ABSTRACT

Nutrient flux, net metabolism, and N₂ fixation and denitrification processes were estimated and compared in two semi-arid subtropical coastal lagoons in the Gulf of California: El Soldado (ES), where no wastewater is discharged, and El Rancho (ER), where shrimp farm effluents are regularly discharged. Biogeochemical processes were evaluated with the LOICZ model. Flushing time was <2 days in both systems. Nutrient fluxes were higher in ER than in ES and both systems acted as nutrient sinks for most of the year. ER showed a larger nutrient flow rate in the summer and autumn due to the input of shrimp-farm effluents. Nitrogen fluxes increased in both ER and ES in the winter in response to the increased nutrient supply from coastal upwellings. ER and ES both showed autotrophic metabolism and N₂ fixation in the spring, autumn, and winter, but heterotrophic metabolism and denitrification in the summer. Denitrification dominated in ER (−2.21 mmol m² day⁻¹) and values were higher than those estimated in ES (−0.45 mmol m² day⁻¹). The comparative analysis between ES and ER evidenced the significant changes in its biogeochemical performance caused by the input of anthropogenic nutrients, and can orient the environmental management of coastal lagoons.

摘要

在加利福尼亚湾的两个半干旱亚热带沿海泻湖中，估算并比较了养分通量，净代谢以及N ₂固定和反硝化过程：El Soldado（ES）（没有废水排放）和El Rancho（ER），定期排出虾养殖场废水的地方。用LOICZ模型评估了生物地球化学过程。在两个系统中，冲洗时间均小于2天。ER中的养分通量高于ES中的养分通量，并且这两个系统在一年中的大部分时间内都作为营养池。ER在夏季和秋季表现出较大的养分流量，这是由于虾类养殖场废水的输入所致。冬季，由于沿海上升流的养分供应增加，氮素通量在ER和ES中均增加。ER和ES均显示自养代谢和N ₂在春季，秋季和冬季固定，但在夏季异养代谢和反硝化作用。ER中的反硝化作用占主导地位（-2.21 mmol m ² day ^-1），其值高于ES中的反硝化作用估计值（-0.45 mmol m ² day ^-1）。ES和ER的对比分析表明，由于人为营养素的输入，其生物地球化学性能发生了显着变化，并可以指导沿海泻湖的环境管理。