Eubostrichopsis johnpearsei n. gen., n. sp., the first stilbonematid nematode (Nematoda, Desmodoridae) from the US West Coast

A new genus of the marine Stilbonematinae (Nematoda, Desmodoridae) is described from the Pacific coast of the United States of America. The worms inhabit the sulfidic sediment among the roots of the surfgrass Phyllospadix sp. in the rocky intertidal. The ectosymbiotic coat is of a new type for Stilbonematinae. It consists of rod-shaped bacteria pointed at both poles densely attached with one pole to the host cuticle. This is the first report of this symbiotic nematode subfamily from the US West Coast.

Survey of Motile Microaerophilic Bacterial Morphotypes in the Oxygen Gradient above a Marine Sulfidic Sediment

ABSTRACT Enrichment cultures for free-swimming microaerophilic bacteria were prepared from marine sulfidic sediment samples (Nivå Bay, Denmark). We observed nine different morphotypes; three of these morphotypes represented already-described species, i.e., Thiovulum majus, “Candidatus Ovobacter propellens,” and an as-yet-unnamed large vibrioid bacterium. In addition, we observed several morphotypes of spirilla and one vibrioid morphotype. A common feature of all investigated bacteria was that they aggregated chemotactically at the oxic-anoxic interface, whereas preferred oxygen concentration were in the range of 1 to 10 μM. The motile behavior and flagellar dynamics are analyzed in detail with an emphasis on spirilla.

Occurrence of marcasite in an organic-rich Holocene estuarine mud

Substantial marcasite and pyrite were recently identified in the upper-most unoxidised Holocene clay–peat sediments at Bungawalbin Swamp, a coastal backswamp on the Richmond River floodplain, north-east New South Wales, Australia. Marcasite (FeS2), the mineral dimorph of pyrite, is considered a rare secondary mineral in estuarine sediments and its abundance at Bungawalbin Swamp is highly unusual. The morphology and distribution of marcasite in the sulfidic sedimentary profile was examined and compared with the palynological record. Marcasite, recognised by its distinctive platy morphology and disulfide composition, occurred exclusively within organic remnants in only the upper most 1 m of the sulfidic sediment layer. Pyrite occurred throughout the sulfidic profile. A dramatic change in the sedimentary conditions at Bungawalbin Swamp from a marine environment, characterised by the presence of avicenniaceae (i.e. mangrove), to a fresh–brackish environment correlates directly with the occurrence of marcasite. The occurrence of substantial marcasite may provide a valuable environmental proxy of fresh–brackish depositional swamp environments.