Zooplankton Biodiversity and Lake Trophic State: Explanations Invoking Resource Abundance and Distribution

Abstract

While empirical studies linking biodiversity to local environmental gradients have emphasized the importance of lake trophic status (related to primary productivity), theoretical studies have implicated resource spatial heterogeneity and resource relative ratios as mechanisms behind these biodiversity patterns. To test the feasibility of these mechanisms in natural aquatic systems, the biodiversity of crustacean zooplankton communities along gradients of total phosphorus (TP) as well as the vertical heterogeneity and relative abundance of their phytoplankton resources were assessed in 18 lakes in Quebec, Canada. Zooplankton community richness was regressed against TP, the spatial distribution of phytoplankton spectral groups, and the relative biomass of spectral groups. Since species richness does not adequately capture ecological function and life history of different taxa, features which are important for mechanistic theories, relationships between zooplankton functional diversity (FD) and resource conditions were examined. Zooplankton species richness showed the previously established tendency to a unimodal relationship with TP, but functional diversity declined linearly over the same gradient. Changes in zooplankton functional diversity could be attributed to changes in both the spatial distribution and type of phytoplankton resource. In the studied lakes, spatial heterogeneity of phytoplankton groups declined with TP, even while biomass of all groups increased. Zooplankton functional diversity was positively related to increased heterogeneity in cyanobacteria spatial distribution. However, a smaller amount of variation in functional diversity was also positively related to the ratio of biomass in diatoms/chrysophytes to cyanobacteria. In all observed relationships, a greater variation of functional diversity than species richness measures was explained by measured factors, suggesting that functional measures of zooplankton communities will benefit ecological research attempting to identify mechanisms behind environmental gradients affecting diversity.

Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

“…Functional diversity (FD) has been defined as the value and the range of functional traits of the organisms present in a given ecosystem (Diaz and Cabido 2001). The ecological literature about the measurement of functional diversity, which captures how functional trait composition varies among assemblages, has grown during the last decade (i.e., Thompson et al 2005;Barnett and Beisner 2007). Functional diversity can be expressed as the measurement of the branch length of a dendrogram based on similarities between functional traits Gaston 2002, 2009;Cianciaruso et al 2009).…”

Response of rotifer community to environmental changes in five shallow lakes in the middle reach of Changjiang River, China

“…However, it is diffi cult to explain this variability because of differences in the lake areas, sampling frequency, and the small numbers of samples collected from each lake (Duggan et al, 2002). Interestingly though, a number of studies have demonstrated a relationship between trophic status (Jeppesen et al, 2000), lake size or area (Dodson, 1992), or phytoplankton spatial heterogeneity (Barnett and Beisner, 2007) and species richness or diversity. Our data suggest a trend towards higher diversity associated with increased macrophyte coverage in LZH, WHL, and NSH than in TXH and BDT.…”

A global analysis of zooplankton in natural and artificial fresh waters

“…The unimodal productivityzooplankton diversity model (e.g. Dodson et al, 2000;Barnett and Beisner, 2007) suggests that there is an optimum productivity at which zooplankton communities are most diverse. Above this, changes in phytoplankton composition associated with eutrophication lead to the development of zooplankton communities better adapted for dominance by blue-green algae species (Richman and Dodson, 1983;Smith, 1983;Gliwicz and Lampert, 1990;Watson et al, 1997).…”

“…Although the precise nature of these effects is debated, the generally accepted models are that richness and composition change unimodally (e.g. Dodson et al, 2000;Barnett and Beisner, 2007) or linearly with productivity (Chase and Ryberg, 2004;Hoffmann and Dodson, 2005), depending on the scale of observation (Chase and Ryberg, 2004) and the metric used to measure productivity (Thackeray, 2007).…”