Seasonal variation in fatty acid composition of seston and the copepod Calanus sinicus(Brodsky,1962)in Jiaozhou Bay and its trophic implications

The fatty acid compositions of seston and Calanus sinicus were investigated to study trophic relationships in Jiaozhou Bay. Principal component analysis was carried out to ordinate the fatty acid patterns of seston in stations and months. The results showed that diatoms were most abundant in the phytoplankton at station A5 (located in the northwest of the bay:36°9′N, 120°20′E) and least abundant at station D7 (located outside of the bay: 35°59′N, 120°26′E). By contrast, dinoflagellates were most abundant at station D7 and least abundant at station A5. According to the annual variations of 16:1ω7 and 18:4ω3/ 16:1ω7, diatoms flourished mainly in spring and summer, while dinoflagellates bloomed exclusively in summer. A distinctive feature of the fatty acid composition of C. sinicus was the prevalence of 20:5ω3 and 22:6ω3. The higher content of 16:1ω7 over 18:4ω3 in females indicated that diatoms contributed more than dinoflagellates to the diet of C. sinicus. The feeding intensity of C. sinicus on diatoms was higher in spring and autumn than in other seasons. The herbivorous indicators 20:1 and 22:1 were comparatively low, suggesting that besides phytoplankton, C. sinicus might feed on a wider range of particles including organic detritus, bacteria and small copepods.

The fatty acid compositions of seston and Calanus sinicus were investigated to study trophic relationships in Jiaozhou Bay. Principal component analysis was carried out to ordinate the fatty acid patterns of seston in stations and months. The results showed that diatoms were most abundant in the phytoplankton at station A5 （located in the northwest of the bay： 36~9＇N, 120~20＇E） and least abundant at station D7 （located outside of the bay： 35~59＇N, 120~26＇E）. By contrast, dinoflagellates were most abundant at station D7 and least abundant at station A5. According to the annual variations of 16：1 （o7 and 18：4（o3/ 16：1（o7, diatoms flourished mainly in spring and summer, while dinoflagellates bloomed exclusively in summer. A distinctive feature of the fatty acid composition of C. sinicus was the prevalence of 20：5o3 and 22：6（o3. The higher content of 16：1（o7 over 18：4（o3 in females indicated that diatoms contributed more than dinoflagellates to the diet of C. sinicus. The feeding intensity of C. sinicus on diatoms was higher in spring and autumn than in other seasons. The herbivorous indicators 20：1 and 22：1 were comparatively low, suggesting that besides phytoplankton, C. sinicus might feed on a wider range of particles including organic detritus, bacteria and small copepods.