Two phytoplankton blooms near Luzon Strait triggered by Typhoon Parma in 2009 were investigated using remote sensing data and in situ observations. Parma was slow moving (a translation speed of ~2 m s⁻¹) and relatively weak (a maximum sustained wind of ~30 m s⁻¹) during its lingering path northwest of Luzon Island. After it reached a point (120.5°E, 20.3°N) west of Luzon Strait, Parma turned sharply back toward the northern Philippines along approximately the same course. Such long (~7 days) lingering typhoons are rather rare in the South China Sea (SCS). Before Parma, low Chl‐a concentrations ( 0.6 mg m⁻³) appeared west of the central Luzon Strait; a nearshore phytoplankton increase was also observed north of Luzon Island, together with high CDOM (color dissolved organic matter). During and after the typhoon, sea‐surface cooling (~3°C), stronger wind (>20 m s⁻¹), and heavy rainfall (>100 mm day⁻¹) were seen in the above regions. The offshore bloom occurred where Parma's translation speed was the slowest (~1 m s⁻¹). It may be caused primarily by the Ekman pumping which brought nutrients upward to the euphotic zone and also by the entrainment mixing. The nearshore bloom may be triggered by the heavy typhoon‐induced rainfall, which supplied nutrients for the coast region north of Luzon Island. The rapid increase of CDOM in the nearshore region implied that terrestrial input may be the source of nutrients.

Tropical cyclones may augment nutrients in the ocean surface layer through mixing, entrainment, and upwelling, triggering phytoplankton blooms in oligotrophic waters such as the South China Sea (SCS). Previous studies focused mainly on responses of marine environments to strong or slow‐moving typhoons in the SCS. In this study, we analyze variations of chlorophyll a (Chl a) and oceanic conditions in the continental shelf region east of Hainan Island during the fast‐moving tropical storm Washi and investigate its influences on phytoplankton bloom and related dynamic mechanisms. Results indicate that there was significant variation of Chl a concentration in the continental shelf region, with low values (about 0.1 mg m⁻³) before the storm and a 30% increase after the storm. This increase was spatially variable, much larger nearshore than offshore. Power spectral analysis of Acoustic Doppler Current Profiler (ADCP) data at a shelf site near the study region reveals strong near‐inertial oscillations (NIOs) in the upper layer, with a period of about 36 h, close to the local inertial period. The NIOs intensified mixing and modified the stratification of the upper layer, inducing uplift of nutrients and Chl a into the mixed layer from below, and leading to surface Chl a increase. The relatively shallow nutricline and thermocline in the continental shelf region before the storm were favorable for upwelling of nutrients and generation of NIOs. Advection of nutrients from enhanced runoff during and after the storm may be responsible for the larger increase of the Chl a nearshore.

Summer upwelling occurs frequently off the southeast Vietnam coast in the western South China Sea (SCS), where summer phytoplankton blooms generally appear during June-August. In this study, we investigate inter-annual variation of Ekman pumping and offshore transport, and its modulation on summer blooms southeast of Vietnam. The results indicate that there are low intensities of summer blooms in El Niño years, under higher sea surface temperatures (SST) and weaker winds. However, a different pattern of monthly chlorophyll a (Chl-a) blooms occurred in summer of 2007, a transitional stage from El Niño to La Niña, with weak (strong) wind and high (low) SST before (after) early July. There is a weak phytoplankton bloom before July 2007 and a strong phytoplankton bloom after July 2007. The abrupt change in the wind intensity may enhance the upwelling associated with Ekman pumping and offshore Ekman transport, bringing more high-nutrient water into the upper layer from the subsurface, and thus leading to an evident Chl-a bloom in the region.

Spring bloom is a dominant feature of seasonal phytoplankton cycles in the northwest Atlantic continental shelf. In this study, we investigate temporal and spatial variations of spring‐bloom timing and intensity over the Grand Banks of Newfoundland, using satellite ocean color data and other oceanographic measurements from January 1998 to December 2009. The spring bloom has strong interannual and meridional changes in its timing and intensities. Physical oceanographic conditions including the sea surface temperature (SST), wind speed, and mixed layer depth (MLD) also show evident interannual variations. The spring boom starts first in the southern Bank in February–March and often in the central and northern Bank in April, respectively. An early initiation of spring blooms is generally associated with high SST, weak winds, and shallow MLD at the beginning stage of the spring blooms, and tends to result in stronger intensities. However, the photosynthesis available radiance does not seem to affect the bloom initiation in the southern area or the bloom intensity over the entire Banks. In the southern area, higher SST does not lead to larger bloom magnitude. Our analysis shows that the effect of the SST in the northern area is primarily through the earlier ice melting. It also indicates that Sverdrup's critical depth criteria are suitable for conditions over the Grand Banks. The present study points to the significant sub‐bank‐scale differences in the timing and magnitude of the spring bloom attributable to underlying physical environments, important for the integrated management of the Grand Banks ecosystem.