Предварительные результаты комплексной оценки загрязнения и токсического воздействия донных осадков мелководных бухт Аамурского залива (Японское море)

Abstract

In August 2023, samples of surface bottom sediments (top 5 cm layer) were collected from three bays of Amur Bay: Melkovodnaya Bight (V1) and Krugloya Bight (V2), which are located in Voevoda Bight, and Ugolovoy Bight(U1). V1 and V2, despite being neighboring bays, exhibit significant differences in granulometric composition, distribution of heavy metal content, and organic carbon content. Elevated levels of heavy metals and organic carbon were detected at station V2 in Krugloya Bight. At station V2, the enrichment factor (EF) values for each of the analyzed metals in the bottom sediments exceeded the natural weathering levels of heavy metals, with the exception of Co. A high level of enrichment was noted for Cd (EF = 24.08), a moderately high level for Cu (EF = 6.15) and Pb (EF = 5.51), and a moderate level for Ni, Zn, and Cr (EF = 4.5; 4.3; 3.21, respectively). The modified degree of contamination index (mCd) calculation indicated a moderate degree of contamination at station V2 (mCd = 4.38). In the bottom sediments from station V1, most metals were characterized by a low level of enrichment, except for Cd, which showed a moderate level of accumulation (EF = 4.07). The EF values for bottom sediments from station U1 were significantly below 1.5, indicating the input of heavy metals as a result of natural weathering processes. For the first time, bioassays with the sea urchin Scaphechinus mirabilis were conducted in the studied bays. During the bioassays, the highest number of abnormally developed larvae was found at station V2. In the aqueous extracts of sediments from station V2, none of the larvae developed to the gastrula stage, and the integral toxicity index (ITI) values were 9.84 points. In the aqueous extracts from stations V1 and U1, normally developed larvae at the late gastrula stage predominated 18 hours after the start of the experiment. In extracts of sediments from Melkovodnaya Bight (V1), the vast majority of larvae developed with severe morphological abnormalities. Larvae at the prism and early pluteus stages were characterized by poorly developed or absent skeletal rods. Additionally, exoform larvae were observed, characterized by the absence of an intestine in the body cavity, which was protruded outside. The ITI value for bottom sediments from station V1 was twice as high as for samples from station U1 (ITI = 7.72 and 3.5, respectively). The obtained data indicate a combination of factors leading to the concentration of heavy metals in Krugloya Bight. High concentrations of heavy metals, as well as organic carbon, in turn, may lead to unfavorable living conditions for benthic organisms.

Keywords: Amur Bay, biotesting, bottom sediments, heavy metals, organic carbon, Scaphechinus mirabilis