Biological Response Matrix for risk management of bottom-cultured Peruvian scallops under oxygen deficiency, temperature, and exposure-time stressors

Global warming and ocean deoxygenation represent increasing threats to the sustainability of bivalve aquaculture. In this study, we developed a categorical Biological Response Matrix (BRM) for the Peruvian scallop (Argopecten purpuratus), integrating dissolved oxygen saturation, temperature, and exposure time to these stressors to classify environmental conditions into four physiologically defined categories: innocuous (no documented physiological impairment), stressful (threshold-level physiological responses without mortality), sublethal (<50% mortality), and lethal (≥50% mortality). The BRM was constructed from published experimental evidence and retrospectively applied to time series of environmental data from bottom-cultured scallops in Sechura Bay (Peru), including two documented mass mortality events (2017 and 2019) and three summers without reported mortality (2014, 2015 and 2018). Results show that in 2017, mortality was associated with a thermal anomaly (up to 27.7 °C) under normoxic conditions, whereas in 2019 it was linked to severe and prolonged hypoxia (<5% dissolved oxygen saturation for 116 h). The BRM identified and characterized critical environmental conditions underlying both events and accurately distinguished non-mortality scenarios, which were marked by intermittent physiological stress and compensatory reoxygenation. These findings demonstrate the diagnostic utility of the BRM in distinguishing mortality and non-mortality environmental conditions and support its future integration into early-warning monitoring systems to enhance adaptive aquaculture management under climate change.