Aquatic biodiversity considers the extent of species richness, both plants and animals, existing in aquatic ecosystems. In a study from 2011, it was estimated that on Earth there are approximately 8.7 million species, although only a small percentage have been discovered, and of this about 2.2 million species are marine1. Clearly, the world’s waters are comprised of a vast amount of unique species.
Aquatic biodiversity is not only limited to marine ecosystems, it includes freshwater habitats as well. However, considering that marine environments are much deeper, larger and represent 97% of the globe’s water, the degree of biodiversity is much greater.
There are many species which reside solely in water bodies such as different species of fish and others which spend their time both in the water and on land, such as toads. There are also species which switch between living in freshwater and marine environments. Anadromous species like salmon spawn in freshwater and then migrate to marine environments. Conversely, catadromous species such as eels, breed in marine environments and then migrate to freshwater habitats.
Furthermore, aquatic biodiversity in ocean varies with depth and location. For example, the ocean is home to coral reefs and kelp forests which are found in shallow waters. Additionally, the deep ocean preserves species capable of chemosynthesis living in undersea hot springs.
Aquatic biodiversity is expansive and thus, preserving this biodiversity is of the upmost importance. It is believed that the ocean is home to the largest amount of endemic phyla, about 132. Being endemic means that these phyla can only be found in one geographical region. To put this into perspective, on land there is only 1 endemic phylum present2. Evidently, aquatic ecosystems are anything but ordinary.
References:
1. Mora, C., Tittensor, D.P., Adl, S., Simpson, A.G.B., and Worm, B. (2011). How many species are there on Earth and in the ocean. PLOS Biology, 9(8): e1001127. doi:10.1371/journal.pbio.1001127
2. Angel, V.M. (1993). Biodiversity of the pelagic ocean. Conservation Biology, 7(4): 760-772.
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