Global arthropod beta-diversity is spatially and temporally structured by latitude.

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.

Coupling and confinement of current in thermoacoustic phased arrays.

When a medium is rapidly heated and cooled, heat transfers to its surroundings as sound. A controllable source of this sound is realized through joule heating of thin, conductive films by an alternating current. Here, we show that arrays of these sources generate sound unique to this mechanism. From the sound alone, we spatially resolve current flow by varying the film geometry and electrical phase. Confinement concentrates heat to such a degree that the film properties become largely irrelevant. Electrical coupling between sources creates its own distinctive sound that depends on the current flow direction, making it unusually sensitive to the interactions of multiple currents sharing the same space. By controlling the flow, a full phased array can be created from just a single film.

Broad and Fine Scale Variability in Bacterial Diversity and Cyanotoxin Quotas in Benthic Cyanobacterial Mats.

Benthic proliferations of Microcoleus autumnalis (basionym Phormidium autumnale) and closely related taxa are being reported with increasing frequency in streams and rivers worldwide. This species commonly produces the potent neurotoxin anatoxin, and exposure to this has resulted in animal fatalities and human health concerns. Bacterial communities within cyanobacterial assemblages can facilitate processes such as nutrient cycling and are posited to influence cyanobacterial growth and function. However, there is limited knowledge on spatial variability of bacterial communities associated with benthic cyanobacteria and anatoxin content and quotas. In this study, M. autumnalis-dominated mat samples were collected from six sites in two New Zealand streams. Associated bacterial communities were characterized using 16S rRNA metabarcoding, anatoxin content by liquid chromatography-mass spectrometry and anaC copies using droplet digital PCR. Bacterial assemblages differed significantly when amplicon sequence variants were compared between streams and most sites within streams. These differences were associated with conductivity, DRP, DIN, temperature, anatoxin concentration, and quota. Despite the differences in bacterial community composition; at phyla, class and order levels there was high similarity across spatial scales, with Bacteroidetes (ca. 67%) and Proteobacteria (ca. 25%) dominant. There was significant variability in total anatoxin concentrations between sites in both streams (p < 0.001). When the data were converted to anatoxin quotas variability was reduced, suggesting that the relative abundance of toxic genotypes is a key driver of total anatoxin concentrations in mats. This study demonstrates the complexity of microbial communities within M. autumnalis-dominated mats and highlights their likely important role in within-mat nutrient cycling processes.

Multiple processes acting from local to large geographical scales shape bacterial communities associated with Phormidium (cyanobacteria) biofilms in French and New Zealand rivers.

River biofilms dominated by Phormidium (cyanobacteria) are receiving increased attention worldwide because of a recent expansion in their distribution and their ability to produce neurotoxins leading to animal mortalities. Limited data are available on the composition and structure of bacterial communities (BCs) associated with Phormidium biofilms despite the important role they potentially play in biofilm functioning. By using a high-throughput sequencing approach, we compared the BCs associated with Phormidium biofilms in several sampling sites of the Tarn River (France) and in eight New Zealand rivers. The structure of the BCs from both countries displayed spatial and temporal variations but were well conserved at the order level and 28% of the OTUs containing 90% of the reads were shared by these BCs. This suggests that micro-environmental conditions occurring within thick Phormidium biofilms strongly shape the associated BCs. A strong and significant distance-decay relationship (rp = 0.7; P = 0.001) was found in BCs from New Zealand rivers but the Bray-Curtis dissimilarities between French and New Zealand BCs are in the same order of magnitude of those found between New Zealand BCs. All these findings suggest that local environmental conditions seem to have more impact on BCs than dispersal capacities of bacteria.

Application of a spectrofluorimetric tool (bbe BenthoTorch) for monitoring potentially toxic benthic cyanobacteria in rivers.

Over the last decade reports of animal poisoning following accidental consumption of neurotoxin-producing benthic cyanobacteria (mainly Phormidium spp.) have increased. There is a need for rapid and cost-effective tools to survey benthic cyanobacteria. In this study we assessed the performance of the BenthoTorch, a fluorometric probe that provides in situ estimations of cyanobacteria, diatoms and green algae biomass in biofilms. Biofilms (n = 288) were analysed from two rivers in France and eight in New Zealand. Correlations between chlorophyll-a measured using the BenthoTorch and spectrophotometry were higher for thin (<2 mm) compared to thick (>2 mm) biofilms (r(2) = 0.58 and 0.27 respectively; p < 0.001). When cyanobacteria represented less than 50% of the total biomass (based on biovolumes), microscopic and BenthoTorch compositional estimations were significantly correlated (r(2) = 0.53, p < 0.001). Conversely, there was no correlation when cyanobacteria exceeded 50% of the total biomass. Under this scenario diatoms were overestimated. Our results suggest that the observed biases occur because the BenthoTorch only measures the upper biofilm layer and it underestimates the biomass of phycoerythrin-containing cyanobacteria. To improve the performance of this sensor and render it a useful tool for a rapid evaluation of benthic cyanobacterial biomass in rivers, we propose that: (i) the algorithms based on the LEDs responses currently available on this tool need revision, (ii) new excitation wavelengths should be included that allow the fingerprints of phycoerythrin-containing cyanobacteria to be discriminated, and (iii) a sensor that penetrates the biofilms is needed to obtain more accurate estimates of cyanobacterial biomass.

The role of nitrogen and phosphorus in regulating Phormidium sp. (cyanobacteria) growth and anatoxin production.

Benthic proliferations of the cyanobacteria Phormidium can cover many kilometres of riverbed. Phormidium can produce neurotoxic anatoxins and ingestion of benthic mats has resulted in numerous animal poisonings in the last decade. Despite this, there is a poor understanding of the environmental factors regulating growth and anatoxin production. In this study, the effects of nitrogen and phosphorus on the growth of two Phormidium strains (anatoxin-producing and non-anatoxin-producing) were examined in batch monocultures. Cell concentrations were significantly reduced under reduced nitrogen (ca. <0.100 mM) and phosphorus conditions (ca. <0.003 mM). Cell concentrations and maximum growth rates were higher for the non-anatoxin-producing strain in all treatments, suggesting there may be an energetic cost to toxin production. Cellular anatoxin concentrations were lowest (169 fg cell(-1)) under the high-nitrogen and high-phosphorus treatment. This supports the growth-differentiation balance hypothesis that suggests actively dividing and expanding cells are less likely to produce secondary-metabolites. Anatoxin quota was highest (>407 fg cell(-1)) in the reduced phosphorus treatments, possibly suggesting that it is produced as a stress response to growth limiting conditions. In all treatments there was a 4-5-fold increase in anatoxin quota in the lag growth phase, possibly indicating it may provide a physiological benefit during initial substrate colonization.

Successional change in microbial communities of benthic Phormidium-dominated biofilms.

Benthic cyanobacterial blooms are increasing worldwide and can be harmful to human and animal health if they contain toxin-producing species. Microbial interactions are important in the formation of benthic biofilms and can lead to increased dominance and/or toxin production of one or few taxa. This study investigated how microbial interactions contribute to proliferation of benthic blooms dominated by the neurotoxin-producing Phormidium autumnale. Following a rainfall event that cleared the substrate, biofilm succession was characterised at a site on the Hutt River (New Zealand) by sampling every 2-3 days over 32 days. A combination of morphological and molecular community analyses (automated ribosomal intergenic spacer analysis and Illumina™ MiSeq sequencing) identified three distinct phases of succession in both the micro-algal and bacterial communities within P. autumnale-dominated biofilms. Bacterial composition shifted between the phases, and these changes occurred several days before those of the micro-algal community. Alphaproteobacteria and Betaproteobacteria dominate in the early phase; Alphaproteobacteria, Betaproteobacteria, Sphingobacteria and Flavobacteria in the mid-phase; and Sphingobacteria and Flavobacteria in the late phase. Collectively, the results suggest that succession is driven by bacteria in the early stages but becomes dependent on micro-algae in the mid- and late stages of biofilm formation.

Effects of nitrogen and phosphorus on anatoxin-a, homoanatoxin-a, dihydroanatoxin-a and dihydrohomoanatoxin-a production by Phormidium autumnale.

Anatoxins are powerful neuromuscular blocking agents produced by some cyanobacteria. Consumption of anatoxin-producing cyanobacterial mats or the water containing them has been linked to numerous animal poisonings and fatalities worldwide. Despite this health risk, there is a poor understanding of the environmental factors regulating anatoxin production. Non-axenic Phormidium autumnale strain CAWBG557 produces anatoxin-a (ATX), homoanatoxin-a (HTX) and their dihydrogen-derivatives dihydroanatoxin-a (dhATX) and dihydrohomoanatoxin-a (dhHTX). The effects of varying nitrogen and phosphorus concentrations on the production of these four variants were examined in batch monocultures. The anatoxin quota (anatoxin per cell) of all four variants increased up to four fold in the initial growth phase (days 0-9) coinciding with the spread of filaments across the culture vessel during substrate attachment. Dihydroanatoxin-a and dhHTX, accounted for over 60% of the total anatoxin quota in each nitrogen and phosphorus treatment. This suggests they are being internally synthesised and not just derived following cell lysis and environmental degradation. The four anatoxin variants differed in their response to varying nitrogen and phosphorus concentrations. Notably, dhATX quota significantly decreased (P ≤ 0.03) when nitrogen and phosphorus concentrations were elevated (nitrogen = 21 mg L(-1); phosphorus = 3 mg L(-1)), while HTX quota increased when the phosphorus concentrations were reduced (ca. < 0.08 mg L(-1)). This is of concern as HTX has a high toxicity and anatoxin producing P. autumnale blooms in New Zealand usually occur in rivers with low water column dissolved reactive phosphorus.

Within-mat variability in anatoxin-a and homoanatoxin-a production among benthic Phormidium (cyanobacteria) strains.

Benthic Phormidium mats can contain high concentrations of the neurotoxins anatoxin-a and homoanatoxin-a. However, little is known about the co-occurrence of anatoxin-producing and non-anatoxin-producing strains within mats. There is also no data on variation in anatoxin content among toxic genotypes isolated from the same mat. In this study, 30 Phormidium strains were isolated from 1 cm(2) sections of Phormidium-dominated mats collected from three different sites. Strains were grown to stationary phase and their anatoxin-a, homoanatoxin-a, dihydroanatoxin-a and dihydrohomoanatoxin-a concentrations determined using liquid chromatography-mass spectrometry. Each strain was characterized using morphological and molecular (16S rRNA gene sequences) techniques. Eighteen strains produced anatoxin-a, dihydroanatoxin-a or homoanatoxin-a. Strains isolated from each mat either all produced toxins, or were a mixture of anatoxin and non-anatoxin-producing genotypes. Based on morphology these genotypes could not be separated. The 16S rRNA gene sequence comparisons showed a difference of at least 17 nucleotides among anatoxin and non-anatoxin-producing strains and these formed two separate sub-clades during phylogenetic analysis. The total anatoxin concentration among toxic strains varied from 2.21 to 211.88 mg kg(-1) (freeze dried weight), representing a 100 fold variation in toxin content. These data indicate that both the relative abundance of anatoxin and non-anatoxin-producing genotypes, and variations in anatoxin producing capability, can influence the overall toxin concentration of benthic Phormidium mat samples.

Polyphasic assessment of fresh-water benthic mat-forming cyanobacteria isolated from New Zealand.

Mat-forming benthic cyanobacteria are widespread throughout New Zealand rivers, and their ingestion has been linked to animal poisonings. In this study, potentially toxic benthic cyanobacterial proliferations were collected from 21 rivers and lakes throughout New Zealand. Each environmental sample was screened for anatoxins using liquid chromatography-MS (LC-MS). Thirty-six cyanobacterial strains were isolated and cultured from these samples. A polyphasic approach was used to identify each isolate; this included genotypic analyses [16S rRNA gene sequences and intergenic spacer (ITS)] and morphological characterization. Each culture was analysed for anatoxins using LC-MS and screened for microcystin production potential using targeted PCR. The morphospecies Phormidium autumnale was found to be the dominant cyanobacterium in mat samples. Polyphasic analyses revealed multiple slight morphological variants within the P. autumnale clade and highlighted the difficulties in identifying Oscillatoriaceae. Only one morphospecies (comprising the two strains CYN52 and CYN53) of P. autumnale was found to produce anatoxins. These strains formed their own clade based on partial 16S rRNA gene sequences. These data indicate that benthic P. autumnale mats are composed of multiple morphospecies and toxin production is dependent on the presence of toxin-producing genotypes. Further cyanobacteria are also characterized, including Phormidium murrayi, which was identified for the first time outside of Antarctica.

Identification of a benthic microcystin-producing filamentous cyanobacterium (Oscillatoriales) associated with a dog poisoning in New Zealand.

In November 2008 a dog died soon after ingesting benthic "algal" mat material from the Waitaki River, New Zealand. Based on a morphological examination of environmental material, the causative organism was putatively identified as the filamentous cyanobacterium Phormidium sp. Two strains (VUW25 and CYN61) were isolated and cultured to enable further taxonomic and cyanotoxin characterisation. Phylogenetic analyses based on a region of the 16S rRNA gene sequence, intergenic spacer (ITS) region and the mcyE gene demonstrated that the species was likely to be a new Planktothrix species that is either benthic or has a biphasic life cycle. Using liquid chromatography-mass spectrometry (LC-MS), microcystin-LR, [D-Asp(3), Dha(7)] microcystin-LR, [D-Asp(3)] microcystin-LR, and minor proportions of [D-Asp(3), ADMAdda(5)] microcystin-LhR were identified. This is the first report of [D-Asp(3)] microcystin-LR, [D-Asp(3), Dha(7)] microcystin-LR and an ADMAadda variant in New Zealand. No cylindrospermopsins, saxitoxins or anatoxins were detected. Dog deaths caused by the consumption of cyanobacterial mats containing anatoxins have previously been reported in New Zealand. To our knowledge, however, this is the first instance of a benthic microcystin-producing species causing an animal death in New Zealand.