Abstract
The benthic scyphopolyp population is an important stage in the scyphozoan lifecycle. Nevertheless, few studies have detailed the natural feeding and quantified the energy flux of polyps based on field research. To better understand the scyphopolyp natural diet and seasonal variation patterns in the ingestion rate, in situ feeding experiments were conducted on Aurelia coerulea polyps in Jiaozhou Bay, China from August 2018 to April 2019. The diet of A. coerulea polyps was determined by gut content analysis. Digestion rates were also measured. Ingestion rates, based on the gut contents and digestion rates, were assessed monthly. Copepods, copepod nauplii, and ciliates were identified in the guts of A. coerulea polyps. Copepods with the bulk of total prey intake in number are an important source of nutrition for A. coerulea polyps in Jiaozhou Bay. Prey capture of A. coerulea polyps (prey polyp–1) varied among months, and was highly dependent upon the abundance of planktonic prey in the habitat. Copepods and copepod nauplii were digested more rapidly as temperature increased. Carbon weight-specific ingestion rate exhibited an obvious seasonal change, with the mean value of 0.13 ± 0.12 μg C μg C–1 d–1. More rapid digestion of prey at higher temperatures and larger prey availability would cause a higher ingestion rate in polyps. Scyphopolyps are widely distributed predators in littoral ecosystems and they may play an important role in plankton–benthos coupling by transferring energy from the water column to the benthos. Massive scyphopolyps blooms may influence pelagic ecosystems.
Highlights
Interest in the importance of jellyfish in the material cycle and the energy flow of marine ecosystems has increased as outbreaks of jellyfish populations attract public and scientific attention (Dong et al, 2010; Uye, 2011; Condon et al, 2013; Duarte et al, 2013)
To better understand the scyphopolyp diet and seasonal variation in ingestion rate in the field, in situ feeding experiments were conducted on A. coerulea polyps in Jiaozhou Bay between August 2018 and April 2019 year; this provides a realistic environment for the prey capture of polyps
Zooplankton collected by a II plankton net (160-μm mesh size) within the study area were comprised of 54.04 ± 9.60% copepods, 4.82 ± 3.34% copepod nauplii, 7.20 ± 8.43% tunicates, 10.53 ± 5.61% chaetognaths, 7.17 ± 4.71% small medusae, and 16.23 ± 9.18% others in abundance
Summary
Interest in the importance of jellyfish in the material cycle and the energy flow of marine ecosystems has increased as outbreaks of jellyfish populations attract public and scientific attention (Dong et al, 2010; Uye, 2011; Condon et al, 2013; Duarte et al, 2013). Mass occurrences of Aurelia medusae have been reported from many parts of the world (Möller, 1980; Olesen et al, 1994; Omori et al, 1995; Dong et al, 2010). This jellyfish has metagenic life cycles, with pelagic stages (ephyra, medusa, and planula) and benthic stages (polyp, strobila, and podocyst) (Arai, 1997; Lucas et al, 2012). The majority of field studies have been confined to the population dynamics and locations of polyp, the timing and rate of strobilation, and the substrates of polyp colonization (e.g., Lucas and Williams, 1994; Uye and Shimauchi, 2005; Purcell et al, 2009; Ishii and Katsukoshi, 2010; Feng et al, 2017)
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