¹ (IQR: 45–115 particles L⁻¹), ranging from 8 to 218 particles L⁻¹. A total of 11 polymer types were identified, with polyethylene (PE), polypropylene (PP), and polyamide (PA) dominating the assemblages and accounting for approximately 77% of detected particles. While these polymers were consistently observed across all sites, suggesting a pervasive regional background signal, highly impacted reefs exhibited more heterogeneous polymer profiles, including increased contributions of polyurethane (PU), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC), consistent with localized anthropogenic influence. Multivariate analysis revealed moderate compositional structuring among reef sites and suggested broad differences in polymer assemblages associated with contrasting contamination settings. Notably, some reefs exhibited elevated microplastic abundances while remaining dominated by common polymers, indicating a partial decoupling between contamination levels and polymer-specific signatures. This pattern is consistent with the influence of regional transport and mixing processes across the Caribbean basin, potentially including circulation associated with the Yucatán Channel, although hydrodynamic processes were not directly assessed in this study. Overall, the findings highlight the value of polymer-resolved analysis for improving interpretation of microplastic contamination patterns in coral reef environments. The integration of polymer composition with abundance and diversity metrics provides a useful framework for distinguishing between localized contamination signals and broader regional background influences. This study represents a regional baseline assessment of small microplastics in Caribbean coral reef systems using high-resolution spectroscopic characterization.