[Distribution of zooplankton community in Mediterranean-climate lakes].
The sometimes sharp thermal variations and irregular precipitations and force concentrated over short periods characterize the Mediterranean climate. The structure of the zooplanktonic settlement was analyzed during one year in three Algerian reservoirs (lakes) with different geographical and climatic situation, in relation to abiotic factors (temperature, dissolved oxygen, pH, suspended matter, carbonates, nitrogenized and phosphorated nutritive salts). A canonical correspondence analysis was used to estimate the influence of the abiotic factors on the temporal distribution. The studied lakes are located, on the one hand, in northern Algeria, in a sub-humid area (Lake Boukourdane) and, on the other hand, in the South of the country, in the arid region (Foum El Ghorza and Djorf Torba). Analysis of the environmental parameters indicates that there is a seasonal variation in the three reservoirs. In Lake Foum El Ghorza, the temperature and hydrology variations, linked with the arid climate, affects the concentration of dissolved oxygen, which strongly decreases (1.5 mg/l), involving a pH reduction; suspended matters are sometimes high, coming from the stripped catchment area, causing a turbidity in this not very deep lake. The study of the distribution of the species allowed us to highlight a seasonal temporal variation. Lake Boukourdane, in the sub-humid zone, has an increased specific richness (SR=13). The various species evolve in alternation during the annual cycle. The representative species of this lake is Copidodiaptomus numidicus, characteristic of the rainy and endemic zone of the western Mediterranean; it is dominant (67%) in the spring. The Stenothermal species Diaphanosoma brachyurum, endemic of hot waters, is common to the two lakes; it evolves particularly in the summer (51.3%) at Boukourdane, whereas it is perennial and dominant (55%) in the spring at Djorf Torba. The specific richness is lower in Djorf Torba (SR=7) and in Foum El Ghorza (SR=6). The species collected in these two lakes are common and cosmopolitan, but they are adapted to the extreme conditions of the arid climate. Nevertheless, the species evolving in Lake Foum El Ghorza have undergone a significant decline, which has reduced the number of species and their density in the summer-autumn period. Thus, we can say that in the studied lakes, the hydrological factors and the temperature related to the Mediterranean climate would be two of the principal causes of the temporal distribution of the species.
Cherbi
Malika
M
Université des sciences et de la technologie Houari-Boumediène, faculté des sciences biologiques, Alger, Algérie.
Lek-Ang
Sithan
S
Lek
Sovan
S
Arab
Abdeslem
A
D000462:Algeria; D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000032:analysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D033361:Cladocera; D002980:Climate; D003621:Daphnia; D005618:Fresh Water / Q000737:chemistry*; D019083:Mediterranean Region; D009566:Nitrates / Q000032:analysis; D011153:Population; D012403:Rotifera; D015048:Zooplankton
D009566:Nitrates; D002734:Chlorophyll; D002118:Calcium; D000077194:Chlorophyll A