Correlations between fatty acid composition of seston and zooplankton and effects of environmental parameters in a eutrophic Siberian reservoir

Abstract

a b s t r a c tDuring two sampling seasons we analyzed on weekly basis fatty acid (FA) composition of seston fraction o 130 mm and zooplankton fraction 4130 mm, and compared them using a multivariate canonical correlation analysis (CCA). Besides, we evaluated a possible impact of water temperature and inorganic nutrients on FA composition of the seston and the zooplankton.In spite of significant differences in percentages of several individual FAs, we found very strong canonical correlation (cross-correlation, 1-week lag) between FA composition of the seston and the zooplankton. The most important factor, providing the overall canonical cross-correlation between FA profiles of the seston and the zooplankton fractions was eicosapentaenoic acid (20:5o3, EPA). FA composition of the zooplankton fraction had comparatively poor correlations with taxonomic composition of the zooplankton. Thus, seasonal variations of FA composition of the zooplankton were determined primarily by seasonal changes in FA composition of the seston, rather than by taxonomic differences of FA profiles between rotifers, cyclopoids and cladocerans. FA composition of the seston was strongly affected by its taxonomic composition, namely by that of phytoplankton. According to CCA, the highest factor loadings pertained to diatoms interacting with their marker acids, including EPA, and cyanobacteria and greens, interacting with their marker acids. Ciliates and small rotifers composed considerable and sometimes major part of the seston biomass, but according to CCA their contributions to seasonal variations of the total FA profile of the seston were insignificant. This finding indirectly support the conclusion of the other authors, that the main source of FAs presented in ciliates and rotifers must be sought in algae and that they do not modify FA composition of food consumed, apart from repackaging it.Water temperature was the principal environmental parameter which drove the overall variations of FA composition. Factor loadings for the inorganic nutrients were comparatively negligible. The main contribution in the seasonal variation of FA composition of the seston was given by negative interaction between water temperature and percentage of EPA in the seston.

Fatty acid composition as biomarkers of freshwater microalgae: analysis of 37 strains of microalgae in 22 genera and in seven classes

“…Colder temperatures generally increase the unsaturation of microalgae membrane FAs, and thus temperature lowering can increase the relative amount of EPA or DHA which have melting points of −45 to −50°C (Tatsuzawa & Takizawa 1995, Ravet et al 2010). This negative correlation between temperature and EPA was found for the seston of a eutrophic Siberian reservoir (Gladyshev et al 2010) and could have an impact on zooplankton production. Our study shows that algal phylogenetic relationships (class level differences) are the dominant source of FA variation (66%) in our dataset, which included algal strains cultivated in taxon-specific optimal growth conditions.…”

“…Even though the FA profiles of some freshwater Cyanophyceae, Chlorophyceae, and Cryptophyceae classes were characterized by Ahlgren et al (1992) over 20 yr ago, there is still poor knowledge and no studies of FA profiles of freshwater Chrysophyceae and Raphidophyceae, which are common microalgae in many boreal lakes. Because the FA composition of zooplankton in freshwater systems closely reflects seston FA composition (Taipale et al 2009, Gladyshev et al 2010, Ravet et al 2010, FAs would be more useful in freshwater food web studies if the FA composition of a diversity of freshwater phytoplankton was better defined. FAs that are common in microalgae or bacteria can be called characteristic FAs, but can be called diagnostic FAs only if they are not found in other groups.…”

Effect of temperature on contents of essential highly unsaturated fatty acids in freshwater zooplankton

“…Increases of HUFA levels in zooplankton with decrease of water temperature were found in laboratory experiments (Farkas 1979;Schlechtriem et al 2006;Masclaux et al 2009) and also in some lakes as results of inter-annual and (or) seasonal temperature variability (Farkas and Herodek 1964;Maazouzi et al 2008;Gladyshev et al 2010). However, data on short-term laboratory experiments and also data on seasonal variations within a single ecosystem (community) may not be decisive for a conclusion on a possible effect of global warming on HUFA production in aquatic ecosystems.…”

“…The content of HUFA in seston, especially, that of EPA, had significant negative correlation with the water temperature, although this correlation was lower, than that for HUFA content in zooplankton. Decrease of EPA and other polyunsaturated fatty acids in seston in response to increase of temperature is well known (e.g., Sushchik et al 2003b;Gladyshev et al 2010). Also dependence of HUFA levels of zooplankton on that of their diet, seston, is evident (Kainz et al 2004;Rossi et al 2006;Smyntek et al 2008).…”

Efficiency of transfer of essential polyunsaturated fatty acids versus organic carbon from producers to consumers in a eutrophic reservoir

“…However, the transfer between trophic levels evidently is not carried out instantly but has a certain time lag. For instance, FA composition of zooplankton best correlated with that of phytoplankton (seston) with a lag of about 1 week (Taipale et al 2009;Gladyshev et al 2010b). Thus, the second means of TTE calculation was based upon relating of the secondary production for each sampling date to that of primary production for the sampling date a week earlier.…”