Distribution of meiobenthos at bathyal depths in the Mediterranean Sea. A comparison between sites of contrasting productivity

Abstract

The Mediterranean Sea, one of the most oligotrophic basins in the world, is characterised by a west-east productivity gradient because of the hydrographic differences between its two subbasins, the different productivity levels in the surface waters and the variability in vertical fluxes of organic carbon to the seafloor (Danovaro et al., 1999 In order to study the distribution of meiobenthos (Metazoa and Foraminifera) at bathyal depths along a westeast productivity gradient in the Mediterranean Sea, stations along the continental slopes of the Balearic Sea, west Ionian and east Ionian Seas were sampled during the DESEAS Trans-Mediterranean Cruise in June-July 2001. Standing stock of total meiobenthos differed considerably among the sampling stations, with marked differences occurring between sampling depths and sites. At 600 m depth, meiobenthic abundances were slightly higher over the Balearic continental slope, whereas at the deeper stations (800 m and 1500-1700 m), abundances were significantly higher in the west Ionian Sea. Significant relationships were found between the abundances of major groups and the chloroplastic pigments, indicating that food availability is a major factor controlling the distribution of meiobenthos. Apart from the overall differences in productivity between the western and eastern Mediterranean Sea, local hydrographic features and topographic differences greatly influence the spatial variability of the environmental parameters within each sub-basin and thus the distribution of meiobenthos in the bathyal zone.Key words: meiobenthos, deep-sea, bathyal, Mediterranean Sea, Balearic Sea, Ionian Sea. RESUMEN: DISTRIBUCIÓN DEL MEIOBENTOS EN FONDOS BATIALES DEL MEDITERRÁNEO: UNA COMPARACIÓN ENTRE LUGARES DIS-TANTES. -Para el estudio del meiobenthos (Metazoa y foraminifera) en los fondos batiales del Mediterráneo a lo largo del gradiente de productividad oeste-este, se hicieron muestreos en la plataforma continental del mar Balear y del mar Iónico oriental y occidental, durante la campaña transmediterránea DESEAS (junio-julio, 2001). La biomasa permanente del meiobentos total difiere considerablemente entre las muestras de las distintas estaciones y profundidades. A 600 m de profundidad las abundancias de meiobentos fueron un poco más altas en la plataforma de Baleares, mientras que en las estaciones más profundas (800 y 1500-1700 m), las abundancias fueron significativamente más altas en el Iónico occidental. Se encontraron relaciones significativas entre las abundancias de los grupos mayoritarios y los pigmentos cloroplásticos, indicando que la disponibilidad de alimento es el principal factor que controla la distribución del meiobentos. Aparte de las diferencias globales entre la productividad del Mediterráneo oriental y occidental, son las características hidrográficas y las diferencias topográficas quienes influencian fuertemente en la variabilidad espacial de los parámetros ambientales en cada sub-cubeta, y por tanto, en la distribución del meibentos en la zona batial.

Deep-sea decapod crustaceans in the western and central Mediterranean Sea: preliminary aspects of species distribution, biomass and population structure

“…Our results are consistent with this suggestion, in that the abundance of decapods was higher than that of fishes (see Fig. 2 for depths below 1500 m) in the less productive waters in the eastern Ionian Sea (Tselepides et al, 2004). Like the above-mentioned west-east productivity gradient, increasing depth has also been positively correlated with a marked decrease in global productivity (Gage and Tyler, 1991 and citations therein).…”

“…The west-east productivity gradient reported in the Mediterranean Sea (Psarra et al, 2000;Tselepides et al, 2000Tselepides et al, , 2004 is an environmental feature that needs to be taken into account when one is comparing both the species distribution and the population characteristics considered in this study. Thus, the relative abundance of decapods vs. fish found among the sampling areas might be correlated to this west-east gradient.…”

Meiobenthos and nematode assemblages from different deep-sea habitats of the Strait of Sicily (Central Mediterranean Sea)

“…The composition on metazoan meiobenthic community at higher taxon level follows the general pattern characteristic for the continental slope of the temperate zone (Mokievskii et al, 2007). The relative percentage values of the most abundant meiobenthic groups fall within the limit reported from the Mediterranean slope (Soetaert et al, 1991;Danovaro et al, , 2000Danovaro et al, , 2013Tselepides et al, 2004;Lampadariou and Tselepides, Bianchelli et al, 2010). The ubiquitous presence of kinorhynchs is noticeable, confirming that this phylum is mainly composed by mud-dwelling species, well represented also in deep-sea sediments (e.g.…”

Latitudinal, longitudinal and bathymetric patterns of abundance, biomass of metazoan meiofauna: importance of the rare taxa and anomalies in the deep Mediterranean Sea

“…Indeed, the larger number of taxa (up to 17 taxa) was observed in the far Eastern basin, in sediments collected from a slope (ca. 1000 m) located in front of the Israeli coast and in sediments collected from the Nile fan [32].…”

“…Gambi et al sediments in the oceans worldwide (Table 1). These might be due to the fact that the Mediterranean basin (in particular its Eastern sector) is one of the most oligotrophic regions of the world [55], and since deep-sea fauna depends on the energy inputs coming from the euphotic zone [9,10,15,27,28,32,33,[42][43][44][45][46]59], the low quantity of organic matter reaching the deep-sea floor of the Mediterranean Sea limits the abundance and biomass of the meiofaunal assemblages. Surprisingly, we also found opposite spatial patterns of meiofaunal abundance and biomass moving across the deep-sea sediments of the Mediterranean Sea, as meiofaunal abundance decreased moving from the Western to the Eastern basin, while biomass increased (Table 1).…”