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Little is known about the hypogean fauna of Algeria, with studies mostly dating to the beginning of the twentieth century (Gurney 1908; Racovitza 1912; Monod 1924; Pesce and Tetè 1978); moreover, the knowledge varies markedly among regions. In this study, we examined the composition and distribution of the invertebrate communities in the phreatic zone of the Tafna aquifer (N-W Algeria). Twelve wells close to the Tafna wadi, ranging between 120 and 1100 m a.s.l., were studied from May 2005 to March 2006. Many specimens belonging to 37 taxa were collected, the most frequent taxa being Typhlocirolana sp., a stygobitic Gammaridae species, Cyclopidae and Ostracoda. Other crustacean species were relatively scarce, with discontinuous distribution, being present only in a few wells. The taxonomic richness and abundance of stygobitic crustacean communities were relatively constant over time. The spatial distribution of stygobionts was mainly related to the exchanges with surface water. [ABSTRACT FROM AUTHOR]

A new species of hypogean cirolanid isopod, Typhlocirolana longimera sp. n. is reported and described from a region located in north-western Algeria. Typhlocirolana longimera sp. n. can be distinguished from all other species of the genus especially by the peculiar shape of the merus of pereiopod I longer than in any other Typhlocirolana species, and for the presence of 6 molariform robust conical robust setae, the bottle shape of uropods and the aesthetasc formula of flagellum in antennulae. The presence in the same region of the two already known species T. fontis and T. gurneyi is also discussed. [ABSTRACT FROM AUTHOR]

This study investigated temporal changes in the vertical distribution of invertebrates during periods of low flows in the Tafna wadi, a semi-arid Mediterranean river characterised by a general decline in average flows. The hyporheos was sampled along a 130-m stretch at depths of 0.3, 0.6 and 1 m in a pool-riffle sequence and a lateral gravel bar. Benthic fauna was collected on each sampling occasion from different locations in the studied sections. Sampling was conducted in two consecutive years (2014 and 2015) at the end of the spring (high waters) and over a 2-month period during the low summer flow. The results indicated that high surface water temperatures may initiate the movement of some taxa into the interstitial habitat, thus supporting the hyporheic refuge hypothesis. In the hyporheic zone, the low oxygen rates recorded deeper in the sediment and in the last low-flow months caused significant declines in taxonomic richness, and lower pH values resulted in a reduction in invertebrate abundances. In the benthic zone, high flow velocities increased richness but decreased invertebrate abundances. A large number of taxa were found in the gravel bar section reflecting the more suitable living conditions in this habitat compared with the river reach (high DO rates). [ABSTRACT FROM AUTHOR]

This study investigated the biodiversity and hydrochemistry of seven unconfined aquifers located in two hydrogeological complexes in the north-western region of Algeria. The aim of the study was to: (1) contribute new data on the biodiversity and distribution patterns of groundwater fauna in groundwater bodies in North Africa, (2) assess whether the current biodiversity patterns of groundwater taxa reflect the difference in aquifer type, hydrogeological conditions and hydrochemistry, and (3) evaluate the role of hydrogeological, geographical and physicochemical variables in determining the distribution pattern of groundwater invertebrates. Sixty-three wells were investigated between August 2010 and June 2013. In total, 41,297 specimens belonging to 51 taxa, 10 of which were crustaceans, were collected during the survey. Taxa abundances varied significantly between aquifer types, but not between the two hydrogeological complexes (continental and littoral). The groundwater assemblages collected in seven aquifers in northwest Algeria differed significantly between aquifer types in this region. The distribution of groundwater fauna across the whole study area was primarily affected by distance to streams, the geological period and electrical conductivity. Overall, the assemblages showed a spatial distribution that to some extent mirrored the hydrogeological and hydrochemical conditions of groundwater in the north-western part of Algeria. These findings suggest that groundwater biota, and crustaceans in particular, may play a key role in distinguishing between the typologies of the investigated aquifers. This study contributes to knowledge of current groundwater biodiversity in northwest Algeria and demonstrates that this knowledge is still far from being complete. [ABSTRACT FROM AUTHOR]