The impact of the accumulation of algal blooms on reed wetlands in the littoral zones of Chaohu Lake

In a large eutrophic lake,the littoral zone is normally an area with high-density elevated aquatic plant life,including algal blooms,where the presence of reed wetlands allows the accumulation of algae.In this study,the impact of accumulated algal blooms in reed wetlands in the littoral zone s of Chaohu Lake was investigated seasonally from 2018 to 2019.The concentrations of chlorophyll a(Chl a),total nitrogen(TN),and total phosphorus(TP)were much higher in the reed-covered littoral zones(RCLZ)than in the unvegetated littoral zones(ULZ),indicating that more algal biomass was trapped and accumulated in the RCLZ.Algal biomass could be horizontally transported to downwind littoral zones under low wind speeds,favoring the establishment of blooms.Algal accumulation levels were highest in summer due to high water temperatures and algal biomasses.Likewise,the northern littoral zones were conducive to the development of large algal blooms because of the wind pattern.The values of TN,TP,Chl a,and loss on ignition in surface sediments were higher in the RCLZ than in the ULZ.Moreover,the diffusive fluxes of ammonium and soluble reactive pho sphorus were also higher in the RCLZ than in the ULZ.Considering the capability of reed wetlands to trap algae,mechanical salvage and other physical methods should be adopted to eliminate algal biomass when massive blooms accumulate in the RCLZ.

Landscape eco-environmental research on littoral zone in China

Littoral zone is a special land/ landscape type. As an important kind of land resource in support, the use of littoral zone is vital to eastern coastal areas in China. And the research on littoral zone relates to the key theory of landscape ecology. Based on the theory of landscape ecology, the littoral zone was divided into four types: mud flat, sand beach, bench, and biological flat. The distribution of each type in China is pointed out. As a typical open system, littoral zone has six landscape ecological characteristics: (1) high sensitivity to disturbance; (2) distinct edge effect; (3) spatial aggregation of natural resources; (4) frequently spatial oscillation; (5) obviously spatial heterogeneity; and (6) noticeably spatial differentiation. Some proposals are also put forward on the land use and development of littoral zone for environmental protection and environmental management.

Spatial distribution of archaeal and bacterial ammonia oxidizers in the littoral buffer zone of a nitrogen-rich lake

The spatial distribution and diversity of archaeal and bacterial ammonia oxidizers （AOA and AOB） were evaluated targeting amoA genes in the gradient of a littoral buffer zone which has been identified as a hot spot for N cycling. Here we found high spatial heterogeneity in the nitrification rate and abundance of ammonia oxidizers in the five sampling sites. The bacterial amoA gene was numerically dominant in most of the surface soil but decreased dramatically in deep layers. Higher nitrification potentials were detected in two sites near the land/water interface at 4.4–6.1 μg NO2-N/（g dry weight soil·hr）, while only 1.0–1.7 μg NO2-N/（g dry weight soil·hr） was measured at other sites. The potential nitrification rates were proportional to the amoA gene abundance for AOB, but with no significant correlation with AOA. The NH4＋ concentration was the most determinative parameter for the abundance of AOB and potential nitrification rates in this study. Higher richness in the surface layer was found in the analysis of biodiversity. Phylogenetic analysis revealed that most of the bacterial amoA sequences in surface soil were affiliated with the genus of Nitrosopira while the archaeal sequences were almost equally affiliated with Candidatus ‘Nitrososphaera gargensis’ and Candidatus ‘Nitrosocaldus yellowstonii’. The spatial distribution of AOA and AOB indicated that bacteria may play a more important role in nitrification in the littoral buffer zone of a N-rich lake.

Tsunami hazard assessment in the South China Sea:A review of recent progress and research gaps

The South China Sea region is potentially threatened by tsunami hazards originated from multiple sources:the Manila subduction zone in the east,the Littoral Fault Zone(LFZ)in the north,numerous submarine landslides on the continental slopes and the volcanic islands in the Luzon Strait.Infrequent but potentially devastating tsunami hazard poses a great threat to the populous coastal region,fishery,oil and gas exploitation in the deep sea,etc.Here we review the recent progress in tsunami hazard assessment in the South China Sea region,focusing on two primary sources:submarine earthquakes and landslides.We sort and review the literature by the two commonly used approaches:deterministic and probabilistic tsunami hazard assessment for both source types.By simulating tsunamis generated by typical earthquakes originated from the Manila Trench,the LFZ and landslides in the continental slopes,we investigate their tsunamigenic mechanism and key tsunami characteristics in the South China Sea region.We point out the research gaps and highlight the key issues to be addressed in the future.