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811.
H. P. Jeffries M. S. Berman A. D. Poularikas C. Katsinis I. Melas K. Sherman L. Bivins 《Marine Biology》1984,78(3):329-334
A computerized system was developed to automate the analysis of zooplankton samples. Classification to major taxonomic group was based on discriminant analysis of morphological features. Images were generated either from preserved organisms or from silhouette photographs. The latter technique simplified large-scale sample storage. Accuracy of correct classification, among organisms regularly occurring in New England coastal waters, exceeded 90%. Critical problems were due to limitations inherent to the imaging of low contrast, randomly oriented objects by a vidicon camera. One solution would utilize an incoherent-to-coherent transducer in a binocular field of observation through which plankton entrained in a flowing medium passed.This work was supported in part by NOAA grant NA80AA-4 00023 相似文献
812.
Environmental conditions, primary production, and zooplankton populations were studied from May, 1969 to November, 1970 at one station in Kungsbacka Fjord, Sweden. The fjord, with an arca of 53 km2, is a moderately polluted estuary, with a small tidal range. Data for primary production and environmental parameters were correlated using Spearman's rank correlation coefficient. The annual rate of primary production in 1970 was about 100 gC·m-2. Carbon fixation was about 80 g·m-2 in May–November in1969 and 1970. The average monthly rate was highest in June, 1970, with 25 gC·m-2; about 15 gC·m-2 was recorded in August–October of both years. Carbon fixation by the phytoplankton was estimated to be about 2,800 tons in the whole fjord in 1970. The average fresh-water inflow to the fjord, amounting to about 13 m3·sec-1, added about 380 tons of organic carbon, 45 tons of nitrogen, and 4.5 tons of phosphorus per month. Primary production displayed strong correlation with temperature at different depths (P<0.05 to 0.001), indicating the sediments to be the most important nutrient source. A total of 19 holoplanktonic zooplankton species was identified, copepods being the dominant group. The highest zooplankton biomass, 800 to 900 mg·m-3, was recorded in June of both years. The production of copepods in May–October was about 1 gC·m-2 in both years. The total secondary production of the zooplankton was calculated as only 1.8 gC·m-2 in 1970. 相似文献
813.
Fast-growing macroalgae, including Ulva lactuca Linnaeus, respond rapidly to changes in nutrient conditions, particularly to short-term N supply. This ability to rapidly
take up and assimilate N contributes to the increasing occurrence of macroalgal blooms in heavily N loaded coastal ecosystems.
To determine whether long-term nutrient histories affect short-term responses in activity of N-assimilating enzymes, including
nitrate reductase (NRA) and glutamine synthetase activity (GSA), internal N storage, and macroalgal growth, we conducted an
in situ nitrate fertilization experiment between 7 and 22 July 2004, with fronds of U. lactuca collected from estuaries with high and low N loads in Waquoit Bay, Cape Cod, Massachusetts, USA (N 41° and W 70°). Initial
NRA, GSA, % N, δ15N, and growth of U. lactuca fronds were higher in the site where nitrate was in high supply. Differences in NRA persisted even after short-term experimental
enrichment. Differences in internal N pools, δ15N, and growth, in contrast, mirrored the changes of nutrient supply. The rate of turnover of the internal N content of U. lactuca was quite short (<2 d), and turnover of enzyme activity may have been even shorter. N isotopic fractionation by U. lactuca appeared to be of small magnitude, unlike the case of phytoplankton, and similar to that of vascular plants. δ15N was a better indicator of short-term response to external and internal nutrient supplies in U. lactuca than enzyme activity or N content, and may reliably detect rapid changes in N availability, source, and uptake and assimilation
processes. 相似文献
814.
A. Triantafyllidis I. Leonardos I. Bista I. D. Kyriazis M. Th. Stoumboudi I. Kappas F. Amat T. J. Abatzopoulos 《Marine Biology》2007,152(5):1159-1167
The purpose of this study was to determine the phylogeographic structure of the brackish-hypersaline cyprinodont fish Aphanius fasciatus (Valenciennes, 1821), using sequencing and RFLP analysis of a 1,330 bp mitochondrial DNA segment containing part of the 16S
rRNA gene as well as the genes for tRNA-Leu, NADH subunit 1 and tRNA-Ile. Individuals were collected from 13 different sites
in Greece and Turkey, while seven published A. fasciatus sequences were also included to cover the area of distribution of the species. Pairwise sequence divergence values ranged
from 0 to 4.51%. Congruent phylogenies were recovered with maximum likelihood, maximum parsimony and neighbour-joining methods.
All analyses revealed two main groups. The first group consists of populations from almost all localities that drain into
the Aegean Sea. The second group comprises the remaining population samples, which in some cases seem to consist of population-specific
subgroups. Our results show that vicariant events have predominantly affected the evolution of A. fasciatus, with the Messinian salinity crisis having shaped the present genetic structure of its populations. Additionally, the life-history
traits of the species, which determine a low potential for dispersal, coupled with the typical fragmentation of brackish-hypersaline
water habitats have led to a high degree of isolation of A. fasciatus populations, even at restricted spatial scales. Analysis of the partitioning of the total amount of polymorphism with analyses
of molecular variance (AMOVA) gave a value of F
ST = 84.6%. Potential conservation policies concerning A. fasciatus should also consider the low-genetic variability in the majority of its populations and the presence of fixed haplotypes
in some of them. 相似文献
815.
M. I. Silva H. D. Burrows S. J. Formosinho L. Alves A. Godinho M. J. Antunes D. Ferreira 《Environmental Chemistry Letters》2007,5(3):143-149
Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this
study, the lowest excited state (3MLCT) of Ru(bpy)32+ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light
and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted
chlorophenols has been followed in the presence of Ru(bpy)32+/S2O82− with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques.
Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl−, H+ and SO42− ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant
organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic
process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first
order behaviour. Further studies on this were made by following Cl− release with respect to the initial Ru(bpy)32+ and S2O82− concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied
at acidic and alkaline pH. 相似文献
816.
Sampling design trade-offs in occupancy studies with imperfect detection: examples and software. 总被引:2,自引:0,他引:2
Larissa L Bailey James E Hines James D Nichols Darryl I MacKenzie 《Ecological applications》2007,17(1):281-290
Researchers have used occupancy, or probability of occupancy, as a response or state variable in a variety of studies (e.g., habitat modeling), and occupancy is increasingly favored by numerous state, federal, and international agencies engaged in monitoring programs. Recent advances in estimation methods have emphasized that reliable inferences can be made from these types of studies if detection and occupancy probabilities are simultaneously estimated. The need for temporal replication at sampled sites to estimate detection probability creates a trade-off between spatial replication (number of sample sites distributed within the area of interest/inference) and temporal replication (number of repeated surveys at each site). Here, we discuss a suite of questions commonly encountered during the design phase of occupancy studies, and we describe software (program GENPRES) developed to allow investigators to easily explore design trade-offs focused on particularities of their study system and sampling limitations. We illustrate the utility of program GENPRES using an amphibian example from Greater Yellowstone National Park, U.S.A. 相似文献
817.
Concentrations of the naturally-ocurring radionuclides 210Po and 210Pb were measured in krill (Euphausia superba), mesozooplankton, phytoplankton and sea water collected during the South African SIBEX cruise to the Antarctic in autumn 1984. The data reported constitute the first substantial measurements on 210Po and 210Pb in such samples in the Antarctic Ocean. The concentrations of 210Po in mesozooplankton and phytoplankton are unexceptional in comparison with those from other oceans. The SIBEX E. superba, however, have higher levels of 210Po than usually found in euphausiids. The 210Po data, combined with reasonable estimates of biological quantitites such as the fractional assimilation, are used to obtain information about the diet of E. superba. It is suggested that the higher 210Po in the SIBEX E. superba reflects a change from an almost entirely phytoplanktonic diet in summer to a more omnivorous diet as winter approaches. The data show that there are allometric relationships between the 210Po content of euphausiids and animal size; these are discussed briefly. The limited sea-water data presented are characterized by unusually high 210Po:210Pb activity ratios and need further investigation. 相似文献
818.
Immediate-energy-supply pathways were analysed during burst-swimming in white muscle of the Antarctic fish Notothenia neglecta, (collected during Austral summer 1984 near Signy Island, South Orkneys). Selected enzyme activities were determined, and tissue metabolites were measured, before and after 3 min of burst-work. The activity of glycolytic enzymes is very low compared to that in other fish, while the activities of creatine phosphokinase, adenylate kinase and AMPdeaminase are relatively high. Concentrations of metabolites associated with cellular energy status declined with exercise. At the same time, there was no change in the concentrations of most of the glycolytic metabolites measured (including glycogen, glucose and lactate), while [creatine phosphate] declined and [inosine monophosphate] increased. These observations were used to propose that the potential for ATP generation via creatine-phosphate hydrolysis is enhanced in N. neglecta, while glycolytic capacity is relatively reduced. This is an unusual pattern of ATP production and places severe constraints upon the behavior of the fish. While the capacity for very short-term, high-power-output swimming is increased, the capacity for medium-duration swimming is reduced. Ecological repercussions are discussed. 相似文献
819.
Two marine mussels, Geukensia demissa (Dillwyn) and Mytilus edulis (L.) collected in 1990 in Old Silver Beach, Falmouth, Massachusetts, incorporated nitrogen when fed 15N-labelled organic aggregates produced from dissolved organic nitrogen released by the brown sea-weed Fucus vesiculosis. Uptake of 15N on the aggregate diet was linear over the course of 24 h, and unincorporated 15N was eliminated from the gut after 48 h. Both species of mussels incorporated approximately five times more N when they were fed organic aggregates than when they were fed either 15N-labelled dissolved organic material (DOM) or particulate detritus, both of which were also derived from the seaweed. Nitrogen uptake was greatest in controls fed the diatom Thalassiosira weissflogii; mussels fed phytoplankton incorporated seven times more nitrogen than those fed aggregates. However, aggregates could supply an estimated 7 to 14% of the N requirements for both mussels, whereas DOM or particulate detritus could only supply 1 to 3%. These data provide evidence that a food web pathway exists from primary producer to released dissolved organic nitrogen to microbial organic aggregate to metazoan consumer, and, further, that it can be more important in a detrital food web than either particulate detritus or DOM. 相似文献
820.
The widely held assumption that gene frequencies within samples of multi-aged organisms are temporally stable has rarely been tested. In order to test this assumption in the commercially exploited bivalve scallop Aequipecten (Chlamys) opercularis (L.), 12 populations were sampled from around the UK over the period 1988–1990 and each was assayed at four putative polymorphic enzyme loci. Most populations were comprised of 3 to 4 year-classes, distinguishable by annual rings laid down on the shell. Three alleles from each locus were used as discriminant-function variables. Discriminant-function analysis based on allele frequencies averaged for each inividual year-class (45 demes) revealed highly significant inter-site heterogeneity. A posteriori classification of individual year-classes based on the discriminant analysis resulted in assignment of year-classes to the correct home site in 80% of cases. If allozyme neutrality is assumed, the phenomenon of predominant local allele frequency-stability through time within populations which are genetically heterogeneous from one site to another raises the possibility that queen scallop populations may be self-recruiting. Despite a planktonic larval phase lasting up to several weeks, this possibility is not excluded by the available hydrographic data. 相似文献