Seasonal Diatom Variability and Paleolimnological Inferences – A Case Study

Abstract

The seasonality of physical, chemical, and biological water variables is a major characteristic of temperate, dimictic lakes. Yet, few investigations have considered the potential information that is encoded in seasonal dynamics with respect to the paleolimnological record. We used a one-year sequence of diatoms obtained from sediment traps and water samples, as well as the sedimentary diatom record covering the past ca. 1000 years in Bates Pond, Connecticut (USA), to investigate which variables influence the seasonal distribution of diatoms and how this can be used for the interpretation of the fossil record. The seasonal patterns in diatom assemblages were related to stratification and, to a lesser extent, to nitrate, silica, and phosphorus. During mixing periods in spring and autumn, both planktonic and benthic species were collected in the traps, while few lightly silicified, spindle-shaped planktonic diatoms dominated during thermal stratification in summer. Changes in fossil diatom assemblages reflected human activity in the watershed after European settlement and subsequent recovery in the 20th century. A long-term trend in diatom assemblage change initiated before European settlement was probably related to increased length of mixing periods during the Little Ice Age, indicated by the increase of taxa that presently grow during mixing periods and by application of a preliminary seasonal temperature model. We argue that the analysis of seasonal diatom dynamics in temperate lakes may provide important information for the refinement of paleolimnological interpretations. However, investigations of several lakes and years would be desirable in order to establish a more robust seasonal data set for the enhancement of paleolimnological interpretations.

Seasonal and interannual dynamics of diatom assemblages in Sacrower See (NE Germany): a sediment trap study

“…In contrast, the diatom assemblages of spring and early summer 2004 are grouped with assemblages deposited in late autumn and winter. A relationship of diatom assemblages with stratification dynamics was also found in sediment trap samples of Bates Pond, Connecticut (USA) (Köster & Pienitz, 2006).…”

“…This suggests that on short time scales the response of diatom communities to seasonal temperature variations may be more prominent than the forcing by mean annual temperatures. Other studies focused on the annual succession of diatoms in dimictic lowland lakes (Raubitschek et al, 1999;Schönfelder et al, 2002;Köster & Pienitz, 2006). These studies demonstrate that the seasonal succession of diatoms differs among lakes depending on factors, such as stratification, temperature, nutrients, pH, oxygen saturation, dissolved iron and calcium, maximum water depth, and dissolved organic carbon.…”

Climate-driven shifts in diatom assemblages recorded in annually laminated sediments of Sacrower See (NE Germany)

“…Si, P, N), the stratification of the water column, as well as light and temperature (Kilham et al 1996;Köster and Pienitz 2006;Kirilova et al 2008). In an attempt to identify the factors that drive the annual and seasonal changes in the composition of the diatom assemblages in Sacrower See, we carried out a series of RDAs with forward selection of climatic parameters as independent explanatory variables that explain a statistically significant amount (P \ 0.05) of the variance in the diatom data (Table 3).…”

Time continuum and true long-term ecology: from theory to practice

“…But even in the case of very short life spans, for example in planktonic organisms, there is a seasonal environmental control that makes year round studies (ideally multi-year studies) necessary for a sound understanding of the ecological functioning of these communities (e.g., Köster and Pienitz, 2006;Bunbury and Gajewski, 2008). In palaeoecology, annual resolution is possible in a special type of laminated sediments, referred to as varved sediments, or in cases of very high accumulation rates (Ojala et al, 2012).…”