Lake water and lake sediment geochemistry, NEA/IAEA Athabasca Test area

To understand current phosphorus (P) cycling, which encompasses disturbances caused by human activity, it is necessary to quantify the long-term natural P cycles on which modern drivers act.&#160;The shortness of monitored P records renders this difficult by only covering the post-disturbance period and therefore fail to capture pre-disturbance baselines. Target driven management of sensitive ecosystems suffering from eutrophication uses baselines for P that cannot be reliably quantified at present. Recovery will only be possible if P loadings can be brought under control and this requires an understanding of what water quality targets are both desirable and achievable on a site-specific basis. This matters because a well-functioning ecosystem will be more resilient under future climate change and increasing human pressure on the landscape.Where lakes are present in the landscape, there is the opportunity to use the sediment archive to provide long records of past P concentration.&#160; At present, these reconstructions rely on diatoms or related microfossil indicators. These require time and resource intensive tailored training sets and furthermore the records do not preserve in all lakes. Here we present a novel geochemical method for reconstructing water P concentrations based on lake sediment P burial fluxes, which in principle is universally applicable.Tested at six published lake sites, the method produces results that agree very well with overlapping monitoring data for those lakes (r2 = 0.8). We want to share our method with the research community to identify additional sites to further verify the general applicability.To illustrate the value of this approach to site-specific management, we compare past lake water total P reconstructions at Crosemere (UK) with a record of Holocene land cover change to identify the drivers of acceleration in the P cycle. Wider application of this lake sediment geochemical method will allow more critical evaluation of the human and natural drivers of the P cycle and be of benefit to &#8216;systems understanding&#8217; spanning terrestrial and aquatic ecosystems.

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The relation of lake sediment geochemistry to mineralization in the northwest Ontario region of the Canadian Shield

Economic Geology ◽

10.2113/gsecongeo.70.1.202 ◽

1975 ◽

Vol 70 (1) ◽

pp. 202-218 ◽

Cited By ~ 13

Author(s):

W. B. Coker ◽

Ian Nichol

Keyword(s):

Lake Sediment ◽

Canadian Shield ◽

Sediment Geochemistry ◽

Northwest Ontario

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Carbon Isotope Composition of Lake Sediments in Relation to Lake Productivity and Radiocarbon Dating

Quaternary Research ◽

10.1016/0033-5894(92)90071-p ◽

1992 ◽

Vol 37 (3) ◽

pp. 333-345 ◽

Cited By ~ 63

Author(s):

Ramon Aravena ◽

Barry G. Warner ◽

Glen M. MacDonald ◽

Karen I. Hanf

Keyword(s):

Lake Sediments ◽

Lake Sediment ◽

Lake Water ◽

Dissolved Inorganic Carbon ◽

Isotope Composition ◽

Hard Water ◽

Lake Basin ◽

Lake Productivity ◽

Radiocarbon Dates ◽

Organic Sediment

AbstractCarbon-13 profiles and radiocarbon dates were obtained from two Canadian kettle basins having similar geological and hydrological characteristics to develop criteria for evaluating the validity of radiocarbon dates on lake sediment from basins in calcareous terrain. Radiocarbon dates from a site in Alberta show a variable hard-water effect related to local hydrological changes during postglacial history of the lake basin, whereas radiocarbon dates from the other site in Ontario show no noticeable influence of old carbon during its history. These differences are mainly related to lake water residence time, which has influenced carbon isotopic exchange between atmospheric CO2 and dissolved inorganic carbon in lake water. δ13C values for bulk organic sediment and terrestrial and aquatic macrofossils reveal that the main component of lake sediment at both sites is autocthonous in origin. Furthermore, each site supported different submerged aquatic plant communities that used different sources of carbon for photosynthesis, thereby imprinting the organic sediments with a characteristic 13C composition. Both sites reflect a clear relationship between 13C values and paleoproductivity. This study shows the individualistic response of the developing lake system to the hydrology, lake biota, and local geology, and demonstrates the problem of using 13C in lake sediments as a single criterion to recognize the validity of radiocarbon dates of lake sediment without supporting paleoecological information.

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