The perils of using sedimentary phosphorus concentrations for inferring long-term changes in lake nutrient levels: Comments on Hiriart-Baer et al., 2011

Tracking past changes in lake-water phosphorus with a 251-lake calibration dataset in British Columbia: tool development and application in a multiproxy assessment of eutrophication and recovery in Osoyoos Lake, a transboundary lake in Western North America

“…The long-term perspective of paleolimnological approaches, which pre-date high-quality records of water chemistry and/or ecological monitoring, makes paleolimnology well-suited to study cultural eutrophication, a process that typically occurs over decades. Paleolimnological approaches have been developed to study eutrophication (reviewed by Davidson and Jeppesen, 2013) have included changes in: (i) the relative composition and/or abundance of proxies of primary producers from lake sediments, including sub-fossil pigments, diatoms and other algal remains, as well as changes in plant composition from aquatic macrophytes; (ii) changes in the composition, abundance and size structure of many invertebrate groups (e.g., cladocera, and chironomids); and (iii) chemical proxies including direct measurements of total phosphorus (TP), that can be problematic (Ginn et al, 2012), as well as isotopic changes in carbon (C), nitrogen (N), and silica (Si) that can be related to changes in lake production (Davidson and Jeppesen, 2013). Given the limitations of many approaches and the complexities of lake ecosystems, most researchers advocate a multiproxy approach to reconstruct changes in nutrient dynamics, as well as a combination of both limnological and paleolimnological approaches (e.g., Battarbee et al, 2005).…”

Sedimentary geochemical record of human-induced environmental changes in Huanggaihu Lake in the middle reach of the Yangtze River, China

“…Total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and their composition and ratios in lake sediments have been used to assess the trophic state and organic matter sources in numerous lakes (Brenner et al, 2001(Brenner et al, , 2006Liu et al, 2010). The drawback of these proxies is that they are easily affected by post-depositional processes (Hodell and Schelske, 1998;Ginn et al, 2012). Stable isotopic carbon and nitrogen (δ 13 C org and δ 15 N) in sediment organic matter (OM) have proved to be effective geochemical proxies of historic changes in a lacustrine trophic state in many studies Hodell, 1991, 1995;Routh et al, 2004), although bacterial degradation during early diagenesis in the anoxic sediments may change the isotopic signal (Lehmann et al, 2002).…”

Response to comment on ‘Temporal trends in phosphorus and lacustrine productivity in Lake Simcoe inferred from lake sediment’

“…1970 coupled with an increase in primary production inferred from carbon stable isotope signatures of organic matter which could be explained by a change in the P cycle in Lake Simcoe. Ginn et al (2012) objected to our interpretation of the results stating that (1) geochemical estimates of past P from Lake Simcoe cores report opposite trends to long-term observational/monitoring data; (2) monitoring data does not record increased algal primary production; and (3) geochemical estimates of past P from dated sediment cores are not tracking changes in lake trophic status. We maintain that (1) water column total P concentrations are not adequately related to loads and cannot be used to reject sediment P concentrations; (2) independent evidence supports our data that primary production has generally increased in Lake Simcoe over the last four decades; and (3) organic P is indeed a reliable proxy for paleolimnological reconstructions.…”

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IntroductionWe wish to thank Ginn et al (2012) for their comments regarding our paper "Temporal trends in phosphorus and lacustrine productivity in Lake Simcoe inferred from lake sediment" . In this paper we demonstrated that organic phosphorus (P) concentrations in Lake Simcoe sediment cores have increased since ca.

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“…2) and, from this, infer that sediment P concentrations are not correlated with P loadings. To explore the validity of the argument presented by Ginn et al (2012) that water column P is correlated with P load, we examined the relationship between P loads and mean annual total P concentrations at Lake Simcoe stations K-42 and C-6 ( Fig. 1).…”