Development of subfossil Daphnia and Chaoborus assemblages in relation to progressive acidification and fish community alterations in SW Sweden

Abstract

Dated sediment cores from acidified and fishless Lake Gaffeln and Lake Härsvatten, SW Sweden, were analyzed for Daphnia ephippia and Chaoborus mandibles to test whether acidification history and fish extirpations could be reconstructed in a paleo-study using these easily identifiable animal remains. According to monitoring data fish were lost in both lakes from the 1950s to the 1970s. Progressive acidification prior to monitoring was confirmed by a gradual decrease and eventual loss of Daphnia ephippia in both study lakes during the first half of the twentieth century. In Lake Gaffeln mandibles of C. obscuripes appeared immediately after fish loss in 1973, and the regular presence of this species confirmed the succeeding fishless state of this lake. In Lake Härsvatten sediments C. obscuripes appeared only recently, i.e. three decades after fish extirpation, showing that the absence of C. obscuripes mandibles is not a trustworthy indicator of fish presence. Hence, the appearance of C. obscuripes was not temporally related to fish loss but confirmed the present fishless condition. Known historical presence of cyprinid fish in Lake Gaffeln was confirmed by a significantly higher proportion of fragmented mandibles of C. flavicans compared to the historically cyprinid-free Lake Härsvatten. In addition, both lake profiles displayed zero-proportions of fragmented mandibles during fishless periods. We conclude that acidification history and fish extirpations can be inferred by integrated studies on subfossil Daphnia ephippia and Chaoborus mandibles. However, during extreme ultraoligotrophic conditions in acidified clear-water lakes subfossil Chaoborus mandibles may be too scarce to infer fish absence/presence.

Fossil chironomid assemblages and inferred summer temperatures for the past 14,000 years from a low-elevation lake in Pacific Canada

“…Below this, Chaoborus mandibles exceed 3% only once. Mandible concentrations are low with a maximum of only 6 individuals/cm , which is comparable to concentrations at some sites (Uutala 1990), but orders of magnitude less than at others (Palm et al 2012;Tolonen et al 2012). Mandibles in most samples are either Chaoborus flavicans or C. trivittatus.…”

“…The sedimentary remains of Chaoborus species have been used in paleolimnological studies as a proxy for fish presence (e.g. Uutala 1990;Lamontagne and Schindler 1994;Uutala and Smol 1996;Palm et al 2012) and even fish biomass and population density (Tolonen et al 2012). The basis for this approach centers on whether Chaoborus species are capable of diurnal migration to avoid predation by fish, which is the case in C. flavicans and C. trivittatus (Uutala 1990).…”

A review of potential methods for zooplankton control in wastewater treatment High Rate Algal Ponds and algal production raceways

“…are a type of a midge whose larvae (~6-23 mm) can live up to several months in anoxic sediments of small ponds. They are found on all continents excluding Antarctica, particularly in temperate and tropical climates and under eutrophic conditions [259][260][261][262] and prefer environments with standing water [263]. They prey on cladocerans, copepods and rotifers, preferring the smallest available prey [264].…”

The coming and going of a marl lake: multi-indicator palaeolimnology reveals abrupt ecological change and alternative views of reference conditions

“…Historical presence of fish in Cunswick Tarn was determined by identification of chaoborid larval mandibles using the cladoceran method. Chaoborus obscuripes and Chaoborus crystallinus are non-migratory species associated with fishless lakes (Luoto and Nevalainen, 2009;Palm et al, 2012;Tolonen et al, 2012) and therefore their consistent presence in the core record was interpreted as a proxy for fishlessness. Mandibles were identified using Aitken (1954), Uutala (1990), Živić and Marković (2006), and Palm et al (2011).…”