An important concept in ecology is the concept of ecosystem services. A service is a benefit that is provided to humans, in a direct or indirect way. Among the services provided by ocean ecosystem are: food production, absorption of excess heat caused by anthropogenic forcings in the atmosphere, absorption of co2 from atmosphere, reservoir of biological diversity, cultural, recreational services. Climate change is altering the ocean ecosystem in profound ways, and some of its impact will be felt for decades or centuries because of the committed climate change. In lec 1, we discussed many of the stressors on ecosystems due to human activity, and climate change impacts on ecosystems have to be seen in this context: pollution of air, water and soil, deforestation, fragmentation of habitats. Most of the surface is warming up, but there are important regional differences. For example, warming is stronger in the north atlantic ocean.