Distribution, biomass, and species composition of salps and doliolids in the Oyashio–Kuroshio transitional region: potential impact of massive bloom on the pelagic food web

• Published in: Journal of oceanography 2020-10, Vol.76 (5), p.351-363
• Main Authors: Ishak, Nurul Huda Ahmad, Tadokoro, Kazuaki, Okazaki, Yuji, Kakehi, Shigeho, Suyama, Satoshi, Takahashi, Kazutaka
• Format: Article
• Language: English
• Subjects: Biogeochemical cycle; Biogeochemical cycles; Biogeochemistry; Biomass; Community composition; Composition; Distribution; Earth and Environmental Science; Earth Sciences; Feeding; Filter feeders; Food chains; Food webs; Foods; Freshwater & Marine Ecology; Geographical distribution; Marine invertebrates; Multivariate statistical analysis; Nursery grounds; Oceanography; Original Article; Pelagic fish; Prey; Saline water; Salp blooms; Salpida; Species composition; Statistical analysis; Statistical methods; Water masses; Zooplankton
• ISSN: 0916-8370; 1573-868X
• DOI: 10.1007/s10872-020-00549-3

The Oyashio–Kuroshio Transitional Region (OKTR) is a nursery ground for pelagic fishes; thus, community succession of mesozooplankton is pivotal to understand prey availability, and it subsequently affects recruitment success. We investigated the surface distribution, biomass, and species composition of thaliaceans (salps and doliolids) that potentially have a significant impact on the food web and biogeochemical cycle by forming intensive blooms. A total of 11 thaliacean species were recorded from 62 locations along two transects at 36° N and 38.5° N extending from 142° E to 180° in May to June 1993. Salps and doliolids were found at 93% and 84% of the stations, respectively, and their biomass values varied widely in space (0.00011–79.56 and 0.00001–5.11 mg C m −3 for salps and doliolids, respectively). Thalia democratica was the most dominant salp and particularly abundant at stations east of 165°E on the 36°N-line; the abundance varied from 103 to 1379 ind m −3 . Dolioletta gegenbauri and Doliolum denticulatum were dominant doliolids, although their biomass values were far lower than that of salps. Multivariate statistical analysis with PRIMER revealed that the distribution of thaliaceans in the OKTR was not uniform in space and was affected by oceanographic conditions; doliolids tended to occur in much warmer (14.10–15.63 °C) and saline water mass (34.54–34.72) than salps (13.16–14.95 °C and 34.40–34.53). In terms of population clearance rates, the most dense salp blooms have the potential to sweep > 200% of their resident water per day, indicating that salp blooms cause deleterious feeding conditions for pelagic fishes through non-selective filter feeding.