MEPS 358:103-114 (2008)  -  DOI: https://doi.org/10.3354/meps07327

ABSTRACT: Multiple stable isotope and fatty acid analyses were applied to examine food web dynamics in an eelgrass Zostera marina L. system in the western Baltic Sea. Samples of eelgrass, epiphytic algae, sand microflora, red algae, phytoplankton and main consumer species were collected in June 2002. δ¹³C values of primary producers ranged from –9.6‰ for eelgrass to the most depleted value of –34.9‰ for the most abundant red alga, Delesseria sanguinea. Epiphyte δ¹³C (–11.3‰) was close to the value for eelgrass, whereas sand microflora and phytoplankton showed intermediate values (–20.0 and –22.6‰, respectively). δ¹³C values of consumer species varied from –12.2‰ in the gastropod Lacuna vincta to –23.9‰ in the amphipod Amphitoe rubricata. Epiphytes, sand microflora and phytoplankton had relatively similar fatty acid signatures, indicating a dominance of diatoms. Fatty acid composition of the main consumers included the biomarker fatty acids for diatoms and red algae, whereas those for eelgrass were negligible. The stable isotope data in combination with the results of the fatty acid analysis strongly indicated that the food web in this eelgrass community was based on epiphytes, sand microflora and red algae. Additionally, the continuous distribution of δ¹⁵N values implied a food web that was characterized by a large proportion of generalist feeders in every group of consumers and by a high degree of omnivory.

KEY WORDS: Food web structure · Seagrass · Epiphytes · Microphytobenthos · IsoSource