Mapping habitats for the suitability of jellyfish blooms around the UK and Ireland

Abstract

There is increasing focus on the frequency of jellyfish blooms in the Northeast Atlantic because of negative interactions with humans. However, uncertainty exists as to whether perceptions of increasing bloom frequencies reflect reality due to limitations within long-term population trend data. This study therefore developed and applied a semi-quantitative mapping approach to visualise bloom suitability based on the physiological tolerance of seven jellyfish to ocean temperature, salinity, and a prey index across the Northeast Atlantic. A 10% increase and a 10% decrease in the environmental parameters was then applied to the maps to assess model sensitivity and the potential influence of environmental change on bloom suitability. The study found that optimal physiological temperatures and salinities combined with peaks in prey abundance drove higher bloom suitability and determined distribution. Several locations predicted to be at high risk of bloom occurrence off British and Irish coasts were found to coincide with areas of high anthropogenic activity that could be impacted by blooms. In the absence of long-term datasets on jellyfish population dynamics, the results and methods developed in this study allow an understanding of historic bloom events and predictions of future populations that will be useful in informing monitoring and management.

Coupling hydrodynamic drifting simulations and seasonal demographics to forecast the occurrence of jellyfish blooms

“…In addition, we also used auxiliary data to describe the physiological limits of medusae survival and reproduction. Irrespective of how temperature and salinity combine to influence the dynamics of A. aurita populations, there are certain environmental conditions that remain unsuitable for the establishment of medusae populations, and therefore bloom events (Kennerley et al, 2021). Consequently, corresponding with the environmental and physiological thresholds of A. aurita outlined in Conley & Uye (2015), Lucas (2001), and Widmer et al (2016), we introduced minimum temperature and salinity thresholds into our demographic models, below which medusae survival (≤-1°C & ≤14ppt) and/or reproduction (≤13°C & ≤15ppt) are inhibited.…”

“…Moreover, while it is debated whether the causal mechanisms are increasing global jellyfish abundances or increased human exploitation of coastal environments, there is a growing perception that the recurrence frequency of jellyfish bloom events is increasing (Condon et al, 2013). Regardless of this apparent increase, however, the dynamics of jellyfish populations and thus the causal mechanisms of bloom formation remain poorly understood (Fernández-Alías et al, 2024; Goldstein & Steiner, 2020; Kennerley et al, 2021), leaving us unable to mitigate their broad ecological and economic impacts (Condon et al, 2013).…”

“…Our limited knowledge of jellyfish population dynamics arises due to their complex metagenic life cycles which consist of pelagic and benthic stages separated in both time and space (Lucas, 2001). These complex life cycles are further complicated by high stage-specific plasticity in response to changing environmental conditions (Goldstein & Steiner, 2020; Hirst & Lucas, 1998; Kennerley et al, 2021). Here, we introduce a predictive framework, combining hydrodynamic simulations and seasonal demographic patterns, that aims to enhance our understanding of the mechanisms governing the timing and geographical location of jellyfish blooms.…”