Description: Deep-sea sediments beneath double-ridged crawling trails and around two sessile epibenthic species, the sea anemone Bathyphellia margaritacea Danielssen, 1890 and the demosponge Thenea abyssorum Koltun, 1959, were investigated to test whether they support a bacterial colonisation significantly higher than that of nearby control sediments. The centimetre-scale features and the control sites with a virtually undisturbed sediment surface were sampled in two basin-like depressions in Fram Strait (Molloy Deep, 5552 m; Hayes Deep, 3668 m), and on the eastern Greenland continental rise (3139 m) using a Remotely Operated Vehicle. The uppermost 5 cm-thick layer of the sediment around the two species and beneath the trails contained a significantly higher total bacterial biomass (TBB) than the control sediments. The higher TBB values resulted either from higher total numbers of sedimentary bacteria (TBN), from a higher mean biomass per cell (MBC), or both. Sediments beneath the crawling trails were inhabited by significantly more bacteria than the control sediment. The mean cell biomass of the bacteria did not differ. The TBN around the sea anemone B. margaritacea and in control samples were almost in the same range; the MBC around the anemones, however, was significantly higher than in the control sediments. The higher TBB in the sediment around the sponge T. abyssorum resulted from higher values of both TBN and MBC. Our results confirmed that small epibenthic species and crawling trails sufficiently modify the surrounding sediment-seawater interface to affect the abundance and biomass of sediment-associated biota. The biogenic structures locally increase bacterial colonisation at the sediment-water interface and thus potentially increase habitat heterogeneity for the smallest benthic organisms.

Description: The meiobenthos (including foraminiferans) of the Molloy Deep (Fram Strait, Arctic Ocean) was studied along a 15 km transect crossing the deep in NW-SE direction. Four stations between 5416 and 5569 m water depth were sampled during summer months between 1997 and 2001. In comparison with other abyssal and hadal regions of the World Ocean, meiofauna abundances were extremely high, ranging from 2153 to 2968 ind. / 10 cm² (values for the uppermost 5 cm of the sediments). The analysis of biogenic sediment compounds (e.g. chloroplastic pigments, particulate proteins) confirmed comparably high amounts of organic matter in the sediments, presumably favouring increased faunal densities and biomasses. Subsurface peaks in meiobenthic abundances at 1 - 2 cm sediment depth are most probably due to substantial disturbance and/or predation by dense herds of small holothurians (Elpidia glacialis), obviously inhabiting the entire Molloy Deep in very high numbers. Faunal composition of the meiobenthic community of the Molloy Deep was similar to other deep-sea regions. Foraminiferans were the dominant taxa of the total meiobenthos (48.5 - 59.9 %), whereas nematodes dominated the metazoan meiofauna (91.7 - 95.8 %). The total meiofauna of the Molloy Deep consisted of relatively small organisms compared to other/shallower oceanic regions, which could not be explained by reduced food availability to the benthos.

Description: The nematode assemblages of experimentally impacted and adjacent sediments in abyssal depths of the eastern equatorial Pacific were investigated seven years after a physical disturbance was set. A total of 3048 nematodes belonging to 68 genera and 26 families were identified. Abundance data were subjected to univariate and multivariate statistical analyses, which discriminate between sites based on their faunistic attributes. The nematode fauna at both disturbed and control sites was dominated by specimens belonging to the genera Acantholaimus, Chromadorita, Thalassomonhystera, Desmoscolex, Halalaimus and Diplopeltula. These genera contribute to about 55 % and 50 % of total nematode fauna in the disturbed and control sites, respectively. The mean relative abundance of the dominant genus Acantholaimus amounted to about 20 %. Generic diversity, evenness and richness at the undisturbed sites do not significantly differ from the corresponding median values at the disturbed sites. Mean k-dominance curves show differences in community structure between treatments. Ordination of Ö- and ÖÖ-transformed family abundances revealed groupings of the disturbed and undisturbed samples (significant at the 5 % level), whereas ordination of genus abundances did not. Sample variability was investigated by inspection of the relationship between variance and mean abundance of genera and families in each sample group and by calculating the comparative Index of Multivariate Dispersion (IMD). There is a clear increase in the standard deviation for a given mean of genus or family abundances at the disturbed sites. A higher variability among the disturbed samples, however, does not appear to be true in the multivariate sense.

Description: Six new nematode species are described from the sediment of a manganese nodule area of the abyssal eastern South Pacific: Aponema nympha sp.n., Caligocanna mirabilis gen.n. sp.n., Microlaimus discolensis sp.n., M. clancularius sp.n., M. porosus sp.n., and Bathynox clavata gen.n. sp.n.. The new genera Caligocanna and Bathynox are considered to belong to the Microlaimidae MICOLETZKY, 1922. The genus Caligocanna gen.n. differs from all other genera of the family Microlaimidae in combining the following characters: The six cephalic setae of the second circlet longer than the four cephalic setae of the third circlet. Annulated cuticle; annules with numerous longitudinal bars. Monospiral amphids turn ventrally. The genus Bathynox gen.n. differs from all other genera of the family Microlaimidae in having projecting, club-shaped corpora gelata and somatic setae positioned on peduncles.