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Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

ABSTRACT: Many studies have concluded terrestrial carbon inputs contribute 20-70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. We conducted a quantitative analysis of terrestrial carbon mass influx and algal primary production estimates for oligo/mesotrophic lakes (i.e., TP ? 20 µg L(-1)). In keeping with the principle of mass conservation, only the flux of terrestrial carbon retained within lakes can be utilized by zooplankton. Our field data compilation showed the median (inter-quartile range) terrestrial particulate organic carbon (t-POC), available dissolved organic carbon (t-DOC) inputs, and in-lake bacterial and algal production were 11 (8-17), 34 (11-78), 74 (37-165), and 253 (115-546) mg C m(-2) d(-1), respectively. Despite the widespread view that terrestrial inputs dominate the carbon flux of many lakes, our analysis indicates algal production is a factor 4-7 greater than the available flux of allochthonous basal resources in low productivity lakes. Lakes with high loading of t-DOC also have high hydraulic flushing rates. Because t-DOC is processed, i.e., mineralized or lost to the sediments, in lakes at ? 0.1% d(-1), in systems with the highest t-DOC inputs (i.e., 1000 mg m(-2) d(-1)) a median of 98% of the t-DOC flux is advected and therefore is not available to support zooplankton production. Further, advection is the primary fate of t-DOC in lakes with hydraulic retention times <3 years. When taking into account the availability and quality of terrestrial and autochthonous fluxes, this analysis indicates ? 95-99% of aquatic herbivore production is supported by in-lake primary production.

SUBMITTER: Brett MT

PROVIDER: S-EPMC3383696 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

Brett Michael T MT Arhonditsis George B GB Chandra Sudeep S Kainz Martin J MJ

PloS one 20120626 6

Many studies have concluded terrestrial carbon inputs contribute 20-70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. W ...[more]

PMID: 22761808

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Project description:Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 ?m > virus > 0.02 ?m. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h(-1)) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during hydrological events and then decay once there.

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Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

Publications

Mass flux calculations show strong allochthonous support of freshwater zooplankton production is unlikely.

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