Climate stress in freshwater detritivores: mortality and resilience of Gammarus pulex to temperature and drought

Eleanor Pippen *

*Faculty of Biological Sciences, University of Leeds, LS2 9JT.

Pages: 65-70 ⏐ Published: 02 July 2026 ⏐ DOI: https://doi.org/10.70145/BiSh0012

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Abstract

Gammarus pulex is a key detritivore in cool, temperate freshwater systems, yet its responses to short-term climate-related stressors remain incompletely understood. With climate change projected to drive rising temperatures and more frequent summer low-flow periods across their temperate European range, understanding how short-term warming and drought affect this species is important for predicting potential disruptions to detritus processing and wider ecosystem functioning. This study examined how acute thermal stress affects survival in G. pulex, and whether prior heat exposure alters two subsequent responses in surviving individuals: tolerance to a drought-like stressor and leaf-shredding behaviour. Amphipods collected from a UK stream were exposed to eight temperatures ranging between 15–36 °C for 72 hours, after which survivors were assigned to either a 24-hour drought simulation or a feeding assay. Survival remained high at 15–20 °C, with 92% of amphipods surviving under both conditions but declined at 25 °C and more sharply at 27.5 °C, with substantial mortality at 30 °C (39% survival) and no individuals surviving at 32 °C or above, indicating the upper physiological limits of this population. In contrast, neither feeding activity nor drought tolerance showed detectable changes following thermal exposure under the short-term laboratory conditions used, and surviving individuals displayed no immediate impairment in feeding or short-term recovery capacity. Although the warmest temperatures exceeded those typically experienced in their natural habitats across the UK and cooler regions of northern and central Europe, temperatures within the 25–27.5 °C range can occur in shallow, sun-exposed, low-flow microhabitats during warm, dry periods, suggesting that localised thermal hotspots may elevate mortality in natural populations. Given the role of G. pulex in detritus processing, even modest reductions in abundance during warm periods could diminish leaf-litter breakdown and affect ecosystem functioning.

Keywords: Gammarus pulex, climate change, thermal stress, freshwater ecology, drought tolerance

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