Spatial variation in periphyton fatty acid composition in subtropical streams

Abstract

1. Benthic algae play an important role in many stream food webs, not only serving as a major carbon source but also influencing energy transfer as the primary source of polyunsaturated fatty acids (PUFA). Dietary deficiency in PUFA can limit animal growth and reproduction. Algal PUFA content can vary considerably in response to abiotic factors. 2. We conducted a field investigation in streams in South-East Queensland, Australia, to identify environmental factors affecting the fatty acid composition of periphyton. 3. Riparian canopy cover and NO x -N concentrations explained most of the observed variation in periphyton fatty acid profiles. NO x -N concentrations showed negative relationships with most saturated fatty acids (SAFA), while mono-unsaturated fatty acids (MUFA) and the fatty acids 16:0 and 16:1x7 were negatively correlated with canopy cover. In contrast, the percentage of highly unsaturated fatty acids (HUFA) in periphyton was greater with increasing canopy cover regardless of NO x -N concentrations. 4. Variation in riparian canopy cover and nutrients gave rise to opposite outcomes in terms of periphyton food quality and quantity. The highest periphyton food quality, measured by HUFA content, occurred in streams with high canopy cover and low nutrients, while the highest periphyton food quantity occurred in streams with low canopy cover. 5. Our study suggests that changes in riparian vegetation and/or nutrient inputs can significantly alter the fatty acid content of periphyton, with important implications for aquatic consumers. We recommend that future studies on impacts of riparian clearing or nutrient enrichment in stream ecosystems place more attention on the effects of food quality rather than quantity.

Feeding strategies for the acquisition of high‐quality food sources in stream macroinvertebrates: Collecting, integrating, and mixed feeding

“…Our results provide field evidence that periphyton in fall (low temperature) contained more EPA% compared with periphyton in summer (high temperature), since most previous studies focused primarily on individual algal species in the laboratory (Guschina and Harwood ; Piepho et al ). As for riparian canopy, periphyton ARA% increased as riparian canopy increased within seasons, which is consistent with earlier studies in temperate and subtropical streams (Hill et al ; Guo et al ). Nutrient concentrations did not show significant effects on periphyton FA, probably because of the very low human perturbation in our study area.…”

“…The LC‐PUFA content of periphyton is sensitive to seasonal and spatial variation in stream environmental conditions (Hill et al ; Cashman et al ; Guo et al ). For example, the extent of FA unsaturation in algae can vary with temperature.…”

“…Moreover, spatial differences in riparian canopy cover along the river continuum may regulate periphyton LC‐PUFA synthesis. High‐canopy cover generally increases the relative content of EPA and ARA and reduces ALA and LIN (Hill et al ; Guo et al ), whereas low canopy is required for the synthesis of saturated fatty acids (SAFAs), which are often used for energy storage (Brett and Müller‐Navarra ). In addition, periphyton LC‐PUFA content is also influenced by nutrient levels, pollutant inputs, and streambed drying (Guschina and Harwood ; Sanpera‐Calbet et al ).…”

Subsidies of long‐chain polyunsaturated fatty acids from aquatic to terrestrial environments via amphibian emergence

“…Whiles et al., ). Some of the study ponds were more heavily shaded than others, and this could affect algal production and LC‐PUFA content, and therefore availability of dietary EPA and DHA (Guo, Kainz, Sheldon, & Bunn, , ). Studies specifically designed to examine the roles of light availability, primary production, and algal community structure on LC‐PUFA export to terrestrial predators will provide important insight into factors influencing the abundance and distribution of these nutrients, as well as the effects of anthropogenic modifications to landscapes.…”

Lipid biomarkers and pertinent indices from aquatic environment record paleoclimate and paleoenvironment changes

“…Lipid biomarkers from aquatic sediments, which are used as paleoclimate and paleoenvironment proxies, mainly consist of alkanes, alkenes, alkanols, sterols, ketones, fatty acids, GDGTs and so forth. These biomarkers are derived from a wide variety of origins, including but not limit to (1) upland terrestrial plants (Street et al, 2013;Vogts et al, 2009), (2) emergent macrophytes (Cranwell, 1973(Cranwell, , 1974Cranwell et al, 1987;Eglinton and Hamilton, 1967;Street et al, 2013;Wiesenberg and Schwark, 2006), (3) floating and submerged macrophytes (Seki et al, 2009;Street et al, 2013), (4) algae (Cranwell et al, 1987;Guo et al, 2015), (5) fauna (Fulco, 1983;Volkman et al, 1980a), (6) bacteria (including archaea) (Horikawa et al, 2010;Vogts et al, 2009), and moss (Nott et al, 2000).…”