Meiofauna and harpacticoid copepods in different habitats of a Mediterranean seagrass meadow

Abstract

This study investigated whether associated meiobenthic communities, especially harpacticoid copepods, differed amongst habitats. Five pre-defined habitats within and next to the Posidonia oceanica seagrass meadow were sampled: living seagrass canopy leaves (LL), small (SMF) and large (LMF) macrophytodetritus fragment accumulations and sand, bare (BS) and covered (CS). The highest meiofauna abundances were recorded in the BS for the core sampled habitats (BS, CS, SMF and LMF) and in the LMF for seagrass material habitats (SMF, LMF and LL). Harpacticoid copepods were the most abundant taxon in all habitats. The assemblage composition at copepod family level showed two distinct habitats clusters: a leaf (LMF and LL) and a sediment cluster (BS, CS and SMF). Subsequently, stable isotope analyses were conducted to analyse the relationship between copepods and their potential food sources in seagrass material habitats. Based on d 13 C isotopic analyses and SIAR mixing model, harpacticoid copepods relied for 70% on epiphytes and for 30% on P. oceanica leaf material in the LMF and LL habitats.

Seasonal variability of meiofauna, especially harpacticoid copepods, in Posidonia oceanica macrophytodetritus accumulations

“…The macrophytodetritus accumulations harboured the same density in order of magnitude (10 4 -10 5 indiv. m −2 ) as P. oceanica meadows (Mascart et al, 2013;Novak, 1982). The diversity, around 30 to 50 harpacticoid species, was similar to other phytal ecosystems (De Troch et al, 2008;Heip et al, 1983;Hicks, 1977;Johnson and Scheibling, 1987;Steinarsdóttir et al, 2003).…”

“…The most abundant species in the macrophytodetritus accumulations were also commonly found in adjacent habitats (Hicks and Coull, 1983;Mascart et al, 2013;Novak, 1982). Colonisation by invertebrates is rapid, however, it is limited in its extent and magnitude (Norkko and Bonsdorff, 1996;Palmer, 1988).…”

“…No study, to our current knowledge, was ever performed on the harpacticoid copepod assemblage associated with seagrass macrophytodetritus. Mascart et al (2013) compared P. oceanica meadows, sediment and two types of macrophytodetritus accumulations. The macrophytodetritus accumulations showed higher meiofauna abundances than living seagrasses, without expressing a higher diversity.…”

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

“…Grazing meiofauna stimulate microbial activity by keeping the microbial population in its reproductive log-phase (Giere 2009). Many studies show that meiofauna feed on benthic microalgae, freshly sedimented phytodetritus and seagrass detritus (Lee 1980;Rudnick 1989;Riera et al 1996;Olafsson and Elmgren 1997;Buffan-Dubau and Carman 2000;Gooday 2003;Murray 2006;Torres-Pratts and Schizas 2007;Mascart et al 2013Mascart et al , 2015. Nematode responses to food availability as well as to other environmental factors can be species-specific with a complex relationship between species diversity and function (Dos Santos et al 2008).…”

“…They are the most abundant size class in the benthos and are closely connected to other compartments of the benthos (including prokaryotes and macrofauna; Baldrighi et al 2013). They play an important role in benthic food webs, not only as consumers (feeding on detritus, diatoms and algae, and preying on other small metazoans; Pergent et al 1994;Duarte and Cebrian 1996;Gee and Somerfield 1997;Mateo and Romero 1997;Gwyther 2003;Torres-Pratts and Schizas 2007;Mascart et al 2013Mascart et al , 2015, but also as producers (being a food source for macrofauna and fish; Gerlach 1978; Lebreton et al 2011;Vinagre et al 2012;Carpentier et al 2014). The abundance, diversity, distribution and functional properties of meiofauna can be affected by several abiotic factors, including temperature, salinity, hydrodynamic and sedimentary processes, sediment grain size, oxygenation level and food availability (Ingels et al 2011;Lizhe et al 2012;Ngo et al 2013;Zeppilli et al 2013;Górska et al 2014;Pusceddu et al 2014b), and also, by biotic factors such as predation and competition (Tita et al 2000;Danovaro et al 2007;Nascimento et al 2011;Braeckman et al 2013;Boldina et al 2014).…”