Calanus finmarchicus

Calanus finmarchicus
Name	Calanus finmarchicus
Regnum	Animalia
Phylum	Arthropoda
Subphylum	Crustacea
Classis	Copepoda
Ordo	Calanoida
Familia	Calanidae
Genus	Calanus
Species	C. finmarchicus
Binomial	Calanus finmarchicus
Binomial authority	(Gunnerus, 1770)

Calanus finmarchicus is a species of marine copepod found throughout the North Atlantic Ocean and adjacent seas. It is a keystone species in pelagic ecosystems, forming a critical link between primary production and higher trophic levels. Its population dynamics have significant implications for fisheries and biogeochemical cycles.

Description and morphology

The species exhibits a classic calanoid body plan, with a segmented structure comprising a cephalothorax and an abdomen. Adults typically range from 2.5 to 4 millimeters in length, with females being slightly larger than males. The body is translucent with distinctive red pigmentation from carotenoid pigments, particularly astaxanthin. Key morphological features include long, sensory first antennae (antennules), five pairs of thoracic appendages used for feeding and locomotion, and a prominent rostrum projecting from the head. The caudal rami at the posterior end are equipped with setae. Internally, a large oil sac is a defining characteristic, used for energy storage and buoyancy control.

Life cycle and reproduction

The life cycle involves six nauplius larval stages followed by five copepodite stages before reaching adulthood, a process heavily influenced by water temperature and food availability. Reproduction is closely tied to the spring bloom of phytoplankton, with females producing successive batches of eggs following mating. Egg production rates are a key metric studied at institutions like the Sir Alister Hardy Foundation for Ocean Science. A crucial adaptation is the ability to enter a state of diapause, typically during the fifth copepodite stage (CV), where they migrate to deep waters and remain in a state of physiological dormancy for several months to overwinter.

Distribution and habitat

It is a cold-temperate species with a core distribution spanning the Norwegian Sea, the Iceland Basin, the Labrador Sea, and the North Sea. Its range extends from the Gulf of Maine in the west to the Barents Sea in the east. It is predominantly an oceanic species, inhabiting the epipelagic zone and mesopelagic zone down to depths of over 1000 meters during diapause. Distribution patterns are strongly influenced by major ocean current systems such as the North Atlantic Current and the East Greenland Current. It is notably absent from the warmer waters of the Mediterranean Sea.

Ecological role and importance

This copepod is a fundamental component of the North Atlantic food web, often constituting over 50% of the zooplankton biomass. It is a primary grazer on diatoms and other phytoplankton, effectively transferring energy from primary producers to higher predators. It serves as the principal prey for a vast array of species, including larval Atlantic cod, Atlantic herring, North Atlantic right whale, and basking shark. Its grazing activity and subsequent production of fecal pellets facilitate the biological pump, exporting carbon from the surface ocean to the deep sea. Changes in its abundance, monitored by programs like the Continuous Plankton Recorder survey, are considered a key indicator of ecosystem health and climate change impacts.

Physiology and adaptations

Physiological adaptations are central to its success in a variable environment. The large lipid reserves, primarily wax esters, provide energy for overwintering, reproduction, and buoyancy regulation. Enzyme systems like citrate synthase are studied as biomarkers of metabolic activity. It exhibits vertical migration behaviors, moving to surface waters at night to feed and descending during the day to avoid visual predators like sand eel. Its respiration rate and ingestion rate are highly temperature-dependent, making it sensitive to ocean warming. The diapause phase involves dramatic reductions in metabolic rate and the activation of specific molecular chaperone proteins for cellular protection.

Research and economic significance

It is one of the most studied marine zooplankton species globally, with foundational work conducted at the Marine Biological Association of the United Kingdom and the University of Oslo. Research focuses on its role in ecosystem-based management of fisheries, as its abundance directly affects recruitment of commercially important gadoids. It is also harvested in limited quantities in the North Sea for use as a live feed in aquaculture, particularly for Atlantic halibut and turbot larvae. Its lipids are of interest to the nutraceutical industry. Long-term data from the Continuous Plankton Recorder survey, initiated by Sir Alister Hardy, have been instrumental in documenting its responses to phenomena like the North Atlantic Oscillation and broader climate variability.

Category:Calanoida Category:Zooplankton Category:Fauna of the Atlantic Ocean