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  • 1
    Electronic Resource
    Electronic Resource
    High turnover of inorganic carbon in kelp habitats as a cause of δ13C variability in marine food webs (1993)
    Springer
    Marine biology 116 (1993), S. 147-160 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a study to assess qualitatively the importance of organic matter derived from kelp production in the Aleutian Islands of subarctic Alaka, replicated samples of autotrophic sources and primary and secondary consumer organisms were sampled for δ13C among sources, sites, (treatment) islands, and years. Unanticipated variation in the δ13C of kelps occurred among overtly similar sites at different islands. Variation in the δ13C of the surface canopy-forming kelp Alaria fistulosa was particularly extreme, ranging from-15.5 to-28.0‰ compared to the understory kelps, Laminaria spp. A. fistulosa δ13C varied by as much as 6 to 7‰ among similar sites at a given island within years, and by as much as 3 to 4‰ between years at the same sampling site. In serveral cases, δ13C variation was weakly tracked by some consumer organisms, suggesting that even detritus pathways through the food web can be localized and tightly coupled. Dynamic cycles in the concentration and δ13C of dissolved inorganic carbon (DIC) and aqueous CO2 concentration ([CO2]aq) were measured at three sites on one island. The δ13C or organic carbon fixed by A. fistulosa, calculated from diurnal DIC concentration and δ13C measurements, varied by 15‰ and varied inversely with [CO2]aq concentrations. Local DIC variability, probably resulting from high productivity and decreased turbulence in dense kelp habitats, provides a possible mechanism of variation in kelp δ13C. The short-term variability in the δ13C of organic carbon fixed by kelps indicates that sampling methodology and design must assess this potential variation in marine macrophyte δ13C before making assumptions about the transfer of δ13C-invariate organic matter to higher trophic levels. On the positive side, a predictable relationship between [CO2]aq concentration and kelp δ13C offers a potentially robust means to assess productivity effects on CO2 limination in kelps and other complex aquatic macrophyte habitats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350742
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  • 2
    Electronic Resource
    Electronic Resource
    Sink or swim? Copepod population maintenance in the Columbia River estuarine turbidity-maxima region (1997)
    Springer
    Marine biology 129 (1997), S. 309-317 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maintenance of estuarine zooplankton populations in large river-dominated estuaries with short residence times has been an intriguing subject of investigation. During three different hydrological seasons, autumn 1990, summer 1991, and spring 1992, we intensively sampled zooplankton populations in the estuarine turbidity maxima (ETM) region of the Columbia River estuary of Oregon and Washington, USA. One of the principal objectives was to investigate retention mechanisms of the predominant zooplankton species, the harpacticoid copepod Coullana canadensis and the epibenthic calanoid copepod Eurytemora affinis. In the ETM, C. canadensis densities mirrored those of turbidity gradients and were almost always greater at the river bed, while E. affinis densities were greater higher in the water column during the flood and lower in the water column during the ebb. Cross-correlation and time-series analyses determined that C. canadensis densities were highly positively correlated with turbidity and that most of the variability was explained by the lunisolar diurnal (K1) and principal lunar (M2) tidal components occurring once every 23.93  h and once every 12.42 h, respectively. This indicates that C. canadensis populations are most probably maintained in the estuary through the same near-bottom circulation features that trap and concentrate particles in the ETM. In contrast, densities of the more motile species E. affinis were highly correlated with negative velocities, or ebb tide, and most of the variability in population densities could be explained by the principal lunar tidal component; therefore, we hypothesize that this species is probably vertically migrating on a tidal cycle into different flow layers to avoid population losses out of the estuary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050171
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  • 3
    Electronic Resource
    Electronic Resource
    Biogeochemical gradients in the lower Columbia River (1997)
    Springer
    Hydrobiologia 361 (1997), S. 37-52 
    Details
    ISSN: 1573-5117
    Keywords: Suspended particulate material ; composition ; organiccarbon ; phytoplankton production ; methanotrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water, suspended particulate materials (SPM), and biota were sampled between June 14 and 22, 1992 at forty-five mid-channel sites along a downstream gradient in the lower 350 km of the Columbia River drainage, at four mid-channel sites in the lower 27 km of the Willamette drainage and at the mouths of nine smaller tributaries to the Columbia. Water samples were analyzed for nutrient (ammonium, nitrate, phosphate, silicate), dissolved organic carbon (DOC) and SPM concentrations, bacterial cell density and activity, and zooplankton composition and density. The SPM samples were analyzed for particulate organic carbon (POC), plant pigment (chlorophyll and pheopigment) and major metal (Al, Mn, Ti, V) content as well as stable isotopic ( $$\delta ^1 $$ 3C) composition of the POC. Willamette waters displayed significantly higher nutrient and DOC concentrations than those in the mainstem Columbia or any of the smaller tributaries. Elevated nutrient and DOC concentrations are attributed to runoff from the extensive agricultural lands found throughout the Willamette Valley. Regardless of collection site, total Al content of all riverborne particles was high (5.8 ± 0.5% by weight), indicating total SPM mass was predominantly (∼ 70±) detrital mineral. Nonetheless, the majority of riverborne organic matter was not allochthonous but rather derived from healthy phytoplankton as indicated by high chlorophyll a to POC (Chl:POC) values. Chlorophyll a concentration increased by almost 100% downstream in the mainstem Columbia between Bonneville Dam and the estuary. This apparent increase in phytoplankton biomass was not accompanied by a parallel decrease in any nutrient concentration probably because non-point source additions occurred all along the drainage and compensated for nutrient loss due to phytoplankton growth. Despite nutrient concentrations near eutrophic levels, phytoplankton biomass in the Willamette was significantly lower than that in the mainstem Columbia. This particular contrast between the Willamette and the mainstem Columbia is likely due to light limitation imposed on the phytoplankton by specific differences in the mixing dynamics of the two flow regimes. POC in Willamette waters displayed a 50% reduced chlorophyll content and 2–2.5% 13C-depletion relative to that present in waters from the mainstem Columbia. These compositional dissimilarities may simply reflect physiological difference between the diatom communities that comprised the bulk of phytoplankton in these two systems at the time of sampling. Alternatively, they may be caused by greater contribution of POC from non-phytoplankton sources in the Willamette. An argument is advanced suggesting that methanotrophy has contributed up to 5% of the POC that was measured in the Willamette River at the time of our study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003129124747
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