Band 68, Heft 4

This study examined the three-dimensional distribution of nutrients and phytoplankton biomass, as measured by chlorophyll- a (Chl- a ) concentration, in the Bay of La Paz, Gulf of California, during different phases of the El Niño Southern Oscillation (ENSO). Two multidisciplinary research cruises were conducted in November 2014 and November 2016, corresponding to El Niño and La Niña conditions, respectively. A CTD Rosette System was used to gather high-resolution hydrographic data and collect seawater samples at different depths for chemical analyses (nutrients and Chl- a ). Meteorological data were obtained from a local weather station. The results indicated significant differences between the two study periods. The composition of water masses varied during both events. Notable contrasts were observed in nutrient concentrations, especially at 30 m depth; the maximum concentration of Soluble Reactive Si was 152.46 µM in 2014, compared to only 8.48 µM in 2016. Chl- a levels also showed variations with depth and between the two cruises, being significantly higher in 2014 (7.60 mg m −3 ) than in 2016 (1.70 mg m −3 ). This study enhances the understanding of the dynamics of ENSO events, given that the collections were conducted during both an El Niño and a La Niña phase. However, it is worth noting that the La Niña was influenced by an extreme El Niño event occurring in the same year, which likely masked the effects of the subsequent La Niña.

The spread of non-indigenous species is a critical concern for marine ecosystems, particularly in regions with high biodiversity and economic reliance on coastal resources. This study investigates the distribution, abundance, and expansion of the invasive kelp Undaria pinnatifida along the Atlantic coast of the Iberian Peninsula. A comprehensive survey was conducted in 2024, covering 59 locations across Spain and Portugal. This dataset was complemented by biodiversity records from citizen science platforms. Historical records were also reviewed to assess changes in its distribution over time. Results indicate that U. pinnatifida has notably increased its presence in Portugal since its first record, now occurring at 16 sites (compared to only 2 in 2007), while remaining well-established in Galicia. However, the species co-occurs with native kelps and, at this stage, does not dominate the communities where it has established itself. Furthermore, it remains absent from southern Iberia and the Bay of Biscay. Hence, environmental conditions and biotic interactions might be shaping their distribution, which warrants further investigation. Given the ongoing environmental changes and human-mediated dispersal, continuous monitoring is essential to track future range shifts. This study also showcases how integrating citizen science data can enhance the spatial and temporal resolution of non-indigenous species monitoring.

Thraustochytrids are fungus-like organisms that are the most promising microbial sources for commercial production of industrially important fatty acids. In this study, nineteen Brazilian thraustochytrid isolates were evaluated for their biomass production and fatty acid profile. Aurantiochytrium spp. produced up to 52.87 % of docosahexaenoic acid (DHA), while Parietichytrium sarkarianum isolates produced up to 26.59 % of palmitic acid (C16:0) and up to 30.90 % of oleic acid (C18:1), of the total fatty acids. The results suggest the importance of the optimization studies for scale-up production of these fatty acids using the Brazilian isolates.

The Arabian Sea hosts one of the major perennial, oceanic oxygen-depleted environments (ODE) in the water column, influencing the seabed beneath it. These regions harbor a vast diversity of microbial communities, which play a significant role in the global budgets of key biogenic elements like carbon, nitrogen and oxygen. This study assessed the relative importance of bacterial and fungal communities in the Arabian Sea ODE using eDNA metabarcoding tools. Sediment samples from four stations at ∼200–1,200 m depths were analyzed across a hypoxic gradient, with 5–35 μM dissolved oxygen levels. Species diversity and richness indices revealed that bacterial and fungal communities were the highest at an oxygen threshold of 10–20 μM, with variations in their community composition along the hypoxic gradient. The bacterial phylum Proteobacteria was dominant in the sediment of all stations. However, the relative abundances of phyla such as Firmicutes, Chloroflexi, Bacteroidetes, Planctomycetes and Actinobacteria varied across the stations. The phyla Ascomycota and Basidiomycota dominated the fungal communities at all the stations. However, Mucoromycota was present only at stations with 20–35 μM oxygen levels. These results enhance our understanding of microbial community distribution in the Arabian Sea ODE.

Ulva is a genus of green algae common to intertidal and shallow subtidal marine, estuarine, and freshwater habitats worldwide, including North Carolina. To accurately determine the Ulva species diversity in North Carolina, both DNA sequencing and morphological/anatomical assessments were performed. Specimens were collected from sites across the coastal region of the state, and three DNA loci, nuclear-encoded ITS, plastid-encoded rbc L and plastid-encoded tufA , were sequenced for each specimen. Species names were determined where possible by homology of sequence data with that from type specimens. Through DNA sequence cluster and phylogenetic analyses, nine species of Ulva were identified in the collections. Seven, U. gigantea , U. lacinulata , U. lactuca , U. ohnoi , U. prolifera , U. ‘torta’ , and U. tepida were confirmed by comparing to available type or topotype sequences. The remaining two are either undescribed species or species for which there is no sequence available from the type specimen. One of these is described as a new species, U. carsoniae . Morpho-anatomical characters were not useful in distinguishing these nine species or determining their identifications. Only the DNA sequenced loci provided an accurate diversity assessment of Ulva species in North Carolina.

Prorocentrum includes ∼80 species inhabiting benthic and planktonic marine environments. Some species, such as Prorocentrum cassubicum and P . norrisianum , have similar morphology, which complicates their identification based solely on morphological characters. This study describes the morphometrics of two Prorocentrum strains (PNCETMAR-1 and PNCETMAR-2) isolated from the Ensenada de La Paz, Gulf of California. Sequences of the 28S and ITS regions of rDNA of both strains and the growth curve of strain PNCETMAR-1 were obtained. Strain PNCETMAR-1 was grown in modified GSe medium and f/2 medium at a salinity of 34, at 24 °C and 120–150 μmol m −2  s −1 in a 12 h light: 12 h dark cycle. There was no significant difference in growth between the culture media. In f/2 medium the maximum abundance was 74,312 ± 2,008 cells ml −1 , while in GSe medium it reached 69,766 ± 2,154 cells ml −1 . Morphometric and molecular analyses indicate that both strains belong to the same species. However, because the morphological and molecular information on P . cassubicum and P . norrisianum is contradictory, in this study they are reported as Prorocentrum cf. cassubicum , contributing to the first report of the occurrence and the growth of this species in the Gulf of California.

Olpidiopsis is one of the major pathogens of commercially valuable red algae. Despite being such an important pathogen, the infection process has been studied and documented mainly in the Olpidiopsis species infecting Pyropia spp., but less so in other red algae. We collected an Olpidiopsis -like pathogen infecting Dasysiphonia japonica in Japan, and it is different from any previous described Olpidiopsis species. Molecular phylogeny inferred from 18S rRNA gene, cox 1, and cox 2 sequences and species delimitation analyses (i.e., Assemble Species by Automatic Partitioning, single-threshold General Mixed Yule Coalescent, Bayesian Poisson Tree Processes) showed that the collected Olpidiopsis sp. formed a supported clade with other Rhodophyta-infecting Olpidiopsis species, and was considered a distinct species by all species-delimitation methods. Furthermore, we tested the host range of this pathogen and studied its morphology through microscopic analysis. This new pathogen was distinguished from other species by the presence of only one sporangium per host cell and, during development, the sporangium became irregularly shaped, almost filling the entire host cell and produced up to 14 discharge tubes to release zoospores. The host range tests found that it only infected species of Dasysiphonia spp. Therefore, we propose the name, Olpidiopsis dasysiphoniae sp. nov., for this new species.

The ability of macroalgae to extract inorganic nutrients is crucial in selecting species for integrated multitrophic aquaculture (IMTA). This study assessed the nutrient removal capacities of five commercially important marine macroalgae – Caulerpa microphysa , Ulva ohnoi , Kappaphycus alvarezii , Kappaphycus striatus , and Eucheuma denticulatum  – using eutrophic seawater from a mariculture farm. All species simultaneously took up three inorganic nitrogen species (NH 4 + , NO 3 − and NO 2 − ), with a strong preference for NH 4 + (11.8–24.5 µmol gDW −1  h −1 ) over NO 3 − (0.04–2.31 µmol gDW −1  h −1 ) and NO 2 − (0.02–0.38 µmol gDW −1  h −1 ). Specifically, C. microphysa had the highest PO 4 3− uptake (0.43 ± 0.04 µmol gDW −1  h −1 ), while K. alvarezii had the highest NH 4 + uptake (20.6 ± 0.68 µmol gDW −1  h −1 ) and U. ohnoi showed the highest NO 3 − (1.92 ± 0.25 µmol gDW −1  h −1 ) and NO 2 − (0.30 ± 0.04 µmol gDW −1  h −1 ) uptake rates. Principal component analysis grouped species by uptake rates, and projections indicated that U. ohnoi and K. alvarezii would have absorbed the most nitrogen and phosphorus, respectively, over 45 days. These findings highlight the potential of these macroalgae as extractive species in IMTA, reducing eutrophication risks and promoting sustainable aquaculture.