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301.
Tolun LG Okay OS Gaines AF Tolay M Tüfekçi H Kiratli N 《Environment international》2001,26(3):163-168
Izmit Bay is one of the most polluted and populated enclosed sea in Turkey. It has been the centre of industrial activities for the last 30 years. Seven major sources enter the bay waters along the north coastline of the bay. This investigation forms part of continuing ecotoxicology studies in the Izmit Bay designed to constrain and minimise the pollution caused by flourishing industry and a growing population. Sediments sampled from the mouths of the major discharges of Izmit Bay were analysed for their organic carbon, total polycyclic aromatic hydrocarbon (t-PAH) and trace inorganic element (Cd, Al, As, Pb, Hg and Cu) contents and compared with those found in the sediments from the reference station in the outer bay (in the Marmara Sea). The toxicity of sediments was determined in the bulk and elutriate samples by using algal (Phaeodactylum tricornutum) batch bioassays. Chemical data showed that the sediments collected from the inner sites of the bay have been contaminated with Cd, Hg, As and PAHs. Organic carbon contents were also found higher. All the major industrial discharges into the bay are now biologically treated but bioassays performed with bulk sediments revealed that the recent sediments are toxic to the microalgae throughout the bay. The results are consistent with the previous toxicity studies performed with the industrial discharges. 相似文献
302.
Jean-Pierre Lechaire Ghislaine Frébourg Françoise Gaill Olivier Gros 《Marine Biology》2008,154(4):693-700
In this study, Codakia orbicularis gill-tissues were cryo-fixed by using high-pressure freezing, a freeze substitution process and finally by cryo-embedding
in Lowicryl. Ultrathin sections were then used for an EFTEM microanalysis. Results show that intracellular bacterial symbionts
contain elemental sulphur in periplasmic vesicles as indicated by conventional TEM. When sulphur is temporarily depleted in
the environment, such structures may act as energy sources for bacterial metabolism. Moreover, sulphate was detected in the
cytoplasm of the bacterial symbionts, suggesting the oxidation of elemental sulphur, located in periplasmic granules, to sulphate
(the final step in sulphur oxidation) by these chemoautotrophic bacteria. To assess the effects of host starvation on the
bacterial sulphur content, adult individuals of C. orbicularis were maintained in starvation for 6 weeks in sterile artificial seawater depleted in sulphur. During starvation, both (1)
the number of bacteria inside the bacteriocytes and (2) the number of periplasmic granules per prokaryotic cell decreased.
The content of the remaining periplasmic granules had been modified to sulphate. This observation suggests that bacterial
gill-endosymbionts used the elemental sulphur in their periplasmic granules as stored substrate for oxidation in order to
produce energy in case of sulphur depletion. 相似文献
303.
The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological
studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female
reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this,
we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins (Delphinus delphis) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age
at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be
a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue.
Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females.
Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a
half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential
for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian
scars to reconstruct individual life reproductive histories in cetaceans is suggested. 相似文献
304.
Combining field and laboratory work, this study investigated the reproductive cycle, aggregative behavior, spawning periodicity,
development and early growth of the sea star Henricia lisa living at bathyal depths off eastern Canada. Marked differences were found between individuals from ~1,300 and ~600 m deep.
The former had a male biased sex ratio and an aperiodic reproductive cycle, whereas the latter displayed an equal sex ratio
and a biannual breeding pattern. Furthermore, the maximum size was larger and female fecundity roughly five times higher in
shallower compared to deeper populations. In the tanks, aggregative behavior was recorded twice a year during the summer and
winter breeding periods. The onset of aggregations and spawning coincided with a temperature of 3–4°C. Males spawned first
and females typically responded inside 30–60 min. Between 12 and 20 eggs were retained to be brooded under the arched arms
of the female, whereas the remainder were broadcasted and developed without parental care. The fertilized eggs underwent a
first cleavage after 12 h, reached the brachiolaria stage in 1 month, became juveniles within 3–4 months and reached ~ 4 mm
in diameter after 14–17 months of growth. The embryos and juveniles developed at the same rate whether brooded or not, and
development of winter cohorts was typically slower due to lower prevailing temperatures. This study of H. lisa provides the first evidence of lecithotrophy in a seasonally breeding deep-sea echinoderm and of brooding in a deep-sea asteroid. 相似文献
305.
Frank Rosell Gry Gundersen Jean-François Le Galliard 《Behavioral ecology and sociobiology》2008,62(10):1559-1568
Neighbour–stranger discrimination occurs when individuals respond with more aggression to strangers than to territorial neighbours—a
phenomenon termed the “dear enemy phenomenon” (DEP). We investigated the DEP with male and female root voles (Microtus oeconomus Pallas 1776) using field dyadic arena tests conducted in enclosures where we could test for the effects of familiarity (familiar
versus stranger), ownership (resident versus intruder status) and resource-holding potential (body mass) on territorial behaviours.
The results showed that males put more effort into territorial defence than females, and males could discriminate between
neighbours and strangers. In males, aggressiveness was influenced by a significant two-way interaction between treatment and
ownership. Male residents were more aggressive towards stranger intruders than towards neighbour intruders, while male intruders
were less aggressive towards stranger residents than towards neighbour residents. In females, neither treatment nor ownership
status had a significant effect on aggressiveness. Familiar males performed more social behaviours but less non-social behaviours
than stranger males. Furthermore, there was a clear dominance hierarchy between residents and intruders in stranger dyads,
with the male territory holders dominating the intruder in pairwise interactions. To our knowledge, these results demonstrate
for the first time DEP in a small mammal with a known pedigree and present the first evidence for “prior resident advantage”
in voles. We argue that both ownership status and familiarity status affect how much an individual invests in territory defence.
The benefits of neighbour–stranger discrimination for male root voles and the absence of neighbour–stranger discrimination
in female root voles are discussed. 相似文献
306.
Estimating parameters of neutral communities: from one single large to several small samples 总被引:3,自引:0,他引:3
The neutral theory of S. P. Hubbell postulates a two-scale hierarchical framework consisting of a metacommunity following the speciation-drift equilibrium characterized by the "biodiversity number" theta, and local communities following the migration-drift equilibrium characterized by the "migration rate" m (or the "fundamental dispersal number" I). While Etienne's sampling formula allows simultaneous estimation of theta and m from a single sample of a local community, its applicability to a network of (rather small) samples is questionable. We define here an alternative two-stage approach estimating theta from an adequate subset of the individuals sampled in the field (using Ewens' sampling formula) and m from community samples (using Etienne's sampling formula). We compare its results with the simultaneous estimation of theta and m (one-stage estimation), for simulated neutral samples and for 50 1-ha plots of evergreen forest in South India. The one-stage approach exhibits problems of bias and of poor differentiability between high-theta, low-m and low-theta, high-m solution domains. Conversely, the two-stage approach yielded reasonable estimates and is to be preferred when several small, scattered plots are available instead of a single large one. 相似文献
307.
308.
309.
Towards a framework for assessment and management of cumulative human impacts on marine food webs
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Sylvaine Giakoumi Benjamin S. Halpern Loïc N. Michel Sylvie Gobert Maria Sini Charles‐François Boudouresque Maria‐Cristina Gambi Stelios Katsanevakis Pierre Lejeune Monica Montefalcone Gerard Pergent Christine Pergent‐Martini Pablo Sanchez‐Jerez Branko Velimirov Salvatrice Vizzini Arnaud Abadie Marta Coll Paolo Guidetti Fiorenza Micheli Hugh P. Possingham 《Conservation biology》2015,29(4):1228-1234
Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. 相似文献
310.