Planktonic bivalve larvae identification and quantification in Gomso Bay, South Korea, using next-generation sequencing analysis and microscopic observations

Abstract

The planktonic larval stages of bivalves are notoriously difficult to identify due to their similar morphological characteristics. To identify planktonic bivalve larvae and evaluate changes in their abundance patterns, three different sites within Gomso Bay (Yellow Sea, South Korea), were twice a month sampled and analysed using a next-generation sequencing (NGS) and microscopic observations. Although these techniques identified 114 and 112 taxa, respectively, they revealed different patterns, and at least five bivalve taxa were only detected by NGS. According to NGS results, Crassostrea gigas was the most abundant bivalve larvae (37%), followed by Ruditapes philippinarum (26%) and Solen strictus (23%) Mactra chinensis and M. veneriformis accounted for less than 1% of the bivalve larvae. Crassostrea gigas and S. strictus were the most abundant in late June and rare in the other investigated periods, while R. philippinarum was more abundant in June and late September. Microscopic observations showed a similar trend to NGS in terms of bivalve larvae presence, although bivalve larvae accounted for less than 0.0001% of the plankton communities according to morphological data. Thus, morphological and molecular approaches should be combined in future studies to provide accurate sequences of correctly identified specimens to develop NGS libraries. within Gomso Bay (Yellow Sea, South Korea), were twice a month sampled and analysed using a next-generation sequencing (NGS) and microscopic observations. Although these techniques identified 114 and 112 taxa, respectively, they revealed different patterns, and at least five bivalve taxa were only detected by NGS. According to NGS results, Crassostrea gigas was the most abundant bivalve larvae (37%), followed by Ruditapes philippinarum (26%) and Solen strictus (23%) Mactra chinensis and M. veneriformis accounted for less than 1% of the bivalve larvae. Crassostrea gigas and S. strictus were the most abundant in late June and rare in the other investigated periods, while R. philippinarum was more abundant in June and late September. Microscopic observations showed a similar trend to NGS in terms of bivalve larvae presence, although bivalve larvae accounted for less than 0.0001% of the plankton communities according to morphological data. Thus, morphological and molecular approaches should be combined in future studies to provide accurate sequences of correctly identified specimens to develop NGS libraries.