POSTER SESSION 3
15:30–17:30, Wednesday, September 16
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1256 | POSTER 43
VERTICAL STRUCTURE OF PHYTOPLANKTON BIOMASS AND BIO-OPTICAL PROPERTIES DURING BLOOM PERIODS IN SAGAMI BAY, JAPAN (2016-2026)
Phytoplankton blooms in temperate coastal waters often occur in spring and autumn; the physical and biological processes that shape their development vary from year to year. Remote sensing observations alone capture only the upper optical depth and therefore represent a limited fraction of chlorophyll-a (Chl-a) in the water column. Consequently, resolving the subsurface expression of phytoplankton biomass and the vertical development preceding surface proliferation is required. Various mechanisms, such as light availability, nutrient supply, mixing intensity, and the stratification onset, govern bloom initiation patterns and vertical distribution. These dynamic processes fluctuate interannually, making it difficult to characterize bloom mechanisms from surface data alone. Long-term, depth-resolved in-situ datasets are essential for distinguishing recurring vertical patterns and determining the conditions that initiate bloom development. This study focuses on seasonal bloom formations in the temperate coastal waters of Sagami Bay, Japan, using bio-optical measurements (2016-2026) to (1) identify the physical processes that regulate the variability of Chl-a before and during blooming periods; and (2) evaluate to what extent surface observations represent phytoplankton biomass at relevant optical depths.
Preliminary results show that the first optical depth (1/Kd) represents the surface Chl-a concentration better than the euphotic zone depth (Zeu). While spring bloom timing aligns with mixed layer depth (MLD) shoaling, significant pigment signatures persist below the MLD within the Zeu. Further analysis will investigate the physical processes, bloom initiation thresholds, and potential shifts in phytoplankton functional types (PFTs) that influence the vertical structure and bloom development across years.
Mia Castillo*, Soka University, [email protected], https://orcid.org/0009-0005-1258-7253
Koichi Yano, Soka University, [email protected]
Robel Ashenafi, Soka University, [email protected]
Shinji Shimode, Yokohama National University, [email protected]
Victor Kuwahara, Soka University, [email protected]
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
