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131.
132.
Changes in size, morphology, and biochemical composition in adults and embryos of a brooding sea star, Neosmilaster georgianus (Sladen), were studied in a population adjacent to Anvers Island, Antarctic Peninsula (64°46′S; 64°04′W) during the austral
spring, 1991. Five morphological stages of development were designated in 24 broods, and for each the weight and biochemical
composition of the brooding adults and their embryos were determined. Between Stage 1 and 2, the dry weight (dw) and organic weight (ow) of the embryo did not change. From Stage 2 to 3, the dw and ow increased significantly by 10%. Stage 2 and 3 embryos were in clusters of a few (2 to 10) to as many as 40 individuals. In
the smaller clusters, individual embryos were attached by tissue cords to another, sometimes atrophied, brood member. In the
larger clusters, they were attached to a central mass of tissue containing remnants of embryos. We interpret these interactions
as a form of cannibalism which may account for the weight gains between Stage 2 and 3. During Stages 4 and 5, as juvenile
form was approached, the dw and ash weight of the young increased significantly and the ow decreased significantly. The calculated energy content for the juvenile (Stage 5) was not significantly different from the
energy content of the earliest undifferentiated stage (Stage 1), an indication that most of the organic matter in the egg
is the primary contribution to the large juvenile. In brooding females, pyloric caeca indices declined by 52% from Stage 1
to Stage 5 and pyloric energy stores declined by 63% due to proportionately equivalent declines in protein and lipid. The
ovary index was low and increased only slightly during brood protection, while the size of the largest oocytes remained approximately
23% that of ova. Energy stores in the pyloric caeca of brooding N. georgianus thus become depleted over a long period of incubation during which the adults apparently starve. This may delay oocyte development
and ultimately limit the frequency of individual reproduction.
Received: 15 September 1998 / Accepted: 9 March 1999 相似文献
133.
Teresa Catry Jaime A. Ramos Matthieu Le Corre Jessica Kojadinovic Paco Bustamante 《Marine Biology》2008,155(6):637-647
Nitrogen (δ15N) and carbon (δ13C) stable isotopes and contaminants, such as mercury, have been widely used to characterise foraging ecology of temperate
and polar seabirds. In this study, for the first time, we used isotopic signatures and mercury levels of feathers and blood
of eight tropical seabird species, that forage in a range-gradient between inshore and offshore areas, to describe the foraging
habits of a large tropical seabird community (from two neighboring islands of the Seychelles archipelago, western Indian Ocean)
during both the breeding and inter-breeding periods. Overall, we found a high overlap in both δ15N and δ13C signatures among species. The high inter-specific overlap in δ15N values was expected, given the similarities in the diet of the species from this community. However, several unexpected
results, such as (1) the consistently higher δ15N signatures of white terns (Gygis alba), (2) the large variation in inter-specific differences in δ15N signatures among the sampling groups (season, age, island and tissue) and (3) the consistent low δ15N values of breeding birds during the northwest monsoon (austral summer), suggest that δ15N signatures cannot be used as indicators of seabird trophic levels in this community. The high inter-specific overlap in
δ13C signatures and the absence, during the breeding season, of a δ13C gradient that follows the inshore-offshore foraging gradient within the community can be explained by the habitat homogeneity
of the Seychelles continental shelf and suggest that birds forage mostly within the limits of this “plateau”. On the other
hand, the similarities in δ13C values between the breeding and inter-breeding periods in species that are known to show post-breeding dispersal, strongly
support the hypothesis of a lack of latitudinal variation in δ13C signatures of POM in the central Indian Ocean, and the consequent inaccuracy of δ13C values to track seabird movements within this geographic area. Inter-specific differences in mercury levels seem to be related
to prey size, while consistent higher mercury concentrations in one of the studied islands suggest different island mercury-backgrounds
and possible segregation in foraging areas between the seabirds of the two islands.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
134.
Princewill C. Ogbonna Scholastica N. Nwokolo Jaime A. Teixeira da Silva 《毒物与环境化学》2013,95(10):1925-1933
This study determined the heavy metal concentration in soil and plants at a bone char site in Umuahia, Nigeria. Soil and plant samples collected in a randomized complete block design (RCBD) were analyzed for zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), and arsenic (As). The concentration of metals in soil and plants in the vicinity of the bone char site are as follows: Zn (172?mg?kg?1) and Ni (0.62?mg?kg?1) in soil were highest at site P3, Pb (2.37?mg?kg?1) and As (0.08?mg?kg?1) at site P1, and Cd (18.30?mg?kg?1) at site P2. In plants, the concentrations of Zn (41.17?mg?kg?1) and Cd (3?mg?kg?1) were highest in Albizia ferruginea, Ni in Dialium guineense (0.09?mg?kg?1), while Pb was in D. guineense (0.08?mg?kg?1) and Spathodea companulata (0.06?mg?kg?1). The levels of Zn, Cd, Pb, Ni, and As in soil ranged from 11.2 to 172, 2.68 to 18.2, 0.026 to 2.37, 0.33 to 0.62, and 0.02 to 0.08?mg?kg?1, respectively. In plants, the concentration of Zn, Cd, Pb, and Ni ranged from 2.01 to 41.17, 0.12 to 3, 0.02 to 0.08, and 0.03 to 0.09?mg?kg?1, respectively. There were significant correlations between Zn and Cd, and Pb and As in soil. The high concentration of Cd in soil might affect soil productivity. 相似文献
135.
136.
Combined effects of constant versus variable intensity simulated rainfall and reduced tillage management on cotton preemergence herbicide runoff 总被引:1,自引:0,他引:1
Potter TL Truman CC Strickland TC Bosch DD Webster TM Franklin DH Bednarz CW 《Journal of environmental quality》2006,35(5):1894-1902
Pesticide runoff research relies heavily on rainfall simulation experiments. Most are conducted at a constant intensity, i.e., at a fixed rainfall rate; however, large differences in natural rainfall intensity is common. To assess implications we quantified runoff of two herbicides, fluometuron and pendimethalin, and applied preemergence after planting cotton on Tifton loamy sand. Rainfall at constant and variable intensity patterns representative of late spring thunderstorms in the Atlantic Coastal Plain region of Georgia (USA) were simulated on 6-m2 plots under strip- (ST) and conventional-tillage (CT) management. The variable pattern produced significantly higher runoff rates of both compounds from CT but not ST plots. However, on an event-basis, runoff totals (% applied) were not significantly different, with one exception: fluometuron runoff from CT plots. There was about 25% more fluometuron runoff with the variable versus the constant intensity pattern (P = 0.10). Study results suggest that conduct of simulations using variable intensity storm patterns may provide more representative rainfall simulation-based estimates of pesticide runoff and that the greatest impacts will be observed with CT. The study also found significantly more fluometuron in runoff from ST than CT plots. Further work is needed to determine whether this behavior may be generalized to other active ingredients with similar properties [low K(oc) (organic carbon partition coefficient) approximately 100 mL g(-1); high water solubility approximately 100 mg L(-1)]. If so, it should be considered when making tillage-specific herbicide recommendations to reduce runoff potential. 相似文献
137.
Peimer Alex W. Krzywicka Adrianna E. Cohen Dora B. Van den Bosch Kyle Buxton Valerie L. Stevenson Natalie A. Matthews Jeffrey W. 《Environmental management》2017,59(1):141-153
Environmental Management - Growing recognition of the importance of wetlands to human and ecosystem well-being has led countries worldwide to implement wetland protection policies. Different... 相似文献
138.
139.
Rutter AP Hanford KL Zwers JT Perillo-Nicholas AL Schauer JJ Olson ML 《Journal of the Air & Waste Management Association (1995)》2008,58(3):377-383
Reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected in Milwaukee, WI, between April 2004 and May 2005, and in Riverside, CA, between July 25 and August 7, 2005 using sorbent and filter substrates. The substrates were analyzed for mercury by thermal desorption analysis (TDA) using a purpose-built instrument. Results from this offline-TDA method were compared with measurements using a real-time atmospheric mercury analyzer. RGM measurements made with the offline-TDA agreed well with a commercial real-time method. However, the offline TDA reported PHg concentrations 2.7 times higher than the real-time method, indicating evaporative losses might be occurring from the real-time instrument during sample collection. TDA combined with reactive mercury collection on filter and absorbent substrates was cheap, relatively easy to use, did not introduce biases due to a semicontinuous sample collection strategy, and had a dynamic range appropriate for use in rural and urban locations. The results of this study demonstrate that offline-TDA is a feasible method for collecting reactive mercury concentrations in a large network of filter-based samplers. 相似文献
140.
This paper investigated the photochemical behaviour of the herbicide norflurazon (NFL) in the presence of different soil colloidal components and several cyclodextrins (CDs). The interaction of NFL with CDs yielded the formation of inclusion complexes at 1:1 stoichiometric ratio in solution, with an increase of the herbicide solubility. The irradiation of NFL aqueous solutions in the presence of CDs showed that the higher the formation constant of NFL-CD complexes (Kc) and their solubility, the higher their photocatalytic effects, following the CDs in the order: RAMEB>HPBCD>beta-CD>alpha-CD>gamma-CD. The presence of the different soil colloidal components in aqueous suspension provoked the reduction of the NFL photodegradation rate, due to a screening effect, especially when goethite and humic acids were present. No disappearance of NFL was detected in parallel studies carried out in the dark, except in the case of humic acids, where a 5% adsorption of the initial amount of NFL was adsorbed in the dark control. The presence of the different CDs in such systems showed an inductive photodegradation effect on the herbicide. This could be largely explained by the inclusion effects of CDs in catalyzing interactions between NFL and certain reactive radicals generated by the different colloidal components. Although this work was carried out at laboratory scale and therefore, has limited applications, it reveals that cyclodextrins increase solubilization of hydrophobic herbicides and could lead to their increased photodegradation. This could be a promising method for pesticide-contaminated water remediation. However, it is important to consider the effect of the soil colloidal components in the different aquatic systems and their concentrations, since they can alter the photodegradative effects of the cyclodextrins. 相似文献