Diatom Diversity in Chronically versus Episodically Acidified Adirondack Streams

Abstract

The relationship between algal species richness and diversity, and pH is controversial. Furthermore, it is still unknown how episodic stream acidification following atmospheric deposition affects species richness and diversity. Here we analyzed water chemistry and diatom epiphyton dynamics and showed their contrasting behavior in chronically vs. episodically acidic streams in the Adirondack region. Species richness and diversity were significantly higher in the chronically acidic brown water stream, where organic acidity was significantly higher and the ratio of inorganic to organic monomeric aluminum significantly lower. Conversely, in the episodically acidic clear water stream, the inorganic acidity and pH were significantly higher and the diatom communities were very species-poor. This suggests that episodic acidification in the Adirondacks may be more stressful for stream biota than chronic acidity. Strong negative linear relationships between species diversity, Eunotia exigua, and dissolved organic carbon against pH were revealed after the influence of non-linear temporal trends was partialled out using a novel way of temporal modeling.Internat. Rev. Hydrobiol.

Hydrogeomorphology explains acidification‐driven variation in aquatic biological communities in the Neversink Basin, USA

“…The weaker prediction of diatoms compared to those of macroinvertebrate and fish populations in upslope ungaged watersheds suggests that aquatic biota more strongly influenced by episodic changes in water sources (i.e., groundwater vs. surface water) are more difficult to predict with our model. This finding is consistent with evidence that water chemistry during runoff events has greater influence on diatom species richness and diversity than water chemistry during baseflow (Passy et al 2006, Burns et al 2008. Almost certainly there are some dynamic characteristics of RR, such as antecedent conditions and rainfall intensity, that are not included in the simple regression model that only applied 20 storms during 1991-1993.…”

Chronic and Episodic Acidification of Adirondack Streams from Acid Rain in 2003–2005

“…Acidification episodes timed with sensitive life stages can result in the elimination of an annual age class (McComick and Leino, 1999). Taxonomic richness of macroinvertebrate communities was also found to be lower in episodically acidified streams than in streams with similar base‐flow chemistry that did not episodically acidify (Lepori et al, 2003), and diversity of diatom communities was found to be lower in an episodically acidified stream than a neighboring stream that was chronically acidified (Passy et al, 2006). Assessing the extent of acidic deposition effects on stream ecosystems therefore requires that the variability of stream chemistry be characterized.…”

Stream geochemical response to reductions in acid deposition in headwater streams: Chronic versus episodic acidification recovery

“…The finding that improvements in pH and Al can occur at high flow, in the absence of trends for lower flow conditions in the most acid sensitive watershed, has consequences for the assessment of biological recovery. Both chronic and episodic acidification have been shown to have negative impacts on aquatic biota, including fish (Baker et al, ), macroinvertebrates (Lepori & Ormerod, ), and diatoms (Passy, Ciugulea, & Lawrence, ), yet aquatic health assessments consistently use the more widely available trends in chronic streamwater chemistry, which cannot always adequately explain changes in biological indicators. For example, in SHEN, improvements in brook trout abundance at the most acidic sites (including Paine Run) did not match the chronic stream chemical trends at those sites (Jastram, Snyder, Hitt, & Rice, ).…”