Living on the pH Edge: Diatom Assemblages of Low-pH Lakes in Western Pomerania (NW Poland)

Abstract

AbstractDiatom communities were studied in 2003 in three low-pH peatbog lakes in Western Pomerania (NW Poland); two of the lakes (LK and ZB) represented natural acid water bodies (NAWB), the third lake (LP) being least acid stressed. The three lakes differed markedly in their abiotic regimes, mainly on account of water pH in the two NAWBs being consistently below 5.0, while the pH range in the non-NAWB extended well into the alkaline part of the pH scale. In terms of all the important environmental variables studied (pH, conductivity, dissolved organic C, dissolved Si, dissolved P, nitrate and ammonia N), the three lakes followed an environmental gradient with LP on one end and ZB, a fully natural peatbog reservoir with high acidity, lower conductivity, higher upper limit of dissolved organic C and higher dissolved P contents and much lower dissolved Si contents, on the other. The study confirmed the general pattern of a low taxonomic richness in waterborne and bryophyte-associated diatom assemblages inhabiting low-pH habitats. The diatom assemblages differed between the three lakes and conformed to the environmental gradient. The LP assemblage (216 taxa), dominated by the common neutrophile Achnanthidium minutissimum, showed a preponderance of circumneutral and alkaliphilous taxa; the LK diatoms (15 taxa) represented mostly acidobiontic and acidophilous taxa, while the ZB assemblage (11 taxa) consisted predominantly of acidobionts. The study supplied information on the distribution of taxa having a high conservation value on the European scale. Important in the NAWBs were rare and endangered diatoms, primarily members of Eunotia, as well as Frustulia crassinervia. Their occurrence, coupled with other environmental and biotic characteristics of the lakes studied, makes the latter ideal candidates for conservation and protection.KeywordsAcid watersDiatomsEunotiaPeatbogsLow pHDiversityConservationWestern Pomerania