Seasonality, water quality trends and biological responses in four streams in the Cairngorm Mountains, Scotland

Abstract

The chemical composition and invertebrate communities found in four streams in the Cairngorms, Scotland, were monitored between [1985][1986][1987][1988][1989][1990][1991][1992][1993][1994][1995][1996][1997]. Stream waters were mildly acidic (mean pH ca. 6.5), with low alkalinity (mean acid neutralising capacity varying from 35-117 meq l -1 ) and low ionic strength. Subtle differences in the chemistry of each stream were reflected in their invertebrate faunas. Strong seasonality in water chemistry occurred, with the most acid, low alkalinity waters observed during the winter and early spring. This was particularly marked during snowmelt between January and April. In contrast, summer flows were usually groundwater dominated and characterised by higher alkalinity and higher concentrations of most other weathering-derived solutes. Seasonality was also clear in the invertebrate data, with Canonical Correspondence Analysis (CCA) separating seasonal samples along axes related to water temperature and discharge characteristics. Inter-annual hydrological and chemical differences were marked, particularly with respect to the winter period. Invertebrate communities found in each of the streams also varied from year to year, with spring communities significantly more variable (P<0.01) than other seasons (quantified using Euclidean distance on CCA ordinations). Hydrochemical trends over the study period were analysed using a seasonal Kendall test, LOcally WEighted Scatterplot Smoothing (LOWESS) and graphical techniques. These indicated that a reduction in sulphate concentrations in stream water is occurring, consistent with declining levels of atmospheric deposition. This may be matched by increases in pH and declining calcium concentrations, though available evidence is inconclusive. Other parameters, such as chloride, total organic carbon and zinc, reveal somewhat random patterns, probably reflecting irregular variations in climatic factors and/or atmospheric deposition. Previous studies have shown that the stream invertebrate communities have remained stable over this period (i.e. no significant linear trends) and show no evidence of acid-related impoverishment. Thus, over longer timescales invertebrates in these streams appear robust to the short-term (seasonal and inter-annual) environmental variability and long-term (decadal) chemical changes identified.

Spatial distribution of benthic algae in the Gangqu River, Shangrila, China

“…Therefore, the results of the CCA reflected the lack of flow regime influence on the benthic communities, as evidenced by the eigenvalues. The eigenvalues of the four axes (axis1: 0.165, axis 2: 0.118, axis 3: 0.095, axis 4: 0.056) were lower than those reported by Tang et al (2002) and Leland and Porter (2000), suggesting that variables other than those measured (e.g., alkalinity, Na, Mg, K, SO 4 , and HCO 3 content) may have an important influence on benthic-algal community characteristics (Soulsby et al 2001).…”

Increasing silicon concentrations in Bohemian Forest lakes

“…2) when surface warming supports Si and NO 3 depletion by phytoplankton and uptake of Si from soil solutions by vegetation (Farmer et al, 2005;Soulsby et al, 2001). This seasonal variation occurs only in this lake and is superimposed on the long-term increase of Si concentrations observed for both the July and October sampling (Fig.…”

“…Si may inhibit Al-induced reduction of bioavailable phosphorus by binding Al preferentially. Short-term variability of Si concentrations in streams relates to hydrology (Johnson et al, 1969), season (Norton et al, 1999;Gèrard et al, 2002;Soulsby et al, 2001) and diatom utilisation (Clarke, 2003).…”

Seasonal variability in the Macroinvertebrate Community Index: Are seasonal correction factors required?

“…He attributed the differences in community composition (and hence BI values) to the influences of temperature seasonality on invertebrate life histories, but noted that "stream temperature does not appear to affect the BI, except for its influence on seasonal differences" (Hilsenhoff 1988). Soulsby et al (2001) found that invertebrate communities change seasonally largely as a result of variation in their species life cycles. However, we expected that biotic index seasonality in New Zealand would not be strongly linked to the presence, absence, or relative abundances of invertebrates owing to their life histories.…”