Untangling the complex issue of dissolved organic carbon uptake: a stable isotope approach

Kaplan, Louis; Wiegner, Tracy N.; Newbold, J. Denis; Ostrom, Peggy H.; Gandhi, Hasand

doi:10.1111/j.1365-2427.2007.01941.x

Cited by 80 publications

(88 citation statements)

References 40 publications

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“…Freshwater habitats, in particular, often receive significant inputs of terrigeneous DOC from watersheds (Dodds and Cole, 2007), which can be assimilated by microorganisms (Pace et al, 2004;Kaplan et al, 2008). This study suggests that, compared to the bacteria-protozoan food chain, osmotrophic activity in algae represents an alternative link to convert terrestrial DOC into biomass of aquatic organisms.…”

Section: Discussionmentioning

confidence: 96%

Utilisation of terrestrial carbon by osmotrophic algae

et al. 2009

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Terrestrial-derived dissolved organic carbon (DOC) contributes significantly to the energetic basis of many aquatic food webs. Although heterotrophic bacteria are generally considered to be the sole consumers of DOC, algae and cyanobacteria of various taxonomic groups are also capable of exploiting this resource. We tested the hypothesis that algae can utilise DOC in the presence of bacteria if organic resources are supplied in intervals by photolysis of recalcitrant DOC. In short-term uptake experiments, we changed irradiation in the range of minutes. As model substrates, polymers of radiolabelled coumaric acid (PCA) were used, which during photolysis are known to release aromatic compounds comparable to terrestrial-derived and refractory DOC. Three cultured freshwater algae readily assimilated PCA photoproducts equivalent to a biomass-specific uptake of 5 -60 % of the bacterial competitors present. Algal substrate acquisition did not depend on whether PCA was photolysed continuously or in intervals. However, the data show that photoproducts of terrestrial DOC can be a significant resource for osmotrophic algae. In long-term growth experiments, interval light was applied one hour per day. We allowed cultured Chlamydomonas to compete for ambient DOC of low concentration. We found higher abundances of Chlamydomonas when cultures were irradiated intermittently rather than continuously. These data suggest that photolysis of DOC supports algal heterotrophy, and potentially facilitates growth, when light fluctuations are large, as during the diurnal light cycle. We concluded that osmotrophic algae can efficiently convert terrestrial carbon into the biomass of larger organisms of aquatic food webs.

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Section: Discussionmentioning

confidence: 96%

Utilisation of terrestrial carbon by osmotrophic algae

et al. 2009

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“…Alternatively, semi-labile DOC might be introduced from rivers (allochthonous source). This proposition is supported by the fact that Lake Biwa receives large amounts of organic carbon from the watershed, with an annual river flux on the order of 7.6 9 10 8 mol C year -1 (Somiya 2000), although the contribution of semi-labile DOC to the bulk organic carbon in river waters is not entirely clear (Tranvik 1998;Kaplan et al 2008). In short, there are two potentially important mechanisms by which a semi-labile DOC pool is built up in Lake Biwa, i.e., production by pelagic communities (autochthonous) and delivery from rivers (allochthonous).…”

Section: Introductionmentioning

confidence: 92%

Autochthonous origin of semi-labile dissolved organic carbon in a large monomictic lake (Lake Biwa): carbon stable isotopic evidence

et al. 2009

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Semi-labile dissolved organic carbon (DOC) plays an important role in the transport and hypolimnetic remineralization of carbon in large freshwater lakes. However, sources of semi-labile DOC in lakes remain unclear. This study used a carbon stable isotope approach to examine relative contributions of autochthonous and allochthonous sources to semi-labile DOC. Vertical and seasonal variations in the concentration and carbon stable isotope ratio (d 13 C) of DOC were determined in large (surface area 674 km 2 ; maximum depth 104 m), monomictic Lake Biwa. A sharp vertical gradient of d 13 C of DOC (d 13 C-DOC) during the stratification period [mean ± standard error (SE) -25.5 ± 0.1 and -26.0 ± 0.0% in the epi-and hypolimnion, respectively] indicated the accumulation of 13 C-rich DOC in the epilimnion. Vertical mixing explained the intermediate values of d 13 C-DOC (-25.7 ± 0.0%) measured throughout the water column during the overturn period. Both DOC concentration and d 13 C-DOC decreased in the hypolimnion during stratification, indicating selective remineralization of 13 C-rich DOC. Using a two-component mixing model, we estimated the d 13 C value of semi-labile DOC to be -22.2 ± 0.3%, which was close to the d 13 C of particulate organic carbon collected in the epilimnion during productive seasons (-22.7 ± 0.7%) but much higher than the d 13 C-DOC in river waters (-26.5 ± 0.1%). Semi-labile DOC appeared to be mainly autochthonous in origin, produced by planktonic communities during productive seasons. The spatiotemporal uncoupling between production and remineralization of semi-labile DOC implies that hypolimnetic oxygen consumption may be affected by pelagic primary production during productive seasons of the preceding year.Keywords Semi-labile dissolved organic carbon Á Autochthony and allochthony Á Mixing model Á Carbon stable isotope ratio Á Large lake

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“…This was the first study to show evidence of the influence of geological variation and DOM quality on bacterial and microbial community structures in stream sediments. In addition, this correlative experimental design clearly demonstrated the influence of geological (38), and it is reasonable to expect that different microbial communities alter DOM quality to a lesser or greater extent. Nonetheless, this study provides further support for the second half of BaasBecking's "everything is everywhere, but the environment selects" dictum.…”

Section: Vol 77 2011 Bedrock Influences Microbial Communities In Stmentioning

confidence: 99%

Direct and Indirect Influence of Parental Bedrock on Streambed Microbial Community Structure in Forested Streams

Mosher

Findlay

2011

Appl Environ Microbiol

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A correlative study was performed to determine if variation in streambed microbial community structure in low-order forested streams can be directly or indirectly linked to the chemical nature of the parental bedrock of the environments through which the streams flow. Total microbial and photosynthetic biomass (phospholipid phosphate [PLP] and chlorophyll a), community structure (phospholipid fatty acid analysis), and physical and chemical parameters were measured in six streams, three located in sandstone and three in limestone regions of the Bankhead National Forest in northern Alabama. Although stream water flowing through the two different bedrock types differed significantly in chemical composition, there were no significant differences in total microbial and photosynthetic biomass in the sediments. In contrast, sedimentary microbial community structure differed between the bedrock types and was significantly correlated with stream water ion concentrations. A pattern of seasonal variation in microbial community structure was also observed. Further statistical analysis indicated dissolved organic matter (DOM) quality, which was previously shown to be influenced by geological variation, correlated with variation in bacterial community structure. These results indicate that the geology of underlying bedrock influences benthic microbial communities directly via changes in water chemistry and also indirectly via stream water DOM quality.Microorganisms are one of the most important groups of living organisms. Their small size, ubiquitous distribution, metabolic diversity, and genetic plasticity cast microorganisms in the role of recycling agents for the biosphere, making life possible for more complex organisms (47). To better understand the ecology of microbial communities, it is important not only to describe the community composition but also to identify biological and/or environmental factors that regulate their diversity (34, 52).Baas-Becking's dictum that "everything is everywhere, but the environment selects" has inspired many studies and debates since its inception and is considered the precursor to the niche concept adopted by macroecologists (10). Microbes were thought to be cosmopolitan due to large population sizes and short generation times, resulting in high dispersal rates (18,22). Many studies in the past were limited by methodological tools to elucidate bacterial species, as most bacteria found in the natural environment have yet to be cultured and functional roles and diversity were largely unknown (56, 64). With the recent advances in non-culture-dependent techniques, there has been an increase of studies that have shown evidence of varying distributions, abundance, and diversity of microorganisms in the natural environment across spatial and environmental scales, including freshwater lakes and rivers (60, 65, 70), streams (28), soils (8,21,51,57), and marine ecosystems (33,54). Yet, it is not clear whether limits in distribution or strong environmental selection lead to the observed patterns....

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Untangling the complex issue of dissolved organic carbon uptake: a stable isotope approach

Cited by 80 publications

References 40 publications

Utilisation of terrestrial carbon by osmotrophic algae

Utilisation of terrestrial carbon by osmotrophic algae

Autochthonous origin of semi-labile dissolved organic carbon in a large monomictic lake (Lake Biwa): carbon stable isotopic evidence

Direct and Indirect Influence of Parental Bedrock on Streambed Microbial Community Structure in Forested Streams

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