Climate warming and heat waves affect reproductive strategies and interactions between submerged macrophytes

Abstract

Extreme climatic events, such as heat waves, are predicted to increase in frequency and intensity during the next hundred years, which may accelerate shifts in hydrological regimes and submerged macrophyte composition in freshwater ecosystems. Since macrophytes are profound components of aquatic systems, predicting their response to extreme climatic events is crucial for implementation of climate change adaptation strategies. We therefore performed an experiment in 24 outdoor enclosures (400 L) separating the impact of a 4 °C increase in mean temperature with the same increase, that is the same total amount of energy input, but resembling a climate scenario with extreme variability, oscillating between 0 °C and 8 °C above present conditions. We show that at the moderate nutrient conditions provided in our study, neither an increase in mean temperature nor heat waves lead to a shift from a plant-dominated to an algal-dominated system. Instead, we show that species-specific responses to climate change among submerged macrophytes may critically influence species composition and thereby ecosystem functioning. Our results also imply that more fluctuating temperatures affect the number of flowers produced per plant leading to less sexual reproduction. Our findings therefore suggest that predicted alterations in climate regimes may influence both plant interactions and reproductive strategies, which have the potential to inflict changes in biodiversity, community structure and ecosystem functioning.

Persistence of submerged macrophytes in a drying world: Unravelling the timing and the environmental drivers to produce drought‐resistant propagules

“…The growth of C. aspera shoots from the LSP was positively influenced by experimental salinities of 4 g L –1 (Rojo et al, ), but its reproduction declined during the summer in the pond, where salinity reached a maximum of barely 2.6 g L –1 . This suggests that other factors, such as a mean temperature that is too high, or the occurrence of heat waves (Li et al, ), affected the phenological pattern of the species. A complex interaction between the specific life‐history traits and the species‐specific environmental requirements and tolerances (Rey‐Boissezon & Auderset Joye, ) may explain the observed divergent phenological patterns when several species coexist within an ecosystem under the same ecological conditions (Figure a).…”

“…This fact also explains the earlier reproduction observed in the high‐irradiance and shallower conditions. Water‐level variations encompass shifts in light conditions, temperature, and salinity, all of which are interrelated determinants of the development of submerged macrophytes (Li et al, ; Rojo et al, ; Santamaría & Hootsmans, ). Thus, besides temperature, salinity and light availability seemed to determine the development of charophytes in these Mediterranean ecosystems, supporting the fourth hypothesis.…”

Joint forcing by heat waves and mowing poses a threat to grassland ecosystems: Evidence from a manipulative experiment

“…Mounting evidence points to an increase in the frequency and intensity of HWs, which have affected more than 73% of the global terrestrial area since the mid‐20th century (IPCC, ; Perkins‐Kirkpatrick et al, ) and have caused large and widespread impacts at all ecological scales from the species level to the ecosystem level. Severe HW events not only rapidly reduce plant photosynthesis and respiration (Crous Kristine et al, ), decrease aboveground and belowground biomass accumulation (Qu, Chen, Dong, & Shao, 2018), and alter the (re)allocation of carbon and nitrogen within a plant (Li et al, ), but also result in a decrease in ecosystem gross primary productivity and net ecosystem carbon exchange (Ciais et al, ; Qu et al, 2018; Tatarinov et al, ). However, these studies mostly concentrate on HWs effects on plant growth (photosynthesis system) or ecosystem carbon exchange, but how plant morphology, phenology, and community structure respond to such extreme events remains poorly understood.…”

Life‐history traits buffer against heat wave effects on predator–prey dynamics in zooplankton

“…Understanding the effects of predicted extreme climatic events is crucial since they are likely to affect both individual organisms and interactions among species, leading to complex responses at the community and ecosystem levels (Li et al, ; Sentis et al, ). A few studies have indicated that heat waves may trigger regime shifts (Bertani, Primicerio, & Rossetti, ), fluctuation in planktonic communities (Huber, Adrian, & Gerten, ), and the formation of cyanobacterial blooms (Huber, Wagner, Gerten, & Adrian, ).…”

“…A few studies have indicated that heat waves may trigger regime shifts (Bertani, Primicerio, & Rossetti, ), fluctuation in planktonic communities (Huber, Adrian, & Gerten, ), and the formation of cyanobacterial blooms (Huber, Wagner, Gerten, & Adrian, ). Most of those studies have been based either on field monitoring data (Adrian et al, ; Bertani et al, ; Huber et al, ) or modeling (Vasseur, et al, ), whereas few experimental studies have addressed the mechanisms and magnitudes in responses (but see Sentis et al, , Li et al, ). Therefore, experimental studies are crucial for providing a mechanistic understanding on how ecological processes may alter, allowing for adjustments in predictions of ecosystem function in future systems.…”