Home » Diversity of Planktonic Copepods in the Black Sea

Diversity of Planktonic Copepods in the Black Sea

In their paper, A. Gubanova and D. Altukhov tell about what happened with the Black Sea copepods for the last 40 years

Text, photos, figures: Аlexandra Gubanova, Denis Altukhov, 2009.
Authorised Translation, videos: Antonina Khanaychenko, 2009

Copepods are the most abundant and diverse group of Crustaceans. Their name originates from two Greek words: kope – oar/paddle, and poda – leg, and describes the shape of their swimming legs. Despite copepods size is rather small – for free swimming copepods it varies from 0,3 to 15 mm , they play significant role in the seas and oceans, being the central component of marine ecosystems. That is because the copepods – is the most abundant group of metazoan (multi-cells animals) on the Earth, and copepod aggregations are the hugest bulk of proteins in the World Ocean. Besides, most of them, being phytophages (microalgae feeders) link the phytoplankton production and fish production (as a lot of fish species and their larvae graze on copepods). Moreover, a lot of other marine animals, the oceanic giants – cetaceans as well, eat the copepods. Copepods are very widely spread. They inhabit marine and fresh waters, live on the sea floor and in water column. A large part of copepod species are parasites. Copepoda subclass is divided into 10 different orders. But the majority of marine plankton (living in water column and moving with water masses) copepods are those from Сalanoida and Cyclopoida orders.

 

Variability of body forms in subclass СOPEPODA- 10 orders: 1 - PLATYCOPIOIDA; 2 - CALANOIDA; 3 - MORMONILLOIDA, 4 - HARPACTICOIDA; 5 - POECILOSTOMATOIDA; 6 - SIPHONOSTOMATOIDA; 7 - MONSTRILLOIDA; 8 - MISOPHRIOIDA; 9 - CYCLOPOIDA; 10 - GELYELLOIDA (Huys and Boxhall, 1991)

The Black Sea copepod species are not numerous. This fact is explained by rather low (brakishwater) salinity -18‰ – 18 g per litre (about 2 times less than in the Mediterranean Sea), cold winter temperatures (sometimes below 5 Celcium degrees) and hydrosulphuric lifeless zone from the depths 150-200 m to more than 2000 m Black Sea depths. From 170 species of plankton copepods of the neighbor sea (Aegean Sea) only about 10 species were able to overcome the double ecological barrier and settle in the Black Sea. But even these several Black Sea copepod species belong to very different ecological groups. Pseudocalanus elongatus (Boeck, 1872), Calanus euxinus Karavaev, 1894, Oithona similis Claus, 1866 – are the representatives of the cold water zooplankton. During the summer-time these species inhabit deep waters, during the winter time – inhabit the surface waters.

 

 

 

Acartia clausi Giesbrecht, 1889 , A. margalefi Alcaraz, 1976, Oithona nana Giesbrecht, 1892, Paracalanus parvus (Claus, 1863) are abundant in the Black Sea all year round.

 


 

 

 

 

 

Stenothermic thermophilic species (those prefer rather constant warm temperatures): A. tonsa Dana, 1849 and Centropages ponticus Karavaev, 1894 – are absent in plankton during the cold season, and appear in May when the water temperature increase to 15 – 16°С. During the summer-time these crustaceans reproduce very quickly and increase to maximum their number. Besides so called, summer, or subitant eggs, females of these copepods during the temperature decrease produce latent, or diapauses, or resting eggs. This adaptation garantees survival of eggs (and thus species population) in the bottom deposits of the seabed during unfavourite conditions. Increase of day length and temperature, besides oxygen saturation after winter- spring storms works like a biological trigger and stimulates embryos development, hatching (video) and practically simulataneous copepods “bloom”. But part of eggs can stay in bottom deposits, presenting genetic “bank” of population inaccessible for plankton predators and well protected for future against any unfavourable conditions.

 

 

  

 

Look on the following Table how the Black Sea coastal copepod species composition has been changed since 60-s of the XX century till present (example of Sevastopol Bay)

 

Table. Changes of the copepod species composition in Sevastopol Bay (results of 40 years observations)

 


In 1976 г. 12 copepod species inhabited Sevastopol Bay. In 1970-s the species composition started to change: new species – Acartia tonsa, supposed to be brought to the Black Sea with ballast waters from its native North America Atlantic Ocean coastal zones. During the same period, another species - Paracartia latisetisa - decreased its number and disappeared forever.



Even more significant changes in the Black Sea Species composition were observed during 1989-1990 when two species more: Oithona nana and A margalefi – disappeared while till 1990-s they dominated zooplankton in the Black Sea coastal zone. During this period the number of the Black Sea species decreased from 10 to 7. Thereafter, from 1995 till 2000-s, not the species number but the total abundance of copepod number decreased 10 times in comparison with 70-s. These Dramatic changes in Black Sea zooplankton were observed after the introduction (again through ballast waters) of the new predator – jelly fish Mnemiopsis leidiy. In September 1990 its number in Sevastopol Bay increased to 5157 specimens per м2, and in summer 1995 – to 7000 specimens per м2. Fortunately after introduction of another jelly fish Beroe ovata (grazing specifically and only on Mnemiopsis leidiy) into the Black Sea waters the copepod species increased in 2002.

In 2005 new species, copepod Oithona brevicornis was as other alien species introduced into the Black Sea with the ship ballast waters. In the autumn 2006 new alien copepod Oithona brevicornis dominated in Sevastopol Bay. Thus, during 30 years monitoring (1976-2006) 2 species disappear and 1 new species appear in Sevastopol Bay.