Active Carbon Flux of Mesozooplankton in South China Sea and Western Philippine Sea

Abstract

The active carbon flux mediated by diel vertical migration (DVM) of zooplankton is an important component of the downward carbon flux in the ocean. However, active fluxes transported by zooplankton DVM are poorly known in the South China Sea (SCS) and the Western Philippine Sea (WPS). In this study, active carbon fluxes in the SCS and WPS were evaluated on the basis of the data of mesozooplankton community and DVM at two stations of these areas. The mesozooplankton community in the SCS was obviously different from that in the WPS, and higher species number and abundance in the SCS were observed, which may be related to the higher chlorophyll a (Chl a) concentration and the wide gradients of temperature and salinity in this sea. Moreover, shallow depth Chl a maximum and strong thermocline were detected in the SCS, causing lower migration amplitudes of mesozooplankton in the SCS than those in the WPS. However, the migrant biomass of mesozooplankton in the SCS was 98.40 mg C m–2, higher than that in the WPS at 25.12 mg C m–2. The mesozooplankton active carbon flux in the SCS (4.64 mg C m–2⋅d–1) was also higher than that in the WPS (1.80 mg C m–2⋅d–1). The mesozooplankton active fluxes were equivalent to 8.3 and 8.1% of the total flux (active flux plus passive flux) of the SCS and WPS, respectively, and they play an important role in the biological pump functioning in the two regions.

Zooplankton Fecal Pellet Characteristics and Contribution to the Deep‐Sea Carbon Export in the Southern South China Sea

“…As an important pathway of POC export, diel vertical migrators feed in surface waters at night and metabolize the food they ingested in the mesopelagic or bathypelagic zones during the day, which brings additional carbon flux to the deep sea (Buesseler & Boyd, 2009; Manno et al., 2015; Steinberg & Landry, 2017). Studies in the SCS indicate that zooplankton DVM occurs throughout the year, with different zooplankton taxa showing distinct patterns (Ge et al., 2021; Yang et al., 2019). For instance, the calanoid copepod species Metridia spp.…”

“…(1992) described a distinct vertical distribution of copepods: detritvores and herbivores cyclopoid copepods dominated in the shallow layers (0–500 m), while omnivorous calanoid copepods were most abundant in the deep layers (>500 m). In the SCS, calanoid and cyclopoid copepods dominate the zooplankton species and abundances (Ge et al., 2021; Ren et al., 2021). Small cyclopoid copepods ( Oithona plumifera, Oithona similis, Oithona gracilis, Oncaea media, Oncaea similis ) are also abundant in the shallow layers, while larger copepods ( Rhincalanus cornutus, Calanoides carinatus, Pleuromamma robusta ) mainly occupy the deep layers (Du et al., 2014; Gong et al., 2017; K. Li et al., 2021).…”

“…In this area, the percentage distribution of different zooplankton groups is relatively stable from ocean surface to the upper mesopelagic zone (Figure 2b). Copepods typically dominate the zooplankton species, accounting for 47% of total species richness (Du et al., 2014), with calanoid copepods, cyclopoid copepods, and copepod nauplii making up the major part (Ge et al., 2021; Ren et al., 2021; Yin et al., 2006). Ostracods and amphipods are also abundant, accounting for 9% and 7% of total species richness, respectively (Du et al., 2014).…”

The diel vertical distribution and carbon biomass of the zooplankton community in the Caroline Seamount area of the western tropical Pacific Ocean

“…Our study area, the Caroline Seamount, is located in the WTPO, a typical "oligotrophic" region. In the Western Pacific Ocean, the zooplankton CF in oligotrophic regions ranges from 1.8 to 5.3 mg C/(m 2 •d) 26,[52][53][54] . In the mesotrophic subarctic Pacific, the active carbon flux (CO 2 and DOC) transport by migrator respiration and excretion was found to be 16-46 mg C/(m 2 •d) measured by sediment traps at 150 m, compared with 2-8 mg C/ (m 2 •d) in the oligotrophic North Pacific subtropical gyre 55 .…”

The diel vertical distribution and carbon biomass of the zooplankton community in the Caroline Seamount area of the western tropical Pacific Ocean

“…8 to 5.3 mg C/(m 2 •d)47,48,49,50 . In the mesotrophic subarctic Paci c, the active carbon ux (CO 2 and DOC) transport by migrator respiration and excretion was found to be 16-46 mg C/(m 2 •d) measured by sediment traps at 150 m, compared with 2-8 mg C/(m 2 •d) in the oligotrophic North Paci c subtropical gyre9 .…”