The oceans form the largest connected ecosystem in the world. However, only a small excerpt of their huge biodiversity is probably known so far, as a study based on around 48 million data sets on more than 184,000 marine species shows. The results reveal which influencing factors shape the patterns of biodiversity in the world’s oceans – and also point to major research gaps. To date, there is hardly any data available, particularly on life in the deep sea. Further knowledge is therefore urgently needed to effectively protect species communities in the ocean.
More than 70 percent of the earth’s surface is covered by oceans. They play a central role in the global climate system and also provide a habitat for numerous organisms, from tiny single-celled organisms to giant whales. “Despite their great importance – also for us humans – the oceans are still only very incompletely researched. According to estimates, there are over 2.2 million marine species, of which around 90 percent have not yet been scientifically described,” explains Hanieh Saeedi from the Senckenberg Research Institute and Nature Museum Frankfurt. “Despite decades of research and extensive data collection, our knowledge of global marine biodiversity is still distorted and incomplete. Where are hotspots of marine biodiversity? Where are there gaps in knowledge? And what are the drivers of biodiversity?”
Unexplored depths
To get to the bottom of these questions, Saeedi evaluated around 48 million publicly available data sets with information on 184,141 marine species. “This corresponds to about 90 percent of the scientifically described and accepted marine fauna,” says Saeedi. “The aim was – for the first time on this scale – to create a global picture of marine biodiversity. Not only to recognize distribution patterns, but also to systematically show where data is missing and which factors influence these patterns.”
To do this, the researcher examined the distribution of this data across different ocean areas and the entire depth gradient, from the sea surface through shallow coastal waters to extreme depths of around 11,000 meters. Depending on the depth and region, different amounts of data were available. “Around 50 percent of the world’s oceans are still inadequately recorded, with no data available for more than 160 million square kilometers below 200 meters,” reports the researcher. “Sampling is concentrated in developed regions, particularly the North Atlantic, while significant gaps remain in the equatorial regions and the Global South.”
In particular, tropical areas, which are likely to have a particularly high level of biodiversity, so far contribute less than 2.5 percent to the available data sets. “This unequal distribution means that certain patterns of biodiversity may be distorted. In some cases, hotspots are underestimated or not recognized at all, especially in the deep sea and in poorly researched regions,” says Saeedi.
More knowledge for better protection
But what drives biodiversity in different regions? At least for the well-researched shallow marine areas, the data show that water temperature has a decisive influence on species composition. In deeper ocean regions, however, nutrient cycles and human activities seem to play a role. However, according to Saeedi, these results could be distorted by the fact that previous deep-sea expeditions have only covered very small areas and therefore do not provide a comprehensive picture.
Saeedi emphasizes that there is still a great need for research and that more comprehensive knowledge is also important for effective protection of the oceans. “Protection planning that is based on incomplete and geographically distorted data can result in particularly vulnerable ecosystems remaining ‘invisible’ to science and politics. You cannot effectively protect what has never been sampled, documented or digitally recorded,” she warns. “In order to close the existing knowledge gaps, significant international investments are necessary – for example in long-term monitoring programs, targeted deep-sea expeditions, standardized data collection, the large-scale digitization and merging of biodiversity data as well as more coordinated international research collaborations. This is the only way to realistically record and effectively protect the actual diversity of life in the oceans.”
Source: Hanieh Saeedi (Senckenberg Research Institute and Nature Museum Frankfurt), Nature Communications, doi: 10.1038/s41467-026-73613-z