Carbon sources of Antarctic nematodes as revealed by natural carbon isotope ratios and a pulse-chase experiment

δ13C of nematode communities in 27 sites was analyzed, spanning a large depth range (from 130 to 2,021 m) in five Antarctic regions, and compared to isotopic signatures of sediment organic matter. Sediment organic matter δ13C ranged from −24.4 to −21.9‰ without significant differences between regions, substrate types or depths. Nematode δ13C showed a larger range, from −34.6 to −19.3‰, and was more depleted than sediment organic matter typically by 1‰ and by up to 3‰ in silty substrata. These, and the isotopically heavy meiofauna at some stations, suggest substantial selectivity of some meiofauna for specific components of the sedimenting plankton. However, 13C-depletion in lipids and a potential contribution of chemoautotrophic carbon in the diet of the abundant genus Sabatieria may confound this interpretation. Carbon sources for Antarctic nematodes were also explored by means of an experiment in which the fate of a fresh pulse of labile carbon to the benthos was followed. This organic carbon was remineralized at a rate (11–20 mg C m−2 day−1) comparable to mineralization rates in continental slope sediments. There was no lag between sedimentation and mineralization; uptake by nematodes, however, did show such a lag. Nematodes contributed negligibly to benthic carbon mineralization

Deep-Sea Nematodes Actively Colonise Sediments, Irrespective of the Presence of a Pulse of Organic Matter: Results from an In-Situ Experiment

A colonisation experiment was performed in situ at 2500 m water depth at the Arctic deep-sea long-term observatory HAUSGARTEN to determine the response of deep-sea nematodes to disturbed, newly available patches, enriched with organic matter. Cylindrical tubes,laterally covered with a 500 µm mesh, were filled with azoic deep-sea sediment and 13C-labelled food sources (diatoms and bacteria). After 10 days of incubation the tubes were analysed for nematode response in terms of colonisation and uptake. Nematodes actively colonised the tubes,however with densities that only accounted for a maximum of 2.13% (51 ind.10 cm−2) of the ambient nematode assemblages. Densities did not differ according to the presence or absence of organic matter, nor according to the type of organic matter added. The fact that the organic matter did not function as an attractant to nematodes was confirmed by the absence of notable 13C assimilation by the colonising nematodes. Overall, colonisationappears to be a process that yields reproducible abundance and diversity patterns, with certain taxa showing more efficiency. Together with the high variability between the colonising nematode assemblages, this lends experimental support to the existence of a spatio-temporal mosaic that emerges from highly localised, partially stochastic community dynamics

Colonization of azoic sediment by sublittoral meiofauna in Gullmar Fjord -- Swedish west coast

Settling boxes with azoic, artificial or natural, sediment were exposed on a soft bottom at 27 m depth in May 1979. One box of each type was sampled every other month for one year and also in October 1980 and 1981. The harpacticoids dominated the early colonizations, with 67% of total abundance in both sediments after two months. Temporary meiofauna showed high autumn numbers. Other meiofauna groups showed low colonizaton rates. After 1 1/2 year of exposure the total abundance (3.6.10 super(3) ind./10 cm super(2)) and biomass (2.5.10 super(-3) g ash-free dry weight/10 cm super(2)) were still significantly lower than in the surrounding sediment

Effekter på bentisk meiofauna i modellekosystem exponerade för två olika raffinaderiavloppsvatten

Meiofauna dvs djur som kan insamlas på såll med maskstorleken 0.04-1 mm, utgör en grupp som är mycket väl lämpad för biologiska tester av olika substanser. Genom att dessa djur är så små och ofta förekommer med flera miljoner individer per kvadratmeter, kan man här studera effekter på samhällsnivå inom en mycket begränsad yta. Även om den undersökta substansen inte har direkt letala effekter, gör meiofaunans vanligtvis korta generationstid att exempelvis effekter på reproduktionen snabbt kan återspeglas i minskande antal och biomassa.Meiofauna dvs djur som kan insamlas på såll med maskstorleken 0.04-1 mm, utgör en grupp som är mycket väl lämpad för biologiska tester av olika substanser. Genom att dessa djur är så små och ofta förekommer med flera miljoner individer per kvadratmeter, kan man här studera effekter på samhällsnivå inom en mycket begränsad yta. Även om den undersökta substansen inte har direkt letala effekter, gör meiofaunans vanligtvis korta generationstid att exempelvis effekter på reproduktionen snabbt kan återspeglas i minskande antal och biomassa