Volume 68, Issue 2

In this study, we analyzed the abundance and distribution of eight major phytoplankton groups and their relationship to hydrography and nutrient concentrations in oceanic waters of the southern Gulf of Mexico based on 63 stations sampled during April and May 2017. At each location, a CTD/Rosette system configured with Niskin bottles was used to acquire high-resolution hydrographic data and collect water samples at standard depths for chemical determination (nutrients and chlorophyll- a ) and identification of phytoplankton cells. Cold and warm cores corresponding to cyclonic/anticyclonic eddies were recorded, which influenced the vertical and horizontal distributions of nutrients and chlorophyll- a . In terms of phytoplankton, Dinophyceae was the most abundant group, accounting for 454,160 cells l −1 . Phytoflagellates recorded 171,939 cells l −1 ; Cyanophyceae 50,720 cells l −1 ; Bacillariophyceae 25,457 cells l −1 ; Haptophyta 15,851 cells l −1 ; and Silicoflagellata 7,940 cells l −1 . The two groups with the lowest abundances were Raphidophyceae and Chlorophyceae, with 1,557 and 882 cells l −1 , respectively. The vertical distributions and abundances of the eight groups showed different patterns. Three main large regions of high abundance (>10,000 cells l −1 ) coincided with nutrient-rich cold cores, particularly in the southern portion. Each phytoplankton group is related to specific hydrographic and chemical parameters.

In tropical ecosystems worldwide, benthic marine algae are important primary producers and habitat providers for many juvenile fish and invertebrate species. Calcified species are known to provide structural support to their respective communities, thus enhancing the overall system’s productivity. In the Republic of the Maldives, algae are an important yet currently poorly studied biological resource. We reviewed the literature around algal diversity and distribution across Maldivian atolls and compiled an extensive and updated taxonomic list. The list contains 353 species, of which 31 are Cyanobacteria, 26 Phaeophyceae, 109 Chlorophyta, and 187 Rhodophyta. Algal collections have been reported from 12 out of 20 atolls, and these mostly occurred during 20th century expeditions. The taxonomic status of 110 species has changed since first reported. While several species have been documented from the country, identifications have thus far almost solely relied on morphological assessments. Many of the reported algal groups require molecular confirmation. This suggests that benthic algal diversity from the Maldives is likely an underestimate. Since anthropogenic activities can significantly alter algal community dynamics, a baseline understanding of algal diversity is necessary to determine how such shifts affect the ecosystem as a whole, thus underpinning future management and conservation efforts.

We measured baseline growth rates of perennial understory kelps, Agarum clathratum and Hedophyllum nigripes , and canopy-forming Eualaria fistulosa from March 1977 through October 1978 in Jakolof Bay, Kachemak Bay, Alaska. We measured density and biomass of several kelp species in the entrance to Jakolof Bay, at Seldovia Point, and at Latouche Point, Latouche Is., in an ocean entrance into Prince William Sound. We used Kachemak Bay data to estimate primary productivity in these kelp beds. In view of current records demonstrating increasing sea-surface temperatures in the Gulf of Alaska, these baseline data provide a useful basis for evaluating effects of climate change or other environmental effects. Growth rates, highest from late winter/early spring and lowest from late summer until mid-winter, changed seasonally. Rates were fastest in  Eualaria , the largest of these kelps, and slowest in Agarum , the smallest. Rates and seasonality of stipe growth varied among species. Stipe growth, observed seasonally in Agarum and Hedophyllum , occurred from spring through mid-summer; rates were slowest in Agarum . Stipe growth in the annual Eualaria occurred throughout its life span. Tissue growth and primary production varied among species; all produced appreciable quantities of fixed carbon annually. Estimated production for understory kelps off Seldovia Point varied from 73 g C m −2  yr −1 for Agarum to 87 g C m −2  yr −1 for Hedophyllum . Estimated production for canopy-forming kelps was an order of magnitude higher. Value of these decades-old baseline data cannot be over-emphasized in view of growing awareness of effects of climate change on kelps.

This study investigated the phylogeny of 17 isolates of Aspergillus terreus , cultured from soil, macroalgae, hydrothermal vent sediment in terrestrial and marine environments, and their growth response under combined effect of sea salt concentration (0 g l −1 or 30 g l −1 ), temperature (25 °C or 45 °C), pH (3 or 7). The isolates did not form clades corresponding to their ecological origin based on a combined phylogenetic analysis of five DNA regions (internal transcribed spacers of ribosomal DNA, calmodulin, β-tubulin, elongation factor 1-α, RNA-polymerase second large subunit). All isolates were able to grow under all tested conditions, including 45 °C/pH 3, environmental conditions possible at a hydrothermal vent site. The growth rate of the isolates was generally higher at 25 °C than at 45 °C and at pH 7 than at pH 3, and was similar at 0 g l −1 and 30 g l −1 sea salt concentrations. These results collectively suggest that the ocean is a sink of both marine and terrestrial isolates of A . terreus , which has the physiological and genetic capacities to grow in both environments.

In this study, we introduce a novel saprobic taxon Paraloratospora edkuensis , from a decaying stem of Phragmites australis collected at Lake Edku, El-Behera Governorate, Egypt. Multi-locus analyses of the combined ITS (internal transcribed spacers of rDNA), LSU (nuclear large subunit rDNA) and tef 1-α (translation elongation factor) sequence data placed the new taxon within Paraloratospora as a phylogenetically distinct species in a clade containing two aquatic species P . fructigena and P . marina . The new species is characterized by having globose to subglobose, dark brown to black ascomata with a short neck, 4–8-spored, cylindrical to obclavate asci, and 3-septate, hyaline and fusiform ascospores. Paraloratospora edkuensis differs from P . fructigena and P . marina by having smaller ascomata with a single neck, asci with four or eight ascospores, different mycelial colony morphology, and nucleotide differences of 2.1–3 %, 0.6–1.4 %, and 1.3–6.9 % in the ITS, LSU and tef 1-α genes, respectively.

Kuwait’s waters were first faced with a bloom of ichthyotoxic dinoflagellate Karenia and fish kill in 1999. Since then, there have been sporadic blooms and records of various kareniacean taxa, but accurate species identification has been challenging due to the high morphological similarity among morphotypes and the lack of molecular studies. Ten clonal kareniacean strains isolated from Kuwait’s coastal waters were characterized based on light and fluorescence microscopy and the LSU rDNA gene sequencing. Seven strains represented the distinctive morphology of Karenia papilionacea and showed LSU rDNA sequences with > 99 % similarity to the type material of this species. One Karenia strain represented the typical morphology of Karenia selliformis and the LSU rDNA sequence fell within a well-supported K. selliformis clade. Two other strains showed the typical morphology of Karlodinium ballantinum and phylogenetic analysis supported the morphological results. Consequently, a combination of morphological and molecular analyses confirmed the presence of K. papilionacea and K. selliformis in Kuwait’s waters, thereby resolving the previous regional taxonomic uncertainty regarding these species. The identification of K. ballantinum represents the first regional record. Investigating the morphology and phylogeny of commonly occurring Kareniaceae enhances the monitoring and risk assessment of harmful algal blooms in Kuwait’s marine environment.

The present study elucidates the bioactive metabolites, antioxidants, and antibacterial potential of selected seaweeds – Kappaphycus alvarezii , Caulerpa chemnitzia , and Sargassum tenerrimum – collected from the southwest coast of India. Biomolecules were extracted using six solvents: hexane, dichloromethane, ethyl acetate, acetone, methanol, and ethanol. Among these, ethanol proved to be the most efficient extraction solvent. Notably, the ethanolic extract of S .  tenerrimum exhibited high phenolic and flavonoid contents, contributing to its potent antioxidant and antibacterial properties. In contrast, the extracts of C . chemnitzia were rich in tannins, demonstrating marked antioxidant activity. Gas Chromatography-Mass Spectrometry profiling identified approximately 42 bioactive compounds with antimicrobial, antioxidant, anticancer, antidiabetic, and cardioprotective properties. Key compounds included stigmasta-5, 24(28)-dien-3-ol (3β, 24Z), cholesterol margarate, arachidonic acid, squalene, 1-hexadecanol, and δ-tocopherol, all of which hold significant nutraceutical and cosmetic value. Furthermore, antibacterial susceptibility tests against nine bacterial strains revealed that K . alvarezii was particularly effective against gram-positive bacteria, while the C . chemnitzia and S . tenerrimum extracts showed considerable efficacy against both gram-negative and gram-positive bacterial strains.