Bueno João Vitor Langorte, Kerr Rodrigo, Carvalho Andréa da Consolação de Oliveira, Mendes Carlos Rafael Borges
Laboratório de Fitoplâncton e Microorganismos Marinhos, Instituto de Oceanografia, Universidade Federal do Rio Grande - FURG, Rio Grande, RS, 96203-900, Brazil; Programa de Pós-Graduação em Oceanografia Biológica, Instituto de Oceanografia, Universidade Federal do Rio Grande - FURG, Rio Grande, RS, 96203-900, Brazil.
Laboratório de Estudos dos Oceanos e Clima, Instituto de Oceanografia, Universidade Federal do Rio Grande - FURG, Rio Grande, RS, 96203-900, Brazil.
Mar Environ Res. 2025 Sep;210:107314. doi: 10.1016/j.marenvres.2025.107314. Epub 2025 Jun 19.
Marine phytoplankton acts directly on the carbon biogeochemical cycle as key mediators of the biological carbon pump, and its efficiency is dependent on the composition of phytoplankton communities. Therefore, in the present study, we aimed to investigate the composition of phytoplankton communities in the deep chlorophyll maximum and the role of the different phytoplankton groups in CO dynamics and biogeochemical processes along the South Atlantic Ocean. Environmental and biological data were collected in the deep chlorophyll maximum in 59 stations along a zonal section (34.5°S) in the South Atlantic Ocean. Sampling stations were grouped into Brazil, South Atlantic Gyre and Africa provinces. We identified the chemotaxonomic phytoplankton groups using the HPLC-CHEMTAX approach and evaluated the thermal and non-thermal effects on CO partial pressure (pCO) variability in the region. The relationship between biogeochemical variables and phytoplankton groups was investigated using a canonical correspondence analysis. Our results showed strong gradients in the distribution of biogeochemical parameters among the different provinces, with higher pCO and thermal effects in the coastal regions due to the influence of ocean circulation processes, and lower pCO and higher non-thermal effects in the open ocean due to the upwelling of deeper waters rich in dissolved inorganic carbon and nutrients associated to mesoscale eddies. Haptophytes and Prochlorococcus dominated the deep chlorophyll maximum in the study area, with the highest phytoplankton biomass being recorded in the Africa province. Haptophytes were associated with mixed nutrient-rich waters, and showed higher influence in pCO variation, whereas Prochlorococcus were associated with stratified oligotrophic waters. The results found in this study elucidate the variability in the role of the different phytoplankton groups on CO dynamics across the different biogeochemical provinces of the South Atlantic Ocean. Thus, further investigations on the spatial and temporal patterns of phytoplankton distribution are encouraged to better decouple the thermal and non-thermal effects driving pCO variations in subsurface waters in the region.
海洋浮游植物作为生物碳泵的关键调节者，直接作用于碳生物地球化学循环，其效率取决于浮游植物群落的组成。因此，在本研究中，我们旨在调查南大西洋叶绿素最大值深度处浮游植物群落的组成，以及不同浮游植物类群在该区域二氧化碳动态和生物地球化学过程中的作用。在南大西洋沿纬向剖面（南纬34.5°）的59个站位采集了叶绿素最大值深度处的环境和生物数据。采样站位被分为巴西、南大西洋环流和非洲三个区域。我们使用高效液相色谱-化学分类法（HPLC-CHEMTAX）确定了化学分类的浮游植物类群，并评估了热效应和非热效应对该区域二氧化碳分压（pCO₂）变异性的影响。使用典范对应分析研究了生物地球化学变量与浮游植物类群之间的关系。我们的结果表明，不同区域之间生物地球化学参数的分布存在强烈梯度，由于海洋环流过程的影响，沿海地区的pCO₂和热效应较高，而在开阔海洋中，由于富含溶解无机碳和与中尺度涡旋相关的营养物质的深层海水上涌，pCO₂较低且非热效应较高。定鞭藻和原绿球藻在研究区域的叶绿素最大值深度处占主导地位，非洲区域记录到最高的浮游植物生物量。定鞭藻与富含混合营养的水体相关，对pCO₂变化的影响较大，而原绿球藻则与分层的贫营养水体相关。本研究的结果阐明了不同浮游植物类群在南大西洋不同生物地球化学区域对二氧化碳动态作用的变异性。因此，鼓励进一步研究浮游植物分布的时空模式，以更好地分离驱动该区域次表层水体pCO₂变化的热效应和非热效应。
