A comparison of chironomid-based training sets developed from pupal exuviae and larval head capsules to infer lake trophic history
Luoto, Tomi P.; Raunio, Janne
published: May 1, 2011
ArtNo. ESP141017902002, Price: 29.00 €
In this study, we integrated ecological and palaeoecological perspectives to compare two approaches for tracing nutrient changes in lakes. Total phosphorus (TP) optima of chironomids (Diptera: Chironomidae) derived from a training set (i.e. calibration set) collected using the Chironomid Pupal Exuvial Technique (CPET) and by using surface sediment larval head capsule assemblages were compared and applied to infer long-term nutrient variability in eutrophic Lake Mallusjärvi, southern Finland. Overall, the chironomid-TP optima showed similarities between the training sets with the exception of Paracladopelma, Procladius and Chironomus plumosus whose optima were lower in the larval training set. As a result of this and due to the absence of Microchironomus tener in the CPET training set, there was a large difference in the magnitude of reconstructed change in the downcore profile of Lake Mallusjärvi as the CPET-method inferred significantly lower TP values for the past 200 years. Potential problems with the use of the CPET method in palaeolimnological research, include temporal representativeness of samples, taxonomic differences between pupal exuviae and larval head capsule identification and an unbalanced ratio between the preserving specimens (one exuviae and up to four fossil head capsules per one individual). Our results showed that the use of the training set developed from larval head capsules provided more reliable results from the downcore profile compared to the CPET training set, which in turn, is more suited to use in contemporary water quality assessments.