Seagrass systems are integral components of both local and global carbon cycles and can substantially modify seawater biogeochemistry, which has ecological ramifications. However, the influence of seagrass on porewater biogeochemistry has not been fully described, and the exact role of this marine macrophyte and associated microbial communities in the modification of porewater chemistry remains equivocal. In the present study, carbonate chemistry in the water column and porewater was investigated over diel timescales in contrasting, tidally influenced seagrass systems in Southern California and Bermuda, including vegetated (Zostera marina) and unvegetated biomes (0–16 cm) in Mission Bay, San Diego, USA and a vegetated system (Thallasia testudinium) in Mangrove Bay, Ferry Reach, Bermuda. In Mission Bay, dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited strong increasing gradients with sediment depth. Vertical porewater profiles differed between the sites, with almost twice as high concentrations of DIC and TA observed in the vegetated compared to the unvegetated sediments. In Mangrove Bay, both the range and vertical profiles of porewater carbonate parameters such as DIC and TA were much lower and, in contrast to Mission Bay where no distinct temporal signal was observed, biogeochemical parameters followed the semi-diurnal tidal signal in the water column. The observed differences between the study sites most likely reflect a differential influence of biological (biomass, detritus and infauna) and physical processes (e.g., sediment permeability, residence time and mixing) on porewater carbonate chemistry in the different settings.

海草系统是当地和全球碳循环不可或缺的组成部分，可以显着改变海水生物地球化学，从而产生生态影响。然而，海草对孔隙水生物地球化学的影响尚未得到充分描述，并且这种海洋大型植物和相关微生物群落在改变孔隙水化学方面的确切作用仍然模棱两可。在本研究中，在南加州和百慕大受潮汐影响的海草系统中，在昼夜时间尺度上研究了水柱和孔隙水中的碳酸盐化学，包括使命湾的植被（大叶藻码头）和无植被生物群落（0-16厘米），美国圣地亚哥和百慕大费里里奇红树林湾的植被系统（ Thallasia testudinium ）。在使命湾，溶解无机碳（DIC）和总碱度（TA）随着沉积物深度的增加呈现出强烈的梯度增加。不同地点的垂直孔隙水剖面有所不同，与无植被沉积物相比，在植被沉积物中观察到的 DIC 和 TA 浓度几乎是无植被沉积物的两倍。在红树林湾，孔隙水碳酸盐参数（例如 DIC 和 TA）的范围和垂直剖面都低得多，与没有观察到明显时间信号的 Mission Bay 相比，生物地球化学参数遵循水柱中的半日潮汐信号。研究地点之间观察到的差异很可能反映了不同环境下生物（生物量、碎屑和底栖动物）和物理过程（例如沉积物渗透性、停留时间和混合）对孔隙水碳酸盐化学的不同影响。