There are thought to be up to 2 million species living in the oceans, with some estimates putting the figure higher.
So far, we know about fewer than 250,000 ocean species. But, could there be plenty more fish in the sea?
The Current Count of Ocean Biodiversity
This number encompasses a wide variety of life forms. Below are some statistics on different ocean animal groupings:
Fish: ~32,000 known species.
Corals: ~6,000 known species.
Molluscs: ~85,000 known species.
Crustaceans: ~50,000 known species.
Marine Mammals: ~130 known species.
Plankton and Microorganisms: These tiny but vital creatures are poorly understood, with potentially millions of species still unclassified.
Why Are So Many Ocean Species Undiscovered?
Several factors contribute to the high number of undiscovered ocean species:
Difficulty in accessing depths
The ocean is incredibly deep, with the deepest point, the Mariana Trench, reaching approximately 10,935 metres. Such depths are challenging to explore, requiring specialised equipment and technology.
Vastness of the Ocean
The ocean covers 71% of the Earth’s surface and holds over 1.3 billion cubic km of water. Due to its vastness, it’s difficult to understand where to search for new species.
Species Size and Camouflage
Many marine species have evolved to blend in with their environments, making them difficult to detect. Meiofauna, animals from 500 microns to 63 microns, are abundant but difficult to study because of their size and that many species look similar. There is also a lack of expertise in these groups globally.
Lack of Resources and Technology
Financial and logistical limitations still pose significant barriers. Developing and deploying the necessary equipment for deep-sea exploration is costly and complex. A lack of investment in taxonomic expertise is also a major limiting factor.
Environmental Changes
Through anthropogenic stresses such as overfishing and the destructive effects of fishing, habitat destruction, the effects of invasive species, pollution and the effects of climate change, such as ocean warming and acidification, some species may be becoming extinct before they are even found.
How do we know what we do not know?
The disparity between known and estimated marine species highlights the vastness and complexity of ocean life. Scientists use various methods to estimate the total number of marine species, each with inherent limitations.
One common approach involves understanding the number of unknown species from a specific sample or region, scaling it up to generate a global estimate.
Another approach leverages taxonomic classification, assessing the rate of discovery of new families, orders, or individual species to estimate the total number. This method considers the rate at which new species are described over time to project how many might still be undiscovered.
Due to varying assumptions and data sets, estimates can differ widely.
Interested in following the journey of discovery?
In a time of rapid environmental change, the work of The Ocean Census is more critical than ever.
As a leading force in accelerating marine species discovery, The Ocean Census plays a crucial role in expanding our understanding of the Earth’s biodiversity and underscoring the urgency of conservation efforts.
Join us on our journey of discovery by getting involved.
Featured image credits: Amanda Cotton / Ocean Image Bank
Image on Right credits: Vincent Kneefel / Ocean Image Bank
