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<p>Coastal diatoms are increasingly exposed to multiple, interacting stressors, including salinity fluctuations and chemical pollutants, yet the combined effects of these factors remain poorly understood in tropical systems. This study examined the physiological responses of the cosmopolitan diatom <i>Thalassiosira weissflogii</i>, acclimated to Gulf of Guinea conditions, across a salinity gradient (15–35‰) and cadmium–pyrene mixtures (0–10&#xa0;µg/L Cd; 0–100 nM pyrene). Cell density, chlorophyll-<i>a</i> per cell, and dry biomass per cell were monitored over 72&#xa0;h to assess growth and metabolic responses. Results showed that both reduced salinity and increasing contaminant concentration significantly suppressed cell proliferation, particularly under hyposaline conditions (15‰). The strongest inhibition occurred under the CP-High treatment (10&#xa0;µg/L Cd + 100 nM pyrene), where cell density declined by over 50% relative to the control. In contrast, dry biomass per cell exhibited a modest increase with contaminant exposure, suggesting enhanced storage compound synthesis or reduced division rates under stress. Chlorophyll-<i>a</i> per cell ranged narrowly between 2.57 × 10⁻³ and 2.70 × 10⁻³ µg/cell, indicating that pigment metrics are more sensitive to early stress responses than biomass indicators. Overall, fluctuating salinity amplified pollutant toxicity, underscoring the ecological risk of multiple stressor interactions in tropical estuarine diatoms. The findings highlight the need for integrated management strategies that address hydrological variability and pollutant inputs to sustain coastal productivity and resilience in the Gulf of Guinea.</p>

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Interactive effects of salinity, cadmium, and pyrene on the diatom Thalassiosira weissflogii under simulated tropical coastal conditions

  • 期刊论文

  • 发表日期：

    2025年12月9日

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  • Rael Adhiambo,
  • Albert Koomson,
  • Emmanuel Acheampong,
  • Paul Kojo Mensah

摘要

Coastal diatoms are increasingly exposed to multiple, interacting stressors, including salinity fluctuations and chemical pollutants, yet the combined effects of these factors remain poorly understood in tropical systems. This study examined the physiological responses of the cosmopolitan diatom Thalassiosira weissflogii, acclimated to Gulf of Guinea conditions, across a salinity gradient (15–35‰) and cadmium–pyrene mixtures (0–10 µg/L Cd; 0–100 nM pyrene). Cell density, chlorophyll-a per cell, and dry biomass per cell were monitored over 72 h to assess growth and metabolic responses. Results showed that both reduced salinity and increasing contaminant concentration significantly suppressed cell proliferation, particularly under hyposaline conditions (15‰). The strongest inhibition occurred under the CP-High treatment (10 µg/L Cd + 100 nM pyrene), where cell density declined by over 50% relative to the control. In contrast, dry biomass per cell exhibited a modest increase with contaminant exposure, suggesting enhanced storage compound synthesis or reduced division rates under stress. Chlorophyll-a per cell ranged narrowly between 2.57 × 10⁻³ and 2.70 × 10⁻³ µg/cell, indicating that pigment metrics are more sensitive to early stress responses than biomass indicators. Overall, fluctuating salinity amplified pollutant toxicity, underscoring the ecological risk of multiple stressor interactions in tropical estuarine diatoms. The findings highlight the need for integrated management strategies that address hydrological variability and pollutant inputs to sustain coastal productivity and resilience in the Gulf of Guinea.