Spiegel: It is the starting point for our oceans’ food chain. But stocks of phytoplankton have decreased by 40 percent since 1950, potentially as a result of global warming. It is an astonishing collapse, say researchers, and may have dramatic consequences for both the oceans and for humans. The forms that marine flora and fauna come in are varied and spectacular. From bizarre deep sea creatures to elegant predators and giant marine mammals, the diversity in our planet’s oceans is …