Rob Dunn

weather pattern. In February, the US National Oceanic and Atmospheric Administration (NOAA) warned in its routine forecasts that the bleaching observed in the Pacific last year may be the start of a third global catastrophe for coral reefs. And this time, it cannot be blamed on El Niño. It is simply down to the general warming of the oceans, which in 2014 reached the highest average temperature ever recorded. In addition to suffering from the heat, corals are also susceptible to ocean acidification, although it is not clear yet how well they will cope with these stress factors in the long term. Fish are also adapted to constant environment temperatures, but when their habitat gets warmer, they can easily migrate to find waters with their preferred temperature. That is what Ignasi Montero-Serra at the University of Barcelona and colleagues observed in a recent study based on comprehensive analyses of 57,000 fish censuses from 40 years and new modelling of temperature responses (Glob. Change Biol. (2015) 21, 144–153). Water temperatures in the North Atlantic have increased by up to 1.3oC since the 1980s. The researchers found that this has had a direct effect on the distribution of small fish species. The North Sea, for instance, has seen a rise in subtropical species like sardines and anchovies, and a loss of native species like herring and sprat. Fish stocks moving in response to climate change will have knock-on effects both on their natural predators and on coastal communities depending on fisheries. Ocean warming and acidification, just like plastic pollution (Curr. Biol. (2015) 25, R93–R96) and fertiliser runoffs, are problems that we produce on land, but which affect the ecological function of the oceans most. In return, ocean dysfunction can severely disrupt climate and food security on land. The simultaneous presence of land and open sea is what makes our planet uniquely life-supporting among all the planets we know so far. How to live within this natural balance without destroying it is something we urgently need to figure out if we want to continue enjoying the perks of living on an ocean planet.