Different response of bacterial community to the changes of nutrients and pollutants in sediments from an urban river network

• Bacterial community varied spatially in sediments from the urban river network. • Key environmental factors shaping bacterial community were detected by RDA. • Bacterial co-occurrence networks changed at different levels of nutrient and metal. • Potential indicator species were selected to predict pollution risk in sediment. Microbial communities in sediment are an important indicator linking to environmental pollution in urban river systems. However, how the diversity and structure of bacterial communities in sediments from an urban river network respond to different environmental factors has not been well studied. The goal of this study was to understand the patterns of bacterial communities in sediments from a highly dense urbanized river network in the lower Yangtze River Delta by Illumina MiSeq sequencing. The correlations between bacterial communities, the environmental gradient and geographical distance were analyzed by redundancy analysis (RDA) and network methods. The diversity and richness of bacterial community in sediments increased from upstream to downstream consistently with the accumulation of nutrient in the urban river network. Bacterial community composition and structure showed obvious spatial changes, leading to two distinct groups, which were significantly related to the characteristics of nutrient and heavy metal in sediments. Humic substance, available nitrogen, available phosphorus, Zn, Cu, Hg and As were selected as the key environmental factors shaping the bacterial community in sediments based on RDA. The co-occurrence patterns of bacterial networks showed that positive interaction between bacterial communities increased but the connectivity among bacterial genera and stability of sediment ecosystem reduced under a higher content of nutrient and heavy metal in average. The sensitive and ubiquitous taxa with an overproportional response to key environmental factors were detected as indicator species, which provided a novel method for the prediction of the pollution risk of sediment in an urban river network.     

粤西三座重要供水水库沉积物营养盐负荷与重金属污染特征

为揭示粤西3座供水水库（高州水库、鹤地水库、大水桥水库）沉积物营养盐负荷及重金属污染特征,于2008年6月在各水库大坝前湖泊区采集柱状沉积物,运用SMT法、碱性过硫酸钾消解法、烧失法和ICP-MS法分别测定其柱状沉积物中氮磷营养盐、有机质和7种重金属（Cu、Pb、Zn、Cd、Ni、Cr与Hg）的含量,并采用潜在生态风险指数法对表层重金属污染的潜在生态风险进行评价,同时通过相关性分析重金属的可能来源。结果表明：3座水库沉积物总氮质量分数为1.13~3.37 mg·g-1,有机质为11.83~20.37 mg·g-1,其表层总氮、有机质的质量分数大小顺序为高州水库〉大水桥水库〉鹤地水库,总磷的质量浓度在0.22~0.77 mg·g-1之间,其表层总磷质量分数大小顺序为高州水库〉鹤地水库〉大水桥水库,在垂直剖面上,总氮、总磷与有机质的质量分数在16 cm至表层沉积物垂直断面显著高于其他断面,表明近些年来水库内源营养盐负荷逐渐加重。重金属质量分数平均值均高于广东省土壤环境背景值,总体呈现随深度增加而降低的趋势,但3座水库间重金属质量分数差异较大,其中鹤地和高州水库的Zn和Pb污染相对严重（质量分数分别为Zn：353.15、693.35 mg·kg-1;Pb：74.51、127.91 mg·kg-1）,大水桥水库的Cr和Ni污染相对严重（质量分数分别为Cr：238.69 mg·kg-1;Ni：251.06 mg·kg-1）。潜在生态风险评价表明,3座水库Cd和Hg具有高的生态危害,应引起重视,其他重金属则处于轻微的生态危害等级。同时沉积物高有机质的质量浓度经矿化分解可能加剧水体重金属生态危害。根据相关性分析和其他相关资料可知,粤西农业区大量化肥农药面源污染汇入造成水库初级生产力提高并最终沉降可能是沉积物营养盐、有机质与重金属的主要来源。     

赣江流域中下游底泥中有机氯农药污染特征

为了解赣江流域有机氯农药污染状况,采用索氏提取方法（Soxhlet Extraction,SE）和气相色谱法（GC-ECD）,对所采集的18个底泥样品中10种有机氯农药（OCPs）的残留进行测定,并对其组分分布和来源进行了分析。结果表明,所有样品均检出10种有机氯农药,底泥中∑OCPs质量分数范围为11.813-39.197μg·kg-1,HCHs、DDTs质量分数范围分别为1.636-20.877μg·kg-1和5.590-14.092μg·kg-1,HCHs的质量分数低于DDTs,六氯苯（HCB）和七氯（Heptachlor）的质量分数相对较低,分别为0.229-6.940μg·kg-1和0.507-3.936μg·kg-1。组分分布特征分析表明,它们除了来自环境中的早期残留外,仍然具有大量新的外源HCHs和DDTs的输入,可能是新的林丹输入以及三氯杀螨醇的使用,这可能与近年来沿江农业的发展有关。     

微孔曝气与覆盖对城市重污染河道底泥磷形态分布及释放过程的影响

采用自行研发的泥-水界面微孔曝气系统,开展了底泥表面曝气和覆盖对城市重污染河道底泥磷释放及形态分布规律的影响研究.结果表明,微孔曝气能够有效提高上覆水的溶解氧(DO)和沉积物的氧化还原电位(Eh),能够将泥-水界面Eh维持在-100 m V左右,DO提高到6 mg·L-1以上.与对照比较,原位覆盖处理的上覆水DO和Eh有一定提高,但仍明显低于微孔曝气处理.与对照相比较,微孔曝气处理均有效降低上覆水中总磷(TP)和溶解性正磷酸盐(PO3-4)的含量.试验结束时,微孔曝气(A)和微孔曝气+原位覆盖处理(A+C)上覆水中TP含量由初始的0.201 mg·L-1分别降至0.062 mg·L-1和0.050 mg·L-1;上覆水中PO3-4含量由0.086 mg·L-1和0.078 mg·L-1分别降至0.026 mg·L-1和0.023 mg·L-1.与对照相比,微孔曝气处理明显降低了底泥间隙水中TP的浓度,在整个培养期间,其TP含量平均下降38.8%(A)和47.9%(A+C).底泥原位覆盖处理对抑制泥-水界面磷释放能力要弱于微孔曝气处理,而且在试验后期(50 d),上覆水中TP和PO3-4的含量均有所反弹.不管有无覆盖,泥-水界面微孔曝气处理均显著改变了表层底泥磷形态分布特征,显著降低了底泥中铁铝结合态磷(Fe/Al-P)组分比例,而钙结合态磷(Ca-P)含量比例却出现明显增加.单一的表面覆盖处理对底泥磷形态分布特征没有显著影响(P0.05).研究表明,与单一的处理效果相比较,泥-水界面纳米微孔曝气处理,并结合底泥原位覆盖,更有利于抑制城市重污染河道泥-水界面中磷的释放风险.     

东江流域底泥重金属分析及潜在环境生态风险

对东江流域不同江段水环境的重金属底泥及底泥浸出液中铅、锌、铜、镉、铬、镍等重金属分布进行分析,结果表明铅和镉含量较高,存在一定程度污染或属于高背景值底泥;底泥的重金属因沉积引起,而锌、铜、铬和镍含量具有一定的污染同源性;利用地积累指数法和潜在生态风险指数法评价底泥重金属污染状况,镉污染较为严重,潜在生态风险大,污染程度镉>铜>锌>镍,铅存在一定的潜在生态风险,铅和铬污染风险较小,底泥和底泥浸出液中重金属含量的变化趋势较为一致,结果表明底泥是表面水重金属的重要来源.     

大坞河流域重金属污染与五节芒光谱效应关系研究

以大坞河流域五节芒（Miscanthus floridulus）可见一近红外光谱以及叶片样本Cu、Zn、Fe元素质量分数监测数据为基础，对研究区内五节芒中重金属质量分数特征、光谱特征及两者的相关性进行了探讨。结果表明：五节芒叶片中3种金属元素的质量分数都较高；从上游到下游，五节芒叶片中Cu质量分数整体呈逐渐降低的趋势，五节芒光谱反射率在可见光区和近红外区均增加，红边“红移”（向长波方向飘移）强度逐渐减小；同时，五节芒叶片中Cu质量分数与五节芒可见光区、近红外区光谱反射率积分值呈负相关性，与红边“红移”强度、土壤中Cu质量分数呈正相关。并由此得出五节芒光谱特征中A1、A2、S等3项指标能够较好反映土壤的Cu污染程度，经进一步深入研究，可以将五节芒作为监测矿区土壤Cu污染的指示植物。     

Variation characteristics of atmospheric methane and carbon dioxide in summertime at a coastal site in the South China Sea

● Diurnal patterns of CH₄ and CO₂ are clearly extracted using EEMD. ● CH₄ and CO₂ show mid-morning high and evening low patterns during sea breezes. ● Wind direction significantly modulates the diurnal variations in CH₄ and CO₂. Methane (CH₄) and carbon dioxide (CO₂) are the two most important greenhouse gases (GHGs). To examine the variation characteristics of CH₄ and CO₂ in the coastal South China Sea, atmospheric CH₄ and CO₂ measurements were performed in Bohe (BH), Guangdong, China, in summer 2021. By using an adaptive data analysis method, the diurnal patterns of CH₄ and CO₂ were clearly extracted and analysed in relation to the sea breeze (SB) and land breeze (LB), respectively. The average concentrations of CH₄ and CO₂ were 1876.91 ± 31.13 ppb and 407.99 ± 4.24 ppm during SB, and 1988.12 ± 109.92 ppb and 421.54 ± 14.89 ppm during LB, respectively. The values of CH₄ and CO₂ during SB basically coincided with the values and trends of marine background sites, showing that the BH station could serve as an ideal site for background GHG monitoring and dynamic analysis. The extracted diurnal variations in CH₄ and CO₂ showed sunrise high and sunset low patterns (with peaks at 5:00–7:00) during LB but mid-morning high and evening low patterns (with peaks at 9:00) during SB. The diurnal amplitude changes in both CH₄ and CO₂ during LB were almost two to three times those during SB. Wind direction significantly modulated the diurnal variations in CH₄ and CO₂. The results in this study provide a new way to examine the variations in GHGs on different timescales and can also help us gain a better understanding of GHG sources and distributions in the South China Sea.     

The development of secondary industries through the sustainable utilisation of reeds and forest timber in the Tembe Elephant Park,Maputaland, South Africa

The harvesting of Phragmites australis reeds in the Tembe Elephant Park has to be managed pro-actively. Solutions to potential problems should be sought before they arise. This paper offers a potential solution to the problem of instating a winter-only reed harvest in the Muzi Swamp. The potential for manufacturing finished products such as prefabricated huts from sustainably harvested reeds and forest timber is examined and a cost estimate is presented. A prefabricated reed hut is three-times cheaper than a similarly-sized house made of bricks and cement. The manufacturing of finished products from the harvested material will add secondary value to the resource and also offer an alternative employment to harvesting reeds in the summer. The higher prices obtained for a processed article will also, hopefully, reduce the demand for the resource in its raw form, thereby increasing the perceived value of the resource and reducing wastage from raw materials that are not sold.     

The abundance,characteristics and diversity of microplastics in the South China Sea: Observation around three remote islands

• A high abundance of floating MPs was found in the southern South China Sea. • Transparent film and fiber were predominant in water and organisms, respectively. • 84.7% of floating MPs and 54.5% of MPs in vivo belonged to PP and PE. • Characteristics of MP in organisms were different from those of inshore ones. Surrounded by emerging markets with considerable plastic consumption, the South China Sea has been a focus area of microplastic research. A survey on the floating microplastics (>0.3 mm) and microplastics ingested by fish and mollusks was conducted around three remote islands here. Compared with the results from several previous studies, a high abundance of floating microplastics (with a median of 1.9 × 10⁵ items/km² or 0.7 items/m³) was observed, revealing another “hot spot” for microplastics. Polyolefin, especially polypropylene, was the main component. The diversity index and evenness index were calculated and evaluated based on the composition of microplastics. The characteristic peaks of Raman spectra concerning pigmented microplastics were provided. Transparent sheets/films were predominant in the water sample, which was quite different from a similar study in this sea area (8.9% for film), and only 16.4% of floating microplastics (>0.3 mm) were fibers/lines, implying that the main sources of floating microplastics (>0.3 mm) might be household/agricultural consumption activities. The transparent fiber/line was also dominant in organisms. It is suggested that the main sources of microplastics ingested by organisms might be both fabric fibers and fishing/aquaculture.     

The gastropod Osilinus atrata as a bioindicator of Cd,Cu, Pb and Zn contamination in the coastal waters of the Canary Islands

The aim of this study was to assess the use of Osilinus atrata (Gastropoda, Mollusca) as a biomonitor of heavy metals (Cd, Cu, Pb and Zn) within the coastal zone of the Canary Islands. In general, this top-shell snail showed high intraspecific variability in its tissue metal concentrations, which decreased according to the following sequence: Cu≥Zn>Cd≥Pb. In particular, Cd and Zn concentrations were higher in males than in females, whereas Cu concentrations increased slightly with weight, and Pb concentrations decreased. Cd and Cu concentrations showed notable spatial variability; Cd concentrations were higher in the eastern islands (Alegranza, La Graciosa, Lanzarote and Fuerteventura) and La Palma, whereas Cu levels were highest in some western islands (Gran Canaria, La Gomera and El Hierro). The arrival of waters from the African coastal upwelling, the pollution of coastal waters with agricultural fertilisers and the competition for uptake between metals appear to be the likely causes within these patterns of accumulation. In conclusion, O. atrata presents a great potential as a biomonitor of heavy metals, however, more information and further studies are necessary.     

赤潮多发区深圳湾叶绿素a的时空分布及其影响因素

于2008年2月至2008年11月分四个季度调查了赤潮多发区深圳湾叶绿素a的时空分布,并分析了叶绿素a与主要环境因子之间的关系.结果表明,深圳湾叶绿素a质量浓度范围为3.07～309.94 mg·m~(-3),年平均值为42.29 mg·m~(-3).四季叶绿素a平均质量浓度由高到低排列分别为:春季(108.33 mg·m~(-3))>夏季(35.2 mg·m~(-3))>秋季(16.68 mg·m~(-3))>冬季(8.96 mg·m~(-3)).叶绿素a的质量浓度在冬季和春季呈现由湾内向湾外递减的分布特征,而夏季和秋季呈现由西岸向东岸递减的分布特征,整体则呈现由湾内向湾外递减的分布特征.相关分析显示深圳湾叶绿素a与水温、COD、TOC、PO_4~(3-)-P和浮游植物密度因子显著正相关,与DIN因子极显著正相关,说明叶绿素a与水温、DIN、PO_4~(3-)-P、COD、TOC和浮游植物密度之间有着比其它因子更为密切的关系.以叶绿素a作为富营养化评价标准,发现深圳湾海域富营养化严重,存在随时爆发赤潮的潜在风险.     

The relative roles of predation and sperm competition on the duration of the post-copulatory association between the sexes in the blue crab, Callinectes sapidus

In many species, post-copulatory mate guarding prevents other males from mating with the guarded female. In crabs, males stay with their mates to protect the female from predators because, in some species, mating occurs when she is soft and vulnerable after molting. I tested the relative roles of sperm competition and predation on the duration of the post-copulatory association in the blue crab, Callinectes sapidus. Unpaired females suffered greater predation mortality than paired females and males stayed with the female longer in the presence of predators than in their absence, suggesting that the post-copulatory association protects females during their vulnerable period. However, the association may also occur in blue crabs because of sperm competition since spermathecal contents of females in the field indicate that 12.4% mated twice. Females experimentally mated with two males contained both males ejaculates and each ejaculate had access to the unfertilized eggs, suggesting that the size of a male's ejaculate influences his fertilization rate in a multiply-mated female. Males stayed longest in response to a high risk of sperm competition. Longer post-copulatory associations allowed the first male's ejaculate to harden into a type of sperm plug, which limited the size of a second inseminator's ejaculate in a non-virgin female as compared with a virgin. Males passed larger ejaculates in the presence of rivals and when previous ejaculates were in the female spermathecae, another response to sperm competition. Larger ejaculates may need longer post-copulatory associations before a more effective sperm plug forms. Large males stayed with the female longer, which is consistent with their ability to pass larger ejaculates than small males and suggests that there may be costs to minimizing the duration of the post-copulatory association. In the field, associations last long enough to protect the female during her vulnerable phase and may ensure that the guarding male fertilizes the most eggs in the female, even if she remates. Thus, the post-copulatory association protects female blue crabs from additional inseminators as well as from predators. Received: 23 January 1996 / Accepted after revision: 9 November 1996     

It's a dirty job but someone has to do it: The role of marine benthic macrofauna in organic matter turnover and nutrient recycling to the water column

Benthic macrofaunal populations through their feeding, bioturbation, burrow construction and sediment irrigation activities have profound influences on organic matter inputs to marine sediments (biodeposition) and on the vertical distribution of deposited organic matter within the sediment. These effects in turn influence the rates and pathways of organic matter mineralisation, and element cycles. Similarly, bioturbation, burrow construction and burrow irrigation are major determinants of sediment-water column fluxes of oxygen and nutrients.

In this review, I discuss the influences of the different benthic macrofaunal feeding (functional) groups on mineralisation processes and sediment-water column fluxes of particulate and dissolved nutrients. How these effects influence diagenic processes, the balance between aerobic and anaerobic processes, and the redox status of the surficial sediments. Finally, I discuss some of the limitations of the predominantly laboratory techniques which have been used to study “macrofaunal effects” and how this hinders the inclusion of the effects in quantitative sediment biogeochemical models.     

It's a dirty job but someone has to do it: The role of marine benthic macrofauna in organic matter turnover and nutrient recycling to the water column

Benthic macrofaunal populations through their feeding, bioturbation, burrow construction and sediment irrigation activities have profound influences on organic matter inputs to marine sediments (biodeposition) and on the vertical distribution of deposited organic matter within the sediment. These effects in turn influence the rates and pathways of organic matter mineralisation, and element cycles. Similarly, bioturbation, burrow construction and burrow irrigation are major determinants of sediment-water column fluxes of oxygen and nutrients.

In this review, I discuss the influences of the different benthic macrofaunal feeding (functional) groups on mineralisation processes and sediment-water column fluxes of particulate and dissolved nutrients. How these effects influence diagenic processes, the balance between aerobic and anaerobic processes, and the redox status of the surficial sediments. Finally, I discuss some of the limitations of the predominantly laboratory techniques which have been used to study “macrofaunal effects” and how this hinders the inclusion of the effects in quantitative sediment biogeochemical models.     

The effects of size-dependent predation risk on the interaction between behavioral and life history traits in a stream-dwelling isopod

In field surveys, laboratory observations and field-based assays of behavior, I examined the effects of size-dependent predation risk on the interaction between size at reproductive maturity and maternal care behavior in the stream-dwelling isopod, Lirceus fontinalis. L. fontinalis exhibit population-specific sizes at reproductive maturity which result in population differences in predation risk during the adult phase. Females from streams containing salamander larvae (that prefer small prey) mature at large sizes and then become relatively safe from predation. Females from streams containing fish (that consume all size classes of prey equally) mature at small sizes and remain at risk. I tested whether these differences in expected survival were reflected in the behavior of females during the maternal phase (i.e., the period during which females exhibit maternal care). Female L. fontinalis carry developing juveniles inside a brood pouch. I simulated predatory attacks on gravid female L. fontinalis from the different population types and found that female behavior correlated with population differences in risk. When “attacked”, females from streams with predatory fish (that experience high risk to adult females) released juveniles from the brood pouch, whereas females from populations with predatory salamander larvae (that pose relatively little risk to adult females) did not release juveniles. I discuss the results with reference to the joint evolution of behavioral and life history traits. Received: 6 March 1996 /Accepted after revision: 12 August 1996