Response of the submerged macrophyte Stuckenia pectinata (L.) Börner to warming in different climate regions: A synchronized oligohaline mesocosm experiment

Abstract

Submerged macrophytes play a crucial role as primary producers and contribute essential ecosystem functions and services, but rising temperatures caused by climate change may alter their functional traits. We aimed to assess the effects of simulated climate warming (4.5 °C) on the functional trait responses of a submerged macrophyte, Stuckenia pectinata (L.) Börner, in a synchronized oligohaline (4 ppt salinity) mesocosm experiment conducted in two different climate regions in Turkey: cold semi-arid Ankara and hot, dry Mediterranean Mersin. The experiment was conducted using eight mesocosms at each site, with four replicates of each ambient temperature and warming treatment. Each mesocosm held 5000 L and was inoculated with natural sediment, plankton, macroinvertebrate and fish communities to represent natural oligohaline lake ecosystem. S. pectinata shoots collected from a single population from a coastal lake in Mersin were also inoculated in all mesocosms in similar abundances. Overall, we observed significant differences in macrophyte functional traits between the two sites with different climates, albeit with less pronounced effects of a 4.5 ºC rise in temperature within each site. Specifically, higher macrophyte percent volume infested (PVI) and canopy height were observed in the warmer Mersin than in the colder Ankara, which we attributed to higher shading by phytoplankton (reflected by water column Chlorophyll a, Chl-a). The biomass ratio (%dry weight (DW)/wet weight (WW)) was notably higher in Ankara, suggesting that the macrophytes in Ankara acquired relatively more resources than those in Mersin. The pronounced differences between the two sites likely reflected not only temperature differences but also cascading ecosystem characteristics (e.g., water column Chl-a, water nutrients) due to climatic differences.