Study On Trophic Relationship Of Fishes From Bering-chukchi Sea Based On Stable Isotopes

Climate change,represented by global warming,has become the focus of researchers’attention in recent years.Many researches have proved that the receding sea ice cover and increasing seawater temperature in the Arctic caused by climate warming are changing the habits and interspecific trophic relationships of Arctic marine organisms,which in turn affect the structure and function of Arctic marine food webs and the stability of the whole Arctic marine ecosystem.Fish are key hubs for material transfer and energy flow between upper and lower trophic levels,as well as important nodes linking pelagic and benthic communities.It is important to fully understand the feeding characteristics and interspecific trophic relationships of Arctic fish to reveal key ecological processes in Arctic marine ecosystems.Based on the benthic fish samples collected from the 6th,8th,9th,10th and 11th Chinese Arctic scientific expeditions,this paper explores the trophic levels and interspecific trophic relationships of common fishes in the Bering and Chukchi Seas using stable isotope methods as the main technical means,and analyzes the possible causes of the spatial differences in trophic ecology of major fishes,with a view to providing basic information for future Arctic ecological studies.The study concluded that the following conclusions were drawn from the study:1.Stable isotope techniques were used to calculate the stable isotope ratios(δ¹³C,δ¹⁵N)of 29 fish species collected from the Bering Sea-Chukchi Sea,and the results showed that the isotope ratios of fish communities in the Bering Sea-Chukchi Sea spanned a wide range(δ¹³C span 8.10‰,δ¹⁵N span 8.57‰),the food source diversity and nutrient diversity were high;among them,the carbon and nitrogen isotopes of B.saida had the largest span(δ¹³C:-23.88‰～-17.94‰;δ¹⁵N:13.09‰～19.46‰).2.Based on theδ¹³C andδ¹⁵N clustering analysis and the literature on food habits,three types of food habits were identified in the Bering and Chukchi Seas,including planktonic,which mainly feeds on copepods;benthic,which mainly feeds on benthic telopods,polychaetes and bivalves;and omnivorous,which feeds on both benthic and planktonic species.Among them,the number of benthic feeding species is large.3.The trophic levels of fish in the Bering Sea-Chukchi Sea were estimated and the continuous trophic spectrum was constructed based on a single-source,two-isotope Bayesian isotope mixing model“t Rophic Position”package using the filter-feeding bivalves Yoldia limatula and Serripes laperousii as baseline organisms.The results showed that the total trophic level of fish ranged from 2.42 to 4.62 with a mean value of 3.74.4.The stable isotope Bayesian ellipse model（SIBER）was used to calculate the trophic ecotope area of each fish species and the degree of overlap of trophic ecotopes between species.The results showed that each fish species overlapped to some extent with several other fish species,but most species did not completely overlap with each other and maintained a certain degree of uniqueness,which was consistent with the theory of ecotope construction.5.The common Arctic fishes B.saida,H.elassodon and G.tricuspis,which are representative of the species and sufficient number of samples,were selected for the study,and the comparison between stable isotope characteristics,trophic levels and trophic ecological niches in different seas within species and the same seas between species were explored and analyzed,and the following results were obtained:（1）Comparison between different seas of the same speciesa.B.saida in different seas had different feeding habits and the same trophic level;B.saida in the Northern Chukchi Sea（CN）seas had the highest degree of food source diversity and trophic diversification;the trophic ecological niche of S had mild overlap with CN and the Southern Chukchi Sea（CS）,and the other two did not.b.H.elassodon feeding habits as well as trophic levels differed among different waters;H.elassodon in CS waters had the highest diversity of food sources and trophic diversity;the trophic level of CN was higher than that of the South of st.Lawrence island（SSLI）and CS;the trophic ecological niches of CN did not overlap with CS and SSLI,and CS and The nutrient ecological niches of CN did not overlap with CS and SSLI,and the nutrient ecological niches of CS and SSLI mildly overlapped,probably due to the influence of Bering Chukchi Summer Water（BCSW）,which brought the bait organisms of SSLI to CS waters.c.G.tricuspis in different waters had different feeding habits and the same trophic level;G.tricuspis in CS waters had a higher diversity of food sources and lower trophic diversity;most of the trophic ecological niches of CS and the North of st.Lawrence island（NSLI）overlapped,probably due to the same influence of BCSW,which brought the bait organisms of NSLI to CS waters.（2）Comparison between different species in the same sea areaa.Northern Chukchi Sea:B.saida and H.elassodon differ in their main food sources,as well as in their trophic levels;B.saida has a higher diversity of food sources as well as trophic diversity than H.elassodon.H.elassodon had a trophic level of 4.23,the highest trophic level in this study,probably due to the consumption of shrimp and crabs at higher trophic levels in its diet;there was no overlap in the trophic ecological niches of the two,indicating no interspecific competition.b.Southern Chukchi Sea:B.saida,H.elassodon and G.tricuspis had different feeding habits and similar trophic levels between them;H.elassodon had the highest diversity of food sources,G.tricuspis had the highest trophic diversity;B.saida had no overlap with G.tricuspis in trophic ecological niches,partial overlap with H.elassodon,and mild overlap with the latter two,the reasons for which are related to the feeding habits of the three:B.saida in CS mainly feeds on zooplankton and does not compete with G.tricuspis,which feeds on benthic animals,H.elassodon,although it feeds mainly on benthic organisms,also feeds on pelagic food,so it has no competition with B.saida and G.tricuspis.In this study,we analyzed the carbon（C）and nitrogen（N）stable isotope characteristics of major fishes in the Bering and Chukchi Seas,calculated their trophic positions in the food web,and constructed their continuous trophic spectra and trophic ecological niches,in order to scientifically assess the trophic positions and interspecific trophic relationships of major fishes in the food web,to fill the gaps in the study of trophic relationships of Arctic fishes in China,and to provide basic biological information for future studies on the trophic ecology of Arctic fishes.