No marine ecosystem remains unaffected by human activities. As we previously stated a stressor is  any stimulus producing mental or physical stress in an organism (Collins English Dictionary). We can group marine stressors in two main categories: a group that acts globally such as increased temperature, ocean deoxygenation (the global trend of decreasing oxygen as a result of ocean warming and increasing stratification) and ocean acidification\cite{Portner_2010}; and those that act at a local to regional level but occur globally, such as overfishing, pollution coastal hypoxia and habitat distruction.

The driver of all the global stressors is mainly caused by the excessive release of CO2 in the atmosphere. Although other gasses, like methane (CH₄ )and nitrous oxide (N₂O) have a great negative impact on the atmosphere, their effect will respectively last a decade (CH₄) and about a century (N₂O) \cite{Intergovernmental_Panel_on_Climate_Change}, every time CO2 is released, 40% will stay airborn 100 years and 20% will reside for 1000 years, while the final 10% will take 10,000 years to turn over \cite{2014}.

The ocean is affected directly from the increase of CO2 in the atmosphere. It is estimates that 26 percent of all the carbon released as CO2 is absorbed by the ocean (The global carbon budget 1959–2011 C. Le Quere). 

When sunlight reaches the Earth’s surface, the world’s oceans absorb some of this energy and store it as heat. This heat is first captivated on the surface but ultimately some of it is spreads into lower depths. Currents also spread this heat around the world. Water has a much higher heat capacity than air, meaning the oceans can absorb larger amounts of heat energy with only a slight increase in temperature.

While anthropogenic atmospheric CO2  dominates contributions to ocean acidification (OA) on a global scale, other human induced stresses may affect it on a local scale. \cite{Feely_2010}For example, acid rain from vehicle emissions and industry cause an increase in ocean acidity, which is likely relevant, at least near urbanised regions \cite{Doney_2007}. Any addition of organic carbon to the ocean, such as sewage, decomposes to dissolved inorganic carbon (DIC), and increases acidity \cite{Nagelkerken_2015}. Agricultural run-off provides nutrients which then fuel (an anthropogenic) increase in production of organic carbon in the ocean\cite{Howarth_2002}, again increasing acidity.