Species-Specific Responses of Submerged Macrophytes to Simulated Extreme Precipitation: A Mesocosm Study

Yu Cao,Erik Jeppesen,Yongwei Zhi,Wei Li

doi:10.3390/w11061160

Abstract

More frequent extreme climate events (e.g., extreme precipitation) are to be expected in the future, and such events may potentially have significant effects on freshwater ecosystems. In the present mesocosm study, the effects of simulated extreme precipitation on submerged macrophytes were evaluated for three different macrophyte community (MC) treatments (MC1, MC2 and MC3). MC1 consisted of only Vallisneria denseserrulata, while MC2 and MC3 included three and six species of various growth forms. Two treatments of extreme precipitation (EP) were simulated—an extreme treatment (E) simulating a sudden increase of water level from 75 cm to 150 cm within one day and a gradual treatment (G) simulating an increase to the same water level within 3 months, combined with two control treatments. Total macrophyte community biomass was resilient to the EP and MC treatments, while species-specific variations in responses, in terms of biomass, maximum height, and sexual reproduction, were found. For instance, E led to earlier flowering of Potamogeton lucens and production of more flowers, while it had adverse effects on the flowering of Ottelia alismoides. We conclude that freshwater ecosystems with high coverage of submerged macrophytes may be overall resilient to extreme precipitation under nutrient-limited conditions, especially communities with diverse growth forms.

Highlights

The Intergovernmental Panel on Climate Change predicts more frequent extreme precipitation events in the future with potential strong influence on freshwater ecosystems [1,2]
Prior to the extreme precipitation treatments (EP) treatment, total nitrogen (TN), NO3 -N, total phosphorus (TP), phytoplankton chlorophyll a (Chla), alkalinity, pH, Kd and Dissolved oxygen (DO) did not differ among the three macrophyte community (MC) or four EP treatments after one month of pre-cultivation in
TP generally ranged within 20~25 μg L−1 except on the first sampling event after the simulated extreme precipitation, where it was higher in C_N and G than in C (Table 1, Figure 1)

Summary

Introduction

The Intergovernmental Panel on Climate Change predicts more frequent extreme precipitation events in the future with potential strong influence on freshwater ecosystems [1,2]. The effects of extreme precipitation in shallow lakes may both lead to a sudden increase of water levels and an additional input of nutrient. Studies focusing on either extreme precipitation or nutrient pulses have revealed that a sudden water level increase after extreme rainfall significantly influences primary producers in freshwater ecosystems [3,4,5] and that pulse loading of nitrogen can induce marked changes in macrophyte and phytoplankton communities [6]. Macrophytes compete with phytoplankton for light and nutrients [9], and they create and maintain a clear water state [10], but their ecological effect in shallow lakes may differ among growth forms [11,12,13,14]

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