Temporal variation in stable isotope composition (δ13C, δ15N and δ34S) of a temperate Zostera marina food web

Abstract

Simultaneous triple stable isotope analysis of carbon, nitrogen and sulphur was employed to study the temporal variation in the food web of a subtidal eelgrass Zostera marina bed in the western Baltic Sea. Samples of 3 potential food sources (eelgrass, epiphytes and seston) and consumer species were collected biweekly from March through September 2011. Temporal variation of stable isotope compositions was observed in primary producers and consumer species. However, variation between replicates, particularly omnivores, often exceeded variation over time. The high degree of omnivory among the generalist feeders in this eelgrass community allows for generalist feeders to flexibly switch food sources, thus enhancing food-web stability. As coastal systems are subject to seasonal changes, as well as alterations related to human disturbance and climate, these food webs may retain a certain resilience due to their plentiful omnivores.

Seasonal Variability of the Carbon and Nitrogen Isotopic Signature in a Zostera noltei Meadow at the NW Iberian Peninsula

“…The epiphytic nitrogen isotopic signature did not differ significantly in the growth and non-growth seasons defined for Z. noltei. The difference in seasonal patterns of δ 15 N between seagrass leaves and epiphytes is consistent with the findings by Mittermayr et al (2014) in Kiel Bight. Organisms belonging to the epiphytic fraction are characterized by shorter life cycles than seagrass leaves, thus rapidly assimilating episodic inputs of nutrients (Martínez-Crego et al, 2014).…”

Seasonal fluctuation in food sources of herbivorous gastropods in a subtropical seagrass bed estimated by stable isotope analysis

“…Gastropods with δ 15 N values lower than the averaged δ 15 N value of macrophytes plus 2.4, the fractionation factor of δ 15 N (Mittermayr et al ., 2014), were regarded as herbivores. The food sources of the herbivorous gastropods were estimated using the mixing models in siarmcmcdirichletv4 function of package SIAR (Stable Isotope Analysis in R; Parnell et al ., 2010) in R version 3.3.3 (R Development Core Team, 2017).…”

“…mutabile ) were used for estimating the contribution rates because no phaeophytes or chlorophytes were found at the study site. The fractionation factors were used as 0.5 ± 0.5 for δ 13 C and 2.4 ± 1.1 for δ 15 N, respectively (Mittermayr et al ., 2014).…”

Trophic specializations of damselfishes are tightly associated with reef habitats and social behaviours

“…The influence of these morphological features on the trophic ecology of Pomacentridae is emphasized by the significant differences in S isotope ratios among species. Indeed, δ 34 S has been used to unravel food sources for mobile consumers (Jardine et al 2012) and to ascertain within-producer variability (Connolly et al 2004;Hamilton 2009;Mittermayr et al 2014). Pelagic producers using seawater sulphates (~22.9‰) have higher δ 34 S values, whereas consumers depending on sulphur from sediments (~1‰) have lower δ 34 S values (Kharlamenko et al 2001;Connolly et al 2004).…”

“…More recently, the stable isotope ratio of sulphur (S 34 /S 32 or δ 34 S) has been used as an additional tracer of food sources (McCutchan et al 2003;Connolly et al 2004;Moreno et al 2010). The high variation in δ 34 S values between seawater (~22.9‰) and sediments (~1‰) helps to discriminate the origins of prey and locations of feeding grounds within the marine environment (Kharlamenko et al 2001;Fry et al 2008;Mittermayr et al 2014). Even though δ 34 S is extremely helpful to disentangle trophic interactions among organisms, no study has integrated this element to investigate the ecology of coral reef fishes.…”