Impact of freshwater discharges on the abundance and spatial distribution of moon jellyfish (Aurelia aurita) in Yellow River Estuary, China

Abstract

The frequency of moon jellyfish (Aurelia coerulea) outbreaks has escalated significantly, often resulting in substantial ecological disruptions. Estuarine ecosystems, particularly vulnerable to terrestrial inputs and anthropogenic disturbances, represent key outbreak zones for this species. Utilizing bycatch data from 48 scientific bottom trawl surveys (2011-2022), this study employed species distribution models (SDMs) and structural equation modeling (SEM) to evaluate how Yellow River discharge - China's second-largest river system - influences moon jellyfish distribution patterns. Results demonstrated a unimodal monthly abundance pattern from May to December, with peak densities (2950.12 ind/h) occurring in July during low-discharge years, significantly exceeding high-discharge year averages (1170.18 ind/h). Spatial analysis revealed concentrated distributions near the river mouth during low-discharge periods versus broader dispersion under high-discharge conditions. Notably, 6.39 % of sampling stations (n = 46) in low-discharge years recorded abundances >1000 ind/h, compared to fewer stations in high-discharge years. Habitat suitability modeling identified 15.16 % of the study area as optimal habitat (HSI≥0.8) under low discharge versus 11.35 % during high discharge. Discharge regimes altered ecological drivers: environmental parameters directly governed abundance in high-discharge years, while primary productivity emerged as the primary determinant during low-discharge periods, with environmental factors operating indirectly through productivity mediation. These findings provide mechanistic insights for developing predictive management strategies against jellyfish proliferation in the Yellow River estuary.

Keywords: Freshwater discharges; Jellyfish blooms; Moon jellyfish; Spatial distribution; Suitable habitat; Yellow River.