| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 102 === Limited knowledge concerning the effects of size composition and trophic level (TL) on mercury levels in the demersal fishes associated with human activities in the East China Sea (ECS) still exists. Here we show evidence of strong control of TL on the Hg in fish and its biomagnifications via food webs. The relationship of Hg concentrations in the demersal fishes, collected during the cruise OR1- 870 in July 2008, with environmental variables (e.g., temperature, salinity, dissolved oxygen, nutrients, chlorophyll-a) in the ESC were additionally investigated. The preliminary data of seven selected fish species in the study ranged from 2.6 and 256.2 ng g-1 for total Hg (n=72), 5.1 to 20.5 cm for body length of fish, 0.8 to 173.5 g for body weight, and 3.1 to 3.5 for trophic level, respectively. The results showed that there were good linear relationships between Hg concentrations and fish body length (R2 = 0.79) and weight (R2 = 0.82), respectively, other than environmental variables (R2 = 0 ~ 0.03). It indicates that the Hg concentration in fish is mainly controlled by the growth mechanism of the fish itself through food chain transfer. We further calculated approximately Hg accumulation rate (MAR) via the relationship of Hg concentration with the fish age estimated by using fish body length and its growth coefficient. The results showed a significantly positive correlation of MAR with trophic levels, which relationship is Ln MAR =6.07 TL-15.8 (R2 = 0.89). Globally, the MAR in the demersal fishes of the ECS is much greater than those in other continental margins, suggesting high regional Hg pollution impacts from Mainland China. The MAR as a good indicator hence provides the feasibility to examine the effect of human activities on Hg levels in fish through trophic magnification associated with environmental changes.
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