This study aims to assess ecological effects of the construction of marine ranching in the eastern Guangdong waters. Variations in sea surface temperature (SST), chlorophyll a concentration (Chl-a), catch per unit eff...This study aims to assess ecological effects of the construction of marine ranching in the eastern Guangdong waters. Variations in sea surface temperature (SST), chlorophyll a concentration (Chl-a), catch per unit effort (CPUE), biodiversity, biomass and density of benthos were compared during the pre- (August in 2011) and post- (August in 2013) marine ranching. These were based on satellite remote sensing and survey data. Results showed that the ratio of Nitrogen (N): Phosphorus (P) was closed to 16, Chl-a increased from 7.5 - 12.3 mg·m-3 to 10.4 - 16.2 mg·m-3, and CPUE increased from 2.1 - 5.5 kg·h-1 to 5.8 - 14.5 kg·h-1. The species number of fish, crustaceans, cephalopods and shellfish increased by 25, 3, 2 and 3 respectively. Shannon-Wiener biodiversity index of fish, crustaceans, cephalopods and shellfish increased by 0.5, 0.4, 0.1 and 1.0 respectively. Both biomass and density of benthos increased also. The construction of marine ranching in the eastern Guangdong had restored the habitat to some extent, and played positive effects in the conservation and proliferation of fishery resources in local area.展开更多
GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding tim...GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network.The analysis of data from 120 drifters,deployed in late spring 2018 in the case-study region,shows that the drifters are generally capable of capturing the surface(tidal and residual)currents.The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast,where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay.The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current,while the currents inside Daya Bay are strongly affected by the topography.According to the harmonic analysis,an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay,with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°.The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast,while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s,which agrees well with the one reported in other literatures.展开更多
滑坡空间易发性统计模型的构建需要正样本(滑坡点)和负样本(非滑坡点)两类数据,但历史观测数据仅记录了正样本,而负样本的选取容易受到正样本污染,因为没有滑坡记录的地方也可能在过去或未来发生滑坡,从而导致模型的预测精度与稳定性受...滑坡空间易发性统计模型的构建需要正样本(滑坡点)和负样本(非滑坡点)两类数据,但历史观测数据仅记录了正样本,而负样本的选取容易受到正样本污染,因为没有滑坡记录的地方也可能在过去或未来发生滑坡,从而导致模型的预测精度与稳定性受到影响。针对此问题,将前期提出的半监督学习算法PBLC(positive and background learning with constraints)应用于滑坡空间易发性分析,探讨其解决负样本污染问题的有效性。本文以粤东地区为研究区,选择高程、坡度、坡向、剖面曲率、距离道路最短距离、距离断层线最短距离、距水系最短距离、年平均降雨量、归一化植被指数和地理坐标共11个影响因子作为环境变量。结果表明,与传统的人工神经网络模型相比,基于PBLC算法的预测概率取值范围更为合理,预测结果更加稳定,且预测精度随背景样本数量增加而提高;粤东地区的滑坡灾害高易发区集中于北部和西南区域,坡度和高程是影响该地区滑坡易发性的主要因子。结果表明,半监督学习算法PBLC可以有效解决滑坡统计建模过程负样本污染的问题,提高模型预测精度。展开更多
文摘This study aims to assess ecological effects of the construction of marine ranching in the eastern Guangdong waters. Variations in sea surface temperature (SST), chlorophyll a concentration (Chl-a), catch per unit effort (CPUE), biodiversity, biomass and density of benthos were compared during the pre- (August in 2011) and post- (August in 2013) marine ranching. These were based on satellite remote sensing and survey data. Results showed that the ratio of Nitrogen (N): Phosphorus (P) was closed to 16, Chl-a increased from 7.5 - 12.3 mg·m-3 to 10.4 - 16.2 mg·m-3, and CPUE increased from 2.1 - 5.5 kg·h-1 to 5.8 - 14.5 kg·h-1. The species number of fish, crustaceans, cephalopods and shellfish increased by 25, 3, 2 and 3 respectively. Shannon-Wiener biodiversity index of fish, crustaceans, cephalopods and shellfish increased by 0.5, 0.4, 0.1 and 1.0 respectively. Both biomass and density of benthos increased also. The construction of marine ranching in the eastern Guangdong had restored the habitat to some extent, and played positive effects in the conservation and proliferation of fishery resources in local area.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.91958203,41776027,and 41606009)the Xiamen University Fundamental Research Funds for the Central Universities(Nos.20720180103,20720180099)+1 种基金the Laboratory for Regional Oceanography and Numerical Modeling,Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2017A02)the municipal project of Huizhou City(No.F2017-01-1)
文摘GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network.The analysis of data from 120 drifters,deployed in late spring 2018 in the case-study region,shows that the drifters are generally capable of capturing the surface(tidal and residual)currents.The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast,where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay.The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current,while the currents inside Daya Bay are strongly affected by the topography.According to the harmonic analysis,an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay,with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°.The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast,while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s,which agrees well with the one reported in other literatures.
文摘滑坡空间易发性统计模型的构建需要正样本(滑坡点)和负样本(非滑坡点)两类数据,但历史观测数据仅记录了正样本,而负样本的选取容易受到正样本污染,因为没有滑坡记录的地方也可能在过去或未来发生滑坡,从而导致模型的预测精度与稳定性受到影响。针对此问题,将前期提出的半监督学习算法PBLC(positive and background learning with constraints)应用于滑坡空间易发性分析,探讨其解决负样本污染问题的有效性。本文以粤东地区为研究区,选择高程、坡度、坡向、剖面曲率、距离道路最短距离、距离断层线最短距离、距水系最短距离、年平均降雨量、归一化植被指数和地理坐标共11个影响因子作为环境变量。结果表明,与传统的人工神经网络模型相比,基于PBLC算法的预测概率取值范围更为合理,预测结果更加稳定,且预测精度随背景样本数量增加而提高;粤东地区的滑坡灾害高易发区集中于北部和西南区域,坡度和高程是影响该地区滑坡易发性的主要因子。结果表明,半监督学习算法PBLC可以有效解决滑坡统计建模过程负样本污染的问题,提高模型预测精度。
