Abstract
Temporal heterogeneity in nutrient availability is known to increase phytoplankton diversity by allowing more species to coexist under different resource niches. Spatial heterogeneity has also been positively correlated with species diversity. Here we investigated how temporal and spatial differences in nutrient addition together impact biodiversity in metacommunities varying in the degree of connectivity among the patches. We used a microcosm experimental design to test two spatiotemporal ways of supplying nutrients: synchronously (nutrients were added regionally—to all four patches at the same time) and asynchronously (nutrients were added locally—to a different patch each time), combined with two different degrees of connectivity among the patches (low or high connectivity). We used three species of algae and one species of cyanobacteria as the primary producers; and five ciliate and two rotifer species as the grazers. We expected higher diversity in metacommunities receiving an asynchronous nutrient supply, assuming stronger development of heterogeneous patches with this condition rather than with synchronous nutrient supply. This result was expected, however, to be dependent on the degree of connectivity among patches. We found significant effects of nutrient addition in both groups of organisms. Phytoplankton diversity increased until the fourth week (transiently) and zooplankton richness was persistently higher under asynchronous nutrient addition. Our results were consistent with our hypothesis that asynchronicity in nutrient supply would create a more favorable condition for species to co-occur. However, this effect was, in part, transient and was not influenced by the degree of connectivity.
Highlights
As habitat fragmentation and biodiversity loss continues unabated, the role of metacommunities in preserving diversity and the accompanying ecosystem services is becoming ever more relevant
Despite the strong decrease in diversity during the initial phase of the experiment, phytoplankton diversity showed a faster recovery under asynchronous nutrient addition (LA and HA) than under the synchronous supply (LS and HS)
The factors tested in this experiment resulted in species dynamics which were mainly propelled by the spatiotemporal heterogeneity of nutrient addition and by time
Summary
As habitat fragmentation and biodiversity loss continues unabated, the role of metacommunities in preserving diversity and the accompanying ecosystem services is becoming ever more relevant. Extinctions can occur remarkably quickly, but if patches are interconnected to an appropriate degree, forming a metacommunity, local extinction can be countered by species dispersal, resulting in regional survival High dispersal rates can either increase species coexistence by allowing species persistence even in unfavorable localities (Loreau and Mouquet 1999), or decrease diversity when superior competitors or generalist predators are widespread over all patches (Loreau and Mouquet 1999; Holyoak et al 2005; Limberger and Wickham 2011). In an experimental study that directly manipulated connectivity, both regional diversity and local dissimilarity were highest in metacommunities
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