From microbes to macrofauna: an integrated study of deep benthic communities and their response to environmental variables along the Malta Escarpment (Ionian Sea)

Abstract

SUMMARY: A comparative study for abundance, biomass and diversity was carried out for the prokaryote, meiofauna and macrofauna communities at three depth stations (1200, 1800 and 2100 m) along the Malta Escarpment (Mediterranean Sea). Our investigation showed a two-fold increase with depth in prokaryote abundance; the contribution of prokaryote biomass to the total benthic biomass was predominant at all depths. Bacteria were the dominant prokaryote component and Archaea formed a considerable fraction (20%-30%) of the prokaryote assemblages. The meio-and macrofauna abundances and meiofauna biomass did not decrease significantly with depth but macrofauna biomass did. The α diversity did not follow a clear bathymetric trend for both nematode and macrofauna species. Probably because of the large number of eurybathic nematode genera, nor did the turnover diversity in nematode composition change down the depth gradient. Conversely, for the macrofauna there was a perceptible change in community composition between the shallowest station and the two deeper stations. Food availability affected only the macrobenthic component. The increase in the prokaryote organisms with depth and the dominance of nematodes and macrofauna deposit feeders suggest active grazing by the two benthic components on microbes. This would transfer energy to the higher trophic levels through the microbial compartment.Keywords: prokaryote, meiofauna, macrofauna, abundance, biomass, diversity, Malta Escarpment, Mediterranean Sea.RESUMEN: Desde microorganismos a la macrofauna: un estudio comparativo de las comunidades bentónicas profundas y su respuesta a las variables ambientales a lo largo del talud de Malta (mar Jónico). -Se llevó a cabo un estudio comparativo de las comunidades de procariotas, meiofauna y macrofauna sobre la abundancia, biomasa y diversidad. Fue realizado en tres estaciones en varias profundidades (1200, 1800 y 2100 m) a lo largo del talud de Malta (mar Mediterráneo). Nuestra investigación muestra que, aumentando la profundidad, la abundancia de procariotas se duplica. La contribución de la biomasa procariota al total de la biomasa bentónica predominó en todas las profundidades. Las bacterias eran la fracción procariota dominante y junto con los Archaea representaban al 20-30% del total de procariotas. Por otra parte la abundancia de la meiofauna y macrofauna y la biomasa de la meiofauna no disminuían significativamente con la profundidad, mientras que la biomasa de la macrofauna sí lo hacía. La diversidad α no siguió una tendencia batimétrica muy clara para las especies de los nematodos y macrofauna. Probablemente debido a la gran abundancia de géneros de nematodos eurybatiales, la tasa derenovación de la diversidad en la composición de nematodos tampoco cambió por el gradiente de profundidad. En cambio, para la macrofauna hubo un cambio apreciable en la composición de la comunidad entre la estación más superficial y las dos estaciones más profundas. La disponibilidad de alimentos afectó sólo al componente macrobentónico. El aum...

Syllidae (Annelida: Phyllodocida) from the deep Mediterranean Sea, with the description of three new species

“…Studies on deep-sea meiobenthos usually focus on other, more abundant taxa, such as nematodes, that are considered more informative in studies aimed at assessing biodiversity patterns (Soetaert et al 1995;Danovaro et al 2009). Despite the small size, the Syllidae have been reported as an important component of deep sea assemblages by Kröncke et al (2003), Mamouridis et al (2011) and Baldrighi et al (2013Baldrighi et al ( , 2014. A large part of the material studied in this paper corresponds to that from Baldrighi et al (2014), who followed the taxonomic sufficiency approach (i.e.…”

“…Examined material was obtained during: 1) three oceanographic cruises carried out by the research vessel Urania (2011,2012,2015) (Baldrighi et al 2013;2014), 2) environmental monitoring campaigns carried out off Gorgona andCapraia Islands (Northern Tyrrhenian Sea, 2012-2017), 3) trawl bycatch (2014,2015), and 4) sediment traps placed in the southern Adriatic deepest region (2012) ( Table 1). Samples from Urania cruises were collected by a box corer (surface area 706.7 cm 2 ), other samples were collected by a van Veen grab (surface area 0.1 m 2 ).…”

“…This is particularly true for the assemblage composition and species diversity of several groups of benthic invertebrates (Danovaro et al 2010). Most taxonomic studies focused on molluscs (Bouchet & Taviani 1992;Koutsoubas et al 2000;La Perna 2004;Gofas et al 2014) and nematodes (Soetaert et al 1995;Danovaro et al 2009), while the few available studies dealing with polychaetes usually report their diversity at supra-specific level, focusing on ecology and avoiding taxonomic considerations (Mamouridis et al 2011;Baldrighi et al 2013;Romano et al 2013;Baldrighi et al 2014). The Syllidae (Annelida: Phyllodocida) often represent a major faunal component in hard bottom assemblages and are one of the most diverse polychaete families in shallow water ecosystems (Musco & Giangrande 2005;Musco 2012).…”

“…longocirrata Ørsted, 1845 for sediment traps moored in canyons in the western Mediterranean Sea. Subsequent works on Mediterranean deep-sea assemblages highlighted the occurrence of Syllidae in benthic communities, without a dedicated fine taxonomic analysis (Mamouridis et al 2011;Baldrighi et al 2013;2014).…”

Marine connectivity dynamics: clarifying cosmopolitan distributions of marine interstitial invertebrates and the meiofauna paradox

“…Of these, 40 papers reported an unchanged distribution of some of the focal taxa (accounting for 82 species), 25 reported an increase of distribution (including 112 species) and 22 a decrease of distribution (including 160 species). Only 27 papers used a combination of molecular and morphological data to assess species delineation (Todaro et al 1996(Todaro et al , 2014Curini-Galletti and Puccinelli 1998;Westheide and Hass-Cordes 2001;De Ley et al 2005;Sterrer and Sørensen 2006;Suatoni et al 2006;Leasi and Todaro 2007;Casu et al 2009;Neusser et al 2011;Eder et al 2011;Kieneke et al 2012;Jörger et al 2012; (Schmidt and Westheide 2000;Bhadury et al 2006;Todaro et al 2006;Casu and Curini-Galletti 2006;Bik et al 2010Bik et al , 2012Gruber-Vodicka et al 2011;Tulchinsky et al 2012;Baldrighi et al 2013;Yamasaki et al 2014;Fonseca et al 2014; Norenburg 2014, 2016;Meyer-Wachsmuth et al 2014;Scarpa et al 2015;Sahraean et al 2017). Moreover, 14 papers mentioned difficulties in morphological characterization of the considered taxa (we refer to this issue as the low-morphology problem, see below).…”