Review and conceptual models of agricultural impacts and water quality in waterways of the Great Barrier Reef catchment area

摘要: Adequate conceptual frameworks that link land use to water quality and ecosystem health are lacking for tropical subtropical freshwater systems, so we review here extensive water-quality research undertaken in the Great Barrier Reef catchment area (GBRCA) present models synthesising dynamics of agricultural pollutants their ecological effects. The seasonal flow regime defines following key periods risk over annual hydrological cycle diverse GBRCA ecosystems: initial ‘pre-flush’ flows during transition from dry wet season; early wet-season ‘first flush’ flows; peak flood sustained base or disconnection season. level contrast varies perennial systems tropics intermittent tropics. Major stressors may be scale (e.g. streams draining broad-scale agriculture) more localised cattle access, irrigation tail water). Water-quality such as ammonia toxicity hypoxia (due organic nutrient run-off enhanced plant productivity) low relevance downstream GBR ecosystems but major threats fresh waters. Similarly, whereas high contaminant loads floods highest marine ecosystems, greatest waters is often acute contamination into lentic waters, continuous input contaminants long flow. Because differences nature periods, pollutant-delivery mechanisms, benefits different management options improve can also differ among habitats between environments.