Quantitative effects of pycnocline and dissolved oxygen on vertical distribution of moon jellyfish Aurelia aurita s.l.: a case study of Mikawa Bay, Japan

Abstract

Blooms of moon jellyfish Aurelia aurita s.l. occur in various vertical distribution patterns within the water column. Reasons for these distribution patterns have remained obscure. To quantify the influence of pycnocline and low dissolved oxygen (DO) on the vertical distribution of A. aurita aggregations, we investigated temperature, salinity, DO, and observed densities of A. aurita at 1-2 m depth intervals via video camera in a eutrophicated, enclosed bay, Mikawa Bay, Japan, for 3 years. During the observed period, stratification and hypoxic status of the bay varied seasonally and interannually due to climatic events, such as rainy season and typhoon passage. Both sharp pycnocline and low DO limited A. aurita vertical distribution. The more strongly stratified the water column, the more the upper boundary of A. aurita distribution was restricted. Bottom hypoxic water limited the lower boundary of A. aurita distribution. The DO threshold for in situ distribution was estimated to be *2.5 mg l -1 , which is much higher than the experimentally obtained, sublethal values identified in previous studies. Our results show that climatic events affect A. aurita vertical distribution through changes in the physical characteristics of the water column.

Seasonal alternation of the ontogenetic development of the moon jellyfish Aurelia coerulea in Maizuru Bay, Japan

“…In the bottom layer, where A . coerulea usually aggregates in Japanese coastal waters [61–63], water temperatures of 19.8–22.0°C and 17.1–21.1°C were observed in June and November, respectively (Fig 3). As the water temperature was different between the direct-development and metagenetic periods and showed similar values (approximately 20°C) in the switching periods, a water temperature of 20°C is suggested to be the threshold for switching the egg size and ontogenetic development of A .…”

Jellyfish distribution and abundance in relation to the physical habitat of Jellyfish Lake, Palau

“…The vertical distribution of Mastigias papua etpisoni throughout the lake is probably related to environmental parameters, which is well recognized in other species (Graham et al 2001) but not fully investigated for Mastigias papua etpisoni . For example, the effects of water temperature, salinity, light and dissolved oxygen on growth, reproduction and survival have been documented for other medusae and polyps (Dong et al 2015, Purcell et al 2012, Suzuki et al 2016). During the REMUS surveys, we measured the distribution of Mastigias papua etpisoni in higher resolution than past studies (Dawson & Hamner 2003, Hamner et al 1982) and found significantly more jellyfish between 6–7 m, where PAR was ~200 umol m −2 s −1 and oxygen was ~2 mg L −1 .…”

“…Our findings provide useful insights for future mission planning, validation and analysis that could be used to study jellyfish or other organisms in enclosed or semi-enclosed areas. Ecological concepts, such as habitat choice, diel vertical migration, aggregation structure, predator–prey dynamics and population variability, could be investigated in lagoon, cove and lake systems where jellyfish often live in large populations (Colombo et al 2009, D'ambra et al 2013, Suzuki et al 2016). Therefore, using one platform, behavioural patterns and variability can be examined across many spatiotemporal scales with greater ease and speed compared with traditional methods while also increasing data quantity.…”

Life Cycle of Edible Jellyfish Acromitus hardenbergi Stiasny, 1934 (Scyphozoa: Rhizostomeae) Inhabiting a Brackish-Water Environment

“…At Kitasato University, the optimal salinity for planula settlement was examined at a temperature of 30 °C and salinity of 3, 5, 10, 15, 20, and 30, which mimicked the salinity range (0-20) in the Perak River estuary [15,16] and in normal seawater (30). A batch of 10…”

“…At Kitasato University, the optimal salinity for planula settlement was examined at a temperature of 30 • C and salinity of 3, 5, 10, 15, 20, and 30, which mimicked the salinity range (0-20) in the Perak River estuary [15,16] and in normal seawater (30). A batch of 10 planulae 3 days after the fertilization was introduced into one well of a 12-well microplate filled with 5 mL of seawater with each salinity level.…”