Sigmoid Relationships between Phosphorus, Algal Biomass, and Algal Community Structure

1992 ◽  
Vol 49 (12) ◽  
pp. 2605-2610 ◽  
Author(s):  
Susan Watson ◽  
Edward McCauley ◽  
John A. Downing
Keyword(s):  
Phytoplankton Biomass ◽  
Algal Biomass ◽  
Volume Ratio ◽  
Systematic Variation ◽  
Algal Community ◽  
Published Data ◽  
Nutrient Levels ◽  
Total Phytoplankton Biomass ◽  
Wide Range ◽  
Total Phytoplankton

It has long been recognized that there is a positive relationship between total phytoplankton biomass and eutrophication. Recent independent studies demonstrated that algal biomass (chlorophyll) actually responds in a nonlinear, sigmoidal fashion with increasing phosphorus levels among lakes. Chlorophyll has been considered (by some authors) as an inconsistent estimate of algal biomass. Using a wide range of published data, we first demonstrate that the sigmoidal nature of the phosphorus–biomass relationship is quite robust, and not simply generated by a systematic variation in the relationship between algal chlorophyll to cell volume ratio and nutrient levels. We show that the sigmoid relationship with total phosphorus persists whether algal biomass is measured by chlorophyll or biovolume. We hypothesize that this nonlinearity actually reflects an underlying systematic variation in one or more of the components of total phytoplankton biomass. In this paper, we examine two functional size groups and show that the large inedible fraction exhibits a strong, nonlinear response to increasing nutrient levels, while the small edible algae do not vary systematically with phosphorus. We hypothesize that this discontinuous shift in the ratio of edible to inedible phytoplankton should be accompanied by concomitant shifts in the structure of the herbivore community.

Effects of zooplankton and nutrients on phytoplankton: an experimental analysis in a eutrophic tropical reservoir

2017 ◽  
Vol 68 (6) ◽  
pp. 1061 ◽  
Author(s):  
Juliana dos Santos Severiano ◽  
Viviane Lúcia dos Santos Almeida-Melo ◽  
Enaide Marinho de Melo-Magalhães ◽  
Maria do Carmo Bittencourt-Oliveira ◽  
Ariadne do Nascimento Moura
Keyword(s):  
Experimental Analysis ◽  
Phytoplankton Biomass ◽  
Phytoplankton Community ◽  
N:P Ratio ◽  
Molar Ratio ◽  
Zooplankton Species ◽  
Tropical Reservoir ◽  
Total Phytoplankton Biomass ◽  
Taxonomic Class ◽  
Total Phytoplankton

Experiments were conducted to evaluate the N:P ratio, as well as the effects of the interaction between this ratio and zooplankton, on phytoplankton in a tropical reservoir. Three experiments were performed in the presence (+Z) or absence (–Z) of zooplankton and the addition of N and P in different ratios (N:P molar ratio of 5, 16 and 60).In Experiment I, the total phytoplankton biomass and biomass by taxonomic class and species of the N:P 16–Z treatment did not differ significantly from that of the control, whereas for N:P 16+Z, there was a reduction in total phytoplankton. In Experiment II, there was a significant increase in Bacillariophyceae and the biomass of two species in the N:P 60–Z treatment. For the N:P 60+Z treatment, a significant reduction was observed in the total phytoplankton biomass and the biomass of three phytoplankton classes and three species. In Experiment III, there was an increase in the biomass of Dinophyceae with the N:P 5–Z treatment. In the N:P 5+Z treatment, there was a significant reduction in total phytoplankton biomass and the biomass of the phytoplankton class and five species. The findings of the present study reveal that zooplankton species native to a tropical reservoir can change the structure of the phytoplankton community and the response of these organisms to variations in nutrients.

scholarly journals Phytoplankton adaptation strategies under the influence of climatic changes and anthropogenic pressure on the Black Sea coastal ecosystems on the example Sevastopol Bay

2020 ◽  
Vol 37 ◽  
pp. 34-42
Author(s):  
Liudmila Stelmakh ◽  
Nela Kovrigina ◽  
Tatiana Gorbunova
Keyword(s):  
Water Temperature ◽  
Black Sea ◽  
Phytoplankton Biomass ◽  
Anthropogenic Pollution ◽  
The Black Sea ◽  
Nitrate Content ◽  
Anthropogenic Pressure ◽  
Total Phytoplankton Biomass ◽  
Sevastopol Bay ◽  
Total Phytoplankton

Some ways of the Black Sea coastal waters phytoplankton community adaptation to changes in water temperature, nutrients concentration and anthropogenic pollution have been identified on the example of the Sevastopol Bay. The increase in water temperature and decrease in nutrient content in the studied waters during 2000 – 2014 caused a gradual decrease in the chlorophyll a concentrations, total phytoplankton biomass and its re-composition, predominantly in the summer and autumn periods. The phytoplankton restructuring was predominantly reflected by a decrease in relative diatoms contribution in the total phytoplankton biomass and an increase in dinoflagellates contribution. Among the dominant diatoms species, the share of resistant species to high temperatures, pollution, low nitrate content in the water and microzooplankton grazing was increasing. An increase in nitrate concentration in the studied waters in 2020 led to increase in total phytoplankton biomass and a predominance of diatoms species, which under the stated conditions did not lead to bloom emergence as were regularly observed earlier in the Sevastopol region.

scholarly journals Qualitative and quantitative studies on phytoplankton and chlorophyll content in the pelagic water of Lake Żarnowieckie in 1974

2015 ◽  
Vol 46 (3) ◽  
pp. 403-422
Author(s):  
Józefa Sosnowska
Keyword(s):  
Species Composition ◽  
Chlorophyll Content ◽  
Phytoplankton Biomass ◽  
Seasonal Succession ◽  
Qualitative Composition ◽  
Qualitative And Quantitative ◽  
Total Phytoplankton Biomass ◽  
Quantitative Studies ◽  
Total Phytoplankton

Species composition of phytoplankton, its biomass, share of nannoplankton, and concentration of chlorophyll and pheophytin in phytoplankton and nannoplankton were assessed basing on the materials collected from two pelagic stations of Lakę Żarnowieckie during the period 30 March - 6 December 1974. Average and maximal values of phytoplankton biomass (4-5 and 10-11 mg/1 respectively), as well as the concentration of chlorophyll (1.7 -10.0 μg/l together with pheophytin) point to slightly advanced eutrophication of the lake. Share of nannoplankton in total phytoplankton biomass was very low (as a rule below 3%) with an increase to 15% only in spring. Relatively slight taxonomic differentiation of phytoplankton (164 taxons), its qualitative composition with the predominance of <i>Cyanophyceae</i> in summer, and of <i>Bacillariophyceae</i> in spring and autumn, as also seasonal succession of algae, point to eutrophic character of the lake.

Response of a Phytoplankton Community to Controlled Partial Recovery from Experimental Acidification

1991 ◽  
Vol 48 (6) ◽  
pp. 1022-1029 ◽  
Author(s):  
D. L. Findlay ◽  
S. E. M. Kasian
Keyword(s):  
Species Diversity ◽  
Phytoplankton Biomass ◽  
Phytoplankton Community ◽  
Common Species ◽  
Partial Recovery ◽  
Early Recovery ◽  
Total Phytoplankton Biomass ◽  
Total Phytoplankton ◽  
Experimental Acidification ◽  
Taxonomic Groups

Lake 223 was experimentally acidified with H2SO4 from 1976 to 1989. The pH was reduced from 6.7 (1974) to 5.0 (1981) and held there for 3 yr (1981–83). Beginning in 1984 the pH was allowed to increase at a controlled rate by reduction of acid additions, resulting in a two-step recovery of 4 yr at pH ~5.5 and 2 yr at pH ~5.8. During the first 6 yr of early recovery, species diversity of the phytoplankton community increased linearly with pH and the number of common species increased. Total phytoplankton biomass remained elevated above preacidification estimates or increased. Dinoflagellates and cyanophytes remained codominant with little evidence of other taxonomic groups increasing.

Influence of the phytoplankton community on the hydrochemical structure of the Caspian Sea

2019 ◽  
pp. 23-34
Author(s):  
Kirill K. Kivva ◽  
Tatiana V. Polyakova ◽  
Antonina V. Polyakova
Keyword(s):  
Caspian Sea ◽  
Phytoplankton Biomass ◽  
Dominant Species ◽  
Phytoplankton Community ◽  
Chemical Components ◽  
The Caspian Sea ◽  
Total Phytoplankton Biomass ◽  
Total Phytoplankton

The hydrochemical structure of the Caspian Sea, which is formed and changed under the influence of the dynamics of water and the intensity of production and destruction processes, has been studied. The formation of the biogenic base and hydrochemical structure of the waters of the Caspian Sea is greatly influenced by the phytoplankton community. The dominant species of Pseudosolenia calcar-avis and Prorocentrum cordatum, which constitute 60–95% of the population and more than 80% of the total phytoplankton biomass, are mainly responsible for the redistribution of chemical components in the sea.

scholarly journals The Mediterranean subsurface phytoplankton dynamics and their impact on Mediterranean bioregions

2018 ◽  
Author(s):  
Julien Palmiéri ◽  
Jean-Claude Dutay ◽  
Fabrizio D'Ortenzio ◽  
Loïc Houpert ◽  
Nicolas Mayot ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Phytoplankton Biomass ◽  
Trophic Levels ◽  
Biogeochemical Model ◽  
Limited Area ◽  
Phytoplankton Dynamics ◽  
Total Phytoplankton Biomass ◽  
Total Phytoplankton ◽  
The Mediterranean ◽  
The Impact

Abstract. Ocean bioregions are generally defined using remotely-sensed sea surface chlorophyll fields, based on the assumption that surface chlorophyll is representative of euphotic layer phytoplankton biomass. Here we investigate the impact of subsurface phytoplankton dynamics on the characterisation of ocean bioregions. The Mediterranean Sea is known for its contrasting bioregimes despite its limited area, and represents an appropriate case for this study. We modelled this area using a high resolution regional dynamical model, NEMO-MED12, coupled to a biogeochemical model, PISCES, and focused our analysis on the bioregions derived from lower trophic levels. Validated by satellite and Biogeochemical-Argo float observations, our model shows that chlorophyll phenology can be significantly different when estimated from surface concentrations or integrated over the first 300 m deep layer. This was found in both low chlorophyll, oligotrophic bioregions as well as in high chlorophyll, bloom bioregions. The underlying reason for this difference is the importance of subsurface phytoplankton dynamics, in particular those associated with the Deep Chlorophyll Maximum (DCM) at the base of the upper mixed layer. Subsurface phytoplankton are found to significantly impact the bloom bioregions, while in oligotrophic regions, surface and subsurface chlorophyll are of similar importance. Consequently, our results show that surface chlorophyll is not representative of total phytoplankton biomass. Analysis of the DCM finds that its dynamics are extremely homogeneous throughout the Mediterranean Sea, and that it follows the annual cycle of solar radiation. In the most oligotrophic bioregion, the total phytoplankton biomass is almost constant along the year, implying that the summertime DCM biomass increase is not due to DCM photoacclimation, nor an increase of DCM production, but instead of the migration – with photoacclimation – of surface phytoplankton into the DCM.

It is better an approximate answer to the right question than the exact answer to the wrong question : the case of the psychometric analysis of the ASQ:SE

2020 ◽  
Author(s):  
Luis Anunciacao ◽  
janet squires ◽  
J. Landeira-Fernandez
Keyword(s):  
Internal Structure ◽  
Statistical Methods ◽  
Principal Component ◽  
Psychological Theory ◽  
Published Data ◽  
Multivariate Statistical ◽  
Exact Answer ◽  
Wide Range ◽  
Ages And Stages Questionnaire ◽  
The Right

One of the main activities in psychometrics is to analyze the internal structure of a test. Multivariate statistical methods, including Exploratory Factor analysis (EFA) and Principal Component Analysis (PCA) are frequently used to do this, but the growth of Network Analysis (NA) places this method as a promising candidate. The results obtained by these methods are of valuable interest, as they not only produce evidence to explore if the test is measuring its intended construct, but also to deal with the substantive theory that motivated the test development. However, these different statistical methods come up with different answers, providing the basis for different analytical and theoretical strategies when one needs to choose a solution. In this study, we took advantage of a large volume of published data (n = 22,331) obtained by the Ages and Stages Questionnaire Social-Emotional (ASQ:SE), and formed a subset of 500 children to present and discuss alternative psychometric solutions to its internal structure, and also to its subjacent theory. The analyses were based on a polychoric matrix, the number of factors to retain followed several well-known rules of thumb, and a wide range of exploratory methods was fitted to the data, including EFA, PCA, and NA. The statistical outcomes were divergent, varying from 1 to 6 domains, allowing a flexible interpretation of the results. We argue that the use of statistical methods in the absence of a well-grounded psychological theory has limited applications, despite its appeal. All data and codes are available at https://osf.io/z6gwv/.

Differences between Nearshore and Offshore Phytoplankton Communities in Lake Ontario

1987 ◽  
Vol 44 (12) ◽  
pp. 2155-2163 ◽  
Author(s):  
I. M. Gray
Keyword(s):  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
Algal Biomass ◽  
Phytoplankton Community ◽  
Seasonal Pattern ◽  
Principal Component ◽  
Lake Ontario ◽  
Dominant Group ◽  
Phytoplankton Communities ◽  
Eutrophic Species

Differences between nearshore and offshore phytoplankton biomass and composition were evident in Lake Ontario in 1982. Phytoplankton biomass was characterized by multiple peaks which ranged over three orders of magnitude. Perhaps as a consequence of the three times higher current velocities at the northshore station, phytoplankton biomass ranged from 0.09 to 9.00 g∙m−3 compared with 0.10 to 2.40 g∙m−3 for the midlake station. Bacillariophyceae was the dominant group at the northshore station until September when Cyanophyta contributed most to the biomass (83%). Although Bacillariophyceae was the principal component of the spring phytoplankton community at the midlake station, phytoflagellates (49%) and Chlorophyceae (25%) were responsible for summer biomass, with the Chlorophyceae expanding to 80% in the fall. The seasonal pattern of epilimnetic chlorophyll a correlated with temperature. While chlorophyll a concentrations were similar to values from 1970 and 1972, algal biomass had declined and a number of eutrophic species (Melosira binderana, Stephanodiscus tenuis, S. hantzschii var. pusilla, and S. alpinus) previously found were absent in 1982.

Sign in / Sign up

Export Citation Format

Share Document