A mechanistic basis for underyielding in phytoplankton communities

Abstract

Species richness has been shown to increase biomass production of plant communities. Such overyielding occurs when a community performs better than its component monocultures due to the complementarity or dominance effect and is mostly detected in substrate-bound plant communities (terrestrial plants or submerged macrophytes) where resource use complementarity can be enhanced due to differences in rooting architecture and depth. Here, we investigated whether these findings are generalizeable for free-floating phytoplankton with little potential for spatial differences in resource use. We performed aquatic microcosm experiments with eight phytoplankton species belonging to four functional groups to determine the manner in which species and community biovolume varies in relation to the number of functional groups and hypothesized that an increasing number of functional groups within a community promotes overyielding. Unexpectedly, we did not detect overyielding in any algal community. Instead, total community biovolume tended to decrease with an increasing number of functional groups. This underyielding was mainly caused by the negative dominance effect that originated from a trade-off between growth rate and final biovolume. In monoculture, slow-growing species built up higher biovolumes than fast-growing ones, whereas in mixture a fast-growing but low-productive species monopolized most of the nutrients and prevented competing species from developing high biovolumes expected from monocultures. Our results indicated that the magnitude of the community biovolume was largely determined by the identity of one species. Functional diversity and resource use complementarity were of minor importance among free-floating phytoplankton, possibly reflecting the lack of spatially heterogeneous resource distribution. As a consequence, biodiversity-ecosystem functioning relationships may not be easily generalizeable from substrate-bound plant to phytoplankton communities and vice versa.

The impact of resource dependence of the mechanisms of life on the spatial population dynamics of an in silico microbial community

“…This effect agrees with experimental studies which observed an underyielding of diverse communities compared to their component monocultures due to the competitive suppression of highly productive species. [64][65][66][67] In this paper, we present a more comprehensive study of the model's behaviour, and the insights this can lead to with regard to the mechanisms under investigation. We present and discuss results related to pattern formation, population dynamics, the effects of more than one demographic process being simultaneously substrate-limited, and the effect of resource dependence on the system's critical mobility rate.…”

The Effect of Immigration on the Adaptation of Microbial Communities to Warming

“…In order to identify potential mechanisms behind community responses, we compared Our results match other findings that the dynamics of single species do not always correlate predictably with their dynamics when in a group (Fridley 2002;Schmidtke et al 2010). One reason could be that the dynamics of the isolates depends on whether other species are present; for example through quorum sensing bacteria can alter the chemicals that they produce (Miller & Bassler 2001) or alternatively species may rely on the presence of others to obtain resources (Lawrence et al 2012).…”

Assessing the potential of polyculture to accelerate algal biofuel production

“…Underyielding (i.e., when a polyculture yields less than the average of its component monocultures) can result, for example, when a polyculture is dominated by a fast-growing, low-yielding species [14,24] or due to allelopathy, where a secondary metabolite produced by one species is toxic to another [36]. In order to maximize the potential for overyielding, polycultures can be assembled based on their specific traits (e.g., light, nitrogen, micronutrients, etc.)…”

“…Specific interactions of concern include competition, predation (i.e., grazing pressure), and pathogenic interactions. Competition for nutrients and allelopathy (chemical warfare) with non-target algal strains can significantly reduce production rates and/or alter the quality of the biomass produced [14,15]. Predation by grazers or invasion by algal pathogens can decrease the stability of production by destroying mass cultures in a matter of days [16].…”