were the Radiolaria, Acantharia, Chaetognatha and the copepod Calanoides carinatus. The last two groups were more abundant in the coastal zone.
ZOOPLANKTON COMPOSITION, DISTRIBUTION AND ABUNDANCE IN THE BAY OF BISCAY AND ADJACENTS ATLANTIC WATERS FROM CETACEAN SIGHTING SURVEY Ana Miranda, G. Fernández, C. Eirín & S. Lens. Instituto Español de Oceanografía. Cabo Estai. Canido. Apdo. 1552. 36280 Vigo. Spain. http://www.vi.ieo.es
ABSTRACT In 1989 a Spanish shipboard sighting survey was carried out as part of a combined international cetacean´s survey in the North Atlantic ( NASS-89). The cruise had taken place during JulyAugust covering the Bay of Biscay and adjacent Atlantic waters between 42º- 52º N and 25º W. Zooplankton samples obtained during that cruise has recently being processed and analysed. Due to the relative scarce information available about the zooplankton of the area surveyed it was considered useful to present now this information. Data about the composition, distribution and abundance of the zooplankton fraction between 200 µm and 2 mm were obtained. The dominant groups in the oceanic area were Acantharia, Radiolaria and Amphipoda. In some stations these groups represented more than 50% on the plankton community. In the Bay of Biscay, apart from the groups found in the oceanic area, they also appeared Doliolida and the copepod Calanoides carinatus ( Krøyer, 1848). Abundances had range between 2 and 27 785 ind/m3 accounting for the wide extension and different thermohaline characteristics of the area sample. The groups with more than 500 ind/m3 were the Radiolaria, Acantharia, Chaetognatha and the copepod Calanoides carinatus. The last two groups were more abundant in the coastal zone.
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MATERIAL AND METHODS
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The survey was carried out in July-August 1989. The area covered was limited by the 42º - 52º N parallels, the 25º W meridian and the 200 m depth contour in the adjacent European continental shelf. The survey was carried out in two legs. The first leg covered the western most part of that area and the second one the Bay of Biscay proper.
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16 and 14 zooplankton sampling stations were carried out respectively. Sampling was done daily at dusk with the exception of station 3 (part 1) that was made during daylight, in coincidence witha high concentration of cetacean sightings ( Fig. 1). A BONGO net equipped with flowmeters and mesh size of 200 µm was used. Oblique tows were made using 150 m of wire and one intermediate stop when hauling the net. Zooplankton samples were preserved with a buffered 5% formalin solution. In the lab samples were analysed for taxa identification and abundance using a stereoscope microscope.
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RESULTS
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RESULTS Radiolaria
Gelatinous plankton in the coastal zone was mainly constituted by jellyfish, doliolids and salps. Great amounts of big jellyfish specimens were found in station 6 (part 1). In the more oceanic area apart from these groups, siphonophores also appeared.
Copepod species such as Rhincalanus nasutus (Giesbrecht, 1888), Rhincalanus cornutus (Dana, 1849), Paraeuchaeta tonsa (Giesbrecht, 1895), Centropages kröyeri (Giesbrecht, 1892) y Sapphirina sali (Farran, 1929) were found in some stations of the oceanic area, but normally not in more coastal waters (Rose, M.,1970). During this survey Temora stylifera (Dana, 1849), a thermophilic and very abundant species in the Mediterranean (Halsband –Lenk. C et al., 2001), was found in the inner station of the Bay of Biscay accounting for 7 % of the zooplankton community and an abundance of 8 ind/m3 (Rodríguez, N. & F. Alvarez- Marqués, 2004).
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Amphipods were another important group in the composition of the zooplankton community. Amphipod’s eggs were abundant in one of the most oceanic stations. Ostracods and pteropods were as well present in the most far away stations of the oceanic area. In spite of the high density of cetaceans sightings in some stations euphausiids were not abundant.
Ostracoda
Most common copepod species in the oceanic area were Paraeuchaeta hebes (Giesbrecht, 1888), Pleuromamma gracilis (Clauss,1863) and Centropages typicus (Krøyer,1849). In station 13 (second part), the closest to shore, the dominant species was Calanoides carinatus (Krøyer, 1848) (63 %) with 1,351 ind/m 3 . Although copepod abundances were very low at this station it had the highest copepod diversity.
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Fig. 1.-Situation of stations. NASS.89.
Small organisms such as radiolarids and acantarids were abundant in the mesozooplankton community and in some cases the dominant component (Fig.2 and Fig. 4). In some stations foraminifers, another small size group, were also an important part of the community. Within this group we have found Globigerina bulloides (d’Orbigny, 1826) in the Galician continental shelf waters . The specie Orbulina universa (d’Orbigny, 1839) was regularly found in more oceanic waters (Loeblich, A.R. & H.Tappan, 1988)
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Dominant groups of mesozooplancton
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Fig.2.- Abundance of mesozooplankton. Range of values was 2 ind/m3 to 27 785 ind/m3
REFERENCES
Copepoda
Acantharia
Radiolaria.
Amphipoda
Gelatinous plankton Foraminifera
Fig. 3.- Abundance of dominant groups (ind/m3).
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Ostracoda Other
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RADIOLARIA (0- 27 090 ind/m3)
ACANTHARIA (0- 1 170 ind/m3)
COPEPODA (0- 1 834 ind/m3)
Fig. 4.- Composition of mesozooplankton (%)
Halsband- Lenk, C., S. Nival, F. Carlotti and H. J. Hirche.- 2001. -Seasonal cycles of Egg Production of two planktonic copepods, Centropages typicus and Temora stylifera, in the North- Western Mediterranean Sea. J. Plankton Res., 23, 597-609. Loeblich, A.R. & H. Tappan.- 1988. Foraminiferal genera and their classification. in: Van Nostrand Reinhold ( Ed.) 970 pp. Rodríguez, N. & F. Álvarez-Marqués.- 2004.- Vertical distribution of Temora stylifera and T. longicornis ( SW Bay of Biscay). Poster U.K. Globec Meeting. Rose,M. .- 1970. Faune de France. Copépodes pélagiques.
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