Environmental changes driven by intense human disturbance and natural processes govern the abundance and distribution characteristics of two picophytoplankton groups (Synechococcus and picoeukaryotes). Picophytoplancton and high DNA (HDNA) and low DNA (LDNA) bacterial groups, identified by flow cytometry, were assessed during the autumn monsoon transition period in Daya Bay (South China Sea). The abundance of Synechococcus and picoeukaryotes ranged from 2.16 x 10(4) to 1.45 x 10(5) cell mL-1 and from 0.78 x 10³ to 7.95 x 10³ cell mL-1, respectively. The abundance of HDNA bacteria in surface water (mean: 5.58 x 10(5) cell mL-1) was greater than in bottom water (mean: 3.74 x 10(5) cell mL-1), with significant difference (n = 12, P = 0.05). The difference in LDNA abundances between surface (mean: 7.06 x 10(5) cell mL-1) and bottom (mean: 4.83 x 10(5) cell mL-1) waters was insignificant (n = 12, P > 0.05). The results of the principal component analysis showed that both picophytoplankton (Synechococcus and picoeukaryotes) and bacteria (HDNA and LDNA) were positively related to nutrients (NO3-N, NH4-N, and SiO3-Si). Three subsystems in the bay were identified as follows: the west and east parts, the central and northwest parts, and the mouth and central part.

Los cambios ambientales generados por las actividades humanas y los procesos naturales determinan las características de la distribución y abundancia de dos grupos de picofitoplancton (Synechococcus y picoeucariontes). Se evaluaron las comunidades de picofitoplancton y de bacterias con mayor (MaADN) y menor (MeADN) cantidad de ADN, identificadas mediante citometría de flujo, durante el periodo de transición intermonzónico en otoño en la bahía de Daya (mar de China Meridional). La abundancia de Synechococcus y picoeucariontes varió entre 2.16 x 10(4) y 1.45 x 10(5) cél mL-1 y entre 0.78 x 10³ y 7.95 x 10³ cél mL-1, respectivamente. La abundancia del grupo bacteriano de MaADN fue mayor en el agua superficial (media: 5.58 x 10(5) cél mL-1) que en el fondo de la bahía (media: 3.74 x 10(5) cél mL-1), con una diferencia significativa (n = 12, P = 0.05). No se observó una diferencia significativa entre la abundancia del grupo de MeADN en la superficie (media: 7.06 x 10(5) cél mL-1) y el fondo (media: 4.83 x 10(5) cél mL-1) (n = 12, P > 0.05). Un análisis de componentes principales mostró que ambos grupos de picofitoplancton (Synechococcus y picoeucariontes) y bacterias (MaADN y MeADN) se relacionaron positivamente con nutrientes (NO3-N, NH4-N y SiO3-Si). Se identificaron tres subsistemas en la bahía: las partes oeste y este, las partes central y noroeste, y la boca y parte central.

No presente estudo foi realizada a identificação dos efeitos antropogênicos e das características naturais marinhas das águas da Baía de Sanya, situada ao sul do Mar da China, através de método quimiométrico. A análise de componentes principais (PCA) aplicada aos dados extraiu quatro eixos que explicaram 85,52% da variância total dos dados. Através das análises de Agrupamento e PCA foram identificados três padrões diferentes de qualidade das águas, baseados nos efeitos antropogênicos e nas características marinhas: Grupo I, localizado nas partes externa e mediana da baía; Grupo II, próximo do centro urbano de Sanya; Grupo III, localizado no estuário do Rio Sanya. Quanto ao padrão temporal, as referidas análises distinguiram uma estação seca, de novembro a abril, e uma estação chuvosa, de maio a outubro, relacionadas ao clima e características naturais. Foi visto que tanto a fonte poluidora externa, representada pelo Rio Sanya, quanto as águas do Mar do Sul da China influenciam a qualidade das águas da Baía de Sanya. Esses resultados podem ser relevantes quando considerados sob o ponto de vista do desenvolvimento socioeconômico e de saúde humana dessa região.

In this study, chemometric method is employed to identify anthropogenic effects on the water quality in Sanya Bay, South China Sea, and its marine and natural characteristics. Principal component analysis has extracted the four latent factors, thus explaining 85.52% of the total variance. Cluster analysis and principal component analysis have identified three different patterns of water quality based on anthropogenic effects and marine characteristics: Cluster I located in the outer and middle parts of the bay, Cluster II close to downtown Sanya, Cluster III located in the Sanya River estuary. In terms of the temporal pattern, principal component analysis and cluster analysis have distinguished the dry season from November to the following April, and the rainy season from May to October. The temporal pattern is related to climate and natural characteristics. The similarity index between variables and scores of samples can further distinguish the contribution of the variables to the samples. Both the polluting sources external to the Sanya River and the water from the South China Sea exercise an important influence on the water quality in Sanya Bay. These results may be valuable for socioeconomic development and human health in the Sanya Bay area.