The cyanobacteria Synechococcus spp. are key contributors to marine primary productivity. They are found from equatorial to polar waters where these organisms are exposed to changed levels of pCO2 and solar ultraviolet radiation (UVR, 280–400 nm). To investigate how elevated pCO2 modulates the physiological responses of a coastal pico-cyanobacterium to UVR, Synechococcus XM24 was used and acclimated to periodic (90 min per day) near-surface UVR exposure under ambient (418 µatm) and elevated (1000 µatm) pCO2 conditions for 17 days. Our results indicate that elevated pCO2 markedly enhanced its specific growth, cellular pigment accumulation (chlorophyll a, carotenoids), and particulate organic carbon/nitrogen (POC/PON) quotas in the cells grown under light (without exposure to UVR). However, such stimulatory effects were substantially abolished in UVR-exposed cells. UVR significantly inhibited the effective photochemical quantum yield of photosystem II (PSII) and accelerated PSII damage without a compensatory increase in repair, thereby reducing the repair/damage ratio (r/k) by up to 4-fold. The cells acclimated to the UVR exposures reduced their carbon fixation rate by 56–60% regardless of the pCO2 levels. In addition, UVR exposure led to drastic reductions in cellular POC and PON content, reflecting a potential energy shift from biomass production towards cellular maintenance. Reduced contents of Chl a and carotenoids under the combination of UVR and elevated pCO2 should be responsible for the reductions in photosynthetic carbon fixation and POC/PON contents. Our results imply that while progressive ocean acidification with increasing pCO2 can stimulate growth of the coastal Synechococcus XM24 under PAR-alone conditions, exposures to UV radiation can diminish such enhancement.
Commercial seaweed farming in India began in 1984 and expanded after experimental trials in the late 1990s, with Kappaphycus alvarezii cultivation emerging in 2001. Production peaked in 2013 but subsequently declined because of challenges including mass mortality, with current dry production estimated at 200–300 t annually. To revive the sector, Pradhan Mantri Matsya Sampada Yojana (PMMSY) proposed an investment of USD 76.8 million to achieve 1.12 Mt fresh biomass by 2025. However, expansion is constrained by inadequate availability of quality planting material (QPM), highlighting the need for dedicated seaweed nurseries. To meet 60% of the PMMSY target, approximately 66 nurseries, each producing 102 tons of fresh biomass annually, would be required (model-based projections from laboratory data, not yet validated at commercial scale in India). This would require an estimated 13,254 trained laboratory workers and 13,539 field workers, potentially generating employment equivalent to 0.27% of India’s marine fishers. Successful implementation will require coordinated support from government agencies, research institutions, private enterprises, and NGOs, along with subsidies and incentives for entrepreneurs. Establishing seaweed nurseries can ensure reliable QPM, strengthen raw material supply, create employment, and support India’s seaweed industry toward achieving PMMSY targets and long-term sustainability through resource-efficient nursery infrastructure and training.
This study analyzes the diversity of thin filamentous cyanobacteria from the volcanic Lake Terkhiin-Tsagaan, Mongolia. We isolated and characterized two strains from benthic samples collected from the lake. Using light microscopy, phylogenetic analysis of 16S rRNA gene sequences, and examination of the secondary structures of the 16S–23S ITS helices, we describe a new genus, Dgebuadzia, and a new species, Dgebuadzia mongoliensis. The 16S rRNA gene similarity to Phormidesmis was below the genus-level threshold (89.5% to P. mollis NIES-2126; minimum 94.19% to non-mollis Phormidesmis species), and the strains formed a well-supported monophyletic clade (BI/ML = 1/100) that is distinct from all other Leptolyngbyaceae included in the analysis. The strains also differed from Phormidesmis in the secondary structure of the Box-B and V3 helix. The new genus is closely related to P. arctica, a taxon whose original description is nomenclaturally invalid and which therefore cannot be formally transferred, although its phylogenetic position places it within the Dgebuadzia lineage. The data presented here contribute to our understanding of the diversity of thin filamentous cyanobacteria and expand current knowledge of the algal flora of Mongolian volcanic lakes.
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.
Satellite observations reveal the offshore distribution of pelagic Sargassum, but predicting its occurrence at individual Caribbean coastlines remains challenging where local observational records are limited. This study tests whether forecasts developed on one Caribbean island can transfer to another without retraining or recalibration. Satellite-derived predictors from the 0–10, 10–50, and 50–100 km offshore bands were evaluated at one-, two-, and four-week horizons. Rolling-origin validation in Puerto Rico selected Random Forest models at one and two weeks and a one-dimensional convolutional neural network (CNN1D) ensemble with Platt calibration at four weeks. Frozen pipelines were applied unchanged at nine Dominican Republic sites and evaluated against 283 station-week targets. Puerto Rico 2026 provided independent testing. At one and two weeks, area under the receiver operating characteristic curve (ROC AUC) values were 0.745 and 0.757, area under the precision-recall curve (PR AUC) values were 0.689 and 0.687, and Brier Skill Score (BSS) values were +0.110 and +0.059. After transfer, ROC AUC values were 0.686 and 0.663, PR AUC values were 0.548 and 0.509, and BSS values were +0.098 and +0.056. Site removal did not eliminate short-horizon skill, and BSS remained positive by year. Transfer was clearest at one and two weeks, suggesting potential value for targeted coastal Sargassum monitoring, field verification, and response planning.
