Department of Biology, Faculty of Marine and Environmental Science, University of Cádiz, Pol. Río San Pedro s/n, 11510, Puerto Real, Spain.
Departamento de Biomedicina, Biotecnología y Salud Publica, Universidad de Cádiz, Polígono Rio San Pedro s/n, 11510, Puerto Real, Spain.
J Phycol. 2019 Jun;55(3):625-636. doi: 10.1111/jpy.12838. Epub 2019 Feb 22.
Primary production of microphytobenthos (MPB) contributes significantly to the total production in shallow coastal environments. MPB is a diverse community in which diatoms are usually the main microalgal group. Diatoms require N, P, and other nutrients as with other autotrophs, but in addition require silicate to create their outer cell wall. Therefore, dissolved silica (DSi) might be a potential limiting factor for benthic primary production in areas with reduced freshwater input. To test this hypothesis, a microcosm experiment was conducted using intact sediment cores collected from an intertidal mudflat in the Bay of Cádiz and supplied with increasing concentrations of DSi (0, 5, 10, 25, and 45 μmol · L ). After 7 d of enrichment, we determined chlorophyll a and c (Chl a, c) contents, metabolic rates (Net [P ] and Areal Gross [P ] Production and Light [R ] and Dark [R ] Respiration), as well as fluxes of inorganic nutrients across the sediment-water interface. Chl a and c contents increased significantly with respect to the initial conditions but no differences between treatments were found. Both P and P showed a saturating-like pattern with silicate concentration, reaching maximum rates at a DSi concentration of 45 μmol · L . The addition of DSi also resulted in an increase of DSi and ammonium uptake by the sediment, which was significantly higher in light than in darkness. Our results clearly show that water column DSi concentrations have a direct impact on benthic primary production, also controlling other related processes such as inorganic nutrient fluxes.
微小型底栖生物（MPB）的初级生产力对浅海环境中的总生产力有重要贡献。MPB 是一个多样化的群落，其中硅藻通常是主要的微藻群体。与其他自养生物一样，硅藻需要 N、P 和其他营养物质，但此外还需要硅酸盐来构建其外壳。因此，溶解硅（DSi）可能是淡水输入减少的地区底栖初级生产力的潜在限制因素。为了验证这一假设，使用从卡迪兹湾潮间带泥滩采集的完整沉积物芯进行了微宇宙实验，并添加了不同浓度的 DSi（0、5、10、25 和 45 μmol·L-1）。在富集 7 d 后，我们测定了叶绿素 a 和 c（Chl a、c）含量、代谢率（净[P]和面积总[P]生产力以及光[R]和暗[R]呼吸）以及无机养分在沉积物-水界面的通量。Chl a 和 c 含量与初始条件相比显著增加，但处理之间没有差异。P 和 P 均与硅酸盐浓度呈饱和样模式，在 DSi 浓度为 45 μmol·L-1 时达到最大速率。添加 DSi 还导致沉积物中 DSi 和铵的吸收增加，在光照下明显高于黑暗中。我们的研究结果清楚地表明，水柱 DSi 浓度直接影响底栖初级生产力，还控制着无机养分通量等其他相关过程。
