外源稀土La在沉积物中的形态及其生态可利用性

可沉积物中的外源稀土Ｌａ分为可溶解态，酸可提取态、有机质及硫化物结合态，研究了小球藻对这三种形态Ｌａ的生物可利用性，研究结果表明：这三咱开矿的Ｌａ在沉积物中的含量与在藻中的含量有很好的相关关系，其中可溶解态Ｌａ的生物可利用了大，这说明，沉积物中Ｌａ的释放对其生物可利用性至关重要。     

海洋沉积物中的镉及不同形态镉的生物有效性

镉是一种生物非必需的毒副作用很强的重金属元素.进入海洋环境中的镉,最终有相当部分进入沉积物中,并对底栖生物造成危害.通过测定不同镉质量浓度暴露条件下海水、沉积物和生物体内的镉的形态和含量,研究了海洋沉积物中不同形态镉的生物有效性.结果表明,菲律宾蛤仔对Cd的蓄积随着时间增加,呈现先快速增加的趋势,在24 h内其蓄积速率最大,96 h后生物体内镉的质量分数出现缓慢下降趋势.在蓄积时间一定的条件下,在任何Cd含量沉积物下,菲律宾蛤仔都可以蓄积Cd,而且随着沉积物中镉质量分数升高,生物体内蓄积的镉的质量分数也呈现上升趋势.活性镉(可交换态)是沉积物中镉存在的主要形式(45.48x.96%),硅酸盐结合态和黄铁矿结合态的金属只占较小的比例,活性镉是影响沉积物中重金属镉生物可利用性的最有效形态.     

德兴矿区沉积物中铜的化学形态及其影响因素

采用BCR三步提取法测定了德兴矿区沉积物中铜的化学形态,并对铜化学形态的影响因素进行了研究.结果表明,(1)铜的可氧化态＞残渣晶格态＞酸可溶态＞可还原态,铜以硫化物结合态、有机结合态及残渣晶格态为主;(2)铜的潜在生物可利用形态的平均比例为71.99%,平均浓度为233.88 mg·kg-1,远高于全国沉积物铜的平均值,威胁当地的水生生态系统安全;(3)铜的酸可溶态与阳离子交换量CEC、有机质含量和氧化铁含量成正相关关系,而与铁锰含量和pH值的关系不明显;可氧化态与铁锰含量密切相关;可还原态与有机质含量相关.     

城市环境铂族金属分布特性及生态健康风险研究进展

随着铂族金属铂（Pt）、钯（Pd）、铑（Rh）被广泛应用于汽车尾气催化净化器中,这三种金属在自然界中的含量逐渐升高。越来越多的研究表明,这几种曾被认为对环境影响较小的金属的确会带来潜在的生态健康风险。本文概括了国内外城市各种环境介质的含量分布,重点分析了铂族金属的源解析方法、粒径分布特性、影响其排放的因素和其潜在的生态健康风险。就全世界的城市来看,灰尘、空气、土壤、沉积物等各种环境介质中铂族金属的含量均有显著提高,主要来源于汽车三元催化净化器。这三种金属倾向于富集在细颗粒中,行车模式是影响其排放量的重要因素,自然界的共存物质可增强它们的溶解性和迁移性,从而使它们的生物可利用性大大提高。生物体吸收这类金属后,可与体内的物质发生反应,形态发生变化,毒性增强。在以后的研究中,除了持续跟踪调查这三种金属在环境中的含量水平以外,还应加强研究这三种金属在环境中的颗粒分布、迁移转化、形态变换、生物可利用性以及生物毒性等,使我们能够更好地评估其生态健康风险,并为与之相关的应用研发、防范措施、政策制订提供引导和支持。     

黄河中下游表层沉积物磷的赋存形态及生物有效性

利用磷的连续分级提取方法,研究了黄河中下游16个沉积物样品中磷的赋存形态分布特征,并探讨了沉积物中磷的生物有效性.结果表明,黄河沉积物中总磷的含量为83.79～132.35 μg·g~(-1),其中主要以无机磷的形式存在,而无机麟中以钙结合态磷为主.线性回归分析结果表明,NaOH-P的含量与活性态Fe、BD-P,NaOH-P含量的总和与活性态Fe、BD-P,NH_4Cl-P含量的总和与活性态Fe、Al含量总和,均有一定的线性关系;沉积物中的总无机磷含量与沉积物的总有机质含量呈正相关关系.磷的生物有效性分析结果显示,潜在的生物有效性磷主要包括弱结合态磷、氧化还原敏感态磷、金属(水台)氧化物结合态磷3种赋存形态,黄河沉积物中潜在的生物有效性磷含量在9.02～37.20 μg·g~(-1)范围内,平均值为24.47 μg·g~(-1),平均占沉积物总磷的22.43%、占总无机磷的35.59%.     

深圳湾红树林沉积物-植物体系汞的分布规律和形态分配特征

为了解重金属汞在非根际沉积物-根际沉积物-红树植物连续体系中的分布特征和迁移规律,以及沉积物中汞的化学形态特征,于深圳湾福田红树林实地采集红树植物幼苗样品及其林下沉积物样品,采用连续提取法对沉积物中汞的各种化学形态进行提取,通过冷原子荧光光谱仪进行定量分析。研究对象包括福田红树林3种常见红树植物,包括白骨壤(Avicennia marina)、桐花树(Aegiceras corniculatum)2个本土种和海桑(Sonneratia caseolaris)1个引进种,并以无植被覆盖的光滩作为空白对照。结果表明,在沉积物-红树植物体系中,根际和非根际沉积物中的总汞含量均高于红树植物幼苗。进入植物体后,汞在茎中的含量均小于根和叶。本土种植株表现出较强的汞积累能力。白骨壤幼苗汞积累量最高,质量分数达到45.32 ng·g-1,其次为桐花树幼苗,汞质量分数为23.49 ng·g-1。3种红树植物对汞的生物积累因子在0.02~0.35范围内,迁移因子处于0.4~0.99范围内,均低于1,表明它们从土壤吸收、并向地上部分运输汞的能力较弱,倾向于采取金属排斥策略,以实现植物体的自我保护。非根际沉积物中汞的各个化学形态质量百分比表现为有机结合态可挥发态残渣态可交换态碳酸盐结合态铁锰氧化物结合态,根际沉积物中汞表现为可挥发态机结合态残渣态铁锰氧化物结合态可交换态碳酸盐结合态,总体表现为生物可利用态和潜在可利用态质量分数较高,不可利用态较少。与本土种相比,引进种海桑能够将更多汞以稳定性相对较高的生物不可利用态和潜在可利用态形式固定于土壤中,表现出较好的治理汞污染能力。     

水体沉积物结合态镉对大型溞（Daphnia magna）的生物毒性研究

选择大型溞(Daphnia magna)作为受试生物,以大型溞体内金属积累量、金属硫蛋白含量和死亡率作为测试指标,考察了上覆水体系与水柱-沉积物共存体系中金属镉(Cd)的毒性状况,探讨了水体沉积物中重金属的生物毒性作用机制.结果表明:暴露于水柱-沉积物共存体系和上覆水体系中的大型溞体内的生物积累量均随沉积物Cd含量的升高而升高,且前者显著高于后者,说明沉积物中的Cd可通过食物吸收等途径对生物体致毒、致害;暴露于两种体系中的大型溞体内的MT含量在低浓度条件下随沉积物中Cd含量的升高而升高,当Cd含量高于800μg·g-1时MT含量大幅度下降,并且两体系之间无显著差别;暴露于两种体系中的大型溞幼溞死亡率无显著差别.上覆水中溶解态Cd和沉积物中可交换态Cd是对水生生物重要的毒性影响形态.     

生物炭对重金属污染沉积物的修复效果

采用1%、2%和5%的生物炭钝化污染沉积物中的重金属,并研究生物炭修复对水体的生态影响.结果表明,生物炭添加后水体的p H值显著增大,上覆水和间隙水中溶解态Cu、Zn和Cd浓度均显著降低.1%(W/W)生物炭添加量使上覆水中溶解态Cu比对照降低了82.4%;在不同添加量下间隙水溶解态Zn降低幅度为11.7%—62.8%.通过BCR重金属形态分级发现沉积物中酸溶态重金属均有向残渣态转化的趋势.在5%生物炭添加量时,酸溶态Cu降低了73.08 mg·kg-1,降低幅度达到32.1%,而可氧化态Pb增加幅度达到67.8%.通过生物可利用实验(PBET)发现,当生物炭添加量为5%时,生物可利用性Cu降低9.8%,Zn、Pb和Cd的生物可利用性也有不同程度降低.生物炭添加到沉积物后,用于植物毒性试验的家独行菜(Lepidium sativum)茎长呈现19.5%—25.7%的增加,根长也随之增加,说明生物炭降低了沉积物重金属的植物毒性.     

北京市西城区雨水管道沉积物中重金属特征

在对北京市西城区部分排水管道调研的基础上,对几个典型雨水检查井连接雨水管道沉积物中赋存的主要重金属污染物污染水平及形态分布进行了研究,分析了沉积物粒径及有机质含量对重金属污染物赋存水平的影响.结果表明,排水管道沉积物中:Cr主要以残渣态存在;Cu和Zn以具有活性潜力的铁锰氧化物形态及碳酸盐结合态两种形态为主;Pb的残渣态含量平均值达到了56.4%;Ni的可交换态和碳酸盐结合态含量相对较大;可交换态Cd占其总量的比例最高值达22.4%,而残渣态的Cd含量极小.     

湘南某矿区菜园土中典型重金属的形态分析

分别运用Tessier连续提取法和Leleyter连续提取法研究湘南某矿区菜园土中Pb,Zn,Cu和Cd的形态分布特征.结果表明：菜园土中Pb,Zn,Cu和Cd的总浓度严重超过国家土壤环境质量标准.Pb,Zn,Cu和Cd的主要形态是残渣态,水溶态和交换态所占比例较小.重金属生物可利用性的研究表明,Pb,Zn,Cu和Cd生物可利用的含量较少;在Tessier方法中,除Cu之外,生物不可利用态是主要形态,其次是潜在生物可利用态,而在Leleyter方法中,潜在生物可利用态是主要形态,其次是生物不可利用态.     

微生物和硬毛藻对天鹅湖不同湖区沉积物氮磷释放的影响

荣成天鹅湖为一天然瀉湖,近年来绿潮硬毛藻大量爆发,内源污染日益严重。以大型硬毛藻和不同湖区沉积物为试材,设置沉积物+水、沉积物+水(灭菌)、沉积物+水+藻、沉积物+水+藻(灭菌)4个处理,研究了不同微生物活性及藻类条件下上覆水体氮磷质量浓度的变化,同步监测水土界面DO和pH等理化参数,以探讨藻分解和微生物对天鹅湖不同湖区沉积物氮磷释放的影响,为藻华消亡过程中内源污染的治理提供理论依据。结果表明,微生物存在和硬毛藻分解可使水体氮质量浓度明显增加(P<0.05)。试验过程中,水体总氮在有藻和无藻条件下的质量浓度变幅分别为1.56-14.11 mg·L^?1和0.11-8.96 mg·L^?1,后期灭菌处理明显低于未灭菌处理。藻分解对水体磷质量浓度具有极显著影响(P<0.01),有藻条件下灭菌处理总磷质量浓度为0.31-1.27 mg·L^?1,未灭菌处理为0.27-1.41 mg·L^?1;而无藻条件下灭菌和未灭菌处理变幅分别为0.019-0.047 mg·L^?1和0.025-0.078 mg·L^?1。在天鹅湖,不同湖区沉积物氮磷的释放能力存在差异,水体氮质量浓度在有藻和无藻条件下均表现为西北部>湖中心>湖南部,磷质量浓度有藻条件下与氮一致,而无藻条件下则表现为湖中心>西北部>湖南部。湖中心沉积物处理水体营养盐浓度受微生物活性影响较大。3种因素对水体氮磷质量浓度的影响效应表现为:藻类>微生物>沉积物。可见,在藻类大量暴发且微生物活性较高的湖中心及西北部,沉积物氮磷的释放潜力较大,尤其在藻类堆积腐烂时期,应引起足够重视。     

Inhibition of larval settlement to a soft bottom benthic community by drifting algal mats: An experimental test

The hypothesis that drifting red algal mats inhibit settlement of planktonic larvae was tested in a field experiment in 1986. Substratum free of algae (caged boxes) was compared with substratum covered with algae (natural substratum and open boxes). Whereas settling densities of 1500 to 5500 ind. m^-2 of the bivalves Macoma balthica, Cardium glaucum and Mya arenaria were observed in sediment without algal cover, no recruits of the same species were found beneath the algae during the period of peak settlement (June to July). The same difference was observed for the polychaete Nereis diversicolor, although in this case occasional individuals were found beneath the algae. The results demonstrate that algae mats may be efficient inhibitors of larval settlement to benthic soft-substratum communities. It is concluded that algae act as a larval filter.     

Differences in herbivore preferences, phlorotannin production, and nutritional quality between juvenile and adult tissues from marine brown algae

 Juvenile and adult marine organisms differ in their morphology, chemistry, physiology, behavior, and ecology. Because juvenile algae are thinner, smaller, and have more delicate tissues than adults, they are often assumed to be more susceptible to grazers. We examined within-species food preferences of four common generalist herbivores for juvenile and adult tissues of eight common brown algae in two-choice laboratory food-preference experiments. Our results showed that juvenile algae did not tend to be a preferred food of herbivores. Juvenile tissues were significantly preferred over adult tissues in only four of the 32 combinations of algae and herbivores tested. In 12 experiments, adult tissues were preferred over juvenile tissues, and no choice occurred in the remaining 16 experiments. When sea urchins exhibited a preference, it was always for adult tissues. The other three herbivores, an isopod and two snails, were more variable in their choices, sometimes preferring juveniles, sometimes adults, and sometimes having no preference. We measured nitrogen and phlorotannin concentrations in adult and juvenile seaweeds to see whether these parameters were correlated with herbivore food preferences. Nitrogen levels were similar in juveniles and adults of three algal species and were higher in juveniles of two. Phlorotannin levels were higher in juveniles of four species and lower in juveniles of one. The other three species showed no differences in phlorotannin levels. Phlorotannin concentrations decreased with increasing juvenile size in three species and increased with increasing size in one species. Neither nitrogen nor phlorotannin concentrations explained overall herbivore food preferences for algae of different stages. Our results suggest that preferences of certain grazers for juvenile algae are not as strong as previously assumed and are dependent on herbivore species. Preferences between juveniles and adults are likely to be determined by a combination of morphological and chemical features of the tissues and the unique responses of herbivore species to those features. Received: 10 April 2000 / Accepted: 19 November 2000     

Fresh water blue green algae from three agro-climatic zones of Uttar Pradesh, India: distribution pattern with seasonal variation

The paper deals with 45 species of 21 genera of fresh water blue green algae (BGA) from three different agro-climatic zones of Uttar Pradesh. Samples were collected from different habitats varying in physico-chemical properties. Out of 45 species, 13 species belonged to order Chroococcales, 31 to order Nostocales, while only 1 species belonged to order Stigonimatales i.e. Fischerella mucicola. The physico-chemical parameters like pH, temperature, dissolved oxygen, electrical conductivity, nitrate, nitrite and rainfall play an important role in the periodicity of BGA. A positive correlation was found between dissolved oxygen (DO) of different ponds and species diversity, except in the case of western region of Uttar Pradesh (Farukhabad and Mahoba districts) where a positive correlation was found in electrical conductivity and total dissolved solids.     

Distribution and morphological variation of low-shore algal turfs

The distribution of three functional groups of algae (filamentous, corticated terete and calcareous articulated) was investigated in low-shore, turf-forming assemblages from rocky shores in the western Mediterranean Sea (Italy). Algae were sampled along shores from three different stations. Shores were either exposed to wave action or sheltered and were characterised by various inclinations of the rocky substratum (horizontal, sloping and vertical). The hypotheses tested were: that the relative abundance of the three functional groups of algae (1) varies between sheltered and exposed shores, (2) is influenced by substratum inclination and (3) that these distributions are consistent across stations. There was no clear relationship between the morphology of turf-forming algae and shore characteristics. Covers of filamentous, corticated terete and calcareous articulated algae differed among shores and stations, but patterns were not consistent across shores with similar exposure to waves and substratum inclination. Turfs often comprised algae with different morphologies, in a combination of anchor and epiphytic species. It is suggested that functional groups of algae, as currently identified, are not effective in describing changes in distribution of algae between sheltered and exposed shores, when turf morphologies are considered. Future research on relationships between morphology and ecology of algae should consider the potential importance of positive interactions among associated species, which could override responses of individual functional groups.     

Expansive covers of turf-forming algae on human-dominated coast: the relative effects of increasing nutrient and sediment loads

Turf-forming algae form more extensive habitat on subtidal rock adjacent to urban than non-urban coast of South Australia. This pattern is frequently observed on the worlds temperate coasts and is variously considered to be a result of enhanced concentration of nutrients or rates of sediment deposition on urban coasts. We experimentally tested which of three components of environmental change (increased nutrients in water, increased nutrients in sediments and increased sediment deposition) best explain the expansive covers of turf-forming algae on urban coasts. All three treatments had independent and positive effects on the percentage cover of turf-forming algae. The addition of nutrients from the water column had the largest influence (²=0.55), which was more than six times greater than the effect of nutrients added to sediments (²=0.08). An increase in rate of deposition of sediments had substantial effects (²=0.35), which were about one third less than those of water-borne nutrients. Importantly, the combined effect of all three treatments caused a 77% increase in percentage cover of turf-forming algae, which is comparable to the observed difference in covers between urban and non-urban coast in South Australia (93%). These results suggest that human activities that reduce water quality in both nutrient and sediment loads account for major change observed on human-dominated coasts. Despite this knowledge, we still lack complete information on the mechanisms that switch the primary subtidal habitat from canopy-forming algae to turf-forming algae on human-dominated coasts.Communicated by M.S. Johnson, Crawley     

Variation in benthic communities of eastern Caribbean coral reefs in relation to surface sediment composition

The effects of sedimentation on coral reefs are commonly studied at local scales, but larger-scale patterns have been elusive, making it difficult to determine the role of sedimentation in region-wide changes in these ecosystems. We examined the relationships between characteristics of reef-associated surface sediment and benthic composition of 22 reefs around 11 islands of the eastern Caribbean. The terrigenous fraction in surface sediment increased with proximity to a clear source of sediment input. The percent cover of live coral, macroalgae, and turf algae decreased with higher terrigenous sediment fraction, while sponge cover increased. Sites with sediment containing high and low terrigenous fraction differed in coral species assemblages. In particular, the cover of Montastraea annularis complex decreased with increasing terrigenous sediment fraction. The proportion of fine-grained sediment had no effect on benthic composition. These results suggest that sedimentation may play a role in shaping coral reef communities at a regional scale.     

Defensive mechanisms and ecology of some tropical holothurians

The ecology, defensive behavior and toxicity of three species of reef flat holothurians (Actinopyga mauritiana, Holothuria atra and Holothuria difficilis) were studied at Eniwetok Atoll, Marshall Islands. The average diurnal population density of H. difficilis ranged from 1.4 to 32 holothurians/900 cm²; resting respiratory rates (0.05 ml O₂/g wet wt/h) were comparable during day and night; nourishment in H. difficilis may be primarily from bacteria and foraminifera in which about 2% of the dry weight of sediment consumed is utilized, and the species probably passes at least 3 g dry wt of sediment/m²/day (>1 kg/m²/year). A fundamental difference in energy flow is suggested: considerably more energy is passed from benthic algae to grazing and browsing fishes to predatory fishes on coral reefs whereas, in extra-tropical latitudes, more energy is shunted from benthic algae to invertebrates to predators. The effects of holothurin leading to death in fishes are irreversible. Holothuria difficilis is best protected from predation. Its body wall is toxic and it can accurately eject Cuvierian tubules, which are also toxic. The discharge of tubules was regulated by a circadian rhythm in May. Studies on holothurians and sponges suggest that many exposed coral reef invertebrates have evolved effective defensive mechanisms in association with high intensity predation.Supported by A.E.C. Contract AT (29-2)-226 with the University of Hawaii.     

Benthic invertebrate assemblages of Delaware Bay

During two consecutive summers, the first quantitative bay-wide survey (207 stations) of benthic invertebrates was conducted in Delaware Bay (USA). In 1972, 109 species were collected at 105 stations; and in 1973, 125 species were collected at 102 stations. A total of 169 different species were collected for both summers. The number of species and number of individuals increased with increasing salinity and increasing median grain size. These relationships were compared and were found similar to those in estuaries and bays throughout the world. Average density was 722 individuals m², which is low compared to other estuaries. The relationship of low secondary production to pollution, macroscopic algae, sediment transport, predation, and hydrography is discussed. Deposit feeders comparised the major feeding type. Local species composition was similar to that in Chesapeake Bay, and dominant species occurred in estuaries throughout the Mid-Atlantic Bight. The benthic invertebrates of Delaware Bay were related to the cosmopolitan mode of estuarine faunas. Faunal assemblages were identified by cluster analysis. The assemblages were associated with sediment type and salinity. It was concluded that Delaware Bay comprises a mosaic of animal assemblages, some of which have relatively sharp boundaries similar to classical level bottom type communities, whereas the boundaries of others are almost impossible to detect, and these represent species distributed along an environmental continum.     

Competition, predation and coexistence in a three trophic system

Simple ecological models that mostly operate with population densities using continuous variables, explain quite well the behavior of real populations. In this work we propose and discuss the continuous dynamics of a system of three species, which belongs to the well-known family of Lotka–Volterra models. In particular, the proposed model includes direct effects such as predation and competition among species, and indirect effects such as refuge. The model is proposed to explain recent studies about a group of crustacean (amphipods of genus Hyallela) found in all the plain streams and shallow lakes of the American continent. The studied system includes three compartments: algae, a strictly herbivore amphipod and an omnivore (herbivore and carnivore) one. The analysis of the model shows that there are stable extinction equilibria throughout all the parameters’ space. There are also equilibria with stable coexistence of the three species and two interesting binary equilibria: one with stable coexistence of algae and herbivore and other with coexistence between algae and omnivore amphipods. The presence of Allee effect in the algae growth and the existence of refuge for the herbivore amphipod (prey) determine a bottom-up control.