Effects of Stream Thermal Variability on Macroinvertebrate Community: Emphasis on Native Versus Non-Native Gammarid Species

Abstract

An increase in river water temperatures is being detected worldwide, with some predictions of an up to 4°C rise by 2050. Such stream temperature increase is likely to affect aquatic communities, with predicted declines and range shifts of cold stenothermic species and a facilitated dispersal and population development in temperature-tolerant species, including invasive ones. This study analyzed how thermal changes affect macroinvertebrate community compositions in three differentiated thermal regions within a single stream system. In each thermal region, we used standard surber sampling in combination with in-stream cross-exposure experiments, comparing the thermal response of native vs. non-native gammarids (Gammarus roeselii and Dikerogammarus villosus). Macroinvertebrate species composition was highly dependent on temperature, with indigenous gammarids preferring colder sites and invasive ones such as D. villosus being dominant at higher temperatures. Species composition was also strongly affected by season, substratum and the presence of macrophytes. In light of climate change, consideration of shifts in community composition highly driven by temperature needs to become integrated with biological response patterns related to morphological and flow degradation, chemical pollution and fine sediment. Such an approach is crucial for the effective conservation and restoration of native biodiversity and for a realistic prediction of the ability to reach policy targets for aquatic ecosystems.

Heat Tolerance of Gammarus fossarum (Crustacea, Amphipoda) Is Influenced by the Level of Stress Associated with Reproduction and the Water Quality of Their Habitat

“…Both experiments revealed an increasing mortality when gammarids were exposed to heat stress (25 • C). The importance of rising temperatures beyond the physiological optimum for the survivability of organisms, especially gammarids, has been demonstrated in other studies, showing that heat stress is a major factor negatively affecting all physiological and biochemical processes in the organisms [35,36,38,46,47].…”

Biological invasions are a population‐level rather than a species‐level phenomenon

“…Such new directions are needed, as generalisation at the species level and other oversimplifications of that type hinder effective management interventions. Indeed, aside from boom‐bust dynamics (Strayer et al., 2017), invasions are often generalised as an “increasing” threat, with studies frequently noting predominantly positive growth patterns (Pander et al., 2022; Seebens et al., 2017) ignoring the potential for fluctuating or decreasing trends (Niedrist et al., 2023). Our analysis, focusing on empirical long‐term trends using non‐native species abundances, revealed considerable variability in trends across different macroinvertebrate species, their populations, and invaded regions, underscoring the inability to generalise invasion dynamics, emphasising that each invasion is unique and contingent on a multitude of factors.…”

Contribution of a groundwater-influenced hinterland drainage system to the restoration of salmonid spawning grounds at the upper river Danube

“…During wintertime, when in mid European countries outside temperatures are usually very low, these systems can be much warmer than natural rivers. Due to the groundwater influence, these HDS are very clear, and can thus comprise a large diversity of macrophytes that are known to be important habitat structures for many macroinvertebrate and fish species (Pander et al, 2022a). However, in HDS, particularly during summer, periods of low oxygen supply may occur due to their high percentage of lowoxygen groundwater.…”