Journal of Phycology最新文献

Phytoplankton require specific nutrients in varying quantities for growth, defense, and proper cell functioning. When macronutrients are present in excess, trace metals can exhibit co-limitation on phytoplankton. This experiment aimed to understand how ambient nutrient concentrations impact phytoplankton community persistence (i.e., bloom longevity). To examine potential interactions, three ponds of escalating trophic states were selected. Pond water was transferred into sealed, clear, floating plastic containers inside a floating frame within each pond. The containers were treated with a full factorial design of additions of nitrogen, phosphorus, and/or a mixture of trace metals. In the oligotrophic pond, the containers treated with nitrogen, phosphorus, and trace metals had 39% more phytoplankton than those treated with just nitrogen and phosphorus, by the end of the experiment. In the mesotrophic pond, the containers treated with nitrogen and trace elements had 14% more phytoplankton than those with nitrogen alone, by the conclusion of the experiment. In the eutrophic pond, no combinations of added nutrients affected algal growth when compared to the control treatment. These results show that the addition of trace metals along with nitrogen and phosphorus allowed phytoplankton to resist the effects of nutrient starvation when compared with treatments that only provided nitrogen and phosphorus. These results indicate the utility of trace metals for sustaining rather than limiting algal growth.

Temperate Australian kelp forests are highly vulnerable to range contractions because of ongoing ocean warming and extremes. The current mainland distribution of the bull kelp Durvillaea amatheiae is confined to the far southeastern corner of the continent where warming is occurring two to four times faster than the global average. Extant populations will, thus, require sufficient genetic adaptive capacity to survive these extremes. We examined neutral and adaptive genomic diversity to assess the adaptive capacity and selective pressure on these range edge populations. We have revealed that prevailing ocean currents and dispersal-restrictive life-history traits have resulted in isolated, inbred populations across the southeastern range, particularly at the northern edge. Temperature-related candidate loci exhibited signatures of selection along thermal gradients, with many of these alleles fixed across the species range, suggesting little remaining adaptive capacity, particularly among the warmest populations. Combined, these elements suggest D. amatheiae may be susceptible to range contractions in the face of ongoing climate change.

Overyielding in polyculture systems suggests a potential for greater productivity than that observed in monocultures. Optimized algal polyculture combinations can significantly enhance biomass production and yield valuable biochemicals. The study tested seven different treatments of Nannochloropsis oculata, Chlorella sp., and Dunaliella tertiolecta in different ratios T1: (1:1:1), T2: (1:1:2), T3: (1:2:1), T4: (2:1:1), T5: (1:2:2), T6: (2:2:1), and T7: (2:1:2), respectively, under different photoperiods to assess the best combination for biomass, biochemical, and biodiesel properties. The results showed that under a 12:12 h light:dark photoperiod, T7 had the highest lipid and protein contents. There were also higher degrees of unsaturation in treatments 3, 6, and 7, whereas treatments 1, 2, and 4 had higher values for low carbon fuel standard and cold filter plugging point. Under a 16:8 h photoperiod, T3 had the highest total number of cells, T1 had the highest lipid level, and T3 had the highest protein level. Treatments 2 and 3 had significantly higher iodine values than the others, whereas T3 and T6 had higher cetane numbers. The results indicate that the highest protein and lipid levels were obtained in T3 under a 16:8 h photoperiod, whereas T1 had its highest protein and lipid levels during a 12:12 h photoperiod. Additionally, the highest biomass and mono-unsaturated fatty acids were observed in T3 under a 16:8 h photoperiod, and there were no significant differences in saponification values between treatments. Based on these findings, we recommend conducting algal polyculture with T3 (1:2:1) under a 16:8 h light:dark photoperiod to achieve optimal biomass production, higher protein, lipid, and mono-unsaturated fatty acid levels.

Thermal and cave habitats on nearly all continents have been a substantial source of new cyanobacterial genotypes and morphotypes that expanded with the dawn of the era of molecular phylogenetics. In this study, we investigated the cyanobacterial flora of an extreme habitat of recently discovered caves with sulfur-rich thermal springs, using the polyphasic approach. The methods included cultivation, light and transmission electron microscopy, and molecular methods, including those that can be employed on samples that are not unialgal. Here, we present data on morphological and ultrastructural characteristics, 16S rRNA gene and 16S–23S internal transcribed spacer (ITS) rRNA region sequences, and folding structures. We identified one new trichal genus Xomosiella with the type species X. audyi forming a distinctly isolated clade and three new species in Loriellopsis, Mastigocladus, and Pegethrix. Apart from genetic distance, Xomosiella is distinguished from Limnothrix by its high trichome motility and benthic habitat, with granules likely composed of cyanophycin rather than aerotopes. The coccal cyanobacterium initially identified as “Cyanosarcina” sp. has been proposed as a new species, Loriellopsis vromonerensis, although its classification is complicated by morphological plasticity and phylogenetic uncertainties. The erection of Mastigocladus boudae was supported by a significant genetic divergence and distinct morphological characteristics. A description of a newly revealed cryptic species, Pegethrix sulphurea, has been provided. These results advance our knowledge of the diversity of cyanobacteria in extreme and understudied environments, which could enrich our understanding of microbial adaptability.

Small eukaryotic phytoplankton can account for a considerable amount of biomass and primary production in high nutrient, low chlorophyll (HNLC) regions of the ocean where iron limitation is pronounced. However, the physiological and metabolic strategies these cells invoke to cope under low iron conditions and the extent to which they are responsible for new production (i.e., the fraction of primary production supported by nutrients from outside of the euphotic zone) are unclear. Here, we examined how a representative picoeukaryote—the chlorophyte Micromonas sp., recently isolated from the iron-limited subarctic Northeast Pacific Ocean—responded to iron limitation when grown on nitrate as a nitrogen source. Iron-limited Micromonas exhibited reductions in growth rate, cell volume, and elemental quotas along with a restructuring of cellular metabolism. Gene expression and metabolic pathway analyses showed evidence of strategies to mitigate iron limitation with constitutive expression of genes related to nitrogen uptake and utilization. Additionally, cellular carbon and nitrogen quotas were 20–70 fmol C · cell⁻¹ and 3.3–20 fmol N · cell⁻¹, respectively, as a function of iron status. Based on the measured cellular quotas, we have estimated that representative picoeukaryotes (<2 μm), such as Micromonas, in HNLC Northeast Pacific waters can account for a significant proportion of new production, supporting the need for a reconsideration of the role small eukaryotic phytoplankton play in the global carbon cycle.

Recent phylogenetic studies of the family Hydrodictyaceae (Sphaeropleales, Chlorophyceae) included all but one of the genera, Euastropsis, which was excluded due to a lack of living material. A 2017 discovery of E. richteri in Lake Kocie, Poland, provided an opportunity to study the morphology, ultrastructure, plastome architecture, and phylogenetic placement of this monotypic genus. The overall morphology fit the original description, being two-celled with some variations in size and number of daughter coenobia. The plastome (GenBank accession PQ469705) architecture and gene content of E. richteri are characteristic of Hydrodictyaceae. Phylogenetic analyses placed E. richteri as a sister lineage to morphologically similar Stauridium tetras. These new data add to our understanding of evolutionary trends in the Hydrodictyaceae, whose members exhibit specific colonial morphology varying in size, shape, and complexity.

This study provides a comprehensive investigation of Gonyaulax hyalina, integrating morphological, phylogenetic, and toxicological approaches. Strains were re-isolated from its type locality in the Gulf of Aden (western Indian Ocean) 124 years after its original description by Ostenfeld and Schmidt (1901, p. 141), along with additional Pacific strains collected from Korea and Viet Nam. The primary objective was to clarify the taxonomy of G. hyalina, which has frequently been confused with the morphologically similar G. fragilis. Morphological and molecular data confirmed that the Indo-Pacific strains examined belong to G. hyalina. Diagnostic morphological features supporting this identification included the presence of a characteristic surface ornamentation, a distinct anterior intercalary plate 1a, and comparatively smaller cell dimensions. Phylogenetic analyses based on LSU and SSU rRNA gene sequences revealed that these strains formed a distinct clade, separate from existing G. hyalina sequences in GenBank. This phylogenetic analyses indicated the presence of two ribotypes (A and B) within the species, although morphological characters do not reflect this, providing evidence of cryptic speciation in G. hyalina. Ribotype B corresponded to strains previously associated with gelatinous mucilage aggregates, known from the Mediterranean and New Zealand coastal waters. Toxicological assays conducted on strain DJ_I3 from the Gulf of Aden showed no detectable toxin production. Lastly, analysis of seasonal dynamics in the Gulf of Aden demonstrated that G. hyalina is present throughout the year, with abundance peaking in summer and declining markedly during winter months.

Mitochondrial mRNAs in the green algal class Chlorophyceae have non-template 3' oligo-cytosine-rich additions, also known as oligo(C), polycitydylation, or poly(C) “tails.” These oligonucleotide additions are believed to be unique to green algal mitochondria, as none have been observed in any other organism. Among algae, oligocitydylation had only been observed in species within the Chlorophyceae, with no evidence of it occurring in other taxonomic classes. In this study, evidence is presented that mitochondrial mRNA oligocitydylation occurs in the genus Ulva, demonstrating its presence in the Class Ulvophyceae and Order Ulvales. Two other species in Ulvophyceae, Bryopsis plumosa and Codium fragile, from the Order Bryopsidales were also screened, but no evidence of oligonucleotide additions was observed. This demonstrates that oligocitydylation occurs in Ulvophyceae but suggests it may be limited to the Ulvales. Three species from Trebouxiophyceae were also screened, and there was no evidence of oligonucleotide additions, suggesting it does not occur in this clade. These results demonstrate that oligocitydylation does occur outside of the Chlorophyceae but only in the closely related Ulvales clade, suggesting this could be a biochemical synapomorphy shared by these groups.

The articulated coralline genus Corallina is common in temperate rocky ecosystems and provides settlement substrate and refugia for other organisms. However, our ability to understand species-specific traits and interactions has been confounded by overlapping morphological characteristics among species. DNA sequences from type specimens and recently collected specimens have begun to address these issues by clarifying phylogenetic species boundaries and geographic distributions. We sequenced an rbcL gene barcode from a paratype specimen of Corallina bathybentha (type locality: 0.5 miles south of the west end of Anacapa Is., California, United States) and have provided an updated description. Three cryptic species have been described: C. hommersandiorum and C. saundersii are endemic to the northeastern Pacific, whereas C. americana is anti-tropical in the eastern Pacific. Haplotype network analyses using the COI locus suggested that C. americana naturally dispersed from North to South America; it was not likely a recent or human-mediated introduction. To explore species boundaries, stepwise discriminant models were used to analyze morphological and ecological traits and were visualized in canonical multidimensional plots. Every species overlapped in canonical space with at least one other species, further illustrating that morphological identifications of Corallina species are challenging and unreliable. This work completes the taxonomic study of the currently known diversity of Corallina in the northeast Pacific for which we have access to type specimens. Given that this region is likely the center of origin and home to three-quarters of the known Corallina species, these taxonomic studies, including this one, make a significant contribution to our understanding of coralline diversity.

We applied computational fluid dynamic simulations to three-dimensional (3D) computer models of diatoms to assess the effect of trait functions on niche space without the confounding influence of correlated traits. Sinking behavior of phytoplankton was assessed via computer-simulated experiments to test the physics of life at low Reynolds numbers. Specifically, 3D models of Stephanodiscus niagarae were constructed across the middle of the species size range and were placed in simulations to assess variance in the sinking and acceleration rates of the cells. First, we simulated models of anatomically correct cells as a control group. To assess trait function, in this case the function of the spines that encompass the outer rim of each frustule (cell wall), simulations of the model were rerun under the same conditions with the trait removed from the model as the experimental group. We observed that spines served to reduce the influence of outside forces on the cell, specifically the force of gravity, by reducing the sinking and acceleration rates of spined versus spineless models. We also observed that spines increased the range of sinking rates, which increased the dispersal of a population by increasing the range of responses to turbulence. When Hutchinson (1961) presented the paradox of plankton, there was a caveat “it is hard to believe that in turbulent open water many physical opportunities for niche-diversification exist” (p. 141). Herein we have shown that many opportunities for niche diversification are tied to a single trait. By testing trait function in fluid dynamic simulations, we can examine global trends in biodiversity.