Elemental Homeostasis Deciphers the Multidimensional Stoichiometric Niche of Fish Communities in the Beibu Gulf

The elemental composition of organisms serves as a relatively standardized and easily quantifiable metric, facilitating quantitative analyses that elucidate species coexistence within ecological communities. The recently proposed multidimensional stoichiometric niche (MSN) framework employs the chemical composition of organisms to delineate the ecological niches of various species. This framework presents a perspective for understanding the functional roles and material cycling mechanisms of fish within aquatic ecosystems. To explore the MSN of fish in the Beibu Gulf and its relationship with elemental homeostasis, the content characteristics of carbon (C), nitrogen (N), phosphorus (P), calcium (Ca), potassium (K), iron (Fe), and zinc (Zn) in 46 fish species from 10 families in the Beibu Gulf were analyzed during April and August 2022. The results revealed significant interspecific variations in the elemental composition among fish from different families. These variations resulted in the existence of mutually differentiated and overlapping MSNs between taxonomic groups of different fish families. The differences in elemental content and ecological niches among various fish species are primarily influenced by morphological characteristics and ecological habits. Further analysis uncovered a negative correlation between the MSN of fish and elemental homeostasis in the Beibu Gulf, with species exhibiting higher homeostasis having smaller ecological niches. This reflects the trade-offs organisms make in response to environmental variability: species with higher homeostasis can reduce the risk of mutation by using fewer resources, while species with lower homeostasis enhance their adaptability through a wider niche. This suggests that organisms can respond to elemental limitations by adjusting their niche width. This study expands the application of ecological stoichiometry theory in fish ecology and has important implications for fishery resource management and ecosystem conservation in the Beibu Gulf.