Calanus finmarchicus is a small marine copepod found in immense quantities across the North Atlantic Ocean. This tiny crustacean, though only a few millimeters long, plays a fundamental role in the intricate web of marine life. Understanding this organism provides insight into the health and productivity of one of the world’s most dynamic ocean regions.
Biology and Habitat
Calanus finmarchicus is a type of zooplankton, small animals that drift in ocean currents. It measures between 2 to 4 millimeters, making it a relatively large copepod. This species collectively forms an enormous biomass in the North Atlantic, particularly in the Norwegian Sea, North Sea, off the coast of Canada, and in the Gulf of Maine.
It thrives in the colder North Atlantic, enduring temperatures from approximately -2 °C to 22 °C, though most abundant in cooler conditions. It inhabits depths from the ocean surface down to about 4,000 meters, adapting to various environmental conditions, including salinity levels between 18 and 36 parts per thousand. Its diet primarily consists of phytoplankton, such as diatoms and dinoflagellates, which are microscopic photosynthetic organisms. It may also consume microzooplankton.
Life Cycle and Adaptations
The life cycle of Calanus finmarchicus involves several distinct developmental stages, progressing from eggs through multiple naupliar and copepodite stages before reaching adulthood. A key adaptation is diapause, a state of suspended animation similar to hibernation. This allows the copepod to survive periods of limited food availability and harsh environmental conditions, particularly during the winter months.
During diapause, typically occurring in late pre-adult stages (Copepodite Stage V), Calanus finmarchicus descends into deep waters, often between 500 to 1,500 meters, where it becomes metabolically quiescent. This deep-water refuge helps it conserve energy and avoid predators in the surface waters. The duration of diapause is influenced by the amount of stored lipids and the temperature of the overwintering depths, with warmer temperatures potentially leading to increased lipid depletion.
Ecological Significance
Calanus finmarchicus links primary producers and higher trophic levels in the North Atlantic marine food web. It grazes on phytoplankton, converting this energy into a form consumable by many marine organisms. This makes it a primary food source for many commercially important fish species, including cod, herring, mackerel, and blue whiting. Beyond its role in feeding fish, Calanus finmarchicus also supports seabirds and marine mammals, such as whales.
This copepod contributes to the biological carbon pump, a process that moves carbon from the ocean’s surface to its depths. Through its vertical migrations and dense fecal pellets, Calanus finmarchicus helps sequester carbon, contributing to global carbon cycling. The estimated carbon sequestration rate by the Calanus finmarchicus lipid pump can be as high as 11.5 grams of carbon per square meter per year.
Nutritional Profile and Commercial Relevance
Calanus finmarchicus has a distinct nutritional composition. It is rich in beneficial lipids, including omega-3 fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as astaxanthin, a powerful antioxidant. These oil components distinguish it from other marine oil sources.
The growing aquaculture industry recognizes Calanus finmarchicus as a sustainable and nutritious feed ingredient for farmed fish and shrimp. Its inclusion in aquaculture diets has been shown to improve growth performance, feed utilization, and overall health, including enhanced intestinal health and immune response in species like European sea bass. Beyond aquaculture, its rich lipid profile suggests potential for human consumption as a novel source of health supplements, an alternative to traditional fish oils.