Elwandle Coastal Node, South African Environmental Observation Network, Port Elizabeth, South Africa; Department of Botany and Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa.
Elwandle Coastal Node, South African Environmental Observation Network, Port Elizabeth, South Africa; Department of Botany and Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa; DSI/NRF Research Chair, Shallow Water Ecosystems, Nelson Mandela University, Nelson Mandela University, Port Elizabeth, South Africa.
Sci Total Environ. 2022 Oct 10;842:156955. doi: 10.1016/j.scitotenv.2022.156955. Epub 2022 Jun 25.
Halophytes in estuaries are effective sinks of carbon, nitrogen, and phosphorus. Blue carbon (BC) is carbon stored in coastal habitats such as mangroves, salt marshes and seagrass. The objectives of this study were to firstly assess the biomass and sediment C stocks in salt marsh (Spartina maritima and Salicornia tegetaria) and seagrass (Zostera capensis) habitats of the Swartkops Estuary, South Africa. Secondly, we applied the nutrient pollutant indicator (NPI) to assess the nutrient status of the estuary. Six replicate sediment cores of 1 m (summer) and 0.5 m (winter) per plant species were collected at six sites. Six replicates for biomass of each species were harvested at each site during summer and winter. Biomass and nutrient dynamics showed that there were distinct seasonal differences in the magnitude of C, N, and P stored in the plants. The sediment was the dominant C pool and differed spatially with creek sites storing more C. Out of the three species, S. maritima stored the most C (224 ± 19.1 Mg C ha in sediment, 16.7 ± 1.2 Mg C ha in biomass), followed by S. tegetaria (207 ± 3.5 Mg C ha in sediment, 4.3 ± 0.4 Mg C ha in biomass) and Z. capensis (180 ± 18.4 Mg C ha in sediment, 2.1 ± 0.7 Mg C ha in biomass). The N:biomass ratios were low in both seasons for Z. capensis, S. maritima and S. tegetaria (0.08, 0.02 and 0.04, respectively) indicating consistent eutrophic conditions in the estuary. Resultantly, the plants displayed a significantly lower below-ground standing biomass highlighting the potential variations of BC storage in eutrophic estuaries.
河口盐沼植物是碳、氮和磷的有效汇。蓝碳（BC）是储存在沿海栖息地如红树林、盐沼和海草中的碳。本研究的目的首先是评估南非斯瓦特克普斯河口盐沼（Spartina maritima 和 Salicornia tegetaria）和海草（Zostera capensis）栖息地的生物量和沉积物 C 储量。其次，我们应用养分污染指标（NPI）来评估河口的养分状况。每个植物物种采集了 6 个 1 米（夏季）和 0.5 米（冬季）的重复沉积物芯，每个地点采集了 6 个重复。每个地点在夏季和冬季采集了每个物种的 6 个重复生物量。生物量和养分动态表明，植物中储存的 C、N 和 P 的数量存在明显的季节性差异。沉积物是主要的 C 库，并且在空间上因溪点储存更多的 C 而有所不同。在这三个物种中，S. maritima 储存的 C 最多（沉积物中 224 ± 19.1 Mg C ha-1，生物量中 16.7 ± 1.2 Mg C ha-1），其次是 S. tegetaria（沉积物中 207 ± 3.5 Mg C ha-1，生物量中 4.3 ± 0.4 Mg C ha-1）和 Z. capensis（沉积物中 180 ± 18.4 Mg C ha-1，生物量中 2.1 ± 0.7 Mg C ha-1）。在两个季节中，Z. capensis、S. maritima 和 S. tegetaria 的 N:biomass 比值都较低（分别为 0.08、0.02 和 0.04），表明河口一直处于富营养化状态。结果，植物的地下生物量显著降低，突出了在富营养化河口蓝碳储存的潜在变化。
