Changes in the importance of lotic and littoral diatoms in a high arctic lake over the last 191 years

Abstract

Both habitat preferences and community associations for some of the most prominent pennate taxa in our profile were established using samples from the modern lake and its watershed. Habitat preferences were used to establish a simple indicator for the relative contribution of lotic communities in this lake (Lotic Index) and indicator taxa for both littoral (Achnanthes spp. and Cymbella spp.) and lotic (Hannaea arcus and Meridion circulare) communities.When profiled, the Lotic Index showed a clear positive relationship to sedimentation rate as recorded in the varves, while profiles of littoral indicator taxa show the opposite trends. It seems likely that the patterns we observed in the Lotic Index are related to changes in runoff. Apparently, there was a period of declining runoff beginning ca. two centuries ago and ending in the late 1800's. This was followed by increasing runoff lasting until the middle of the 20th century. A brief minimum occurred in ca. 1970 followed by a recovery by ca. 1980.A strong positive relationship was also found between the dates of major turbidites, exceptionally thick varves and the concentration of valves in the sediment. It is possible that many of the thicker varves in the profiles contain littoral material transported to the site of deposition by turbid interflows and underflows. For this reason, the concentration of valves in the sediment in our cores appears to be a proxy for sediment deposition from turbidity currents.

Changes in diatom assemblages in Lake C2 (Ellesmere Island, Arctic Canada): response to basin isolation from the sea and to other environmental changes

“…The sample is allowed to settle for 24 hours and this wash step is repeated five times. Five depths (76,98,116,136 and 156 cm) were prepared slightly differently according to Ludlam et al (1996).…”

“…Relative (%) and absolute abundances (# valves/wet weight sediment) of diatom taxa were calculated and plotted relative to depth in the core. Taxonomic references used in this study are listed in Douglas &Smol (1993) andLudlam et al (1996). Chrysophyte cysts were counted as well, but no taxonomic differentiation was attempted.…”

“…This study provides a long-term perspective on diatom species changes, from which more recent successional changes (i.e. the last two centuries; Ludlam et al, 1996) can be compared.…”

Late Glacial and Holocene Glacier and Vegetation Fluctuations at Little Swift Lake, Southwestern Alaska, U.S.A

“…further supports decreased meltwater flux to the lake (I. Gregory-Eaves, pers. comm., 2002); Hannaea arcus is found in cold, flowing water and Nitzschia species thrive in turbid, unproductive, river-influenced arctic lakes (e.g., Ludlam et al, 1996;Hay et al, 1997).…”

The Taconite Inlet Lakes Project: a systems approach to paleoclimatic reconstruction

“…Such process-based studies are an essential component of paleoclimatic research, especially in regions where long-term climatic data are sparse or absent. Research focused on: -meteorological controls on snowmelt, discharge and sediment flux (Hardy, 1996) sediment dispersal into lake C-2 (Retelle, 1996) the physical limnology of the lakes and of adjacent Taconite Inlet (Ludlam, 1996a, b) -the near surface sedimentary record (Zolitschka, 1996;Ludlam et al, 1996) the climatic signal in the sediments and…”