Planktotrons: A novel indoor mesocosm facility for aquatic biodiversity and food web research

Andrea Gall,Helmut Hillebrand,Uwe Ebensen,Udo Uebel,Alexander Wacker,Sandra Meier,Maren Striebel,Gabriel Singer

doi:10.1002/lom3.10196

Abstract

AbstractWe established a new indoor mesocosm facility, 12 fully controlled “Planktotrons”, designed to conduct marine and freshwater experiments for biodiversity and food web approaches using natural or artificial, benthic or planktonic communities. The Planktotrons are a unique and custom‐tailored facility allowing long‐term experiments. Wall growth can be inhibited by a rotating gate paddle with silicone lips. Additionally, temperature and light intensity are individually controllable for each Planktotron and the large volume (600 L) enables high‐frequency or volume‐intense measurements. In a pilot freshwater experiment various trophic levels of a pelagic food web were maintained for up to 90 d. First, an artificially assembled phytoplankton community of 11 species was inoculated in all Planktotrons. After 22 d, two ciliates were added to all, and three Daphnia species were added to six Planktotrons. After 72 d, dissolved organic matter (DOM, an alkaline soil extract) was added as an external disturbance to six of the 12 Planktotrons, involving three Planktotrons stocked with Daphnia and three without, respectively. We demonstrate the suitability of the Planktotrons for food web and biodiversity research. Variation among replicated Planktotrons (n = 3 minimum) did not differ from other laboratory systems and field experiments. We investigated population dynamics and interactions among the different trophic levels, and found them affected by the sequence of ciliate and Daphnia addition and the disturbance caused by addition of DOM.

Highlights

We established a new indoor mesocosm facility, 12 fully controlled “Planktotrons”, designed to conduct marine and freshwater experiments for biodiversity and food web approaches using natural or artificial, benthic or planktonic communities
As a proof of concept, we examined the development and response of a freshwater phytoplankton community, ciliates, and various Daphnia species under an external stressor exemplified by the sudden addition of a sizeable amount of allochthonous colored dissolved organic matter
We studied effects of grazing by zooplankton on this phytoplankton community and reactions of both phyto- and zooplankton to an external disturbance in the form of addition of dissolved organic matter

Summary

Introduction

We established a new indoor mesocosm facility, 12 fully controlled “Planktotrons”, designed to conduct marine and freshwater experiments for biodiversity and food web approaches using natural or artificial, benthic or planktonic communities. In a pilot freshwater experiment various trophic levels of a pelagic food web were maintained for up to 90 d. An artificially assembled phytoplankton community of 11 species was inoculated in all Planktotrons. After 22 d, two ciliates were added to all, and three Daphnia species were added to six Planktotrons. We demonstrate the suitability of the Planktotrons for food web and biodiversity research. We investigated population dynamics and interactions among the different trophic levels, and found them affected by the sequence of ciliate and Daphnia addition and the disturbance caused by addition of DO

Methods

Findings

Conclusion