Sea ice phenology and timing of primary production pulses in the Arctic Ocean

Arctic organisms are adapted to the strong seasonality of environmental forcing. A small timing mismatch between biological processes and the environment could potentially have significant consequences for the entire food web. Climate warming causes shrinking ice coverage and earlier ice retreat in the Arctic, which is likely to change the timing of primary production. In this study, we test predictions on the interactions among sea ice phenology and production timing of ice algae and pelagic phytoplankton. We do so using the following (1) a synthesis of available satellite observation data; and (2) the application of a coupled ice‐ocean ecosystem model. The data and model results suggest that, over a large portion of the Arctic marginal seas, the timing variability in ice retreat at a specific location has a strong impact on the timing variability in pelagic phytoplankton peaks, but weak or no impact on the timing of ice‐algae peaks in those regions. The model predicts latitudinal and regional differences in the timing of ice algae biomass peak (varying from April to May) and the time lags between ice algae and pelagic phytoplankton peaks (varying from 45 to 90 days). The correlation between the time lag and ice retreat is significant in areas where ice retreat has no significant impact on ice‐algae peak timing, suggesting that changes in pelagic phytoplankton peak timing control the variability in time lags. Phenological variability in primary production is likely to have consequences for higher trophic levels, particularly for the zooplankton grazers, whose main food source is composed of the dually pulsed algae production of the Arctic.     

Characterization of Dinophysis spp. (Dinophyceae,Dinophysiales) from the mid-Atlantic region of the United States1

Due to the increasing prevalence of Dinophysis spp. and their toxins on every US coast in recent years, the need to identify and monitor for problematic Dinophysis populations has become apparent. Here, we present morphological analyses, using light and scanning electron microscopy, and rDNA sequence analysis, using a ~2-kb sequence of ribosomal ITS1, 5.8S, ITS2, and LSU DNA, of Dinophysis collected in mid-Atlantic estuarine and coastal waters from Virginia to New Jersey to better characterize local populations. In addition, we analyzed for diarrhetic shellfish poisoning (DSP) toxins in water and shellfish samples collected during blooms using liquid-chromatography tandem mass spectrometry and an in vitro protein phosphatase inhibition assay and compared this data to a toxin profile generated from a mid-Atlantic Dinophysis culture. Three distinct morphospecies were documented in mid-Atlantic surface waters: D. acuminata, D. norvegica, and a “small Dinophysis sp.” that was morphologically distinct based on multivariate analysis of morphometric data but was genetically consistent with D. acuminata. While mid-Atlantic D. acuminata could not be distinguished from the other species in the D. acuminata-complex (D. ovum from the Gulf of Mexico and D. sacculus from the western Mediterranean Sea) using the molecular markers chosen, it could be distinguished based on morphometrics. Okadaic acid, dinophysistoxin 1, and pectenotoxin 2 were found in filtered water and shellfish samples during Dinophysis blooms in the mid-Atlantic region, as well as in a locally isolated D. acuminata culture. However, DSP toxins exceeded regulatory guidance concentrations only a few times during the study period and only in noncommercial shellfish samples.     

Ultrafast molecular dynamics of biofuel extraction for microalgae and bacteria milking: blocking membrane folding pathways to damaged lipid-bilayer conformations with nanomicelles

Cell milking is a 100% renewable green energy for CO₂ by extraction of biofuels inside the cytosol of photosynthetic micro-organisms as microalgae and bacteria. The cells are exposed to a hydrophobic solvent forming holes and cracks through their membranes from which the biofuels can leak out. In protein folding, the goal would be to find pathways to the unique functional protein conformer. However, in the lipid-bilayer interaction with the solvent for milking, the objective is to block the pathways for damaged membrane conformations of low free energy with undesired nanostructures, using the solvent properties, as shown with an ab initio structural bioinformatic model. Statistical thermodynamics is used to compute the free energy (including entropy) from the molecular dynamics trajectory of the biomolecular system with many conformational changes. This model can be extended to the general problem of biomolecules folding as for proteins and nucleic acids. Using an adaptation of the Einstein diffusion law, the conformational change dynamics of the lipid bilayer depends on the two diffusion coefficients of the solvent: D₁ before the irreversible folding transition time and the much smaller D₂ thereafter. In contrast to the n-hexane and n-heptane hydrocarbons of smaller size, the residual D₂?=?4.7?×?10^?7?cm²/s of the n-decane solvent, with the highest partition coefficient among the three extractors, is the only to present a D₂ value that is significantly below the critical threshold of 10^?6?cm²/s. Therefore, the membrane would resist to long hydrocarbons and the exposed cells would remain viable for milking.     

Phytoplankton–zooplankton dynamics in periodic environments taking into account eutrophication

In this paper, we derive and analyze a mathematical model for the interactions between phytoplankton and zooplankton in a periodic environment, in which the growth rate and the intrinsic carrying-capacity of phytoplankton are changing with respect to time and nutrient concentration. A threshold value: “Predator’s average growth rate” is introduced and it is proved that the phytoplankton–zooplankton ecosystem is permanent (both populations survive cronically) and possesses a periodic solution if and only if the value is positive. We use TP (Total Phosphorus) concentration to mark the degree of eutrophication. Based on experimental data, we fit the growth rate function and the environmental carrying capacity function with temperature and nutrient concentration as independent variables. Using measured data of temperature on water bodies we fit a periodic temperature function of time, and this leads the growth rate and intrinsic carrying-capacity of phytoplankton to be periodic functions of time. Thus we establish a periodic system with TP concentration as parameter. The simulation results reveal a high diversity of population levels of the ecosystem that are mainly sensitive to TP concentration and the death-rate of zooplankton. It illustrates that the eruption of algal bloom is mainly resulted from the increasing of nutrient concentration while zooplankton only plays a role to alleviate the scale of algal bloom, which might be used to explain the mechanism of algal bloom occurrence in many natural waters. What is more, our results provide a better understanding of the traditional manipulation method.     

Broad Salinity Tolerance as a Refuge from Predation in the Harmful Raphidophyte Alga Heterosigma akashiwo (Raphidophyceae)

The ability of harmful algal species to form dense, nearly monospecific blooms remains an ecological and evolutionary puzzle. We hypothesized that predation interacts with estuarine salinity gradients to promote blooms of Heterosigma akashiwo (Y. Hada) Y. Hada ex Y. Hara et M. Chihara, a cosmopolitan toxic raphidophyte. Specifically, H. akashiwo's broad salinity tolerance appears to provide a refuge from predation that enhances the net growth of H. akashiwo populations through several mechanisms. (1) Contrasting salinity tolerance of predators and prey. Estuarine H. akashiwo isolates from the west coast of North America grew rapidly at salinities as low as six, and distributed throughout experimental salinity gradients to salinities as low as three. In contrast, survival of most protistan predator species was restricted to salinities >15. (2) H. akashiwo physiological and behavioral plasticity. Acclimation to low salinity enhanced H. akashiwo's ability to accumulate and grow in low salinity waters. In addition, the presence of a ciliate predator altered H. akashiwo swimming behavior, promoting accumulation in low‐salinity surface layers inhospitable to the ciliate. (3) Negative effects of low salinity on predation processes. Ciliate predation rates decreased sharply at salinities <25 and, for one species, H. akashiwo toxicity increased at low salinities. Taken together, these behaviors and responses imply that blooms can readily initiate in low salinity waters where H. akashiwo would experience decreased predation pressure while maintaining near‐maximal growth rates. The salinity structure of a typical estuary would provide this HAB species a unique refuge from predation. Broad salinity tolerance in raphidophytes may have evolved in part as a response to selective pressures associated with predation.     

Toxic Microcystis (cyanobacteria) inhibit recruitment of the bloom‐enhancing invasive bivalve Limnoperna fortunei

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A Growth Factor for Malo-lactic Fermentation Bacteria

A growth factor (TJF) for a malo-lactic fermentation bacterium has been isolated from tomato juice, and found to be a β-glucoside. The NMR spectra of TJF and its acetate revealed that the glucosyl residue linked to the hydroxyl group at C-2′ or C-4′ of d- or l-pantothenic acid moiety. Then, 2′-O-(β-d-glucopyranosyl)-dl-pantothenic acid (I), 4′-O-(β-d-glucopyranosyl)-dl-pantothenic acid (II) and 4′-O-(β-d-glucopyranosyl)-d(R)-pantothenic acid (II-a) were synthesized, and Il-a and 4′-O-(β-d-glucopyranosyl)-l-pantothenic acid (II-b) were obtained by the optical resolution of the acetate of II. Among the above compounds, II-a was identical with natural TJF regarding to the biological activity, NMR and ORD spectra, and thin-layer chromatography.     

Strict Binding Specificity of Small-Sized Lectins from the Red Alga Hypnea japonica for Core (α1-6) Fucosylated N-Glycans

Small-sized isolectins (9 KDa) from Hypnea japonica belong to a new lectin family. Here, we describe the carbohydrate-binding properties of the three isolectins (hypninA1, A2, and A3) and the amino acid sequence of hypninA3 (P85888). In frontal affinity chromatography with about 100 pyridylaminated oligosaccharides, the isolectins, which had no affinity for monosaccharides, commonly bound only core (α1-6) fucosylated N-glycans, and did not the other oligosaccharides examined, including (α1-2), (α1-3), and (α1-4) fucosylated glycans. The specific binding of hypninA3 with the fucosylated N-glycans (K _a; 0.52–7.58×10⁶ M^?1) was confirmed by surface plasmon resonance analyses on an immobilized glycoprotein with and without core (α1-6) fucose. Such specificity of hypninA is clearly distinct from those of other known fucose-binding lectins, making it a valuable tool for cancer diagnosis and quality control of medicinal antibodies. HypninA3 is a polypeptide composed of 90 amino acids containing four half-cystines.     

The central role of selenium in the biochemistry and ecology of the harmful pelagophyte,Aureococcus anophagefferens

The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses, and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consists of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by >95% during the peak of blooms to 0.05 nℳ. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.     

Multi-species okadaic acid contamination and human poisoning during a massive bloom of Dinophysis acuminata complex in southern Brazil

On June 2016, a major bloom of Dinophysis acuminata complex was noticed over the coast of Paraná State (PR), southern Brazil, an area unprotected by any official monitoring program. Here we report the results of an extensive sampling effort that ultimately led PR authorities to issue the first State shellfish-harvesting ban due to multi-species okadaic acid (OA) contamination. During its peak, the bloom covered an area of 201 km² (∼2.0–3.5 × 54.0 km), attaining unprecedentedly high cell densities along the shallow (<15 m) continental shelf (mean 2.2 × 10⁵, maximum 2.1 × 10⁶ cells L⁻¹) and adjacent sandy beaches (mean 2.8 × 10⁵, maximum 5.2 × 10⁶ cells L⁻¹). Only OA was detected in suspension (max. 188 ng L⁻¹). Toxin levels measured in bivalves were several times greater than the regulatory limit of 160 ng g⁻¹, reaching up to 3600 ng g⁻¹ in Crassostrea gasar, by far the highest OA concentrations ever reported in oysters worldwide, 7700 ng g⁻¹ in brown mussels, Perna perna, and lower levels in clams, Anomalocardia brasiliana, and mangrove mussels, Mytella spp. Nine cases of human intoxication were officially reported and five people were hospitalized with typical symptoms of Diarrhetic Shellfish Poisoning linked to the consumption of contaminated bivalves. All bivalves quickly converted most of the OA into its esterified form, DTX-3, and eliminated the toxins only a few weeks following the bloom, with C. gasar being the slowest-detoxifying species. Lower OA levels were accumulated in zooplankton, gastropods and several novel toxin vectors, including benthic organisms such as sand dollars Mellita quinquiesperforata and the ghost-shrimp Callichirus major, which may act as a good indicator of the presence of toxins in sandy beaches, and pelagic fish species that can serve as potential alternative sources of OA to humans (Chaetodipterus faber and Mugil liza). Monitoring toxin contamination in seafood other than bivalves is thus recommended to ensure comprehensive human health protection during massive Dinophysis blooms. Additionally, since OA was also present at low concentrations in the liver of Guiana dolphins Sotalia guianensis and penguins Spheniscus magellanicus, exposure to biotoxins should be considered in conservation actions involving threatened and near-threatened marine organisms in this region.