scholarly journals Phytoplankton Diversity Effect on Ecosystem Functioning in a Coastal Upwelling System

2020 ◽  
Vol 7 ◽  
Author(s):  
Jaime Otero ◽  
Xosé Antón Álvarez-Salgado ◽  
Antonio Bode
Keyword(s):  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Coastal Upwelling ◽  
Explanatory Power ◽  
Taxonomic Diversity ◽  
Least Square ◽  
Trophic Levels ◽  
Phytoplankton Diversity ◽  
Positive Effects ◽  
Upwelling System

Species composition plays a key role in ecosystem functioning. Theoretical, experimental and field studies show positive effects of biodiversity on ecosystem processes. However, this link can differ between taxonomic and functional diversity components and also across trophic levels. These relationships have been hardly studied in planktonic communities of coastal upwelling systems. Using a 28-year time series of phytoplankton and zooplankton assemblages, we examined the effects of phytoplankton diversity on resource use efficiency (RUE, ratio of biomass to limiting resource) at the two trophic levels in the Galician upwelling system (NW Iberian peninsula). By fitting generalized least square models, we show that phytoplankton diversity was the best predictor for RUE across planktonic trophic levels. This link varied depending on the biodiversity component considered: while the effect of phytoplankton richness on RUE was positive for phytoplankton RUE and negative for zooplankton RUE, phytoplankton evenness effect was negative for phytoplankton RUE and positive for zooplankton RUE. Overall, taxonomic diversity had higher explanatory power than functional diversity, and variability in phytoplankton and zooplankton RUE decreased with increasing phytoplankton taxonomic diversity. Phytoplankton used resources more efficiently in warmer waters and at greater upwelling intensity, although these effects were not as strong as those for biodiversity. These results suggest that phytoplankton species numbers in highly dynamic upwelling systems are important for maintaining the planktonic biomass production leading us to hypothesize the relevance of complementarity effects. However, we further postulate that a selection effect may operate also because assemblages with low evenness were dominated by diatoms with specific functional traits increasing their ability to exploit resources more efficiently.

scholarly journals Multitrophic functional diversity predicts ecosystem functioning in experimental assemblages of estuarine consumers

2015 ◽  
Author(s):  
Jonathan S Lefcheck ◽  
J. Emmett Duffy
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Structural Equation ◽  
A Priori ◽  
Functional Trait ◽  
Trophic Levels ◽  
Equation Modeling ◽  
Experimental Investigations

The use of functional traits to explain how biodiversity affects ecosystem functioning has attracted intense interest, yet few studies have a priori altered functional diversity, especially in multitrophic communities. Here, we manipulated multivariate functional diversity of estuarine grazers and predators within multiple levels of species richness to test how species richness and functional diversity predicted ecosystem functioning in a multitrophic food web. Community functional diversity was a better predictor than species richness for the majority of ecosystem properties, based on general linear mixed effects models. Combining inferences from 8 traits into a single multivariate index increased prediction accuracy of these models relative to any individual trait. Structural equation modeling revealed that functional diversity of both grazers and predators was important in driving final biomass within trophic levels, with stronger effects observed for predators. We also show that different species drove different ecosystem responses, with evidence for both sampling effects and complementarity. Our study extends experimental investigations of functional trait diversity to a multilevel food web, and demonstrates that functional diversity can be more accurate and effective than species richness in predicting community biomass in a food web context.

scholarly journals Multitrophic functional diversity predicts ecosystem functioning in experimental assemblages of estuarine consumers

2015 ◽  
Author(s):  
Jonathan S Lefcheck ◽  
J. Emmett Duffy
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Structural Equation ◽  
A Priori ◽  
Functional Trait ◽  
Trophic Levels ◽  
Equation Modeling ◽  
Experimental Investigations

The use of functional traits to explain how biodiversity affects ecosystem functioning has attracted intense interest, yet few studies have a priori manipulated functional diversity, especially in multitrophic communities. Here, we manipulated multivariate functional diversity of estuarine grazers and predators within two levels of species richness to test how species richness and functional diversity predicted ecosystem functioning in a multitrophic food web. Community functional diversity was a better predictor than species richness for the majority of ecosystem properties, based on general linear mixed effects models. Combining inferences from 8 traits into a single multivariate index increased prediction accuracy of these properties relative to any individual trait. Structural equation modeling revealed that functional diversity of both grazers and predators was important in driving final biomass within and between trophic levels, with stronger effects observed for predators. We also show that different species drove different ecosystem responses, with evidence for both sampling effects and complementarity. Our study extends experimental investigations of functional trait diversity to a multilevel food web, and demonstrates that functional diversity can be more accurate and effective than species richness in predicting community biomass in a food web context.

scholarly journals Multitrophic functional diversity predicts ecosystem functioning in experimental assemblages of estuarine consumers

2014 ◽  
Author(s):  
Jonathan S Lefcheck ◽  
J. Emmett Duffy
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Functional Diversity ◽  
Functional Traits ◽  
Ecosystem Functioning ◽  
Structural Equation ◽  
Trophic Levels ◽  
Ecosystem Functions ◽  
Equation Modeling ◽  
Experimental Investigations

The use of functional traits to explain biodiversity effects on ecosystem functioning has attracted intense recent interest, yet very few a priori manipulations of functional diversity have been attempted to date, especially from a food web perspective. Here, we simultaneously manipulated multiple functional traits of estuarine grazers and predators within multiple levels of species richness to test whether species richness or functional diversity is a better predictor of ecosystem functioning in multitrophic estuarine food webs. Community functional diversity better predicted the majority of ecosystem responses based on results from generalized linear mixed effects models. Structural equation modeling revealed that this outcome was independently attributable to functional diversity of both trophic levels, with stronger effects observed for predators. Functional complementarity was also important, as species with different combinations of traits influenced different ecosystem functions. Our study is the first to extend experimental investigations of functional diversity to a multilevel food web, and demonstrates that functional diversity is more effective than species richness in predicting ecosystem functioning in a food web context.

scholarly journals Top predators govern multitrophic diversity effects in tritrophic food webs

2020 ◽  
Author(s):  
Ruben Ceulemans ◽  
Christian Guill ◽  
Ursula Gaedke
Keyword(s):  
Temporal Variation ◽  
Food Web ◽  
Food Webs ◽  
Functional Diversity ◽  
Trophic Level ◽  
Ecosystem Functioning ◽  
Initial Conditions ◽  
Trophic Levels ◽  
Natural Food ◽  
Model Parameters

AbstractIt is well known that functional diversity strongly affects ecosystem functioning. However, even in rather simple model communities consisting of only two or, at best, three trophic levels, the relationship between multitrophic functional diversity and ecosystem functioning appears difficult to generalize, due to its high contextuality. In this study, we considered several differently structured tritrophic food webs, in which the amount of functional diversity was varied independently on each trophic level. To achieve generalizable results, largely independent of parametrization, we examined the outcomes of 128, 000 parameter combinations sampled from ecologically plausible intervals, with each tested for 200 randomly sampled initial conditions. Analysis of our data was done by training a Random Forest model. This method enables the identification of complex patterns in the data through partial dependence graphs, and the comparison of the relative influence of model parameters, including the degree of diversity, on food web properties. We found that bottom-up and top-down effects cascade simultaneously throughout the food web, intimately linking the effects of functional diversity of any trophic level to the amount of diversity of other trophic levels, which may explain the difficulty in unifying results from previous studies. Strikingly, only with high diversity throughout the whole food web, different interactions synergize to ensure efficient exploitation of the available nutrients and efficient biomass transfer, ultimately leading to a high biomass and production on the top level. The temporal variation of biomass showed a more complex pattern with increasing multitrophic diversity: while the system initially became less variable, eventually the temporal variation rose again due to the increasingly complex dynamical patterns. Importantly, top predator diversity and food web parameters affecting the top trophic level were of highest importance to determine the biomass and temporal variability of any trophic level. Overall, our study reveals that the mechanisms by which diversity influences ecosystem functioning are affected by every part of the food web, hampering the extrapolation of insights from simple monotrophic or bitrophic systems to complex natural food webs.

scholarly journals Multitrophic functional diversity predicts ecosystem functioning in experimental assemblages of estuarine consumers

2015 ◽  
Author(s):  
Jonathan S Lefcheck ◽  
J. Emmett Duffy
Keyword(s):  
Species Richness ◽  
Food Web ◽  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Structural Equation ◽  
A Priori ◽  
Functional Trait ◽  
Trophic Levels ◽  
Equation Modeling ◽  
Experimental Investigations

The use of functional traits to explain how biodiversity affects ecosystem functioning has attracted intense interest, yet few studies have a priori altered functional diversity, especially in multitrophic communities. Here, we manipulated multivariate functional diversity of estuarine grazers and predators within multiple levels of species richness to test how species richness and functional diversity predicted ecosystem functioning in a multitrophic food web. Community functional diversity was a better predictor than species richness for the majority of ecosystem properties, based on general linear mixed effects models. Combining inferences from 8 traits into a single multivariate index increased prediction accuracy of these models relative to any individual trait. Structural equation modeling revealed that functional diversity of both grazers and predators was important in driving final biomass within trophic levels, with stronger effects observed for predators. We also show that different species drove different ecosystem responses, with evidence for both sampling effects and complementarity. Our study extends experimental investigations of functional trait diversity to a multilevel food web, and demonstrates that functional diversity can be more accurate and effective than species richness in predicting community biomass in a food web context.

scholarly journals Comparison of functional diversity of two Alaskan Arctic shelf epibenthic communities

2020 ◽  
Vol 651 ◽  
pp. 1-21
Author(s):  
L Sutton ◽  
K Iken ◽  
BA Bluhm ◽  
FJ Mueter
Keyword(s):  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Taxonomic Diversity ◽  
Taxonomic Composition ◽  
Arctic Shelf ◽  
Biological Traits ◽  
Body Form ◽  
Alaskan Arctic ◽  
Epibenthic Communities ◽  
Diversity Metrics

Alaskan Arctic shelf communities are currently experiencing dramatic changes that will likely affect ecosystem functioning of Arctic marine benthic communities. Here, functional diversity based on biological traits was used to assess differences and similarities in ecosystem functioning between 2 shelf systems that are geographically close but vary in many environmental influences: the Arctic Beaufort and Chukchi Sea epibenthic communities. We hypothesized that (1) patterns of functional composition and diversity metrics reflect patterns in taxonomic composition and diversity metrics in these 2 shelf communities; and (2) patterns in functional diversity metrics are distinct between the 2 shelves. We evaluated 9 biological traits (body form, body size, feeding habit, fragility, larval development, living habit, movement, reproductive strategy, sociability) for 327 taxa in 2014 and 2015. For each trait, multiple modalities (specific expressions within a trait) were considered. Patterns in functional diversity metrics on both shelves reflected those in taxonomic diversity metrics. However, shelf communities were more similar in functional- than in taxonomic composition. Beaufort Sea communities had higher functional dissimilarity and functional evenness driven by differences in the modalities within body form, body size, larval development, and reproductive strategy. These traits primarily affect nutrient cycling, energy turnover, and recovery from disturbances, suggesting a stronger potential for future maintenance of ecosystem function, and indicating a more even use of resources in the Beaufort Sea. The combination of functional and taxonomic diversity metrics enabled a comprehensive understanding of how ecological niche space is used and how epibenthic communities function in Alaskan Arctic shelf systems.

Freedom Indices and Capital Asset Pricing Model: Some Malaysian Evidence

2020 ◽  
Vol 1 (1) ◽  
pp. 1-21
Author(s):  
Ying Tay Lee ◽  
Devinaga Rasiah ◽  
Ming Ming Lai
Keyword(s):  
Human Rights ◽  
Asset Pricing ◽  
Stock Returns ◽  
Firm Size ◽  
Explanatory Power ◽  
Least Square ◽  
Press Freedom ◽  
Capital Asset Pricing ◽  
Capital Asset ◽  
Cross Sectional

Human rights and fundamental freedoms such as economic, political, and press freedoms vary widely from country to country. It creates opportunity and risk in investment decisions. Thus, this study is carried out to examine if the explanatory power of the model for capital asset pricing could be improved when these human rights movement indices are included in the model. The sample for this study comprises of 495 stocks listed in Bursa Malaysia, covering the sampling period from 2003 to 2013. The model applied in this study employed the pooled ordinary least square regression estimation. In addition, the robustness of the model is tested by using firm size as a controlled variable. The findings show that market beta as well as the economic and press freedom indices could explain the cross-sectional stock returns of the Malaysian stock market. By controlling the firm size, it adds marginally to the explanation of the extended CAP model which incorporated economic, political, and press freedom indices.

ANALISIS EKSPOSUR EKONOMI DAN FAKTOR-FAKTOR YANG MEMPENGARUHINYA PADA PERUSAHAAN ROKOK YANG TERCATAT DI BEI

Wahana ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 98-109
Author(s):  
Ida Musdafia Ibrahim ◽  
Arif Haryono
Keyword(s):  
Exchange Rate ◽  
Exchange Rates ◽  
Cash Flow ◽  
Firm Value ◽  
Tobacco Industry ◽  
Cash Flows ◽  
Least Square ◽  
Exchange Rate Risk ◽  
Positive Effects ◽  
Rate Risk

This study aims to analyze economic exposures and its factors namely exchange rates and inflation, that influence firm value as reflected through firm cash flow. Analytical method used Ordinary Least Square and eviews as analytical tool. This study used secondary data and cigarette industry companies listed on the Indonesia Stock Exchange as samples along 2008 to 2017. Samples choosing method used purposive sampling based on determined criterias. The results showed that partially economic exposure had positive effects on firm value but insignificant. These could be seen from the economic exposure factors influncenced namely exchange rates and inflations.The exchange rate risk has low influenced cash flow was caused of the tobacco industry has low level of export/import.Enhance,inflation also had low effect on cash flow was caused of the tendency of cigarette consumers will continue to buy cigarettes even though its price increases. In short, economic exposure in the tobacco industry has low influence toward firms value. Hence, simultaneously changes in exchange rates and inflation which are economic exposure indicators have a significant effect on cash flows.  Keywords: Economic Exposure, Exchange Rate Risk, Inflation Risk, Firms Value, Cash Flow

Modeling the Central California Coastal Upwelling System: Physics, Ecosystems and Resource Management

2002 ◽  
Author(s):  
Francisco P. Chavez ◽  
Richard T. Barber ◽  
Fei Chai ◽  
Yi Chao ◽  
Andrew P. De Vogelaere ◽  
...  
Keyword(s):  
Resource Management ◽  
Coastal Upwelling ◽  
Central California ◽  
Upwelling System

scholarly journals On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ndague Diogoul ◽  
Patrice Brehmer ◽  
Hervé Demarcq ◽  
Salaheddine El Ayoubi ◽  
Abou Thiam ◽  
...  
Keyword(s):  
Multiple Stressors ◽  
Marine Ecosystem ◽  
Trophic Levels ◽  
Sea Surface ◽  
Relative Index ◽  
Upwelling System ◽  
The North ◽  
Latitudinal Shift ◽  
Large Marine Ecosystem ◽  
North And South

AbstractThe resistance of an east border upwelling system was investigated using relative index of marine pelagic biomass estimates under a changing environment spanning 20-years in the strongly exploited southern Canary Current Large marine Ecosystem (sCCLME). We divided the sCCLME in two parts (north and south of Cap Blanc), based on oceanographic regimes. We delineated two size-based groups (“plankton” and “pelagic fish”) corresponding to lower and higher trophic levels, respectively. Over the 20-year period, all spatial remote sensing environmental variables increased significantly, except in the area south of Cap Blanc where sea surface Chlorophyll-a concentrations declined and the upwelling favorable wind was stable. Relative index of marine pelagic abundance was higher in the south area compared to the north area of Cap Blanc. No significant latitudinal shift to the mass center was detected, regardless of trophic level. Relative pelagic abundance did not change, suggesting sCCLME pelagic organisms were able to adapt to changing environmental conditions. Despite strong annual variability and the presence of major stressors (overfishing, climate change), the marine pelagic ressources, mainly fish and plankton remained relatively stable over the two decades, advancing our understanding on the resistance of this east border upwelling system.

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