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Differences in the trophic ecology of micronekton driven by diel vertical migration

TitleDifferences in the trophic ecology of micronekton driven by diel vertical migration
Publication TypeJournal Article
Year of Publication2019
AuthorsRomero-Romero S., Choy C.A, Hannides C.CS, Popp BN, Drazen J.C
Date Published2019/07
Type of ArticleArticle
ISBN Number0024-3590
Accession NumberWOS:000474301200004
Keywordsadaptive significance; body-size; family myctophidae; feeding-habits; global patterns; Marine & Freshwater Biology; nitrogen; oceanography; pacific subtropical gyre; particle dynamics; stenobrachius-leucopsarus; transitional waters

Many species of micronekton perform diel vertical migrations (DVMs), which ultimately contributes to carbon export to the deep sea. However, not all micronekton species perform DVM, and the nonmigrators, which are often understudied, have different energetic requirements that might be reflected in their trophic ecology. We analyze bulk tissue and whole animal stable nitrogen isotopic compositions (delta N-15 values) of micronekton species collected seasonally between 0 and 1250 m depth to explore differences in the trophic ecology of vertically migrating and nonmigrating micronekton in the central North Pacific. Nonmigrating species exhibit depth-related increases in delta N-15 values mirroring their main prey, zooplankton. Higher variance in delta N-15 values of bathypelagic species points to the increasing reliance of deeper dwelling micronekton on microbially reworked, very small suspended particles. Migrators have higher delta N-15 values than nonmigrators inhabiting the epipelagic zone, suggesting the consumption of material during the day at depth, not only at night when they migrate closer to the surface. Migrating species also appear to eat larger prey and exhibit a higher range of variation in delta N-15 values seasonally than nonmigrators, likely because of their higher energy needs. The dependence on material at depth enriched in N-15 relative to surface particles is higher in migratory fish that ascend only to the lower epipelagic zone. Our results confirm that stark differences in the food habits and dietary sources of micronekton species are driven by vertical migrations.

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