Influence of short periods of increased water temperature on species composition and photosynthetic activity in the Baltic periphyton communities
Biologia
pp 1–6 | Cite as
Influence of short periods of increased water temperature on species composition and photosynthetic activity in the Baltic periphyton communities
AuthorsAuthors and affiliations
Filip PniewskiZuzanna Sylwestrzak
Open Access
Original Article
First Online: 13 September 2018
Received: 08 May 2018
Accepted: 28 August 2018
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Abstract
Periphyton plays a vital ecological role in shallow, well-lit ecosystems which are vulnerable to rapidly changing environmental conditions, including raising temperature due to global warming. Nevertheless, little is known on the effect of increased temperatures on the taxonomic structure and functioning of periphytic communities. In this study, the influence of short-term temperature increase on the species composition and photosynthetic activity of the Baltic periphytic communities was investigated. The collected communities were exposed to increased temperature of 23 °C (ca. 4 °C above the summer average) for 72 h. After this time, species composition of the communities was studied under light microscope and their photosynthetic performance was evaluated using PAM fluorometry. Results showed that the biomass of cyanobacteria slightly increased. There were significant changes in the abundance of diatom species, among which Fragilaria fasciculata and Navicula ramosissima, were negatively affected by the elevated temperature and their cell number significantly decreased, whereas, Diatoma moniliformis and N. perminuta were stimulated by the increased temperature. Additionally, a shift towards higher abundance of smaller taxa was also observed. The higher quantum yield of photosystem II (PSII) (higher ΦPSII) accompanied by the lower value of non-photochemical quenching (NPQ) observed in communities kept at 23 °C showed more efficient photosynthesis. This was further confirmed by the changes in rapid light curves (higher photosynthetic capacity, rETRmax, and photoacclimation index, Ek). The obtained data constitute evidence that short periods of increased temperature significantly affect the structure and functioning of the Baltic periphyton.
KeywordsPeriphyton Chlorophyll fluorescence Diatoms Temperature Baltic Sea
Introduction
Periphyton assemblages (algal biofilms) can be found on a variety of substrata submerged in water. They can thrive on a solid surface-water interface by excreting extracellular polymeric substances. Mature periphytic assemblages have three-dimensional structure, including taxa of different growth forms (Tuji 2000; Gulzar et al. 2017). Periphyton can be responsible for majority of primary production especially in shallow well-lit habitats, in such aquatic environments as lakes, rivers, coastal waters etc. (Dodds et al. 1999). It is also an important source of food for invertebrates (Gulzar et al. 2017). Interacting with the surrounding environment periphyton affects a concentration of nutrients and provides oxygen (Gaiser 2009). Furthermore, periphyton, due to its short life cycle, quickly responds to pollution and changes in environmental conditions, and thus it is often used as an indicator of water quality (Gulzar et al. 2017).
Nowadays, the environment is undergoing a dramatic change due to global warming, including not only continually increasing temperatures but also the frequency and intensity of climate extreme phenomena such as heat waves (Vieira et al. 2013). Recent studies proved temperature increase in the Baltic and have shown that in summer the average temperatures of ca. 19 °C in the Southern Baltic are recorded. However, occasionally short periods (several days) of temperatures above 23 °C can be also observed (http://www.satbaltyk.pl) (Siegel et al. 2006; Bradtke et al. 2010; Woźniak et al. 2011; Rak and Wieczorek 2012; Stramska and Białogrodzka 2015). Despite the ecological importance of periphyton, little is known on the influence of increased temperature on its structure and functioning. The analyses of diatom dominated benthic communities from intertidal mudflats have shown that transient higher temperatures stimulated its photosynthesis, whereas, prolonged high temperature exposer led to the biomass decrease, photosynthesis impairment and changes in species composition promoting growth of cyanobacteria (Hicks et al. 2011; Vieira et al. 2013; Cartaxana et al. 2015). In subtidal systems a shift towards heterotrophic benthic communities was also recorded (Hancke and Guld 2004). Such strong effects observed for benthic microalgae suggest that periphyton may also undergo significant temperature-driven changes.
Thus, the aim of this study was to investigate the influence of short-term temperature increase on the structure and photosynthetic activity of the Baltic periphytic communities. In this study, species composition of periphyton kept at control (18 °C) and elevated (23 °C) temperatures was investigated and their photosynthetic activity was assessed by means of variab (...truncated)