Response of periphyton to nutrient addition in a tufa-depositing environment

Abstract

We examined the effects of added nutrients on primary producers, protozoans and meiofauna -as well as on tufa deposition -in a short-term in situ experiment using nutrientdiffusing substrata. The study was carried out in the tufa-depositing barrage lake system National Park Plitvice Lakes (Croatia). To address the question of whether the extent of tufa deposition and the flow velocity modify the response of periphyton to nutrient addition, we selected 2 sites -fast flow (FF) and slow flow (SF) -on each of the 2 barriers, one barrier having a low rate of tufa deposition (LTD) and the other having a high rate of tufa deposition (HTD). The nutrients examined were nitrogen (N), phosphorus (P), and their combination (N+P). Both N and P were limiting nutrients for autotrophs in periphyton, and the response to nutrient enrichment was lower at HTD sites. A combination of HTD and FF was the most limiting factor for periphyton. Nutrient enrichment did not impede calcite deposition; P enrichment even enhanced calcite deposition -probably as a result of a denser autotrophic periphyton matrix. HTD supported a lower taxa richness of heterotrophs in the periphyton, and flow velocity had taxa-specific effects. The addition of nutrients led to a decrease in the number of heterotrophic taxa at FF sites, while there was no effect at SF sites. The response of ciliates to flow velocity was taxa-specific. The effect of nutrients on the abundance of heterotrophs was rather weak, except for omnivorous and bacterivorous ciliates. Our results showed a direct effect of N and P on autotrophic periphyton in this tufa-depositing system, and only a weak effect on protozoans and micro-metazoans. KEY WORDS: Flow velocity · Chlorophyll a · Protozoa · Nutrient limitation Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 65: [183][184][185][186][187][188][189][190][191][192][193][194][195] 2011 ( Andrushchyshyn et al. 2006). Bernhardt & Likens (2004) showed that eutrophication does not have an effect on the biomass of periphyton. To date, the effects of nutrient enrichment on protozoa have been examined in lakes (Hillebrand et al. 2002), rivers (Rublee & Partusch-Talley 1995) and streams (Domènech et al. 2006). While weak effects of nutrient enrichment on ciliate biomass were reported by Hillebrand et al. (2002), Rublee & Partusch-Talley (1995) ob served a significant increase in the abundance and biomass of heterotrophic microfauna after the addition of N+P, but no significant difference after the addition of P alone. Domènech et al. (2006) attributed an increase in ciliate density to the addition of N+P, whereas flagellates and testate amoebae were reported to be less sensitive to nutrient enrichment.Tufa develops under specific physico-chemical conditions as an ambient temperature freshwater carbonate deposit in which biological remains (particularly those of macrophyte stands) may comprise significant parts of deposited frameworks (Pedley 2000). Tufa formation is also responsible for i...

Seiches in the Plitvice Lakes

“…Špoljar et al, 2007), organisms (e.g. Matoničkin Kepčija et al, 2011;Sertić Perić et al, 2014) and dead-leaf decomposition (Belančić et al, 2009).…”

Restored tufa-depositing streams: a dynamic interface between terrestrial and aquatic ecosystems

“…The close connection between periphytic protists and the process of tufa deposition is an important element of the dynamics of the tufa-depositing ecosystems such as Krka National Park (Matoničkin and Pavletic ́, 1962;Primc-Habdija et al, 2001). The periphyton matrix retains and accumulates both organic matter particles and tufa particles, increasing microhabitat complexity/structural heterogeneity (Matoničkin Kepčija et al, 2011;Risse-Buhl et al, 2015;Dzubakova et al, 2018). Because periphyton is a substrate-bound community, it has shown promise in several studies for restoring lotic ecosystems.…”

The Emergence of the Family Scirtidae (Insecta: Coleoptera) in Lotic Karst Habitats: A Case Study over 15 Years

“…The water in the catchment area is rich in calcium salts and is limited in organic matter with a pH of around 8. These conditions, combined with the presence of algae and bryophytes, favour the formation of tufa [44,45]. Tufa barriers are geological formations characterised by a porous and layered structure.…”

“…Sampling was undertaken monthly, and the collected material was preserved and treated with 80% ethanol. The specimens were identified to the lowest possible taxonomic level following Klausnitzer [45]. Within the family Scirtidae, the genera can be easily distinguished by their external morphological characters, including their antennae, legs, elytra and pronotum.…”