Occurrence and Habitat Characteristics of Aurelia sp. Polyps in a High-Latitude Fjord

Abstract

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling organisms in intertidal and subtidal sectors of Trondheimsfjorden (Norway). In total, 982 polyps were found on 70 substrata of varying material types during a field survey in spring-summer 2018 along a longitudinal gradient within and outside Trondheimsfjorden. The polyps were identified as Aurelia sp. based on molecular species identification. Most polyps were found in bays with macroalgae canopy on the down facing side of artificial and natural substrata (rocks, concrete, iron) and inside rock cracks. Polyp microhabitats included the surface of Ascidia mentula (solitary ascidian), increments of Pomatoceros triqueter (polychete) tubes and dead Balanus balanoides (barnacle) shells. Based on the deployment of settling plates, abundance of Aurelia sp. polyps ranged from 1.2 (± 0.7) to 0.12 (± 0.07) polyps cm–2. Settlement occurred either directly on the PVC settling plates or as epibionts on the ascidian Ascidia mentula and on barnacle shells of Balanus balanoides. This study provides insights into the potential of local Aurelia sp. polyps contributing to the seasonal occurrence and abundance of Aurelia sp. in fjord systems, where intensive blooms occur annually.

Negative and positive interspecific interactions involving jellyfish polyps in marine sessile communities

“…Some potential competitors provide suitable microhabitat for polyps (e.g. Rekstad et al, 2021), and we have observed polyps on potential competitors in the past. However, in our data, there were very few polyps on potential competitors.…”

“…Whomersley and Picken, 2003), relative abundance of A. aurita polyps will decrease again, so that the increase in medusa abundance may be transient (Feng et al, 2017). However, sessile organisms including solitary ascidians and M. edulis provide suitable substrate for A. aurita polyps (Rekstad et al, 2021). There were few A. aurita polyps on these organisms in our experiment, but this is not the case in every year (M. Spencer, personal observation).…”

“…There is observational evidence for competitive and sometimes mutualistic interactions between jellyfish polyps and other sessile organisms, typically inferred from patterns in abundance on settlement panels or natural substrates (e.g. Watanabe and Ishii, 2001; Colin and Kremer, 2002; Willcox et al, 2008; Ishii and Katsukoshi, 2010; Rekstad et al, 2021). However, experimental evidence is limited.…”

Controls of Aurelia coerulea and Nemopilema nomurai (Cnidaria: Scyphozoa) blooms in the coastal sea of China: Strategies and measures

“…For example, on the undersurface of a floating dock "Haiou" in Jiaozhou Bay, China, A. coerulea polyps were found to grow on the surfaces of many ascidians, bryozoans, and mussels (e.g., Styela clava, Watersipora subtorquata, and Mytilus galloprovincialis) besides on the areas without macro-fouling organisms (Figures 2B-E) like some other Aurelia spp. (Willcox et al, 2008;Di Camillo et al, 2010;Rekstad et al, 2021). However, in situ N. nomurai polyps on the plastic plates cultivated in Jiaozhou Bay were gradually covered by some neighboring fouling organisms (Figure 2F, Feng et al, 2017;Feng et al, 2018a).…”

Aggregation process of two disaster-causing jellyfish species, Nemopilema nomurai and Aurelia coerulea, at the intake area of a nuclear power cooling-water system in Eastern Liaodong Bay, China

“…Blooms caused by jellyfish, especially those of the class Scyphozoa, which have metagenic life cycles, have become a common phenomenon in recent years owing to various environmental pressures, including global climate change and anthropogenic activities (Purcell et al, 2007;Richardson et al, 2009;Purcell, 2012;Dawson et al, 2015;Quinones et al, 2018;Goldstein and Steiner, 2020;Rekstad et al, 2021;Riyas et al, 2021). The sudden or aberrant increase in jellyfish biomass has caused jellyfish disasters in several parts of the globe's oceans, affecting fisheries, and damaging the safety of nuclear power cooling-water systems (NPCSs), especially in Europe, Asia, and North America (Lucas and Dawson, 2014;Schiariti et al, 2015).…”