Low faunal diversity on Maltese sandy beaches: fact or artefact?

Abstract

Eight sandy beaches on Malta and two on Gozo were sampled for macrofauna to test the hypothesis that Maltese beaches have an intrinsically low diversity. Stations distributed in the supralittoral (dry zone), mediolittoral (wet zone) and upper infralittoral (submerged zone to 1 m water depth) were sampled by sieving core samples and standardised searching during daytime, and pitfall trapping and standardised sweeping of the water column using a hand-net at night, as appropriate. Physical parameters of the sediment were measured and human occupancy of the beaches was estimated.From the supralittoral and mediolittoral, 39 species represented by 1584 individuals were collected by the combined techniques of pitfall trapping, sieving and standard searching. For Ramla beach, which had the highest diversity, 267 individuals representing 25 infaunal species were collected by sieving from a combined volume of 1.175 m 3 of sand, and 149 individuals representing 28 epifaunal species were collected by standardised searching from a combined area of 700 m 2 of sand during two winter and two summer sampling sessions between 1992 and 1993. For nine other beaches sampled during the summer of 2000, only six macrofaunal species were collected from core samples, with overall population densities ranging from 4.13 to 45.45 individuals m ÿ2 . Only 92 individuals belonging to 12 species were collected by hand-net from the uppermost infralittoral of five beaches sampled using this method during the summer of 2000. Taxa of gastropods, bivalves, decapods, mysids and staphylinid beetles generally abundant on Mediterranean sandy beaches, were entirely absent from the beaches sampled.Few correlations that could explain the impoverishment of Maltese sandy beaches were found between physical parameters and faunal abundances, and other factors such as inadequate sampling effort, human disturbance and marine pollution were also excluded; however, seasonally biased sampling may partly explain the results obtained. One factor that may explain why certain species are missing could be lack of recruitment, due to Malta's geographical isolation from the European and African mainlands.

Distribution patterns of shallow water polychaetes (Annelida) along the Alexandria coast, Egypt (eastern Mediterranean)

“…and S. papillocercus, were clearly dominant. This observation confirms the results of previous studies carried out in the Mediterranean Sea, including the Egyptian coast, indicating that Mediterranean intertidal assemblages are characterized by low diversity if compared to other areas in the world (Dexter, 1989;Deidun et al, 2003;Papageorgiou et al, 2006;Pérez-Domingo et al, 2008).…”

“…In the Mediterranean Sea, the tidal range is limited compared to open oceans, with an average amplitude of a few centimetres. This feature that limits available space for faunal settlement might contribute to the intrinsic low faunal density and diversity characterizing Mediterranean intertidal sandy assemblages (Dexter, 1989;Deidun et al, 2003;Papageorgiou et al, 2006;Pérez-Domingo et al, 2008).…”

Benthic communities on a sandy Ligurian beach (NW Mediterranean)

“…The macrofauna abundance and biomass were lower than on other beaches (Deidun et al, 2003). Warwick and Clarke (2001) pointed out that perturbed benthic environments generally display low species diversity, often consisting of taxonomically closely-related species.…”

Habitat structure and zonation patterns of northwestern Mediterranean shoreline strands

“…Gauci et al (2005) demonstrated the inefficiency of pitfall traps for capturing organisms on shingle beaches. Low animal abundance was also observed in Malta when pitfall traps were used (Deidun et al 2003). The most frequent trap captures were Collembola (often representing more than 94% of the organisms at northern sites), Fucellia maritima and other diptera, as observed on other Mediterranean beaches (Colombini et al 2005).…”

“…Janssen and Mulder 2005, Rodil et al 2006, Rodil et al 2014, most research on the macroinvertebrate fauna from shoreline strands of the Mediterranean Sea has focussed on the organisms inhabiting lower infralittoral habitats (Pinedo et al 1997, Sardá et al 1999, Labrune et al 2007). To date, there are a few comprehensive accounts in the literature about the macroinvertebrates from Mediterranean Sea shoreline strands and beaches in general (Deidun et al 2003, Colombini et al 2003, Gauci et al 2005. Mediterranean shoreline strands are inhabited by animals ranging from tiny Collembola and flying insects to large bivalves and crustaceans (Marques et al 2003, Colombini et al 2005, Covazzi Harriague and Albertelli 2007.…”