Trophic Characteristics of Bivalve Mollusks (Bivalvia) from the Shallow Shelf of the Laptev Sea

Bivalves (Bivalvia) are one of the main components of Arctic ecosystems, but their trophic ecology is poorly understood. This study presents the trophic characteristics of bivalves found along a submeridional transect from the Lena River delta to the northern shelf boundary during an expedition aboard the R/V Akademik Mstislav Keldysh (cruise No. 73) in the Laptev Sea in September–October 2018. Based on the abiotic characteristics of the sampling stations and the δC values in the soft tissues of bivalves, four groups of stations were identified: delta-proximal stations, midshelf stations, methane seep stations, and non-methane stations at the northern shelf boundary. A decrease in the influence of terrigenous organic matter carried by the Lena River runoff on the carbon isotope composition of bivalves was observed with increasing distance from the delta: delta-proximal stations (δC –28.1 ± 0.5‰), midshelf stations (δC –24.9 ± 0.3‰), and background stations near the northern shelf boundary (δC –22.2 ± 0.9‰). At the methane stations, the δC values in Bivalvia tissues were lower than at the background stations (−27.6 ± 0.5‰ and −22.2 ± 0.9‰, respectively).