scholarly journals Uptake of Inorganic and Organic Nitrogen Sources by Dinophysis acuminata and D. acuta

2020 ◽  
Vol 8 (2) ◽  
pp. 187
Author(s):  
María García-Portela ◽  
Beatriz Reguera ◽  
Jesús Gago ◽  
Mickael Le Gac ◽  
Francisco Rodríguez
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Temporal Distribution ◽  
Nitrogen Sources ◽  
Uptake Kinetics ◽  
Nutritional Conditions ◽  
Dinophysis Acuminata ◽  
Uptake Rates ◽  
Spatio Temporal ◽  
Rías Baixas

Dinoflagellate species of Dinophysis are obligate mixotrophs that require light, nutrients, and prey for sustained growth. Information about their nitrogenous nutrient preferences and their uptake kinetics are scarce. This study aimed to determine the preferred nitrogen sources in cultures of D. acuminata and D. acuta strains from the Galician Rías Baixas (NW Spain) and to compare their uptake kinetics. Well-fed versus starved cultures of D. acuminata and D. acuta were supplied with N15 labeled inorganic (nitrate, ammonium) and organic (urea) nutrients. Both species showed a preference for ammonium and urea whereas uptake of nitrate was negligible. Uptake rates by well-fed cells of D. acuminata and D. acuta were 200% and 50% higher, respectively, than by starved cells. Uptake of urea by D. acuminata was significantly higher than that of ammonium in both nutritional conditions. In contrast, similar uptake rates of both compounds were observed in D. acuta. The apparent inability of Dinophysis to take up nitrate suggests the existence of incomplete nitrate-reducing and assimilatory pathways, in line with the paucity of nitrate transporter homologs in the D. acuminata reference transcriptome. Results derived from this study will contribute to understand Harmful Algal Blooms succession and differences in the spatio-temporal distribution of the two Dinophysis species when they co-occur in stratified scenarios.

scholarly journals Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

2018 ◽  
Vol 15 (9) ◽  
pp. 2891-2907 ◽  
Author(s):  
Kateri R. Salk ◽  
George S. Bullerjahn ◽  
Robert Michael L. McKay ◽  
Justin D. Chaffin ◽  
Nathaniel E. Ostrom
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Lake Erie ◽  
N Uptake ◽  
N Fixation ◽  
N Budget ◽  
N2o Production ◽  
N Removal ◽  
Uptake Rates ◽  
N Loading

Abstract. Recent global water quality crises point to an urgent need for greater understanding of cyanobacterial harmful algal blooms (cHABs) and their drivers. Nearshore areas of Lake Erie such as Sandusky Bay may become seasonally limited by nitrogen (N) and are characterized by distinct cHAB compositions (i.e., Planktothrix over Microcystis). This study investigated phytoplankton N uptake pathways, determined drivers of N depletion, and characterized the N budget in Sandusky Bay. Nitrate (NO3-) and ammonium (NH4+) uptake, N fixation, and N removal processes were quantified by stable isotopic approaches. Dissimilatory N reduction was a relatively modest N sink, with denitrification, anammox, and N2O production accounting for 84, 14, and 2 % of sediment N removal, respectively. Phytoplankton assimilation was the dominant N uptake mechanism, and NO3- uptake rates were higher than NH4+ uptake rates. Riverine N loading was sometimes insufficient to meet assimilatory and dissimilatory demands, but N fixation alleviated this deficit. N fixation made up 23.7–85.4 % of total phytoplankton N acquisition and indirectly supports Planktothrix blooms. However, N fixation rates were surprisingly uncorrelated with NO3- or NH4+ concentrations. Owing to temporal separation in sources and sinks of N to Lake Erie, Sandusky Bay oscillates between a conduit and a filter of downstream N loading to Lake Erie, delivering extensively recycled forms of N during periods of low export. Drowned river mouths such as Sandusky Bay are mediators of downstream N loading, but climate-change-induced increases in precipitation and N loading will likely intensify N export from these systems.

scholarly journals Understanding the Differences in the Growth and Toxin Production of Anatoxin-Producing Cuspidothrix issatschenkoi Cultured with Inorganic and Organic N Sources from a New Perspective: Carbon/Nitrogen Metabolic Balance

Toxins ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 724
Author(s):  
Siyi Tao ◽  
Suqin Wang ◽  
Lirong Song ◽  
Nanqin Gan
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nitrogen Sources ◽  
Dry Weight ◽  
Toxin Production ◽  
Organic N ◽  
Control Group ◽  
Metabolic Balance ◽  
N Sources ◽  
Inorganic And Organic

Cyanotoxins are the underlying cause of the threat that globally pervasive Cyanobacteria Harmful algal blooms (CyanoHABs) pose to humans. Major attention has been focused on the cyanobacterial hepatotoxin microcystins (MCs); however, there is a dearth of studies on cyanobacterial neurotoxin anatoxins. In this study, we explored how an anatoxin-producing Cuspidothrix issatschenkoi strain responded to culture with inorganic and organic nitrogen sources in terms of growth and anatoxins production. The results of our study revealed that ʟ- alanine could greatly boost cell growth, and was associated with the highest cell productivity, while urea significantly stimulated anatoxin production with the maximum anatoxin yield reaching 25.86 μg/mg dry weight, which was 1.56-fold higher than that in the control group (BG11). To further understand whether the carbon/nitrogen balance in C. issatschenkoi would affect anatoxin production, we explored growth and toxin production in response to different carbon/nitrogen ratios (C/N). Anatoxin production was mildly promoted when the C/N ratio was within low range, and significantly inhibited when the C/N ratio was within high range, showing approximately a three-fold difference. Furthermore, the transcriptional profile revealed that anaC gene expression was significantly up-regulated over 2–24 h when the C/N ratio was increased, and was significantly down-regulated after 96 h. Overall, our results further enriched the evidence that urea can stimulate cyanotoxin production, and ʟ-alanine could boost C. issatschenkoi proliferation, thus providing information for better management of aquatic systems. Moreover, by focusing on the intracellular C/N metabolic balance, this study explained the anatoxin production dynamics in C. issatschenkoi in response to different N sources.

Predicting water quality variability in a Mediterranean hypereutrophic monomictic reservoir using Sentinel-2 MSI: the importance of model functional form

2021 ◽  
Author(s):  
Ibrahim Alameddine ◽  
Mohamad Abbas
Keyword(s):  
Water Quality ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Multivariate Adaptive Regression Splines ◽  
Support Vector ◽  
Negative Consequences ◽  
Significant Drop ◽  
Chl A ◽  
Spatio Temporal ◽  
Sentinel 2

<p>Anthropogenic eutrophication is a pressing global environmental problem that threatens the ecological functions of many inland freshwaters and diminishes their abilities to meet their designated uses. Water authorities worldwide are being pressed to manage the negative consequences of harmful algal blooms (HABs) based largely on data collected from conventional monitoring programs that lack the needed spatio-temporal resolution for effective lake/reservoir management. This study assesses the potential of using Sentinel 2 MSI to predict and assess the spatio-temporal variability in the water quality of the Qaraoun Reservoir, a poorly-monitored Mediterranean hypereutrophic monomictic reservoir that is subject to extensive HABs during the growing season. The performance and transferability of water quality models previously calibrated based on Landsat 7 and 8 surface reflectance to predict Chlorophyll-a (Chl-a), total suspended solids (TSS), Secchi Disk Depth (SDD), and Phycocyanin (PC) levels in the reservoir are first assessed. The results showed poor transferability between Landsat and Sentinel 2, with all models experiencing a significant drop in their predictive skill. Sentinel 2 specific models were then developed for the reservoir based on 153 water quality samples collected over two years. Different model functional forms were then tested, including multiple linear regressions (MR), multivariate adaptive regression splines (MARS), and support vector regressions (SVR). Our results showed that for Chl-a, the MARS model outperformed MR and SVR, with an R<sup>2</sup> of 60%. Meanwhile, the SVR-based models outperformed their MR and MARS counterparts for TSS, SDD and PC (R<sup>2</sup> = 59%, 94%, and 72% respectively).</p>

Impact of harmful algal blooms (Dinophysis acuminata) on the immune system of oysters and mussels from Santa Catarina, Brazil

2014 ◽  
Vol 95 (4) ◽  
pp. 773-781 ◽  
Author(s):  
Erik Simões ◽  
Renato Campos Vieira ◽  
Mathias Alberto Schramm ◽  
Danielle Ferraz Mello ◽  
Vitor De Almeida Pontinha ◽  
...  
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
The Other ◽  
Bivalve Species ◽  
Santa Catarina ◽  
Immunological Parameters ◽  
Immune Parameters ◽  
Dinophysis Acuminata ◽  
Consistent Manner ◽  
The Impact

Blooms of the harmful alga Dinophysis acuminata, which produces okadaic acid (OA), are becoming recurrent in Santa Catarina coast, where most of the shellfish marine farms in Brazil are located. We evaluated the impact of D. acuminata blooms on various haemato-immunological parameters and on tissue integrity of cultivated oysters (Crassostrea gigas) and mussels (Perna perna). Animals were sampled during two natural algal blooms, one at Praia Alegre (PA: 2950 cells l−1) and the other at Praia de Zimbros (PZ: 4150 cells l−1). Control animals were sampled at the same sites, 30 days after the end of the bloom. The assayed parameters were: total (THC) and differential (DHC) haemocyte counts, percentage of apoptotic haemocytes (AH), phenoloxidase activity (PO), agglutinating titre (AT) and total protein concentration in haemolymph (PC). Histological analyses were carried out in oysters from PZ. The results showed that some immune parameters were modulated during the toxic blooms, but not in a consistent manner, especially in mussels that accumulated more OA (10×) than oysters. For example, mussel THC decreased significantly (54%) during the bloom at PA, whereas it augmented markedly (64%) at PZ. PO activity was significantly altered by the algal blooms in both bivalve species, while PC increased significantly (66%) only in mussels from PZ bloom. The other parameters (DHC, AH and AT) did not vary in both bivalve species. Histological analyses showed an intense haemocytic infiltration throughout the oyster digestive epithelium, particularly into the stomach lumen during the algal bloom.

scholarly journals Nitrification and ammonium dynamics in Taihu Lake, China: seasonal competition for ammonium between nitrifiers and cyanobacteria

2018 ◽  
Vol 15 (3) ◽  
pp. 733-748 ◽  
Author(s):  
Justyna J. Hampel ◽  
Mark J. McCarthy ◽  
Wayne S. Gardner ◽  
Lu Zhang ◽  
Hai Xu ◽  
...  
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Taihu Lake ◽  
Cyanobacterial Bloom ◽  
Amoa Gene ◽  
Ammonia Oxidizing Archaea ◽  
Gene Copies ◽  
Uptake Rates ◽  
N Loading ◽  
Cyanobacterial Harmful Algal Blooms

Abstract. Taihu Lake is hypereutrophic and experiences seasonal, cyanobacterial harmful algal blooms. These Microcystis blooms produce microcystin, a potent liver toxin, and are linked to anthropogenic nitrogen (N) and phosphorus (P) loads to lakes. Microcystis spp. cannot fix atmospheric N and must compete with ammonia-oxidizing and other organisms for ammonium (NH4+). We measured NH4+ regeneration and potential uptake rates and total nitrification using stable-isotope techniques. Nitrification studies included abundance of the functional gene for NH4+ oxidation, amoA, for ammonia-oxidizing archaea (AOA) and bacteria (AOB). Potential NH4+ uptake rates ranged from 0.02 to 6.80 µmol L−1 h−1 in the light and from 0.05 to 3.33 µmol L−1 h−1 in the dark, and NH4+ regeneration rates ranged from 0.03 to 2.37 µmol L−1 h−1. Nitrification rates exceeded previously reported rates in most freshwater systems. Total nitrification often exceeded 200 nmol L−1 d−1 and was  >  1000 nmol L−1 d−1 at one station near a river discharge. AOA amoA gene copies were more abundant than AOB gene copies (p <  0.005) at all times; however, only abundance of AOB amoA (not AOA) was correlated with nitrification rates for all stations and all seasons (p <  0.005). Nitrification rates in Taihu Lake varied seasonally; at most stations, rates were highest in March, lower in June, and lowest in July, corresponding with cyanobacterial bloom progression, suggesting that nitrifiers were poor competitors for NH4+ during the bloom. Regeneration results suggested that cyanobacteria relied extensively on regenerated NH4+ to sustain the bloom. Internal NH4+ regeneration exceeded external N loading to the lake by a factor of 2 but was ultimately fueled by external N loads. Our results thus support the growing literature calling for watershed N loading reductions in concert with existing management of P loads.

scholarly journals Marine Biotoxins and Seafood Poisoning

Toxins ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 558
Author(s):  
Pedro Reis Costa ◽  
António Marques ◽  
Jorge Diogène
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Temporal Distribution ◽  
Harmful Algae ◽  
Marine Biotoxins ◽  
Frequency Intensity

Prevalence of marine biotoxins in seafood has been associated with increasing frequency, intensity, and duration of harmful algal blooms, and an increase of the geographical and temporal distribution of harmful algae [...]

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