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BIOACCUMULATION OF MERCURY ON FISHES IN MINAMATA BAY, BASED ON FOOD WEB ANALYSIS AND CARBON AND NITROGEN ISOTOPE ANALYSIS

From 2010 we have been researching the bioaccumulation of mercury in several fishes in Minamata Bay and surrounding areas in Yatsushiro-Kai, Kumamoto, Japan. For the determination of feeding types of 60 species fishes (600 samples) sampled by gill net at some sampling points, we measured mercury levels of each sample and distinguished food habit, from direct observation and DNA checking of fish gut contents. At this time, we introduced a stable isotope analysis for checking the food history and feeding habits of dominant fish. In about 300 individuals of 30 species of dominant fish selected from the 600 samples, we measured the stable nitrogen and carbon isotope ratios (δ15N, δ13C) of each sample. We also measured δ15N and δ13C of phytoplankton, zooplankton and benthic microalgae. Checking the food items in the gut of fishes, more than 80% were carnivorous, and showed different selectivity of food items, such as fish and crustacean. From the results of stable isotope ratios, benthic fish tended to show a higher ratio of δ13C. Benthic microalgae evidenced a higher ratio of δ13C than planktonic microalgae, and the ratio conservative through the food chain. In general, δ15N increases through the food chain with +3 to +4 ‰ enrichment per trophic step. In these data, carnivorous fishes of benthic and pelagic type showed medium and high ratios of δ15N. From comparing the stable isotope ratio to the mercury concentration of fishes, all of the high-mercury fishes belonged to benthic and carnivorous types. We consider the joint method of food web analysis and stable isotope analysis to be useful for understanding the mechanism of mercury bioaccumulation through the food web.

Authors

MORI, K., National Institute for Minamata Disease, Japan, morik@nimd.go.jp

KANAYA, G., National Institute for Environmental Studies, Japan, Japan, gen@nies.go.jp

SEO, E., The University of Tokyo, Japan, seoe@aori.u-tokyo.ac.jp

ITOH, H., The University of Tokyo, Japan, kojima@aori.u-tokyo.ac.jp

KOJIMA, S., The University of Tokyo, Japan

Details

Poster presentation

Session #:079
Date: 02/27/2017
Time: 11:00 - 12:00
Location: Poster/Exhibit Hall

Presentation is given by student: No

PosterID: 581