Species composition and depth distribution of chaetognaths in a Kuroshio warm-core ring and Oyashio water

• Published in: Journal of plankton research Vol. 25; no. 10; pp. 1279 - 1289
• Main Authors: Johnson, Travis B., Terazaki, Makoto
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.10.2003; Oxford Publishing Limited (England)
• Subjects: Abundance; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Body size; Chaetognatha; Check lists; Depth; Distribution; Dominant species; Eremobelba hamata; Eukrohnia hamata; Fundamental and applied biological sciences. Psychology; Geographical distribution; Marine; Sagitta elegans; Sagitta minima; Sagitta scrippsae; Sea water ecosystems; Species composition; Species diversity; Synecology; Vertical distribution; Kuroshio; Pacific Ocean; West Pacific; North Pacific; INW, Pacific, Kuroshio Current; INW, Japan Sea, Oyashio Water; Japan; Community structure; Chaetognatha; Fauna; Vertical distribution; Environmental factor; Spatial variation; Depth; Coastal zone; Marine environment; Warm front; Species diversity; Body size; Development; Invertebrata; Ecological abundance
• ISSN: 0142-7873; 1464-3774; 1464-3774
• DOI: 10.1093/plankt/fbg085

Chaetognath species composition, diversity and depth distribution were investigated inside and outside a warm-core ring off the north-east coast of Japan. Time series samples were collected at a station inside a Kuroshio warm-core ring (KWCR) and at a station in the surrounding Oyashio water. Greater mean abundance of 2.51 ± 0.116 (mean ± SE) chaetognaths m−3 was found outside the ring compared with 1.75 ± 0.321 chaetognaths m−3 collected within the ring. However, species diversity values were higher within the KWCR (Shannon–Weaver index). Eukrohnia hamata was the dominant species outside the ring, comprising 79.8–87.9% of the total chaetognaths per haul. Inside, Sagitta minima was dominant, comprising 35.1–44.3%. Most E. hamata were collected in deeper layers within the KWCR and their abundance was on average only 9% of that found in the Oyashio region. Only E. hamata and Sagitta scrippsae had different depth distributions in the KWCR. The vertical distribution of E. hamata by body size appeared altered by the KWCR. Although the mean length of E. hamata was not significantly different between regions, sexual development appeared inhibited in the ring. Sagitta elegans collected in the KWCR were mostly small in size (<10 mm), significantly smaller than in the Oyashio water.