Distribution and sources of sedimentary organic matter in different aquaculture areas of northeastern Zhanjiang Bay using stable carbon and nitrogen isotopes

Zhanjiang Bay is a major aquaculture area in China with many types of mariculture products(such as oysters,fish,and shrimp).The culture area and shrimp output in Zhanjiang Bay are ranked first in China.We investigated the total organic carbon(TOC),total nitrogen(TN),TOC/TN ratio,and stable isotopes(δ^(13)C and δ^(15)N) of the fish and shrimp feed,fish and shrimp feces,and sedimentary organic matter(SOM) in and around different aquaculture areas of northeastern Zhanjiang B ay to study the impact of aquaculture activities on SOM.The average TOC contents of fish and shrimp feed were 39.20%±0.91% and 39.29%±0.21%,respectively.The average TOC content in the surface sediments of the oyster culture area,the mixed(fish and shrimp) culture area,and the cage fish farm area were 0.66%,0.88%±0.10%,and 0.58%±0.19%,respectively,which may indicate that mixed culture had a greater impact on SOM.The relatively high TOC and TN contents and relatively low TOC/TN ratios,and δ^(15)N values in the upper layer of the core sediment in the mixed culture area could also support the significant influence of mixed culture.The average δ^(13)C and δ^(15)N values of fish and shrimp feed were -20.6‰±2.2‰ and 1.8‰±1.2‰,respectively,which were different from the isotopic values of SOM in the study area.δ^(13)C and δ^(15)N values for SOM in different aquaculture areas were different from those of nearby reference stations,probably reflecting the influence of aquaculture.The δ^(13)C and δ^(15)N values in the oyster culture area(-25.9‰ and6.0‰,respectively) seemed to have reduced δ^(13)C and enriched δ^(15)N relative to those of the reference station(-24.6‰ and 5.8‰,respectively).This may reflect the influence of organic matter on oyster culture.The δ^(15)N value of the station in the mixed culture area(7.1‰±0.4‰) seemed to be relatively enriched in δ^(15)N relative to that of the reference station(6.6‰).Sedimentation and the subsequent degradation of organic matter from mixed cultures may have contributed to this phenomenon.The surface sediment at the cage fish farm area seemed to be affected by fish feces and primary production based on the indication of δ^(13)C and δ^(15)N values.The sediment core at the mixed culture region(NS6) had lower TOC/TN ratios and more positive δ^(13)C and δ^(15)N values than the sediment core at the oyster culture area,suggesting a higher proportionate contribution of marine organic matter in the mixed culture area.In summary,oyster culture,mixed culture,and cage fish culture in northeastern Zhanjiang Bay had a certain degree of impact on SOM,and mixed culture had more significant influences on SOM based on the high TOC contents and the significant vertical variations of TOC/TN ratio and δ^(15)N value in the sediment of this area.This study provides new insights into the impact of aquaculture activities on SOM content.

Isotope constraints on seasonal dynamics of nitrogen in Zhanjiang Bay, a typical mariculture bay in South China

Eutrophication in coastal waters has been increasing remarkably,severely impacting the water quality in mariculture bays.In this study,we conducted multiple isotopic measurements on suspended particulate nitrogen(δ^(15)N-PN) and dissolved nitrate(δ^(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)) in Zhanjiang Bay,a typical mariculture bay with a high level of eutrophication in South China,to investigate the changes in nitrogen sources and their cycling between the rainy and dry seasons.During the rainy season,the study found no significant relation between δ^(15)NPN and δ^(15)N-NO_(3)^(-)due to the impact of heavy rainfall and terrestrial erosion.In the upper bay,a slight nitrate loss and slightly higher δ_(15)N-NO_(3)^(-)and δ^(18)O-NO_(3)^(-)values were observed,attributed to intense physical sedimentwater interactions.Despite some fluctuations,nitrate concentrations in the lower bay mainly aligned with the theoretical mixing line during the rainy season,suggesting that nitrate was primarily influenced by terrestrial erosion and that nitrate isotopes resembled the source.Consequently,the isotopic values of nitrate can be used for source apportionment in the rainy season.The results indicated that soil nitrogen(36%) and manure and sewage(33%) were the predominant nitrogen sources contributing to nitrogen loads during this period.In contrast,the dry season saw a deficient ammonium concentration(<0.2 μmol/L) in the bay,due to nearly complete consumption by phytoplankton during the red tide period.Additionally,the significant loss of nitrate and simultaneous increase in the stable isotopes of dissolved and particulate nitrogen suggest a strong coupling of assimilation and mineralization during the dry season.More active biogeochemical processes during the dry season may be related to decreased runoff and increased water retention time.Overall,our study illustrated the major seasonal nitrogen sources and their dynamics in Zhanjiang B ay,providing valuable insights for formulating effective policies to mitigate eutrophication in mariculture bays.

Study on the Perceived Value of Zhanjiang Residents to Mangrove Cuisine

Taking mangrove cuisine in Zhanjiang as an example,this paper investigates the residents’perceived value of mangrove cuisine through questionnaire survey.The results show that the overall satisfaction of residents on the mangrove cuisine in Zhanjiang is high.The highest satisfaction of residents on the perceived value of mangrove cuisine is the historical and cultural heritage,and the lowest satisfaction is the local characteristics.The main factor affecting the satisfaction is the utility value.Based on the analysis of the present situation and existing problems of mangrove cuisine resources in Zhanjiang,this paper puts forward some countermeasures and suggestions for the sustainable development of mangrove food in Zhanjiang in terms of strengthening government support,increasing public participation awareness,increasing publicity channels,enhancing popularity and reputation,and paying attention to the inheritance of characteristic food culture.

Numerical Study of the Donghai Dam Impact on the Hydrodynamic Environment of Zhanjiang Bay

In this paper, the Finite Volume Coastal Ocean Model （FVCOM） was employed and configured for 3 dimensional numerical simulations of tide and tidal current based on the field observations in Zhanjiang Bay. The model＇s results agree well with the field observed data. Based on the well validated model, the hydrodynamic fields of zhanjiang bay area were calculated both before the Donghai Dam constructing and after that. Compared the tidal level, current field, tidal capacity and water exchange ratio before the construction of Dohai dam with those after construction of the dam, we analyzed and get some conclusions of effects of Donghai Dam on Hydrodynamic environment of the Zhanjiang Bay.

Construction Features of Small Roadside Parks in Tropical Area——A Case Study of Zhanjiang City

Accessibility and flexibility of small roadside parks make them significant transitional spaces in urban landscape environment. Three representative small parks in Zhanjiang City, a typical tropical city in south China, were selected to analyze their location features, spatial processing, demonstration of regional landscapes and recreational characteristics. It was proposed that construction of small roadside parks in tropical area should put human needs on the priority, present regional features of tropical garden landscapes, and focus on inheritance and innovation of regional cultures.

Residues and sources of HCHs and DDTs in the sediments of land-based sewage outlet to the Zhanjiang Bay, China

Due to the large usage of DDT-containing antifouling paints and lindane in China, heavy residuals of DDTs and HCHs have been found in many fishing harbors, but there is lack of studies on this issue for the Zhanjiang Bay which is an important fishing harbor and mariculture zone in South China. To evaluate the pollution status and sources of HCHs and DDTs in the Zhanjiang Bay, the concentrations, spatial distributions and sources in the sediments of 11 land-based sewage outlets to the Zhanjiang Bay were investigated. Since the 1980 s, HCHs residuals had obviously decreased in studied areas, but DDTs had little change, even abnormally high levels were found in some sites. The content percentages and diagnostic ratios of HCHs isomers and DDTs showed that the source of HCHs was derived from soils around the bay and recent input of lindane, and DDTs were from historical residues of technical DDTs and fresh input of DDT-containing antifouling paints on fishing ships. Based on sediment quality guidelines, DDTs would be of more concern for the ecotoxicological risk on marine environment and adverse effects on benthonic organisms. This study indicated that lindane and DDT-containing products may be still used in some places of Zhanjiang City. It should be urgent to control their usage and clean the DDTs-contaminated sites by the local government.

Investigation of Export Aquaculture in Zhanjiang City and Development Suggestions

History of aquaculture in Zhanjiang City was reviewed by reviewing literatures, human resources, cultured species and culture modes, and distribution of aquaculture system were investigated and summarized. Output and export of processed aquatic products of Zhanjiang in the past years were analyzed, and the role of export aquaculture in economic development and social construction of Zhanjiang City was explored, and suggestions were given for enhancing the development of local export aquaculture.

Independent integration of the 300 t BOF of Zhanjiang in heritage of steelmaking technologies of Baosteel

Through summary and extraction of current steelmaking design,process and equipment technologies and production technologies for 300 t grade converters in Baosteel,the article analyzes and elaborates the significance of independent integration of 300 t grade converters in Zhanjiang,major targets of the independent integration in converter process technologies,equipment packages and controls,the innovated critical technologies and comparison with overseas advanced technologies,major technical difficulties in the integration in Baosteel and their solutions,as well as general mindset and final objectives of the project.The total integration of technology for Shanghai No.1 Steel Making Plant of Baosteel was undertaken by Nippon Steel.And Kawasaki Steel was responsible for the total integration of technology for 4# and 5# converters of Shanghai No.2 Steelmaking Plant of Baosteel.Based on digestion,absorption and innovation of the introduced technologies,Baosteel has firstly achieved the independent integration of 6# converter,5# RH and 3# LF projects in the Shanghai No.2 Steelmaking Plant of Baosteel.Therefore, Baosteel shall take advantages of the favorable conditions and experiences and advanced steel making technologies of Baosteeel to master the imported new steelmaking technologies in the world and then form the advanced complete set steel making technologies and equipment at home and abroad.The achievement of independent integration of Zhanjiang Steel Making Project will make the breakthrough for the construction of large - sized steel making plant in Baosteel.300 t converter technology integration is undertaken by Baosteel independently in instead of by the foreign side in the past.

Practice and Innovation of ＂Teacher Education＂ Training Mode： Take Zhanjiang Normal University for Example

This article adopts the method of case study, thorough analysis of Zhanjiang Normal University in teacher education training model innovation practice, explore its talent training innovation goals： to cultivate beauty, intelligence and physique full scale development ＂responsible, strong ability, good innovation＂. Came to the conclusion that the university talents training mode of innovative practice is specific to subjects and to students.

Development Status and Policy Path of Cultivating Marine Bio-industry Cluster in Zhanjiang City

Cultivating the marine bio-industry cluster is a key industrial strategy for Zhanjiang to seize the manufacturing position of Guangdong's marine economy. By deconstructing the overall scale,characteristics and industrial composition of marine bio-industry cluster and the development status of the industrial parks and bases in Zhanjiang,the resource misallocation coefficient was used to analyze the problems in the marine bio-industry cluster and the resource allocation in Zhanjiang. It is found that in the cultivation of the marine bio-industry cluster in Zhanjiang,the leading effect of leading enterprises needs to be upgraded,the key technologies needs to be broken,the scientific and technological service system needs to be improved,and policy support needs to be strengthened. Moreover,there are serious resource misallocation and high efficiency losses. By optimizing resource allocation,the healthy development of cultivation of marine bio-industry cluster in Zhanjiang will be promoted. To this end,the policy paths that the government can implement are as follows: improving the market access system to appropriately guide medium and small-sized marine enterprises to enter the marine bio-industry,inspiring the marine bio-industry market demand with the industrialization of innovation results as the guide,improving the legal guarantee system to create an innovative atmosphere for the marine bio-industry,and promoting the deepening of the division of labor in the industrial parks.

湛江市古树资源特征分析

为摸清湛江市古树资源情况,加强湛江市古树保护工作,基于广东省古树名木普查成果数据,对湛江市古树资源的树种结构、树龄、分布、生长环境、生长状况等方面进行了分析。结果表明:湛江市共有古树7356株,隶属于46科84属111种;在湛江各县级市、县区均有分布,其中徐闻县古树数量最多;优势树种主要是榕树(Ficusmicrocarpa)、垂叶榕(F.benjamina)、鹊肾树(Streblusasper)、樟(Camphoraofficinarum)等观赏树种和龙眼(Dimocarpuslongan)、荔枝(Litchi chinensis)等果树;古树生长场所主要为乡村,树龄主要分布在100~200年之间,三级古树多达7080株,占比96.25%;古树树高主要分布范围是7~20 m,平均树高为12.97 m,胸径主要分布范围是40~160 cm,平均胸径96.7 cm,冠幅主要分布范围4~20 m,平均冠幅13.55 m。总体而言,湛江市古树生长环境和生长势良好,古树资源物种多样性丰富。

湛江湾人为净磷输入时空演变及驱动因素分析

海湾区域与外界水交换有限且受人类活动影响较大,容易出现水体富营养化、污染物蓄积等问题,进而威胁生态系统的稳定。磷是影响海湾水体质量的关键营养元素,定量评估人为磷输入是区域营养盐管理的重要基础。本研究以湛江湾为研究区域,基于人类活动净磷输入(NAPI)模型,结合该流域所属6个行政单元统计数据,系统核算和剖析湛江湾2001-2021年期间的NAPI强度,并深入探讨演变趋势及其驱动因素。结果表明:①湛江湾平均NAPI强度达2742.46 kg/(km^(2)·a),在时间尺度上,自2001年起整体呈现先升高后下降的趋势,2016年达到最高,随后略有下降并趋于稳定。②在空间尺度上,西部地区的NAPI值高于东部,北部高于南部,遂溪县和开发区NAPI强度的贡献率最高,为67.7%。③基于NAPI的组成结构,化肥施用量是湛江湾NAPI的主要贡献因子,年均贡献率高达88.7%。因此,在湛江湾流域的磷管理措施中,需要重点关注化肥磷输入以及磷元素滞留的协同管理。

广东湛江烟区不同雪茄品种综合性状评价

【目的】综合评价不同雪茄品种的生态适应性,筛选适宜广东湛江烟区种植的雪茄品种。【方法】对8个新引进雪茄品种进行田间试验,分析比较其大田生育期、农艺性状、田间自然发病率、常规化学成分和感官质量评吸的差异,利用综合指数法对其进行综合性状评价。【结果】8个雪茄品种的大田生育期均较长、平均为141.63 d,且品种间差异较大。其中,‘海研108’和‘海研201’大田生育期最短(均为133 d)、‘云雪8号’最长(155 d)。农艺性状以‘云雪8号’和‘海研200’综合表现最好,2个品种的株高、最大叶宽、节距和有效叶数均优于8个品种的平均水平,表明这2个品种的田间生长势强。‘海研200’‘海研101’和‘云雪2号’的烟草普通花叶病发生率均较低,介于5.09%~6.85%,且均无烟草气候斑点病发生,表明这3个品种的抗病性较强;常规化学成分协调性以‘海研200’和‘海研101’较好,综合得分均高于平均水平,但2个品种的钾氯比均低于优质烟叶适宜范围(4~10)。感官质量评吸以‘海研101’得分最高(46.07),特点是香气量稍足、余味尚干净、回甜感较强和燃烧性较好。综合指数计算结果显示,8个雪茄品种的得分排序为:‘海研200’>‘海研101’>‘云雪8号’>‘云雪2号’>‘海研108’>‘海研201’>‘云雪3号’>‘Havana’。【结论】8个新引进雪茄品种中,‘海研200’和‘海研101’的综合性状较好,适宜在湛江烟区引进种植,建议通过优化施肥方案、晾制与发酵工艺进一步提高烟叶质量。

湛江港皮氏叫姑鱼种群生物学特征和资源开发状态

皮氏叫姑鱼(Johnius belangerii)是湛江港海域重要的渔业资源,其种群数量和分布对渔业生产和生态平衡具有重要影响。为探究湛江港皮氏叫姑鱼的生活史特征及其资源开发状态,根据2016—2021年湛江港海域底拖网调查数据,使用ELEFAN I、Pauly经验公式、长度转换捕获曲线法等方法估算了皮氏叫姑鱼的生长、死亡参数,并根据实际种群分析(Virtual population analysis,VPA)、Beverton-Holt动态综合模型评估了该渔业资源的开发状态。结果表明,湛江港海域皮氏叫姑鱼体长介于27.03~182.00 mm,体质量介于0.19~137.34 g。生长方程的极限体长(L∞)为185.85 mm,生长系数(K)为0.61,理论生长年龄(t0)为-0.27。总死亡系数(Z)、自然死亡系数(M)和捕捞死亡系数(F)分别为2.40、0.75和1.65。湛江港皮氏叫姑鱼首次捕捞体长(83.74 mm)远小于最适开捕体长(131.95 mm),捕捞对象多为幼鱼和补充群体,具有小型化趋势。湛江港皮氏叫姑鱼开发率(E)为0.69,高于最大可持续开发率(Emax=0.63),处于过度捕捞状态。研究揭示了皮氏叫姑鱼的生活史特征,可为其资源的可持续利用和科学管理提供参考依据。

基于时序遥感的撂荒地监测及空间格局特征分析

针对耕地撂荒监测的迫切需求,文章发展了一种基于光学时序特征的撂荒地遥感识别方法,利用Sentinel-2时间序列数据构建耕地NDVI时序曲线,基于撂荒地和非撂荒耕地NDVI在监测时间窗口内的振幅差异,通过F1指数迭代式选取撂荒地识别的最佳振幅分割阈值,构建撂荒地识别规则,并在广东省湛江市坡头区开展耕地撂荒监测试验,分析撂荒地块的景观格局特征。研究表明:1)对比撂荒地与非撂荒地的NDVI时序曲线形态发现,撂荒地全年NDVI时序曲线变化平缓,变化幅度较小;非撂荒耕地由于作物生长发育的物候过程,NDVI时序呈现较大的变化幅度。2)通过迭代式选取振幅分割阈值,撂荒地与非撂荒地NDVI振幅的最佳分割阈值为0.42,在该分割阈值下,撂荒地和非撂荒地的识别精度分别为91.83%和90.20%。3)对撂荒地景观格局特征分析结果表明,2020年坡头区耕地撂荒面积为14.65 km^(2),约占耕地总面积的10.1%,撂荒地块普遍面积较小、形状不规则,空间上分布零散,少有大面积撂荒现象。

树种类型和潮滩高程对广东湛江高桥红树林碳储量的影响

红树林位于海洋与陆地的交界处,其高效的碳汇能力易受多方面因素的影响。文章通过分析植物生长指标、生物量、植被碳储量和土壤碳储量以及土壤容重等参数,研究了树种类型和潮滩高程对广东湛江高桥区红树林群落碳汇功能的单独作用和耦合效应。结果表明,高桥红树林的固碳总量为4.98×10^(10)g,碳密度为107.76×10^(6)g·hm^(-2),土壤碳积累是该红树林固碳的重要贡献。不同潮滩红树林的碳储量受树种差异的影响显著,且低潮滩的红树林碳储量显著高于高潮滩和中潮滩,而潮滩高程仅对无瓣海桑群落的碳储量具有显著影响。无论是植物碳库还是土壤碳库,中潮滩红海榄群落和低潮滩无瓣海桑群落的碳密度最高。红树群落的土壤有机碳含量在垂直方向分布均匀,各土层间无显著差异。在高潮滩和中潮滩,土壤有机碳含量的垂直分布受树种影响,大部分桐花树群落的土壤有机碳含量显著高于同土层的秋茄群落、白骨壤群落和无瓣海桑群落,而树种对低潮滩各土层有机碳含量无显著影响。虽然树种类型和潮滩高程可影响土壤容重与土壤有机碳含量间的作用关系,但线性拟合结果以负相关关系为主。

General multidimensional cloud model and its application on spatial clustering in Zhanjiang, Guangdong

Traditional spatial clustering methods have the disadvantage of ＂hardware division＂, and can not describe the physical characteristics of spatial entity effectively. In view of the above, this paper sets forth a general multi-dimensional cloud model, which describes the characteristics of spatial objects more reasonably according to the idea of non-homogeneous and non-symmetry. Based on infrastructures＇ classification and demarcation in Zhanjiang, a detailed interpretation of clustering results is made from the spatial distribution of membership degree of clustering, the comparative study of Fuzzy C-means and a coupled analysis of residential land prices. General multi-dimensional cloud model reflects the integrated char- acteristics of spatial objects better, reveals the spatial distribution of potential information, and realizes spatial division more accurately in complex circumstances. However, due to the complexity of spatial interactions between geographical entities, the generation of cloud model is a specific and challenging task.

湛江红树林生态产品价值的游客感知与补偿意愿研究

近年来,湛江积极打造“红树林之城”,并探索生态保护、旅游发展等多重背景下的红树林生态产品价值实现机制,然而现有研究对游客感知与补偿视角下的红树林生态产品价值关注仍存在着不足。本研究以湛江红树林为研究对象,设计了一份调查问卷,基于游客主体视角获取489份问卷样本,以此分析湛江红树林生态产品价值的游客感知评价状况,并利用多元线性回归方法,进一步探讨生态产品价值感知的游客补偿意愿及其影响关系,研究发现:(1)湛江红树林生态产品价值的游客总体感知度相对较低,不同类型红树林生态产品价值感知评价从高到低依次为调节类、文化类、供给类;(2)游客生态补偿意愿相对较强,年龄、学历、职业、收入和游玩次数对补偿意愿存在显著影响,性别与来源地则无显著影响;(3)文化类生态产品价值感知、地方依恋情感对游客补偿意愿有着显著的正向影响,而调节类、供给类生态产品价值感知、积极心理情绪则对游客补偿意愿不存在显著影响关系。

广州至湛江高速铁路引入广州枢纽方案研究

广州至湛江高速铁路利用广茂铁路通道,并采用双层框架结构设计引入城市中心车站,能够充分利用既有城市配套设施、更好地服务地方客流、最大程度减少征地拆迁,对构建广州枢纽总图“五主三辅”客站布局具有重要作用。本文结合广州枢纽既有及规划布局、城市空间布局等因素,从工程投资及运营时分、衔接线路及运输组织、运输质量、工程实施难度及对既有铁路运营干扰等方面,对广湛高速铁路多个引入广州站方案进行了综合分析比较,得出推荐意见,并对设计中创新采用的双层框架结构进行了介绍。希冀能为类似新建铁路项目引入城市中心的客运枢纽站提供借鉴和参考。

基于形态和分子数据对湛江海域4个江蓠物种(红藻门)的分类学研究

利用分子鉴定和形态学分析,对采自广东湛江的江蓠科物种进行了分类学研究。经鉴定,共发现4种江蓠科物种,即细基江蓠Gracilaria tenuistipitata、硬江蓠G. firma、帚状江蓠G. edulis和异枝拟江蓠Gracilariopsis bailinae。文章详细讨论了这4种江蓠的分类学特征和系统发育关系,在此基础上结合文献数据,明确了细基江蓠、细基江蓠繁枝变种G. tenuistipitata var. liui与长喙江蓠G. longirostris为同一个种,以及硬江蓠G. firma与张氏江蓠G. changii为同一种。本研究修订了我国南方沿海江蓠科物种的分类信息,也为湛江海域大型海藻资源的保护和开发提供了分类学依据。