Growth phase and elemental stoichiometry of bacterial prey influences ciliate grazing selectivity.

Protozoa are known to selectively graze bacteria and can differentiate prey based on size and viability, but less is known about the effects of prey cellular composition on predator selectivity. We measured the effect of growth phase and elemental stoichiometry of Escherichia coli on grazing by two ciliates, Euplotes vannus and Cyclidium glaucoma. Bacterial cells of a single strain were transformed with green and red fluorescent protein and harvested from culture at differing growth stages.

Protozoan migration in bent microfluidic channels.

Microfluidic devices permit direct observation of microbial behavior in defined microstructured settings. Here, the swimming speed and dispersal of individual marine ciliates in straight and bent microfluidic channels were quantified. The dispersal rate and swimming speed increased with channel width, decreased with protozoan size, and was significantly impacted by the channel turning angle.

Dynamics and characterization of refractory dissolved organic matter produced by a pure bacterial culture in an experimental predator-prey system.

We studied the effects of a bacterium (Pseudomonas chlororaphis) and a bactivorous protozoan (Uronema sp.) on transformations of labile dissolved organic carbon (DOC). In 36-day time series experiments, bacteria were grown on glucose both with and without protozoa.

Protozoan grazing increases mineralization of naphthalene in marine sediment.

Bacterial decomposition of organic matter is frequently enhanced when protozoa are present. Various mechanisms have been proposed to account for this phenomenon, including effects associated with grazing by protozoa (such as increased recycling of limiting nutrients, removal of senescent cells, or reduction of competition among bacteria) and indirect effects of grazers (such as excretion of bacterial growth factors). Few studies have examined the role of protozoa in bacterial degradation of xenobiotic compounds in sediment containing a natural community of microbes.

Combined effects of contaminant desorption and toxicity on risk from PAH contaminated sediments.

A strong inverse correlation was observed between the polycyclic aromatic hydrocarbon (PAH) mass fraction desorbed, a surrogate measure of bioavailability, and relative carcinogenicity, as quantified by potency equivalency factors (PEFs), for two study sediments from the New York/New Jersey Harbor estuary. Because compounds with the highest toxicity, such as dibenz(a,h)anthracene and benzo(a)pyrene (BAP), also tended to be the least rapidly and least extensively desorbed, the U.S.

Intra-aggregate mass transport-limited bioavailability of polycyclic aromatic hydrocarbons to Mycobacterium strain PC01.

Biodegradation kinetics for three- and four-ring PAHs by Mycobacterium sp. strain PC01 were measured in whole and density-fractionated estuarine sediments and in a system without intra-aggregate mass transport limitations. The biokinetic data in the systems with and without intra-aggregate mass transport limitations were compared with abiotic PAH desorption kinetics.

Desorption kinetics for field-aged polycyclic aromatic hydrocarbons from sediments.

This study considers desorption kinetics for 12 field-aged polycyclic aromatic hydrocarbons (PAHs) desorbing from size- and density-fractionated sediments collected from two locations in the New York/New Jersey Harbor Estuary. Desorption kinetics for PAHs with a log octanol-water partition coefficient greater than 6 were well-described by a one-domain diffusion model that assumes that PAHs are initially uniformly distributed throughout spherical sediment aggregates. PAH hydrophobicity and sediment specific surface area were the parameters most strongly correlated with the magnitude of the observed diffusivity for the one-domain model.

Activity and distribution of bacterial populations in Middle Atlantic Bight shelf sands.

Abstract Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse-grained Middle Atlantic Bight shelf sediments in relation to pools of dissolved and particulate carbon. Algal cells were present 8->70 mum) fraction of the sediment held the major share (61-98%) of benthic bacteria. Bacterial and algal cell abundances, exoenzymatic activity, and [DOC] generally showed higher values in May/July 2001 than in August/December 2000.

Toxicity of density separation media to Escherichia coli and Mycobacterium strain PC01: implications for density-separation of soils and sediments.

Separation of low-density sediment detritus in CsCl solution is a promising technique for benthic studies. The known toxicity of CsCl suggests the possibility of toxicity in the separated sediment. Fluoranthene biodegradation by Mycobacterium strain PC01 was used to probe microbial activity in sediment following density separation.

Distributed sequestration and release of PAHs in weathered sediment: the role of sediment structure and organic carbon properties.

Polycyclic aromatic hydrocarbon (PAH) contaminated sediments from Piles Creek (PC) and Newtown Creek (NC) in the NY/NJ Harbor estuary were separated into size fractions and further separated into low (<1.7 g cm(-3)) and high (>1.7 g cm(-3)) density fractions.

Recolonization of Deep-Water Hard-Substrate Communities: Potential Impacts From Oil and Gas Development.

Many regions of the California, USA, outer continental shelf are subject to ongoing and planned oil and gas development, but there is very limited information on the recolonization and recovery of deep-water (e.g., 60-300 m) hard-substrate communities that may be affected by these activities.

Optimal foraging by deposit-feeding invertebrates: Roles of particle size and organic coating.

Feeding experiments were conducted on marine, deposit-feeding benthic invertebrates to test the predictions of an optimal foraging model. Food item selection based on sediment particle size and presence or absence of an organic coating on particles was investigated. Animals displaying a wide range of feeding mechanisms were studied in particle size-selection experiments using artificial sediment of closely controlled size composition.