scholarly journals Coexistence of dominant marine phytoplankton species sustained by nutrient specialization

2021 ◽  
Author(s):  
Takako Masuda ◽  
Keisuke Inomura ◽  
Jan Mareš ◽  
Taketoshi Kodama ◽  
Takuhei Shiozaki ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Nitrate Reductase ◽  
Surface Waters ◽  
Nitrate Uptake ◽  
Resource Competition ◽  
Ecological Model ◽  
Marine Phytoplankton ◽  
Phytoplankton Species ◽  
N Limitation

Abstract Prochlorococcus and Synechococcus are the two dominant picocyanobacteria in the low-nutrient surface waters of the subtropical ocean, but the basis for their coexistence in these biomes is still unclear. Here we combine in situ microcosm experiments and an ecological model to show that this coexistence can arise from specialization in the uptake of distinct nitrogen (N) substrates. In field incubations, the response of both Prochlorococcus and Synechococcus to nanomolar N amendments demonstrates N limitation of growth in both populations, but Prochlorococcus showed a higher affinity to ammonium whereas Synechococcus was more adapted to nitrate uptake. A simple ecological model demonstrates that the differential nutrient affinity of these species can explain their coexistence. Phylogenetic analysis of the presence of nitrate reductase and nitrite reductase further support the higher nitrate affinity of Synechococcus compared to Prochlorococcus. Our study suggests that the evolution of differential nutrient affinities is an important mechanism for sustaining coexistence of species under resource competition.

scholarly journals Effect of incubation time and substrate concentration on N-uptake rates by phytoplankton in the Bay of Bengal

2005 ◽  
Vol 2 (5) ◽  
pp. 1331-1352
Author(s):  
S. Kumar ◽  
R. Ramesh ◽  
S. Sardesai ◽  
M. S. Sheshshayee
Keyword(s):  
Incubation Time ◽  
Uptake Rate ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Marine Phytoplankton ◽  
Total Production ◽  
New Production ◽  
Urea Uptake ◽  
Uptake Rates

Abstract. We report here the results of three experiments, which are slight variations of the 15N method (JGOFS protocol) for determination of new production. The first two test the effect of (i) duration of incubation time and (ii) concentration of tracer added on the uptake rates of various N-species (nitrate, ammonium and urea) by marine phytoplankton; while the third compares in situ and deck incubations from dawn to dusk. Results indicate that nitrate uptake can be underestimated by experiments where incubation times shorter than 4h or when more than 10% of the ambient concentration of nitrate is added prior to incubation. The f-ratio increases from 0.28 to 0.42 when the incubation time increases from two to four hours. This may be due to the observed increase in the uptake rate of nitrate and decrease in the urea uptake rate. Unlike ammonium [y{=}2.07x{-}0.002\\, (r2=0.55)] and urea uptakes [y{=}1.88x{+}0.004 (r2=0.88)], the nitrate uptake decreases as the concentration of the substrate (x) increases, showing a negative correlation [y{=}-0.76x+0.05 (r2=0.86)], possibly due to production of glutamine, which might suppress nitrate uptake. This leads to decline in the f-ratio from 0.47 to 0.10, when concentration of tracer varies from 0.01 to 0.04μ M. The column integrated total productions are 519 mg C m-2 d-1 and 251 mg C m-2 d-1 for in situ and deck incubations, respectively. The 14C based production at the same location is ~200 mg C m-2 d-1, which is in closer agreement to the 15N based total production measured by deck incubation.

Nutrient-related selection mechanisms in marine phytoplankton communities and the impact of eutrophication on the planktonic food web

1995 ◽  
Vol 32 (4) ◽  
pp. 63-75 ◽  
Author(s):  
R. Riegman
Keyword(s):  
Algal Blooms ◽  
Algal Biomass ◽  
Resource Competition ◽  
Water Quality Management ◽  
Algal Species ◽  
Marine Phytoplankton ◽  
Commercial Fish ◽  
N Limitation ◽  
Phytoplankton Communities ◽  
The Impact

A general increase in nutrient discharges during the last few decades has caused various changes in the algal community structure along the European continental coast. Coincidentally and maybe consequently, the foodweb structure and functioning has altered in local areas causing various phenomena like oxygen depletion, mortality of groups of organisms, foam on beaches, and an increase in the productivity of benthic communities and some commercial fish species. The observed increases in algal biomass and shifts in species composition are discussed in relation to the involved key mechanisms: resource competition and selective grazing. Along the Dutch coastal zone of the North Sea eutrophication has caused a doubling of the yearly averaged algal biomass during the past three decades. The sudden appearance of Phaeocystis summer blooms coincided with a shift from P-limitation towards N-limitation in the Dutch coastal area due to a stronger increase in P-discharge relative to the increase in N-discharge. Competition experiments in continuous cultures showed Phaeocystis to become dominant under N-limitation. Additionally, the large Phaeocystis colonies, which can reach a diameter up to one centimetre, escape from microzooplankton grazing. A computer model is presented which demonstrates a shift from bottom-up towards top-down control if the pelagic environment becomes eutrophicated. Implementation of this concept in a size-differential phytoplankton control model generates the prediction that algal blooms are dominated by species that escape from grazing by those zooplankton species which have a high potential numerical response. In marine environments these are microzooplankton species. These organisms mainly feed on cyanobacteria, prochlorophytes and some nano-algal species. One of the consequences for foodweb structure and the carbon fluxes in marine foodwebs is that eutrophication will lead to the dominance of poorly edible algal species. Eutrophication favours the downward transport of carbon and nutrients towards the sediments not only due to higher algal biomasses but also as a consequence of a shift towards larger algal species with higher sedimentation characteristics. An example is given how these new insights can be used for water quality management purposes.

Development of a water temperature-ecological model to stimulate global warming effects on lake ecosystem

1996 ◽  
Vol 34 (7-8) ◽  
pp. 237-244 ◽  
Author(s):  
Masaaki Hosomi ◽  
Tetsu Saigusa ◽  
Kenichi Yabunaka ◽  
Takuya Okubo ◽  
Akihiko Murakami
Keyword(s):  
Global Warming ◽  
Water Temperature ◽  
Thermal Stratification ◽  
Ecological Model ◽  
Nutrient Release ◽  
Eddy Diffusion ◽  
Nutrient Concentrations ◽  
Lake Ecosystem ◽  
Phytoplankton Species ◽  
Freezing And Thawing

This paper describes a newly developed combined water temperature-ecological (WT-ECO) model which is employed to simulate the effects of global warming on lake and reservoir ecosystems. The WT model includes (i) variations in the eddy diffusion coefficient based on the degree of thermal stratification and the velocity of wind, and (ii) a sub-model for simulating the freezing and thawing processes of surface water, water temperatures, and the mixing rates between two adjacent layers of water. The ECO model then uses these results to calculate the resultant effect on a lake's ecological dynamics, e.g., composition of phytoplankton species, their respective concentrations, and nutrient concentrations. When the model was benchmarked against Lake Yunoko, a dimictic lake, fairly good agreement was obtained over a 4-yr period; thereby indicating it is suitably calibrated. In addition, to assess the effects of global warming on a lake ecosystem, changes in Lake Yunoko's water temperature/quality were simulated in response to an increase in air temperature of 2 - 4°C. Results indicate that such an increase will (i) increase thermal stratification in summer, which increases the nutrient concentrations in bottom water due to nutrient release from bottom sediment, (ii) increase the concentration of phytoplankton at the beginning of the autumn circulation period, and (iii) change the composition of phytoplankton species.

scholarly journals A Differential Metabarcoding Approach to Describe Taxonomy Profiles of Bacteria and Archaea in the Saltern of Margherita di Savoia (Italy)

2020 ◽  
Vol 8 (6) ◽  
pp. 936 ◽  
Author(s):  
Claudia Leoni ◽  
Mariateresa Volpicella ◽  
Bruno Fosso ◽  
Caterina Manzari ◽  
Elisabetta Piancone ◽  
...  
Keyword(s):  
Ecological Model ◽  
Salinity Range ◽  
Rrna Gene ◽  
Hypervariable Regions ◽  
Cell Counts ◽  
Precious Resource ◽  
Catalyzed Reporter Deposition ◽  
Card Fish ◽  
The 16S Rrna Gene

Microorganisms inhabiting saline environments are an interesting ecological model for the study of the adaptation of organisms to extreme living conditions and constitute a precious resource of enzymes and bioproducts for biotechnological applications. We analyzed the microbial communities in nine ponds with increasing salt concentrations (salinity range 4.9–36.0%) of the Saltern of Margherita di Savoia (Italy), the largest thalassohaline saltern in Europe. A deep-metabarcoding NGS procedure addressing separately the V5-V6 and V3-V4 hypervariable regions of the 16S rRNA gene of Bacteria and Archaea, respectively, and a CARD-FISH (catalyzed reporter deposition fluorescence in situ hybridization) analysis allowed us to profile the dynamics of microbial populations at the different salt concentrations. Both the domains were detected throughout the saltern, even if the low relative abundance of Archaea in the three ponds with the lowest salinities prevented the construction of the relative amplicon libraries. The highest cell counts were recorded at 14.5% salinity for Bacteria and at 24.1% salinity for Archaea. While Bacteria showed the greatest number of genera in the first ponds (salinity range 4.9–14.5%), archaeal genera were more numerous in the last ponds of the saltern (salinity 24.1–36.0%). Among prokaryotes, Salinibacter was the genus with the maximum abundance (~49% at 34.6% salinity). Other genera detected at high abundance were the archaeal Haloquadratum (~43% at 36.0% salinity) and Natronomonas (~18% at 13.1% salinity) and the bacterial “Candidatus Aquiluna” (~19% at 14.5% salinity). Interestingly, “Candidatus Aquiluna” had not been identified before in thalassohaline waters.

scholarly journals Performance of a Handheld Chlorophyll-a Fluorometer: Potential Use for Rapid Algae Monitoring

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1409
Author(s):  
Hamdhani Hamdhani ◽  
Drew E. Eppehimer ◽  
David Walker ◽  
Michael T. Bogan
Keyword(s):  
Chlorophyll A ◽  
Surface Waters ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Water Quality Monitoring ◽  
Ambient Light ◽  
Calibration Equation ◽  
Field Samples ◽  
Potential Use

Chlorophyll-a measurements are an important factor in the water quality monitoring of surface waters, especially for determining the trophic status and ecosystem management. However, a collection of field samples for extractive analysis in a laboratory may not fully represent the field conditions. Handheld fluorometers that can measure chlorophyll-a in situ are available, but their performance in waters with a variety of potential light-interfering substances has not yet been tested. We tested a handheld fluorometer for sensitivity to ambient light and turbidity and compared these findings with EPA Method 445.0 using water samples obtained from two urban lakes in Tucson, Arizona, USA. Our results suggested that the probe was not sensitive to ambient light and performed well at low chlorophyll-a concentrations (<25 µg/L) across a range of turbidity levels (50–70 NTU). However, the performance was lower when the chlorophyll-a concentrations were >25 µg/L and turbidity levels were <50 NTU. To account for this discrepancy, we developed a calibration equation to use for this handheld fluorometer when field monitoring for potential harmful algal blooms in water bodies.

scholarly journals Phenylhydrazone and Quinazoline Derivatives from the Cold-Seep-Derived Fungus Penicillium oxalicum

Marine Drugs ◽  
2020 ◽  
Vol 19 (1) ◽  
pp. 9
Author(s):  
Ya-Ping Liu ◽  
Sheng-Tao Fang ◽  
Zhen-Zhen Shi ◽  
Bin-Gui Wang ◽  
Xiao-Nian Li ◽  
...  
Keyword(s):  
Deep Sea ◽  
Spectroscopic Data ◽  
2D Nmr ◽  
Penicillium Oxalicum ◽  
Marine Phytoplankton ◽  
Cold Seep ◽  
Phytoplankton Species ◽  
X Ray ◽  
X Ray Crystallography ◽  
Quinazoline Derivatives

Three new phenylhydrazones, penoxahydrazones A–C (compounds 1–3), and two new quinazolines, penoxazolones A (compound 4) and B (compound 5), with unique linkages were isolated from the fungus Penicillium oxalicum obtained from the deep sea cold seep. Their structures and relative configurations were assigned by analysis of 1D/2D NMR and mass spectroscopic data, and the absolute configurations of 1, 4, and 5 were established on the basis of X-ray crystallography or ECD calculations. Compound 1 represents the first natural phenylhydrazone-bearing steroid, while compounds 2 and 3 are rarely occurring phenylhydrazone tautomers. Compounds 4 and 5 are enantiomers that feature quinazoline and cinnamic acid units. Some isolates exhibited inhibition of several marine phytoplankton species and marine-derived bacteria.

scholarly journals The evolution of the metazoan Toll receptor family and its expression during protostome development

2021 ◽  
Author(s):  
Andrea Orús-Alcalde ◽  
Tsai-Ming Lu ◽  
Andreas Hejnol
Keyword(s):  
Phylogenetic Analysis ◽  
Transmembrane Domain ◽  
Leucine Rich Repeat ◽  
Animal Development ◽  
Phylogenetic Studies ◽  
Repeat Domain ◽  
Toll Receptor ◽  
P Type

Abstract Background: Toll-like receptors (TLRs) play a crucial role in immunity and development. They contain leucine-rich repeat domains, one transmembrane domain, and one Toll/IL-1 receptor domain. TLRs have been classified into V-type/scc and P-type/mcc TLRs, based on differences in the leucine-rich repeat domain region. Although TLRs are widespread in animals, detailed phylogenetic studies of this gene family are lacking. Here we aim to uncover TLR evolution by conducting a survey and a phylogenetic analysis in species across Bilateria. To discriminate between their role in development and immunity we furthermore analyzed stage-specific transcriptomes of the ecdysozoans Priapulus caudatus and Hypsibius exemplaris, and the spiralians Crassostrea gigas and Terebratalia transversa.Results: We detected a low number of TLRs in ecdysozoan species, and multiple independent radiations within the Spiralia. V-type/scc and P-type/mcc type-receptors are present in cnidarians, protostomes and deuterostomes, and therefore they emerged early in TLR evolution, followed by a loss in xenacoelomorphs. Our phylogenetic analysis shows that TLRs cluster into three major clades: clade α is present in cnidarians, ecdysozoans, and spiralians; clade β in deuterostomes, ecdysozoans, and spiralians; and clade γ is only found in spiralians. Our stage-specific transcriptome and in situ hybridization analyses show that TLRs are expressed during development in all species analyzed, which indicates a broad role of TLRs during animal development.Conclusions: Our findings suggest that the bilaterian TLRs likely emerged by duplication from a single TLR encoding gene (proto-TLR) present in the last common cnidarian-bilaterian ancestor. This proto-TLR gene duplicated before the split of protostomes and deuterostomes; a second duplication occurred in the lineage to the Trochozoa. While all three clades further radiated in several spiralian lineages, specific TLRs clades have been presumably lost in others. Furthermore, the expression of the majority of these genes during protostome ontogeny suggests their involvement in immunity and development.

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