Rhizophora mangle L. is one of the most distributed species of neotropical mangroves. The species exhibits great phenological variability that is associated with saline concentrations of the sediment where it grows. Among the organs that are most affected by interstitial and tidal water salinity concentrations are the leaves. Since the hypersalinity generates water deficiency, it changes photosynthetic and hydraulic processes of the plant. To understand the relationship between the variation in leaf blade parameters and the water stress generated by salinity in two growth stages, morphoanatomical functional traits were quantified in leaves of juveniles and adults of R. mangle in three structurally different mangrove forests with different ranges of natural salinity (Oligohaline: 5.8–11.7 practical salinity units (PSU); Euhaline: 9.2–35.6 PSU and 23.9–47.7 PSU). We hypothesized that water stress caused by salinity generates modification in conductivity, water-storage, and photosynthetic tissues. Our results showed a greater number of morphoanatomical traits affected by salinity in juveniles compared to adults, greater variability in the traits associated with water accumulation and transport. Adults and juveniles subjected to higher values of salinity had traits more tolerant of variability in this factor, allowing superior adaptation to environments with high water deficit than individuals originating in oligohaline environments. This difference in adaptability to salinity between populations of R. mangle may imply different responses to climate change, where populations of oligohaline origin will be more susceptible to hypersalinization resulting from this phenomenon, while populations of euhaline origin could more effectively tolerate the aquatic stresses caused, allowing a prolongation of their permanence and the provision of their ecosystem services over time.

Studies on potentially toxic epibenthic dinoflagellates have been increased in the last years due to growing number of harmful events attributed to some of these microalgae. These events represent a risk to human health, as well as to diverse economic activities. With the aim of confirming the presence of these dinoflagellates in Tayrona National Natural Park, Colombian Caribbean, monthly samples of the seagrass Thalassia testudinum were collected between January 2014 and December 2015 in two coastal systems (Bay and Lagoon) located in Chengue Bay (11°20´ N y 74°07´W). Grass leaves were manually collected, placed in plastic bags with seawater and transferred to laboratory for detachment of epibenthic microalgae by vigorous shaking. To identify the species, three types of microscopy were used (optical, inverted with epifluorescence and scanning electron microscopy). Fourteen species of potentially toxic epiphytic dinoflagellates, distributed in four genera (Gambierdiscus, Coolia, Ostreopsis and Prorocentrum) were identified. Prorocentrum was the most representative genus. Ostreopsis cf. ovata, P. hoffmannianum and P. lima were the most frequent species in the Bay, whereas Prorocentrum sp. 1 and P. rhathymum were the most frequent in the Lagoon. This study depicts the main features of the observed species, considering that precise identification at species level is required for any ecological study that seeks to provide elements for risk management against the toxic or harmful effects caused by epibenthic dinoflagellates.

Mangroves provide multiple ecosystem services and are essential for mitigating global warming owing to their capacity to store large carbon (C) stocks. Due to widespread mangrove degradation, actions have been implemented to restore them worldwide. An important representative case in Colombia is the Ciénaga Grande de Santa Marta’s restoration plan. This management intervention focused on restoring the natural hydrological functioning after massive mangrove mortality (~25,000 ha) due to soil hyper-salinization after river water input from the Magdalena River was eliminated. A partial recovery occurred during subsequent years, and hydrological management is still being implemented today. To understand how the degradation and subsequent management have affected mangrove C stocks, we compared C stocks in stands with different intervention levels reflected in their current forest structure. We found that the total C stock (398–1160 Mg C ha⁻¹) was within the range measured in other neotropical mangroves without vegetation deterioration. The aboveground C was significantly higher in the stands where hydraulic connectivity was restored. By contrast, the belowground C was higher in the stands with low hydraulic connectivity due to channel clogging and a lack of sufficient maintenance. Our results show that hydrological management measures influenced above- and belowground C stocks, even at a 2 m depth. In addition, a strong indirect relationship useful for estimating carbon content from organic matter content was found.

To understand the changes in the position of the mangrove forest fronts, migration trends of Rhizophora mangle along the coast, were analyzed in response to oceanographic, climatic variability and hydrological coast regulators. Due to the large biological, physical and climatic differences between Pacific and insular Caribbean coasts of Colombia, the working hypothesis proposed differences in migration drivers and mangrove responses between the coasts. Remote sensing and photointerpretation techniques were used to identify and quantify the spatial variation of deltaic forest types on the Pacific coast and open-water forest types in the Caribbean. Regression analysis was used to relate mangrove front changes with river water discharge, ENSO climate variability, and wave height and velocity coming from directions in interaction or not with the coral reef (in open water forest). It was found that in 13 years of observation (2010 to 2023), there were constant changes in the position of the mangrove front in both the Caribbean and the Pacific. Wave heights from directions that do not interact with the coral reef barrier, such as during periods of strong hurricane influence, along with ENSO variability, collectively explained the annual changes in the mangrove front of open waters (R^² = 0.91). Freshwater discharge, which was linked to the size of a protective sediment bar in front of the mangroves, significantly accounted for the annual changes in mangrove coverage (R^² = 0.70). During the period analyzed, the open-coast mangrove front exhibited a progradation of 0.45 to 1.02 yr^⁻¹, while the deltaic mangrove in Bocagrande showed a retreat of 1.13 yr^⁻¹. These findings provide valuable insights for marine spatial planning, supporting mangrove conservation efforts.

Dinoflagellates in the genus Gambierdiscus are known to produce potent neurotoxins known as ciguatoxins. These toxins vector through the food web and can reach sufficiently high levels to cause ciguatera fish poisoning (CFP). In many regions of the Caribbean, little is known about the occurrence of CFP-causing species or the incidence of CFP, despite its apparent regional increase over the last few decades. Given the intraspecific variability in content and potencies of these toxins among Gambierdiscus species, the precise identification of local species of this genus is crucial. In this study we confirm the presence of the epibenthic dinoflagellate Gambierdiscus caribaeus in the Colombian continental Caribbean. Cells were collected in seagrass beds of Thalassia testudinum in Bonito Gordo, a site located on the western side of Bahía Concha, Tayrona National Natural Park, near the city of Santa Marta, Colombia. Subsequently, a single strain of Gambierdiscus could be established for further identification. Morphological (light and scanning electron microscopy), and molecular results (partial LSU and ITS rDNA sequencing) were consistent with the original description of G. caribaeus, as well as with the morphological characteristics shown by other authors in organisms obtained near the sampling area.