Combined effects of temperature, inorganic nutrients and organic matter on ecosystem processes in intertidal sediments

Multiple anthropogenic stressors can interact, making it difficult to predict their combined impacts on ecosystem processes. Interactions between localised stressors can be further modified by variations in environmental conditions, such as those arising through climate change. This study investigated the individual and combined effects of increased temperature and nutrients and organic enrichment on ecosystem processes in intertidal sedimentary systems. Three levels of nutrient addition (0, 100 and 200 g m− 2) were crossed with two levels of organic matter (0 and 200 g m− 2) under two temperature regimes (10.0 and 16.5 °C) in laboratory tanks. The influence of organic matter on ecosystem processes moderated by macrofauna did not vary with concentration of inorganic nutrients or temperature. Oxygen consumption, which has repeatedly been shown to increase with increased temperature, was in this case significantly increased by organic matter across all levels of temperature and nutrient enrichment. In addition, temperature affected nutrient cycling regardless of the addition of nutrients or organic matter. Understanding how the combined impacts of multiple stressors may vary depending on environmental conditions is essential for the development of strategies to sustainably manage ecosystems and conserve the delivery of ecosystem services.

Research Highlights
► Effects of multiple stressors on ecosystem functioning were tested in the laboratory.
► Organic matter enrichment caused increased rates of community respiration.
► Temperatures changes consistently modified nutrient cycling.
► No interactive effects were detected.