María Eliana Ramírez

Marine green tides are ecological phenomena caused by the massive proliferation of green macroalgae, particularly species of the genus Ulva, whose frequency and geographic extent have increased worldwide. These events are commonly associated with interacting anthropogenic and environmental drivers, including nutrient enrichment, coastal modification, climatic variability, and hydrodynamic retention. In Chile, green tides have been reported in several coastal bays, including Coliumo Bay; however, systematic studies on their species composition have been largely restricted to Algarrobo Bay, another coastal upwelling-influenced embayment located in central Chile. In this study, we investigated the laminar Ulva species associated with recurrent summer green tides at Dichato Beach, located in Coliumo Bay, Biobío Region, Chile. Twenty specimens were collected during the 2025 green tide and analyzed using an integrative approach that combined detailed morphological characterization with molecular analyses based on the tufA and ITS1 markers. Our results revealed the presence of three laminar, foliose, and distromatic taxa: Ulva australis, Ulva stenophylloides, and an unresolved lineage designated as Ulva sp. (D4). These taxa showed consistent morphological differentiation in traits such as thallus color, frond margin morphology, and perforation patterns. Phylogenetic analyses further indicated that Ulva sp. (D4) did not cluster with any described species included in the analyses, supporting its recognition as a distinct lineage that may represent an undescribed taxon. This study expands the known distribution of U. australis and U. stenophylloides in the southeastern Pacific and highlights the relevance of integrative taxonomy for resolving green tide diversity and supporting future ecological monitoring and management strategies in Chilean coastal systems.

Many red algal species described solely from morphology have historically been assigned to inappropriate genera because of superficial morphological similarity. Laurencia chilensis, originally described for specimens from Chile, has long been recognized as the only representative of Laurencia in Chile, but its systematic position is still understudied. We examined morphology of syntype material and specimens collected in the present study and analyzed rbcL sequences from our collections. One syntype specimen (De Toni herbarium no. 63) is here designated as the lectotype of L. chilensis. Laurencia chilensis specimens possess five pericentral cells per axial segment and plate-like spermatangial branches with sterile marginal cells, typical of the tribe Chondrieae. The rbcL sequences we obtained were identical and recovered the Chilean specimens as a strongly supported, distinct lineage from Chondria and other genera within the Chondrieae. Accordingly, we propose Austrochondria chilensis gen. et comb. nov. This study resolves the long-standing taxonomic position of this Chilean endemic and contributes to a more natural classification of the Chondrieae.

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.

In Peru, the number of species of edible seaweeds within the genera Chondracanthus, Porphyra (hereafter P.), Pyropia (hereafter Py.), and Ulva has not been fully established, nor is there a significant level of information available related to their chemical and nutritional composition. This study involved the biochemical analysis of species belonging to ten genera of macroalgae, known edible and some of which have the potential to be used as food, including six red (Callophyllis, Chondracanthus, Mazzaella, Porphyra, Pyropia, and Rhodymenia), two green (Ulva and Codium), and two brown (Eisenia and Lessonia) species collected along the Peruvian coast (6°–17° S). In the evaluation of 37 specimens, differences were found in the proximal composition, amino acid composition, and fatty acid profiles, which were specific to subgroups and supported their taxonomic classification, mainly at the order level. The red algae Porphyra/Pyropia (Bangiales) had the highest average percentage of protein (24.10%) and carbohydrates (59.85%) and the lowest percentage of ash (7.95%). Conversely, the brown alga Eisenia (Laminariales) had the lowest average percentage of protein, with different values related to the structure: 14.11% at the level of the frond and 9.46% at the level of the stipe. On the other hand, Bryopsidales green algae showed the highest average percentages of lipids (5.38%). The moisture percentages ranged from 4 to 16%, and no relevant significant differences were shown between the orders. The characteristic amino acids in all of the studied groups were glutamic acid, aspartic acid, alanine, and leucine. The highest average of the essential amino acids ratio was obtained for the Gigartinales red algae (48.65%), and the highest values of the essential amino acid index (EAAI) were obtained for the Ulvales, Laminariales, Gigartinales, and Rhodymeniales algae (EAAI > 0.92). The highest average relative percentage of fatty acids was obtained for polyunsaturated fatty acids, followed by saturated fatty acids. The major component of the ω6 fatty acids from red and brown algae was arachidonic acid (C20:4n − 6). The highest level of ω3 fatty acids was observed for the eicosapentaenoic acids (EPA) in red algae. The highest median ω6/ω3 ratio was displayed by the red alga Callophyllis variegata (Gigartinales). A detailed knowledge of edible seaweeds, and those considered potentially edible, would help to diversify the diet based on macroalgae in Peru.

Durante el Crucero 16 CIMAR Fiordos realizado entre el Estrecho de Magallanes y el Canal Beagle (53º11,16'S; 73º24,06'W-55º09'03,92''S, 68º08'27,9''W) se realizó un muestreo intermareal y submareal de 14 estaciones. Estas muestras se obtuvieron manualmente y por buceo apnea, en transectas perpendiculares a la línea de la costa, con orientación sur-este y en ellas se aplicó la metodología establecida en el Crucero CIMAR 15 para la caracterización de los biotopos costeros. Se determinaron 10 biotopos marinos que corresponden a tres grandes grupos: 1) biotopos con fuerte influencia de agua dulce de deshielos y lluvias, con playas extensas sin pendientes rocosas; son de diversidad baja, con presencia notoria de Porphyra spp. en sectores rocosos planos y con salinidades que varían entre 1 y 20‰; 2) biotopos rocosos con mayor pendiente, comparativamente con mayor influencia de mareas y presencia de algas rodófi tas, feófitas y clorófi tas asociadas a bivalvos, gasterópodos, cirripedios y otros invertebrados, y con salinidad de 24 a 28‰; y 3) submareales someros, desde 1 hasta 16,4 m de profundidad, caracterizados principalmente por la presencia de feóficeas, Macrocystis pyrifera principalmente, asociadas con moluscos, crustáceos, poliquetos y equinodermos, y con salinidades entre 32 y 35‰. Se observaron coincidencias con los biotopos descritos para el sector del Parque Nacional Laguna San Rafael, estero Elefantes, archipiélago de los Chonos, y tres biotopos mencionados para los canales Trinidad y Smyth, al norte del Estrecho de Magallanes.