Spatial and Temporal Distribution of Total Phosphorus in Sediments of Shuangtai Estuary Wetland during the Period of Reed Growth

Phosphorus is an essential macronutrient that plays a crucial role in the regulation of the biological productivity and biogeochemical cycling of other biogenic elements. As a large tidal wetland dominated by reeds in Liaoning province, China, the Shuangtai estuary wetland is a unique ecosystem class. To better understand the spatial and temporal distributions of total phosphorus (TP) in the sediments of the Shuangtai estuary wetland during the period of reed growth, eight sampling sites were established within the wetland, approximately 11 to 24 km from Liaohe River. These sites were sampled once a month at multiple sediment depth intervals between April and October in 2018 and 2019, periods of time that corresponded with the reed growth period. An alkali fusion method was used to determine TP in the sediment samples. The results show that sediment TP content of wetland sediments ranged from 0.001 to 0.781 mg/kg, and decreases from southwest to northeast with the increase in sediment depth. The TP content reaches the maximum corresponding to the fastest growth stage of the reeds (June and July), while the minimum occurs in October (i.e., the maturity stage of reeds). The variation law of TP in cross-sectional sediment in the wetland is that the deeper the sediments are, the lower the content; its maximum content occurs in surface soil. The TP content of each site tends to be stable with increasing depth and has a regularly dynamic seasonal variation with the growth of reeds

Spatial and Temporal Distribution of Total Phosphorus in Sediments of Shuangtai Estuary Wetland during the Period of Reed Growth

Phosphorus is an essential macronutrient that plays a crucial role in the regulation of the biological productivity and biogeochemical cycling of other biogenic elements. As a large tidal wetland dominated by reeds in Liaoning province, China, the Shuangtai estuary wetland is a unique ecosystem class. To better understand the spatial and temporal distributions of total phosphorus (TP) in the sediments of the Shuangtai estuary wetland during the period of reed growth, eight sampling sites were established within the wetland, approximately 11 to 24 km from Liaohe River. These sites were sampled once a month at multiple sediment depth intervals between April and October in 2018 and 2019, periods of time that corresponded with the reed growth period. An alkali fusion method was used to determine TP in the sediment samples. The results show that sediment TP content of wetland sediments ranged from 0.001 to 0.781 mg/kg, and decreases from southwest to northeast with the increase in sediment depth. The TP content reaches the maximum corresponding to the fastest growth stage of the reeds (June and July), while the minimum occurs in October (i.e., the maturity stage of reeds). The variation law of TP in cross-sectional sediment in the wetland is that the deeper the sediments are, the lower the content; its maximum content occurs in surface soil. The TP content of each site tends to be stable with increasing depth and has a regularly dynamic seasonal variation with the growth of reeds

Hydrologic fragmentation-induced eutrophication in Dove Sound, Upper Florida Keys, USA

Anthropogenic impacts to island systems can have deleterious effects on coastal aquatic ecosystems. These effects can alter water quality, primary production as well as habitat. Land development often fragments hydrologic connectivity within aquatic ecosystems forcing alterations in nutrient transport and increases the potential for eutrophication. Dove Sound, a tidal lagoon located in the Upper Florida Keys on Key Largo, has been subjected to anthropogenic influences of land development during the last century. To investigate these influences a short sediment core was collected from within Dove Sound and investigated using 210Pb dating, stable isotopes of carbon and nitrogen, and sedimentary pigments. Results indicated that Dove Sound has undergone eutrophication and the primary producer community structure has shifted from dominantly macrophytic to a system that supports substantial algal production. While septic waste was a possible source for eutrophication, low δ15N did not support this conclusion. However, the timing of the shifts in Dove Sound along with indicators of anoxia leads to the conclusion that fragmentation caused by the construction of a railroad was the root cause. The hydrologic fragmentation reduced the flushing rates, thereby enhancing anoxic conditions in the system and increasing the internal nutrient loading

Linking biogeochemical processes and historic primary producer communities in the SE USA sinkhole lake form the mid-Holocene to present.

Many freshwater resources receive materials from human development causing a decrease in ecological services when compared to pre-disturbance periods. As a result, the understanding of eutrophication and limnological change has increased, but less attention has been given to systems under intense human impact that have not eutrophied so that drivers precluding eutrophication can be documented. The primary objective of this research was to reconstruct allochthonous inputs and in-lake processes for Long Pond, Georgia, USA from the mid Holocene to present and link them to primary producer community changes. Long Pond is a mesotrophic lake located in a highly altered watershed from agricultural and municipal land use and housing developments. A 5 m sediment core was collected from Long Pond, and organic matter, nutrients (C, N, P), metals (Al, Fe, Cu), and photosynthetic pigments were measured. Long Pond existed in three limnological states spanning the past ~6000 years. Prior to modern lacustrine conditions, Long Pond was a wetland/peat system that experienced the highest primary producer abundance recorded in the core. The modern lacustrine state began in the late Holocene and was characterized by increased connectivity with the surrounding watershed and low productivity. Human impacts began around 1900 AD and included high levels of phosphorus and metal deposition but moderate levels of primary producer abundance. As a result, in-lake dynamics are believed to be regulating the trophic status of Long Pond. Low concentrations of available phosphorus in the water column combined with high concentrations of sedimentary phosphorus may imply the binding of phosphorus to the sediments by certain materials such as aluminum and iron. Long Pond serves as an example of the complex in-lake processes that can occur from allochthonous inputs and autochthonous responses in lake systems thus complicating management decisions