How Turbidity Mediates the Combined Effects of Nutrient Enrichment and Herbivory on Seagrass Ecosystems

Abstract

While nutrient enrichment and herbivory have been well recognized as the main driving factors of seagrass meadow fragmentation and degradation, there is limited understanding of how their relative importance shifts across large spatial scales where environmental factors such as turbidity can vary. In this study, a field control experiment was conducted in two Zostera japonica meadows distributed on the two banks of the Yellow River Estuary with different turbidity, to investigate the combined effects of nutrient enrichment and herbivory on seagrass and macroalgae. Our results showed that turbidity had the mediating force of shifting the relative importance of nutrient enrichment and herbivory to seagrass and macroalgae. While herbivory played a vital role in maintaining the balance between the two primary producers in a turbid environment, nutrient enrichment tended to offset herbivory-induced biomass loss by promoting seagrass growth in a less turbid system. Additionally, two potential mechanisms that might regulate the responses of seagrasses and macroalgae to nutrient enrichment and herbivory under different turbidity are proposed. On the one hand, turbidity might mediate the feeding preference of herbivores. On the other hand, nutrient enrichment favors the growth of opportunistic macroalgae over seagrass in turbid systems. Our study emphasizes the mediating force of turbidity on seagrass ecosystems, and provides references for the protection and restoration of seagrass meadows under multiple environmental stressors, and prompts further studies on the feedback between sediment dynamics and seagrass meadows in the context of ecogeomorphology.

Black Sea Eutrophication Comparative Analysis of Intensity between Coastal and Offshore Waters

“…When water transparency decreases, it affects the light availability deeper in the water column, which can inhibit the growth of other, light-dependent marine plants and phytoplankton. Opportunistic macroalgae, however, are often capable of surviving and even prospering in lower light conditions compared to their competitors [117]. They can effectively utilise the available light more efficiently or have mechanisms that allow them to capture light across a broader spectrum.…”

Trade‐Off Between Light Deprivation and Desiccation in Intertidal Seagrasses Due To Periodic Tidal Inundation and Exposure: Insights From a Data‐Calibrated Model

“…Similarly, the YRE is a reasonable location choice because it contains the largest habitat of N . japonica in China (Zhou et al., 2022), where we have performed extensive field monitoring and experiments (Wang et al., 2021, 2022).…”

“…N. japonica is a reasonable species choice for this purpose because it is one of the most widely distributed seagrass species in China's coastal areas. Similarly, the YRE is a reasonable location choice because it contains the largest habitat of N. japonica in China (Zhou et al, 2022), where we have performed extensive field monitoring and experiments (Wang et al, 2021(Wang et al, , 2022.…”

Trade-off between light deprivation and desiccation in intertidal seagrasses due to periodic tidal inundation and exposure: insights from a data-calibrated model

“…Z. japonica is a reasonable species choice for this purpose because it is one of the most widely distributed seagrass species in China’s coastal areas. Similarly, the YRE is a reasonable location choice because it contains the largest habitat of Z. japonica in China (Zhou et al 2022), where we have performed extensive field monitoring and experiments (Wang et al 2022; Wang et al 2021).…”