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Life in the ocean

Even though mermaids, water-sprites and sea monsters were probably just dreamt up by early sailors, the unfathomable depths of the oceans still hold mysteries and surprises, even for today's more scientific researchers. As little as one-tenth of the marine kingdom has been even halfway explored. And the sea floor remains largely undiscovered, especially in the deep ocean.


A comparatively friendly sea creature, its body covered in scales, purportedly caught in the Baltic in around 1531. Or so Johann Zahn claimed in his "Specula physico-mathematico-historica notabilium ac mirabilium sciendorum", printed in 1696 in Augsburg. (Treasures of the NOAA Library Collection)

So far, marine research can tell us most about coastal ecosystems and coasts themselves – coral reefs, mangroves, kelp beds, sea grass meadows and tidal flats – along with other habitats that divers can access with simple technology. But it has only a vague understanding of many areas of the marine habitat, or of the organisms to be found in the midwater zone below the sunlit surface waters or in the midnight zone of the deep ocean itself.


It is clear that the diversity of life forms is far greater in the oceans than on land. Of 33 animal phyla, 30 are found in the sea. Half of them are exclusively marine organisms. The reverse seems to be true of the number of species. Around 1.5 million land species have been described to date, mainly vascular plants and insects. Estimates put the total number at five to fifty million. At present, only 250,000 marine species are known. It is estimated that there may be up to half a million. However, it remains to be seen what secrets the largely unexplored deep ocean floor may reveal. Another million species, or even ten million, as some experts expect?


By far the greatest part of the marine ecosystem exists in complete darkness. At a temperature of 2° Celsius, with every increase in depth accompanied by a rise in water pressure, great demands are placed on the adaptive capacities of these organisms. From the land-dweller's point of view, these ocean-dwellers can be alien in appearance, and sometimes quite terrifying. But in the face of conditions which seem so hostile to survival, nature replies with an astonishing diversity of forms, colours and survival strategies.

Life on the coasts

For all their fascination, coastal zones are more than just a habitat for special flora and fauna – they are also an attraction for a growing number of people worldwide. So conflicts are the order of the day. ... more


Down under – On the ocean floor

If we could freely observe the ocean floor, there would be more to see than mere abysses. In fact, the sea hides an imposing marine landscape as varied as that above ground, with mountains and valleys, high plateaus and deep-sea plains ... more


In the waves

Swell, rough sea, wind sea, ground swell or cross sea – are indicative of the varying topography of the ocean surface and its wind-driven dynamics. Only rarely is the sea completely calm ... weiter