Morphological and Molecular Identification of Ulva spp. (Ulvophyceae; Chlorophyta) from Algarrobo Bay, Chile: Understanding the Composition of Green Tides

Green algae blooms of the genus Ulva are occurring globally and are primarily attributed to anthropogenic factors. At Los Tubos beach in Algarrobo Bay along the central Chilean coast, there have been blooms of these algae that persist almost year-round over the past 20 years, leading to environmental, economic, and social issues that affect the local government and communities. The objective of this study was to characterize the species that form these green tides based on a combination of ecological, morpho-anatomical, and molecular information. For this purpose, seasonal surveys of beached algal fronds were conducted between 2021 and 2022. Subsequently, the sampled algae were analyzed morphologically and phylogenetically using the molecular markers ITS1 and tufA, allowing for the identification of at least five taxa. Of these five taxa, three (U. stenophylloides, U. uncialis, U. australis) have laminar, foliose, and distromatic morphology, while the other two (U. compressa, U. aragoensis) have tubular, filamentous, and monostromatic fronds. Intertidal surveys showed that U. stenophylloides showed the highest relative coverage throughout the seasons and all intertidal levels, followed by U. uncialis. Therefore, we can establish that the green tides on the coast of Algarrobo in Chile are multispecific, with differences in relative abundance during different seasons and across the intertidal zone, opening opportunities for diverse future studies, ranging from ecology to algal biotechnology.

Long term environmental variability modulates the epigenetics of maternal traits of kelp crabs in the coast of Chile

The methylation of DNA is an environmentally inducible epigenetic mechanism reflecting the short-term ecological and environmental background of populations. Marine invertebrate populations, which spread along a latitudinal cline, are particularly suitable for profiling DNA methylation, due to the heterogenous environmental conditions experienced. We used the MSAP (Methylation Sensitive Amplified Polymorphism) technique to investigate the natural variation in DNA methylation of different female's tissues (muscle, gonads, and gills) and early-stage eggs from five populations of the kelp crab Taliepus dentatus, distributed along a latitudinal cline in the coast of Chile. We assessed whether, (1) the distribution of DNA methylation profiles can be associated with the temporal variability of long term (18 years) climatologies (sea surface temperature, turbidity and productivity) and (2) the epigenetic diversity of eggs is related to the population-level phenotypic variability of several maternal investment traits (egg volume, egg weight, egg lipids and fecundity). The DNA methylation of eggs correlated positively and negatively with the long term variability in productivity and sea surface temperature, respectively. Furthermore, the diversity of DNA methylation of eggs correlated positively with the population-level phenotypic variability of several maternal investment traits, suggesting a key role of epigenetic mechanisms in generating phenotypic variability at population level for this species. We provide evidence of a strong link between the temporal variability of long term climatologies with the epigenetic profiles of key early ontogenetic traits associated with the maternal investment of kelp crabs. These modulating mechanisms can hence contribute early to phenotypic variability at population levels in response to local and past environmental fluctuation.

Continental shelf off northern Chilean Patagonia: A potential risk zone for the onset of Alexandrium catenella toxic bloom?

Harmful Algal Blooms (HAB) pose a severe socio-economic problem worldwide. The dinoflagellate species Alexandrium catenella produces potent neurotoxins called saxitoxins (STXs) and its blooms are associated with the human intoxication named Paralytic Shellfish Poisoning (PSP). Knowing where and how these blooms originate is crucial to predict blooms. Most studies in the Chilean Patagonia, were focused on coastal areas, considering that blooms from the adjacent oceanic region are almost non-existent. Using a combination of field studies and modelling approaches, we first evaluated the role of the continental shelf off northern Chilean Patagonia as a source of A. catenella resting cysts, which may act as inoculum for their toxic coastal blooms. This area is characterized by a seasonal upwelling system with positive Ekman pumping during spring-summer, and by the presence of six major submarine canyons. We found out that these submarine canyons increase the vertical advection of bottom waters, and thus, significantly enhance the process of coastal upwelling. This is a previously unreported factor, among those involved in bloom initiation. This finding put this offshore area at high risk of resuspension of resting cysts of A. catenella. Here, we discuss in detail the physical processes promoting this resuspension.

Contrasting land-uses in two small river basins impact the colored dissolved organic matter concentration and carbonate system along a river-coastal ocean continuum

Human activities have led to an increase in land use change, with effects on the structure and functioning of ecosystems. The impact of contrasting land uses along river basins on the concentration of colored dissolved organic matter (CDOM) reaching the coastal zone, and its relationship with the carbonate system of the adjacent coastal ocean, is poorly known. To understand the relationship between land use change, CDOM and its influence on the carbonate system, two watersheds with contrasting land uses in southern Chile were studied. The samples were collected at eight stations between river and adjacent coastal areas, during three sampling campaigns in the austral summer and spring. Chemical and biological samples were analyzed in the laboratory according to standard protocols. Landsat 8 satellite images of the study area were used for identification and supervised classification using remote sensing tools. The Yaldad River basin showed 82% of native forest and the Colu River basin around 38% of grassland (agriculture). Low total alkalinity (A_T) and Dissolved Inorganic Carbon (DIC), but high CDOM proportions were typically observed in freshwater. A higher CDOM and humic-like compounds concentration was observed along the river-coastal ocean continuum in the Yaldad basin, characterized by a predominance of native forests. In contrast, nutrient concentrations, A_T and DIC, were higher in the Colu area. Low CaCO₃ saturation state (Ω_Ar < 2) and even undersaturation conditions were observed at the coastal ocean at Yaldad. A strong negative correlation between A_T, DIC and Ω_Ar with CDOM/fDOM, suggested the influence of terrestrial material on the seawater carbon chemistry. Our results provide robust evidence that land uses in river basins can influence CDOM/fDOM proportion and its influence on the carbonate chemistry of the adjacent coastal, with potential implications for the shellfish farming activity in this region.