Determining rates of change and evaluating group-level resiliency differences in hyporheic microbial communities in response to fluvial heavy-metal deposition.
Prior field studies by our group have demonstrated a relationship between fluvial deposition of heavy metals and hyporheic-zone microbial community structure. Here, we determined the rates of change in hyporheic microbial communities in response to heavy-metal contamination and assessed group-level differences in resiliency in response to heavy metals. A controlled laboratory study was performed using 20 flowthrough river mesocosms and a repeated-measurement factorial design. A single hyporheic microbial community was exposed to five different levels of an environmentally relevant metal treatment (0, 4, 8, 16, and 30% sterilized contaminated sediments). Community-level responses were monitored at 1, 2, 4, 8, and 12 weeks via denaturing gradient gel electrophoresis and quantitative PCR using group-specific primer sets for indigenous populations most closely related to the alpha-, beta-, and gamma-proteobacteria. There was a consistent, strong curvilinear relationship between community composition and heavy-metal contamination (R(2) = 0.83; P < 0.001), which was evident after only 7 days of metal exposure (i.e., short-term response). The abundance of each phylogenetic group was negatively affected by the heavy-metal treatments; however, each group recovered from the metal treatments to a different extent and at a unique rate during the course of the experiment. The structure of hyporheic microbial communities responded rapidly and at contamination levels an order of magnitude lower than those shown to elicit a response in aquatic macroinvertebrate assemblages. These studies indicate that hyporheic microbial communities are a sensitive and useful indicator of heavy-metal contamination in streams.
Microbial Ecology Program, Division of Biological Sciences, The University of Montana, Missoula, MT 59812-1006, USA.
Kevin P
KP
Feris
Philip W
PW
Ramsey
Matthias
M
Rillig
Johnnie N
JN
Moore
James E
JE
Gannon
William E
WE
Holben
D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D004586:Electrophoresis / Q000379:methods; D005618:Fresh Water / Q000382:microbiology*; D019015:Geologic Sediments / Q000382:microbiology*; D019216:Metals, Heavy / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D020560:Proteobacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D014877:Water Pollution, Chemical
D004269:DNA, Bacterial; D019216:Metals, Heavy