Heat Waves Alter Macrophyte-Derived Detrital Nutrients Release under Future Climate Warming Scenarios

Abstract

In addition to a rise in global air and water mean temperatures, extreme climate events such as heat waves are increasing in frequency, intensity, and duration in many regions of the globe. Developing a mechanistic understanding of the impacts of heat waves on key ecosystem processes and how they differ from just an increase in mean temperatures is therefore of utmost importance for adaptive management against effects of global change. However, little is known about the impact of extreme events on freshwater ecosystem processes, particularly the decomposition of macrophyte detritus. We performed a mesocosm experiment to evaluate the impact of warming and heat waves on macrophyte detrital decomposition, applied as a fixed increment (+4 °C) above ambient and a fluctuating treatment with similar energy input, ranging from 0 to 6 °C above ambient (i.e., simulating heat waves). We showed that both warming and heat waves significantly accelerate dry mass loss of the detritus and carbon (C) release but found no significant differences between the two heated treatments on the effects on detritus dry mass loss and C release amount. This suggests that moderate warming indirectly enhanced macrophyte detritus dry mass loss and C release mainly by the amount of energy input rather than by the way in which warming was provided (i.e., by a fixed increment or in heat waves). However, we found significantly different amounts of nitrogen (N) and phosphorus (P) released between the two warming treatments, and there was an asymmetric response of N and P release patterns to the two warming treatments, possibly due to species-specific responses of decomposers to short-term temperature fluctuations and litter quality. Our results conclude that future climate scenarios can significantly accelerate organic matter decomposition and C, N, and P release from decaying macrophytes, and more importantly, there are asymmetric alterations in macrophyte-derived detrital N and P release dynamic. Therefore, future climate change scenarios could lead to alterations in N/P ratios in the water column via macrophyte decomposition processes and ultimately affect the structure and function of aquatic ecosystems, especially in the plankton community.

Meteorological and Limnological Precursors to Cyanobacterial Blooms in Seneca and Owasco Lakes, New York, USA

“…Both trends are consistent with global climate change scenarios [41]. Warmer water also promotes faster decomposition of macrophytes and other lake floor organic matter, and provides a potential nutrient source for CyanoHABs and other phytoplankton in these borderline oligotrophic-mesotrophic lakes, e.g., [1,42,43]. The automated cameras faithfully detected a total of 68 and 92 days with blooms in Seneca and Owasco Lakes, respectively, during this study (Figure 3).…”

Heat Transfer by Sweat Droplet Evaporation

“…Global warming, more recently referred to as “global boiling”, has increased the occurrence and intensity of heat waves. This leads to prolonged periods of abnormally high temperatures, often coupled with high humidity levels resulting in aggravated heat-related health risks. − Physiological examinations conducted under various environmental conditions suggest that the apparent temperature of the human body rises in humid weather, making it feel hotter than the actual temperature, as determined by the heat index . This can be hazardous to the body, even at lower temperatures, when the ability to counter heat stress is uncertain.…”

How Eutrophication Promotes Exotic Aquatic Plant Invasion in the Lake Littoral Zone?

“…Aquatic plants, being key main primary producers and ecosystem engineers of the littoral zone of lakes, create complex and diversified habitats and provide a variety of ecological functions. − They provide spawning, incubation, and refuge sites for zooplankton, benthic animal, and fish and act as a trap and a purifier for pollutants flowing into the lake. − Thus, the complex and highly structured environment of the littoral zone has important implications for lake biodiversity conservation. , However, the vegetated area in this zone is shrinking, and the biodiversity is decreasing worldwide due to eutrophication, usually caused by agricultural pollution, extraordinary development of fishery culture, and over-exploitation by tourists. ,, These changes alter the multiple ecological function of the littoral zone …”