Showing papers by "Peter A. Jumars published in 2002"
TL;DR: It is concluded that deposit feeders with low enzyme activity, low amino acid concentration, and high pH values are most vulnerable to harm from sedimentary Cu by this mechanism, although they solubilize less sedimentaryCu than their counterparts with high enzymes activity, high amino acid concentrations, and low gut pH.
Abstract: Digestive systems of deposit and suspension feeders can be exposed to high concentrations of copper (Cu) by ingestion of contaminated sediments. We assessed a potential impact of this Cu exposure on digestive enzyme activities in a wide range of benthic organisms by monitoring enzyme activities in their gut fluids during in vitro titrations with dissolved Cu, which mimics Cu solubilization from sediments. Increasing Cu inhibited digestive protease activities at threshold values, which varied widely among organisms, from 8 microM for an echinoderm to 0.4 M for an echiuran. More Cu was required to inhibit proteases in guts containing higher amino acid concentrations because strong Cu-binding sites on amino acids prevent Cu interaction with the enzymatically active sites. Threshold Cu concentrations were similar for proteases, esterases, lipases, and alpha- and beta-glucosidases, suggesting the same inhibition mechanism. Copper was less effective at inhibiting enzymes at lower pH, suggesting that protons can compete with Cu ion for binding to enzymatically active sites or that enzyme conformation is less vulnerable to Cu inhibition at lower pH. These results lead to the counterintuitive conclusion that deposit feeders with low enzyme activity, low amino acid concentration, and high pH values are most vulnerable to harm from sedimentary Cu by this mechanism, although they solubilize less sedimentary Cu than their counterparts with high enzyme activity, high amino acid concentrations, and low gut pH. In general, digestive systems of echinoderms may therefore be more susceptible to Cu contamination than those of polychaetes, with various other phyla showing intermediate susceptibilities. If threshold Cu values are converted to solid-phase sedimentary Cu concentrations, the thresholds are at least consistent with Cu loadings that have been observed to lead to biological impacts in the field.
61 citations
TL;DR: The bacteria in shrimp hindguts represent new species that have not yet been en-countered in other environments, and gut environments may be a rich source of the difficult-to-culture and novel components of marine bacterial diversity.
Abstract: Microbial colonization of marine invertebrate guts is widespread, but in general the roles that these bacteria play in the nutrition of their hosts are unknown. To examine the diversity and potential nutritional roles of hindgut microbiota in a deposit feeder, PCR-amplified 16S rRNA genes were cloned from the bacterial community attached to the hindguts of the thalassinid shrimp Neotrypaea californiensis exposed to different feeding treatments. Partial 16S rDNA sequences were analyzed for 30 clones for three shrimp per treatment for a total of 270 clones. No effects of host starvation or high-protein diets were apparent on hindgut bacterial community composition. Diversity analyses indicated high variability between bacterial communities in individual shrimp hindguts, but partial 16S rDNA sequences revealed remarkable species-level similarity (>98%) within clusters of sequences from the different shrimp hindguts, and many sequences from different shrimp hindguts were identical. Sequences belonged to three main groups of bacteria: Cytophaga-Flavobacteria-Bacteroides (CFB), proteobacteria, and gram-positives. Of the 270 sequences, 40% belonged to the alpha-proteobacteria, > or = 5% each to the gamma- and epsilon -proteobacteria, and > or =20% each to the gram-positive and CFB groups. All except one sequence are novel with < or = 95% sequence similarity to known genes. Despite weak similarity to known taxa,about 75% of the sequences were most closely related to known symbiotic and sedimentary bacteria. The bacteria in shrimp hindguts represent new species that have not yet been en-countered in other environments, and gut environments may be a rich source of the difficult-to-culture and novel components of marine bacterial diversity.
58 citations
19 citations
30 Sep 2002
TL;DR: In this article, the role played by food quality in controlling sediment mixing by benthic animals in coastal sediments was investigated, and the authors hypothesize that a threshold level of food abundance controls whether or not significant mixing can occur, and that this threshold is driven by protein concentrations.
Abstract: : We focus on the role played by food quality in controlling sediment mixing by benthic animals in coastal sediments. We hypothesize that a threshold level of food abundance controls whether or not significant mixing can occur, that this threshold is driven by protein concentrations, and regional differences in mixing among coastal regions may therefore be explained by differences in protein contents.
1 citations
30 Sep 2002
TL;DR: In this article, the long-term goal is to identify, quantify and understand important interactions among organisms, particles (including sediments), solutes and moving fluids, and the reason is to enable solutions of interesting forward and inverse problems involving benthic biota.
Abstract: : Our long-term goal is to identify, quantify and understand important interactions among organisms, particles (including sediments), solutes and moving fluids. The reason for this goal is to enable solutions of interesting forward and inverse problems involving benthic biota.