Sea background
The pelagic zone

The pelagic zone covers the entire water mass from the surface down to the bottom, the bottom itself excluded. A myriad of organisms of various shapes and sizes can be found there. There the plankton is the base of the food chain.

Plankton is different from other organism because it lives in the water mass, usually in the upper ocean, and has very limited mobility. It is therefore highly dependent on ocean currents. Most planktonic organisms are tiny and poorly or not visible to the naked eye. However, there are also large groups of planktonic animals such as jellyfish.

The plankton is divided into two main groups: phytoplankton, which can photosynthesise and use solar radiation to produce organic matter from inorganic, and zooplankton that obtains organic materials by utilizing other organisms for food.

Zooplankton consists of various animal groups, such as crustaceans, cnidarians and ctenophores, but also the larvae stages of many benthic invertebrates and fish. The single most abundant groups is probably the crustacean copepods.

Zooplankton mainly feeds on phytoplankton, or other zooplankton and are themselves the main food for many other animal groups, from capelin to blue whales. It therefore "transfers" the primary production of the phytoplankton up the food chain to animals that cannot eat phytoplankton directly.

Extensive research on the plankton in Eyjafjörður was conducted from 1992 to 1993. There were found about 48 species or groups of planktonic animals of which 28 species are planktonic their entire life.

Larger animals in the pelagic zone, that can swim against the currents are called nekton. These are fishes, cephalopods and marine mammals. Several species of cephalopods have been found in Eyjafjörður, including the giant squid. However they are rare. Many species of fishes and marine mammals are common in Eyjafjörður.

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dyrasvif-1-bjarni eiriksson Aragrúi af örlitlum svifdýrum (Mynd: Bjarni Eiríksson) Aragrúi af örlitlum svifdýrum (Mynd: Bjarni Eiríksson)

svifdyr Nokkur algeng svifdýr í Eyjafirði - Heilsvif: 1. Þorndís séð að ofan, 2. Rauðáta séð frá hlið, 3. Sviflæg marfló, 4. Pílormur, 5. Rekhyrna, 6. Rekkringla - Hálfsvif: 7. Lirfa hrúðurkarls, 8. Lirfa slöngustjörnu, 9. Loðnulirfa, 10. Þorsklirfa. (Mynd: Kristín Líf Valtýsdóttir) Nokkur algeng svifdýr í Eyjafirði - Heilsvif: 1. Þorndís séð að ofan, 2. Rauðáta séð frá hlið, 3. Sviflæg marfló, 4. Pílormur, 5. Rekhyrna, 6. Rekkringla - Hálfsvif: 7. Lirfa hrúðurkarls, 8. Lirfa slöngustjörnu, 9. Loðnulirfa, 10. Þorsklirfa. (Mynd: Kristín Líf Valtýsdóttir)

 

 

 

 

 


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