Trophic structure of the pelagic food web in the East China Sea.

Mei-Ling Bai,Gwo-Ching Gong,Chih-Hao Hsieh,Yu-Ching Lee,Fan-Sian Lin

doi:10.1186/s40555-014-0089-0

Abstract

Trophic structure and trophic transfer efficiency are among the most fundamental characteristics of an ecosystem. They characterize the transfer of nutrient and energy and are crucial in estimating the yield of harvestable biomass. In this study, we investigated the regulation of trophic structure (phytoplankton, zooplankton, and larval fish abundance) and biomass ratio of zooplankton to phytoplankton (as an indicator of transfer efficiency) in the East China Sea, one of the largest marginal seas in the world and an important fishing ground. Theresults showed that when sea surface temperature was below 25°C, temperature co-acted with resource availability (zooplankton for larval fish and phytoplankton for zooplankton) in determining the trophic structure. When sea surface temperature was above 25°C, resource availability dominated the regulation of trophic structure. Biomass ratio of zooplankton to phytoplankton decreased with increasing phosphate concentration. Our study suggested that the trophic structure of the East China Sea might be controlled by bottom-up processes, and this control is mediated by temperature.

Highlights

Trophic structure and trophic transfer efficiency are among the most fundamental characteristics of an ecosystem
Abrupt changes occurred in its relationships with Sea surface temperature (SST), SSS, and DIN, and the piecewise model based on SST had the best fit among all models
Less than 1% of the variation in larval fish density could be explained by Discussion Our study suggested that the bottom-up control regulates the trophic structure in the East China Sea, and this control is mediated by temperature (Table 2, Figure 3)

Summary

Introduction

Trophic structure and trophic transfer efficiency are among the most fundamental characteristics of an ecosystem. The biomass of each trophic level is largely determined by available resources, suggesting a bottom-up control (e.g., Iverson 1990; Ware and Thomson 2005; Chassot et al 2007), whereas in other marine ecosystems, the predatorprey interaction at higher trophic levels cascades down to the lower ones, demonstrating a top-down process (e.g., Frank et al 2005; Daskalov et al 2007; Casini et al 2008). Great research efforts have been devoted to understand the regulation of trophic transfer efficiency, and the factors proposed include environmental conditions such as temperature, light or nutrients (Dickman et al 2008; Davis et al 2010; Hoekman 2010), the indirect effect from a third trophic level (bottom-up or topdown cascade) (Hairston and Hairston 1993; Dickman et al 2008), and the composition, diversity and structure of the trophic levels in issue (Mallin and Paerl 1994; Ye et al 2013)

Methods

Results

Discussion

Conclusion