Feeding behavior and acquisition of zooxanthellae by planula larvae of the sea anemone Anthopleura elegantissima

Symbiotic associations between cnidarians and photosynthetic dinoflagellates (i.e., zooxanthellae) are common in the marine environment. Many symbiotic cnidarians produce offspring that are initially nonsymbiotic. These new hosts must acquire symbiotic algae from environmental sources. We examined zooxanthella acquisition by laboratory-reared planula larvae of the temperate sea anemone Anthopleura elegantissima. Larvae ingested zooxanthellae while they were feeding. However, the signal that prompted larval feeding behavior did not originate from the symbiotic algae; the addition of algal cells to larval cultures never elicited a feeding response. In contrast, the addition of macerated animal tissue from several sources invariably generated a strong feeding response, which resulted in the larvae indiscriminately ingesting any particulate matter that was present, including zooxanthellae or other unicellular algae. Ingested zooxanthellae were incorporated into endodermal cells, where they remained undigested, while all other ingested material was digested or expelled within 24 h. Our results provide evidence that one source of zooxanthellae likely to serve as a route of infection in the natural environment is zooxanthella-laden mucus egested by anemones. This egested material fulfilled both of the criteria necessary for successful infection: it prompted larvae to begin feeding and provided an abundant supply of zooxanthellae that were ingested and taken up into endodermal cells of the new host.     

Metal uptake, transport and release by wetland plants: implications for phytoremediation and restoration

Marshes have been proposed as sites for phytoremediation of metals. The fate of metals within plant tissues is a critical issue for effectiveness of this process. In this paper we review studies that investigate the effects of plants on metals in wetlands. While most of these marsh plant species are similar in metal uptake patterns and in concentrating metals primarily in roots, some species retain more of their metal burden in below ground structures than other species, which redistribute a greater proportion of metals into above ground tissues, especially leaves. Storage in roots is most beneficial for phytostabilization of the metal contaminants, which are least available when concentrated below ground. Plants may alter the speciation of metals and may also suffer toxic effects as a result of accumulating them. Metals in leaves may be excreted through salt glands and thereby returned to the marsh environment. Metal concentrations of leaf and stem litter may become enriched in metals over time, due in part to cation adsorption or to incorporation of fine particles with adsorbed metals. Several studies suggest that metals in litter are available to deposit feeders and, thus, can enter estuarine food webs. Marshes, therefore, can be sources and well as sinks for metal contaminants. Phragmites australis, an invasive species in the northeast U.S. sequesters more metals below ground than the native Spartina alterniflora, which also releases more via leaf excretion. This information is important for the siting and use of wetlands for phytoremediation as well as for marsh restoration efforts.     

韩国绿色种养循环农业发展概况与经验启示

联合国将碳中和视为当今世界最为紧迫的任务,而农业是温室气体排放最多的产业之一,各国相继出台政策积极开展农业农村减排工作。韩国自2012年开始逐渐减少海洋粪污排泄量,并大力实行绿色种养循环农业,解决本国内畜禽粪污问题。韩国作为中国的重要海上邻国,不论是从研究借鉴角度抑或生态系统共享角度,了解其环境保护政策都是十分必要的。本文从韩国实施的主要政策、各地区农地养分收支现状、代表性运营模式案例、政策关注焦点等方面介绍韩国绿色种养循环农业的发展概况,结合中国绿色种养循环农业现状开展研究。提出三点政策建议：第一,进一步完善畜禽粪污资源化利用机具补贴辅助管理系统,提高系统在农户中的普及率;第二,提高全民环保意识的同时,政府的角色不应局限自上而下的引导型,应该积极促进种植户和养殖户间的自发组织,并大力提倡吸纳社会资本,集结社会各方力量;第三,促进绿色种养循环农业产品的商品化和品牌化,从而调动农户参与绿色种养循环农业的积极性。     

Soil metal concentrations and productivity of Betula populifolia (gray birch) as measured by field spectrometry and incremental annual growth in an abandoned urban Brownfield in New Jersey

A forested brownfield within Liberty State Park, Jersey City, New Jersey, USA, has soils with arsenic, chromium, lead, zinc and vanadium at concentrations above those considered ambient for the area. Using both satellite imagery and field spectral measurements, this study examines plant productivity at the assemblage and individual specimen level. Longer term growth trends (basal area increase in tree cores) were also studied. Leaf chlorophyll content within the hardwood assemblage showed a threshold model for metal tolerance, decreasing significantly beyond a soil total metal load (TML) of 3.0. Biomass production (calculated with RG - Red/Green Ratio Index) in Betula populifolia (gray birch), the co-dominant tree species, had an inverse relationship with the Zn concentration in leaf tissue during the growing season. Growth of B. populifolia exhibited a significant relationship with TML. Assemblage level NDVI and individual tree NDVI also had significant decreases with increasing TML. Ecosystem function measured as plant production is impaired at a critical soil metal load.     

Interactions of metals affect their distribution in tissues of Phragmites australis

Culms of Phragmites australis were grown in vermiculite in a greenhouse. Some plants were exposed to 1000 microg/g Cu or Pb or Zn, or combinations of two or three of those metals. When plants reached senescence, they were harvested and analyzed for metal concentrations in upper leaves, lower leaves, stems and roots. While all metals accumulated in highest concentrations in the roots, Zn accumulated in aboveground tissues far more than the other metals. Furthermore, the concentration of any one metal in the different tissues was affected by the presence of other metals. The amount of copper in upper leaves increased when Zn was also present with the Cu. The amount of Cu in roots was increased in the presence of Pb and/or Zn. The amount of Zn in lower leaves was reduced when Cu was also present along with Zn. Thus, when combinations of metals were present, the distribution of metals was altered. The most important interactions appeared to be of Cu and Zn, which may reflect competition for binding sites on metal-binding proteins.     

Geographical variation of persistent organochlorine concentrations in blubber of ringed seal (Phoca hispida) from the Canadian Arctic: univariate and multivariate approaches

Geographical variation of organochlorine (OC) concentrations in ringed seal (Phoca hispida) in the Canadian Arctic was studied using univariate and multivariate statistical techniques. The dataset consisted of 80 individual OC components (58 PCB congeners plus DDT- and chlordane (CHL)-related compounds, toxaphene, hexachlorocyclohexanes (HCH), chlorobenzenes (CBz), and dieldrin) determined in 221 ringed seal blubber samples from 13 locations throughout the Canadian Arctic from the period 1983 to 1989. Mean concentrations of the major OC groups in ringed seal blubber (SigmaPCBs, SigmaDDT, SigmaCHL and toxaphene), adjusted for the age and sex of the seals, showed few significant geographical differences. Principal components analysis was used to examine geographical trends. Significant differences in mean factor scores for three of four principal components were found between sampling locations. Locations in the western and high Arctic could be distinguished from those in Hudson Bay by highest scores along principal component two which was associated principally with CBz. PCB congeners with six or more chlorine substitutions declined with increasing north latitude, whereas more volatile OCs (CBz, HCH, less chlorinated PCBs) increased in the proportion of total OCs with latitude. Proportions of less chlorinated PCBs also decreased with increasing longitude, whereas slopes of regressions for more highly chlorinated PCBs increased significantly. The results were generally consistent with the 'cold condensation' hypothesis of increasing proportions of more volatile OCs with increasing latitude and distance from sources.     

EFFECTS OF CONTEXT ON EVERYDAY CONVERSATIONS OF TURKISH UNIVERSITY STUDENTS

This study employed a diary method to investigate everyday conversations. Consistent with a dynamic view of partner context interaction, it was predicted that conversations occurring in different contexts would show variations with respect to topics and conversation partners. Turkish university students recorded durations, topics, and conversation partners of their conversations for seven consecutive days. Contexts, topics, and partners were categorized. Respondents were utilized as units of analyses. Analyses revealed that context of conversations were related to topic and partner categories as well as intimacy ratings of partners and topics.     

Schooling behavior of Menidia medidia in the presence of the insecticide Sevin (Carbaryl)

A single application of 100 parts per billion Sevin in seawater caused disruption of schooling behavior of Menidia menidia in an artificial setting. Although the change, primarily a spreading out of the school over a larger area, was observed after 24 h exposure, placing the fish in clean water did not bring about a return of normal schooling patterns until 72 h. This is attributed to the accumulation of 1-naphthol, a toxic product of hydrolysis of Sevin. The adaptive significance of changes in schooling behavior is discussed.     

Methylmercury tolerance of killifish (Fundulus heteroclitus) embryos from a polluted vs non-polluted environment

We have previously found great differences in susceptibility to methylmercury (meHg) among batches of eggs produced by different females. This study compares the range and distribution of susceptibility in two populations of killifish, one from a creek in Montauk, New York, USA a rather pristine area, the other from Pile's Creek in Linden, New Jersey, an area heavily impacted by metal and oil pollution. After treatment with 0.05 ppm meHg, the distribution of craniofacial defects in embryos of the Montauk population ranged from very tolerant to very susceptible. The distribution of cardiovascular defects also ranged from very tolerant to very susceptible. Skeletal defects were prevalent in most batches of eggs. However, in the Pile's Creek population, very few females produced susceptible eggs, and most batches were tolerant with respect to the three types of malformations, especially the craniofacial defects. The ability to adapt to pollution is one reason that this species has remained abundant in such a highly polluted area. The ability of some species to adapt to chronic pollution by developing tolerance is a phenomenon that should be considered in choosing organisms for routine bioassay procedures, since the results will depend on the degree to which the population has become tolerant to the toxicant.     

Interactions of methylmercury,cadmium, and salinity on regeneration in the fiddler crabs Uca pugilator,U. pugnax and U. minax

After multiple autotomy in the fiddler crabs Uca pugilator, U. pugnax and U. minax, both methylmercury and cadmium retard limb regeneration and ecdysis. When crabs in sea water are exposed to a mixture of both metals, the effect is increased, indicating that the two are interacting in an additive way. In 50% sea water (=15% S), the effects of cadmium are greatly intensified so that growth of limb buds is extremely slow, if it occurs at all. When methylmercury is present in the water at the same time, the severe effects of cadmium are somewhat ameliorated, indicating an antogonistic interaction of the two metals under these conditions. Adding additional calcium to the 50% sea water also decreased the severity of the cadmium effect, thus supporting the idea of a calcium-cadmium competition.