According to UN statistics, the ocean absorbs a quarter of global carbon dioxide emissions, but acidification has increased by 30 percent since the industrial revolution, threatening fisheries and coastal communities dependent on shellfish and marine ecosystems. The UN reports that the ocean has absorbed about 90 percent of the heat generated by rising emissions. As excessive heat and energy warm the ocean, the change in temperature leads to unparalleled cascading effects, including ice-melting, sea-level rise, marine heatwaves, and ocean acidification. Those effects are being felt across Greece, where the mussel farming industry is under serious threat. Record-breaking sea temperatures last summer wiped out nearly 90 percent of the harvest in the Thermaic Gulf, leaving dozens of coastal communities reeling.  Scientists say it's yet another warning sign of a rapidly changing climate.