Biol. Mar. Mediterr. (2009), 16 (1): 302-303
R. Sandulli, R. D’Addabbo1, M. Gallo1, F. Semprucci2, P. Colantoni2, G. Baldelli3, M. Balsamo2 Università di Napoli ‘Parthenope’, DiSAm, Centro Direzionale Is. C4 - 80143 Napoli, Italia.
[email protected] 1 Università di Bari, Dipartimento di Zoologia, Via Orabona, 4 - 70125 Bari, Italia. 2 Università di Urbino ‘Carlo Bo’, Dip. SUAN, Campus Scientifico, Loc. Crocicchia - 61029 Urbino, Italia. 3 Istituto di Scienze della Terra, Università di Urbino ‘Carlo Bo’, Italia.
MEIOFAUNAL DISTRIBUTION IN RELATION TO DIFFERENT TYPES OF HABITATS (NORTH ARI ATOLL, MALDIVE ARCHIPELAGO) DISTRIBUZIONE DELLA MEIOFAUNA IN RELAZIONE A DIVERSI TIPI DI HABITAT (ATOLLO DI ARI NORD, ARCIPELAGO DELLE MALDIVE) Abstract - The present study deals with the meiofauna of some subtidal sediments located in the North Ari Atoll. Four types of habitats were sampled: a ‘pass’, a ‘thila’, an inner slope and a cave; showing that the communities were linked to the habitat type and in particular to depth. The new records of some tardigrade species for Maldive Islands and the finding of two species new to science are worth of note. Key-words: Meiofauna, Tardigrada, depth distribution, habitat, Maldives.
Introduction - Scarce information about meiofauna and tardigrades from subtidal sediments of the Maldivian coral reefs is available (Gallo D’Addabbo et al., 2006; Sandulli et al., 2006). We report here the results of an investigation carried out during the XI “Albatros” Scientific Cruise (May 2007) at North Ari Atoll (western side). In particular, the present study aims to investigate the abundance, structure, and diversity of meiofauna, with emphasis on the taxon Tardigrada, in different subtidal typologies of habitat and in a progressive depth gradient. Materials and methods - Overall, 21 stations were sampled at North Ari: a ‘pass’ slope (T1: from 14 m to 51,5 m depth), and an inner reef slope (T2: 8-32 m) at Gangehi Kandu, a ‘thila’ slope at Berucolo Falhu (T3: 14-34 m) and a cave at Feridhoo (T4: 64 m). Samples were collected by means of SCUBA-divers via hand-coring (surface area: 6.2 cm2). Meiofauna were anaesthetized with a MgCl2 solution and preserved with 5% neutralized formalin-seawater. Animals were generally extracted from the sediment by decantation technique and all individuals were sorted and counted per taxa under stereomicroscope. Tardigrades were individually studied in compound microscopy. Results - The meiofaunal abundance showed the lowest value at the cave (T4, 590 ind. 10 cm-2) and the highest one at the ‘pass’ (T1, 2202.87±1255.21 ind. 10 cm-2), very similar to that at the ‘thila’ (T3, 2194.00±995.12 ind. 10 cm-2). The meiofaunal community appeared rather rich and well diversified (15 total major taxa, 1.40≤ H’≤2.76, 0.47 ≤J≤0.74). The community was composed mainly by crustaceans (61%), nematodes (26%), and annelids (7%). The composition and diversity of meiofauna were generally comparable to those previously observed in the communities from the Central part of archipelago, while the abundance was quite lower than that recorded at similar depths (Sandulli et al., 2006; Semprucci et al., 2008). The multivariate analysis showed that the structure of meiofaunal assemblages was affected both by
Meiofaunal distribution in relation to different types of habitats (North Ari Atoll, Maldive Archipelago)
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depth and habitat type. In particular, significant differences among the four habitats have been shown by ANOSIM (Global R=0.40; p=0.002), and a subdivision of the sampled areas into two main groups: T4 (the deepest stations) and T3, T1 and T2 (progressively shallower habitats) was highlighted by the Cluster Analysis (Fig. 1). Also, the diversity index (H’) among the habitats resulted significantly different (ANOVA p
