Macroinvertebrate and ecosystem function data from replicated in-stream experiments in Tasmanian streams (2021–2023)

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This dataset is from an experiment testing stream community responses to catchment conversion to agriculture and short-term flow changes. We used a multiple before–after control–impact (mBACI) design across 8 Tasmanian streams (4 agricultural, 4 forested) during late summers of 2021–2023. Each stream contained three reaches (control, low flow, high flow). Flow was manipulated using temporary semi-porous weirs to create treatment conditions. Macroinvertebrate, physicochemical, and ecosystem function measurements were taken before, during, and after a disturbance (median 24.5 days, range 19–30), followed by a recovery (median 85 days, range 84–92). The sampling sequence was: Sample 1: pre-disturbance (baseline, all reaches), Samples 2–3: weekly during disturbance (weirs in place), Samples 4–6: monthly during recovery (post-weir removal). Macroinvertebrates were sampled with 0.25 m² box sampler; rocks scrubbed, fine material disturbed into 200 µm mesh net; preserved in 70% ethanol and identified to lowest practicable taxonomic level. Physicochemical variables were spot measures of temperature, pH, conductivity, dissolved oxygen (Hach HQ40d), and flow (Schiltknecht MiniAir 2); continuous temperature logging at controls using HOBO loggers and Derwent Estuary Program data. Ecosystem functions were leaf decomposition (mesh bags with ~5 g dried green Eucalyptus viminalis leaves, 45 per site (3 × 15 per treatment/control), retrieved at 5 intervals; leaves dried (40 °C, ~48 h) and weighed; negative controls corrected for transport/set-up loss); cellulose decomposition (45 unbleached cotton strips (65 × 35 mm; EMPA, Switzerland) per site, on submerged ropes, retrieved at 5 intervals; tensile strength loss measured with Salter ElectroSamson scales); algal accrual (45 unglazed ceramic tiles (25 × 25 mm) per site, retrieved at 5 intervals; chlorophyll a extracted with 90% ethanol and quantified spectrophotometrically).