Phosphorus (P) is potentially the most limiting nutrient in the Pearl River estuary, and thus, it is important to understand various sources of P. Suspended particulate matter (SPM) is usually high in the river and carries P. We hypothesize that suspended particulate reactive P (PRP) is a potential source of dissolved P and varies with estuarine hydrodynamics. To test the hypothesis, we conducted a cruise along and cross the Pearl River estuary to examine spatial variability of suspended PRP. Suspended PRP ranged at 0.01–2.65 μM, contributing 1.2–97.4% to total reactive P (TRP). Along the estuary, suspended PRP was 1.49 μM upstream and decreased downstream. Across the estuary, suspended PRP was high (1.58 μM) at low salinity and decreased eastward with increasing salinity. Tidal cycles appeared to play a significant role in regulating the variability of suspended PRP through advection and benthic resuspension of SPM. The proportion of PRP/TRP increased seaward from 1.2 to 94.8%, indicating the increasing importance of PRP in total reactive P downstream. We show that suspended particulate reactive P varied greatly and was an important part of the total phosphorus pool in the Pearl River estuary.

磷（P）可能是珠江口中最限制性的养分，因此了解磷的各种来源很重要。悬浮颗粒物（SPM）通常在河流中较高，并携带P。我们假设悬浮颗粒物反应性P（PRP）是溶解P的潜在来源，并随河口流体动力学而变化。为了验证该假设，我们沿着珠江河口进行了航行并检查了悬浮PRP的空间变异性。悬浮的PRP范围为0.01–2.65μM，占总活性P（TRP）的1.2–97.4％。沿河口，悬浮的PRP上游为1.49μM，下游为下降。在整个河口，低盐度的悬浮PRP较高（1.58μM），并且随着盐度的增加而向东降低。潮汐周期似乎在通过对流和底栖SPM重悬来调节悬浮PRP的变异性中起重要作用。PRP / TRP的比例从1.2上升到94.8％，表明PRP在下游总反应性P中的重要性越来越高。我们表明，悬浮颗粒活性磷变化很大，并且是珠江口总磷库的重要组成部分。