This dataset reports physiological measurements of two bivalve species, Mytilus edulis (blue mussel) and Magallana gigas (Pacific oyster), obtained during a three-month mesocosm experiment conducted in Sylt, Germany, in 2023. Physiological data were collected between 27 April 2023 and 25 June 2023.Twelve mesocosms were used to investigate the effects of temperature on individual-level physiological traits, with treatments including ambient temperature and ambient +3°C. Parameters measured include clearance rate, ingestion rate, and respiration rate. Environmental variables such as water temperature, depth, and sampling time were recorded for each measurement. Individual bivalves were labeled for tracking, and species identification followed WoRMS taxonomy. Measurements were performed using handheld multiparameter instruments and laboratory analyses. The dataset provides high-resolution, individual-based physiological responses of bivalves to moderate warming, supporting research on temperature-dependent feeding, metabolic processes, and energy flux in coastal ecosystems.

Clearance rate (CL)Parameter: Clearance rate (L min⁻¹)Method:Single individuals were enclosed in PVC cores (diameter 15 cm; ~5 cm sediment penetration). A defined algal suspension (Rhodomonas salina) was added to achieve a known chlorophyll-a concentration. Water was mixed continuously. Chlorophyll-a (µg L⁻¹) was measured over 90 min at 10-min intervals using a BBE AlgaeLabAnalyzer (bbe Moldaenke GmbH, Germany). Control incubations without animals were conducted to correct for background chlorophyll-a loss.Calculation:CL = (Vol / t) × ln(Ct₀ / Ct₁)Vol = enclosed water volume (L)t = incubation time (min)Ct₀ = initial chlorophyll-a concentration (µg L⁻¹)Ct₁ = final chlorophyll-a concentration (µg L⁻¹)Control values were subtracted from animal treatments.---Ingestion rate (IR)Parameter: Ingestion rate (µg chl-a min⁻¹)Calculation:IR = CL × XkXk = half-saturation coefficient (µg chl-a L⁻¹):2 for M. edulis12.6 for M. gigas---Respiration rate (R)Parameter: Respiration rate (mg O₂ h⁻¹)Method:Individuals were incubated individually in airtight 500 mL glass bottles containing 0.2 µm-filtered seawater. Oxygen concentration (mg L⁻¹) was measured continuously using an Oxy-4-SMA respirometer (PreSens Precision Sensing GmbH, Germany). Water was mixed magnetically. Temperature was maintained at mesocosm conditions.Control incubations without animals were conducted to correct for background oxygen changes.Oxygen concentration decline was regressed over time; control slopes were subtracted from animal slopes.Ash-free dry weight (AFDW, g) was determined after drying at 60 °C (≥72 h, constant weight) and combustion at 500 °C for 3 h.Calculation (after Tang & Riisgård 2018):R = Vol × 60 × aVol = bottle water volume (L)a = corrected slope of oxygen decline (mg O₂ L⁻¹ min⁻¹)---All calculated rates were converted to h⁻¹ in the published dataset.