The estimated number of marine species on Earth varies widely, with different sources providing different figures. Some estimates range from 2 million to 100 million species, while others suggest even higher numbers. Here are a few widely cited estimates:
World Register of Marine Species (WoRMS): WoRMS, a global information system on marine species, currently lists approximately 245,000 accepted species in the world's oceans. This number is constantly updated as new species are discovered or described, and it only includes species that have been formally described and classified. WoRMS estimates that the total number of marine species could be in the range of 500,000 to 1 million or higher, with most of the undiscovered species likely to be small or less visible organisms like worms, crustaceans, and microscopic zooplankton.
Census of Marine Life (CoML): The Census of Marine Life, a major international research effort completed in 2010, estimated that there could be as many as 10 million marine species on Earth. This estimate is based on extrapolations from the number of known species and estimates of the diversity of various marine habitats. CoML researchers emphasized the challenges of accurately counting marine life, particularly due to the vastness and inaccessibility of the oceans.
Species 2000: Species 2000, a global initiative to catalog all known species on Earth, provides an estimated range of 2 million to 100 million marine species. This range is based on extrapolations from the known number of species in different taxonomic groups and estimates of the potential number of species in underexplored habitats.
It's important to note that the true number of marine species is likely to remain uncertain for some time due to the challenges of exploring and sampling all marine habitats and the complexity and interconnectedness of marine ecosystems. Continuous scientific research and exploration contribute to the increasing knowledge and understanding of marine biodiversity.