Skip to main content
Dryad logo

Regime shifts in a shallow lake: Consequences for taxonomic and functional diversity, and ecosystem multifunctionality

Citation

Moi, Dieison (2022), Regime shifts in a shallow lake: Consequences for taxonomic and functional diversity, and ecosystem multifunctionality, Dryad, Dataset, https://doi.org/10.5061/dryad.xd2547dgn

Abstract

  1. Under increasing nutrient loading, shallow lakes may shift from a state of clear water dominated by submerged macrophytes to a turbid state dominated by phytoplankton or a shaded state dominated by floating macrophytes. How such regime shifts mediate the relationship between taxonomic and functional diversity and lake multifunctionality is poorly understood.
  2. We employed a detailed database describing a shallow lake over a 12-year period during which the lake has displayed all the three states (clear, turbid, and shaded) to investigate how species richness, functional diversity of fish and zooplankton, ecosystem multifunctionality, and five individual ecosystem functions (nitrogen and phosphorus concentrations, standing fish biomass, algae production, and light availability) differ among states. We also evaluated how the relationship between biodiversity (species richness and functional diversity) and multifunctionality is affected by regime shifts.
  3. We showed that species richness and the functional diversity of fish and zooplankton were highest during the clear state. The clear state also maintained the highest values of multifunctionality as well as standing fish biomass production, algae production, and light availability, whereas the turbid and shaded states had higher nutrient concentrations. Functional diversity was the best predictor of multifunctionality. The relationship between functional diversity and multifunctionality was strongly positive during the clear state, but such relationship became flatter after the shift to the turbid or shaded state.
  4. Our findings illustrate that focusing on functional traits may provide a more mechanistic understanding of how regime shifts affect biodiversity and the consequences for ecosystem functioning. Regime shifts towards a turbid or shaded state negatively affect the taxonomic and functional diversity of fish and zooplankton, which in turn impairs the multifunctionality of shallow lakes.

Methods

The research was conducted in Lake Osmar, a shallow lake (1.1 m average depth) located in the Upper Parana floodplain (22 º46´27. 53" S and 53º 19´ 57. 95"), Brazil (Figs. S1 and S2). This region has a tropical climate with a mean annual temperature of 22 °C (mean minimum and maximum temperatures of 10.3 and 33.6 °C, respectively) and a mean annual precipitation of 1500 mm. The data used for the analysis originate from a long-term ecological research project (PELD-Sitio PIAP) and include 12 years (2005 to 2016).

Fish and zooplankton sampling

The sampling campaigns were explicitly designed to assess the taxonomic and functional diversity of fish and zooplankton, as well as ecosystem multifunctionality, during the three alternative states. During the 12 years, four annual samples (summer, fall, winter, and spring) were collected, except in 2014 when only sampling campaigns were conducted, resulting in 48 sampling campaigns in total. Fish were caught using 20 m long seines with a mesh size of 0.5 cm in the littoral and middle zones of the lake for a 24 h period. As the lake is shallow, our sampling always included all lake compartments (i.e., sediment, the pelagic and littoral zones). Zooplankton were sampled in the subsurface of the pelagic zone using a motorized pump and a plankton net (68 µm), filtering 600 L water per sample. The samples were preserved in 4% formaldehyde solution and buffered with calcium carbonate. To identify and enumerate (ind.m-3) organisms, the samples were analyzed in optical microscope under 100 magnification. The abundance of individuals was estimated by analyzing minimum three subsamples, equivalent to 10% of the total sample, in a Sedgewick-Rafter chamber.