The stable nitrogen isotope ratio (δ15N) provides a powerful tool for estimating the trophic positions of consumers in food webs. We measuredδ15N in 28 fish species and 26 invertebrate species that were collected from Liaodong Bay in June and August, 2010. The trophic levels of these organisms ranged from 2.98 to 4.84, but were generally within the range of 3.70–4.56.δ15N values changed in a large proportion (50%) of fish between July and August, suggesting thatδ15N values vary among species and seasonally. The largest increase was in Raja porosa (1.06‰) and the biggest decrease was in Platycephalus indicus (1.84‰). Furthermore, δ15N values decreased in 87.5% of the invertebrates in August. The decrease in 6 invertebrate species was > 1‰ (37.5%), suggesting that invertebrates exhibit greater seasonal variation inδ15N than fish. We compared theδ15N values for 10 invertebrate species in the nearshore waters and offshore waters of Liaodong Bay to determine whether the inshore seawater environment and ecosystem is influenced by anthropogenic nitrogen inputs.% 应用氮稳定同位素技术分析了2010年6月和8月辽东湾海域主要渔业生物的氮稳定同位素比值,研究了28种鱼类和26种无脊椎动物的营养位置.结果表明,辽东湾海域主要渔业生物的营养级处于2.98~4.84,集中在3.70~4.56；相比6月δ15N 值的分析结果,8月有50%的鱼类δ15N 值增加,孔鳐(Raja porosa)增幅最大,增加了1.06‰；9种鱼类δ15N值减少,鯒(Platycephalus indicus)减幅最大,减少了1.84‰,可见鱼类样品的δ15N值随季节的变化因种类而各异；8月有87.5%的无脊椎动物δ15N值减少,其中,减少幅度大于1‰的有6种,占37.5%,可见无脊椎动物的δ15N 值随季节的变化较明显.通过对不同采样点同种生物δ15N 值的比较发现,辽东湾近岸海域的10种无脊椎动物的δ15N值均高于远岸海域,差值范围为0.05‰~1.49‰,差异极显著(P<0.01),说明人类活动引起的陆源污水排放使近岸海洋生物的δ15N值升高.
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