Diversity predicts stability and resource use efficiency in natural phytoplankton communities

Abstract

The relationship between species diversity and ecosystem functioning has been debated for decades, especially in relation to the "macroscopic" realm (higher plants and metazoans). Although there is emerging consensus that diversity enhances productivity and stability in communities of higher organisms; however, we still do not know whether these relationships apply also for communities of unicellular organisms, such as phytoplankton, which contribute approximately 50% to the global primary production. We show here that phytoplankton resource use, and thus carbon fixation, is directly linked to the diversity of phytoplankton communities. Datasets from freshwater and brackish habitats show that diversity is the best predictor for resource use efficiency of phytoplankton communities across considerable environmental gradients. Furthermore, we show that the diversity requirement for stable ecosystem functioning scales with the nutrient level (total phosphorus), as evidenced by the opposing effects of diversity (negative) and resource level (positive) on the variability of both resource use and community composition. Our analyses of large-scale observational data are consistent with experimental and model studies demonstrating causal effects of microbial diversity on functional properties at the system level. Our findings point at potential linkages between eutrophication and pollution-mediated loss of phytoplankton diversity. Factors reducing phytoplankton diversity may have direct detrimental effects on the amount and predictability of aquatic primary production.

Metatranscriptome analyses indicate resource partitioning between diatoms in the field

“…This linkage is well documented in terrestrial systems (3)(4)(5)(6)(7) and is increasingly being established for marine systems (8)(9)(10)(11). Marine phytoplankton generate roughly half of global primary production (12)(13)(14) and play a critical role in oceanic ecosystem structure and function.…”

Trophic complexity in aqueous systems: bacterial species richness and protistan predation regulate dissolved organic carbon and dissolved total nitrogen removal

“…To date, the few findings on the relationship between microbial richness and stability suggest that broad-scale ecosystem processes (such as resource use efficiency) may benefit from diverse microbial systems at least at larger scales [54]. However, for particular ecosystems, results are still contradictory.…”

Interactions between pH and nutrients on benthic algae in streams and consequences for ecological status assessment and species richness patterns

“…good ecological status is supposed to reflect a resilient ecosystem with a high level of adaptive capacity (Josefsson & Baaner, 2011). Ecosystem productivity and resource use efficiency are important ecosystem functions, and the general view today is that both generally depend on primary producer taxon richness, though variations in the shape of the productivity-diversity relationship are observed among individual studies (Mittelbach et al, 2001;Ptacnik et al, 2008). Our data suggest that the relative influence of diatoms and non-diatom benthic algae on ecosystem structure and functioning will vary in response to both pH and nutrient supply.…”