So you know that copepods make a healthy meal for the inhabitants of your reef, but what else do they do? It turns out that copepods are more important to the planet than you might think, and have more use to people beyond their inclusion in aquariums.

To date, there have been around 13,000 species of copepods described, from all around the world. They are of course found in the ocean, but copepods are also found almost anywhere there is moisture; underground caves, swamps, puddles…the list goes on. Being found everywhere and in prolific numbers, copepods as a group are thought to make up the largest biomass on the planet and are thus extremely important to the global carbon cycle.

The top layers of the ocean make up the world’s largest carbon sink, sequestering more carbon (around 2,000,000,000 tons worth) than even the world’s forests, which makes sense since about 70% of our planet’s surface is covered in water. Planktonic copepods contribute to this major carbon sink by feeding on phytoplankton at the surface during the night and then retreating to the depths during the day to avoid predation or through seasonal migration to the depths in the case of Calanus finmarchicus. The excrement and shed exoskeletons produced and respiration performed by copepods while they are deeper in the water column helps seal away carbon in the ocean depths where it is locked away from the atmosphere.

Beyond the aquarium, copepods have uses in mosquito control and ecotoxicity testing of water.Because copepods are ecologically important, easily reared in a laboratory and the nauplii are sensitive to toxins they are a prime organism for testing the toxicity of water.

Copepods of the Mesocyclops genus are known to prey on mosquito larvae and are used in their control as a nontoxic and inexpensive solution. They are administered to tires or other vessels that collect rainwater or temporary pools where mosquitoes lay their eggs. This is an extremely valuable application as mosquitoes are vectors for numerous nasty diseases, including malaria which was responsible for 731,000 deaths in 2015.

For further elucidation of these topics you can check out these papers:

Marten, G.G., Bordes, E.S. & Nguyen, M.,1994.Use of cyclopoid copepods for mosquito control.Hydrobiologia.292/293:491-496

Lavorante, B.R.B.O., Oliveira, D.D., Costa, B.V.M., Souza-Santos, L.P.,2013.A new protocol for ecotoxicological assessment of seawater using nauplii of Tisbe biminiensis (Copepoda:Harpacticoida).Ecotoxicology and Environmental Safety.95:52-59

Jónasdóttir, S.H., Visser, A.W.,Richardson, K.,Heath,M.R., 2015 Seasonal copepod lipid pump promotes carbon sequestration in the deep North Atlantic. Proceedings of the National Academy of Sciences.112(39)

Marine Ecotoxicology: Current Knowledge and Future Issues

Biological and Physical Pumps of Carbon Dioxide, Hannes Grobe 21:52, 12 August 2006 (UTC), Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany