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91.
Tiedemann R Moll K Paulus KB Scheer M Williot P Bartel R Gessner J Kirschbaum F 《Die Naturwissenschaften》2007,94(3):213-217
Recent molecular data on the maternally inherited mitochondrial (mt) DNA have challenged the traditional view that the now
extinct Baltic sturgeon population belonged to the European sturgeon Acipenser sturio. Instead, there is evidence that American sea sturgeon Acipenser oxyrinchus historically immigrated into the Baltic Sea. In this study, we test the hypothesis that A. oxyrinchus introgressed into, rather than replaced, the A. sturio population in the Baltic. We established four single nucleotide polymorphisms (SNPs) in the nuclear MHC II antigen gene with
a species-specific SNP pattern. Using an ancient DNA approach and two independent lines of molecular evidence (sequencing
of allele-specific clones, SNaPshot), we detected both A. sturio and A. oxyrinchus alleles in the available museum material of the now extinct Baltic sturgeon population. The hybrid nature of the Baltic population
was further confirmed by very high levels of heterozygosity. It had been previously postulated that the immigration of the
cold-adapted A. oxyrinchus into the Baltic occurred during the Medieval Little Ice Age, when temperature likely dropped below the degree inducing spawning
in A. sturio. Under this scenario, our new findings suggest that the genetic mosaic pattern in the Baltic sturgeon population (oxyrinchus mtDNA, sturio and oxyrinchus MHC alleles) is possibly caused by sex-biased introgression where spawning was largely restricted to immigrating American
females, while fertilization was predominantly achieved by abundant local European males. The hybrid nature of the former
Baltic sturgeon population should be taken into account in the current reintroduction measures.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
92.
93.
Isabel M. Jimenez Anthony W. D. Larkum Peter J. Ralph Michael Kühl 《Marine Biology》2012,159(8):1773-1782
We studied the diel variation of in situ coral temperature, irradiance and photosynthetic performance of hemispherical colonies of Porites lobata and branching colonies of Porites cylindrica during different bulk water temperature and tidal scenarios on the shallow reef flat of Heron Island, Great Barrier Reef, Australia. Our study presents in situ evidence that coral tissue surface temperatures can exceed that of the surrounding water under environmental conditions typically occurring during low tide in shallow reef or lagoon environments. Such heating may be a regular occurrence on shallow reef flats, triggered by the combined effects of high irradiance and low water flow characteristic of low Spring tides. At these times, solar heating of corals coincides with times of maximum water temperature and high irradiance, where the slow flow and consequent thick boundary layers impede heat exchange between corals and the surrounding water. Despite similar light-absorbing properties, the heating effect was more pronounced for the hemispherical P. lobata than for the branching P. cylindrica. This is consistent with previous laboratory experiments showing the evidence of interspecific variation in coral thermal environment and may result from morphologically influenced variation in convective heat transfer and/or thermal properties of the skeleton. Maximum coral surface warming did not coincide with maximum irradiance, but with maximum water temperature, well into the low-tide period with extremely low water flow in the partially drained reef flat, just prior to flushing by the rising tide. The timing of low tide thus influences the thermal exposure and photophysiological performance of corals, and the timing of tidally driven coral surface warming could potentially have different physiological impacts in the morning or in the afternoon. 相似文献
94.
95.
Martin Plath Katja Kromuszczynski Ralph Tiedemann 《Behavioral ecology and sociobiology》2009,63(3):381-390
Males often face strong mating competition by neighboring males in their social environment. A recent study by Plath et al.
(Anim Behav 75:21–29, 2008a) has demonstrated that the visual presence of a male competitor (i.e., an audience male) affects
the expression of male mating preferences in a poeciliid fish (Poecilia mexicana) with a weaker expression of mating preferences when an audience male observed the focal male. This may be a tactic to reduce
sperm competition, since surrounding males likely share intrinsic preferences for female traits or copy mate choice decisions.
Here, we examined the hypothesis that a same-sex audience would affect female mate preferences less than male mating preferences. Our hypothesis was based on the assumptions that (1) competition for
mates in a fashion that would be comparable in strength to sperm competition or overt male–male aggression is absent among
Poecilia females, and (2) P. mexicana females typically form female-biased shoals, such that almost any female mate choice in nature occurs in front of a female
audience. Poecilia females (P. mexicana, surface and cave form, and the closely related gynogenetic Poecilia formosa) were given a choice between a large and a small male, and the tests were repeated while a conspecific, a heterospecific,
or no audience female (control) was presented. Females spent more time in the neutral zone and, thus, less time near the males
during the second part of a trial when an audience was presented, but—consistent with predictions—females showed only slightly
weaker expression of mate preferences during the second part of the tests. This decline was not specific to the treatment
involving an audience and was significantly weaker than the effect seen in the male sex. 相似文献
96.
Katherina Petrou Scarlett Trimborn Björn Rost Peter J. Ralph Christel S. Hassler 《Marine Biology》2014,161(4):925-937
Iron availability strongly governs the growth of Southern Ocean phytoplankton. To investigate how iron limitation affects photosynthesis as well as the uptake of carbon and iron in the Antarctic diatom Chaetoceros simplex, a combination of chlorophyll a fluorescence measurements and radiotracer incubations in the presence and absence of chemical inhibitors was conducted. Iron limitation in C. simplex led to a decline in growth rates, photochemical efficiency and structural changes in photosystem II (PSII), including a reorganisation of photosynthetic units in PSII and an increase in size of the functional absorption cross section of PSII. Iron-limited cells further exhibited a reduced plastoquinone pool and decreased photosynthetic electron transport rate, while non-photochemical quenching and relative xanthophyll pigment content were strongly increased, suggesting a photoprotective response. Additionally, iron limitation resulted in a strong decline in carbon fixation and thus the particulate organic carbon quotas. Inhibitor studies demonstrated that, independent of the iron supply, carbon fixation was dependent on internal, but not on extracellular carbonic anhydrase activity. Orthovanadate more strongly inhibited iron uptake in iron-limited cells, indicating that P-type ATPase transporters are involved in iron uptake. The stronger reduction in iron uptake by ascorbate in iron-limited cells suggests that the re-oxidation of iron is required before it can be taken up and further supports the presence of a high-affinity iron transport pathway. The measured changes to photosystem architecture and shifts in carbon and iron uptake strategies in C. simplex as a result of iron limitation provide evidence for a complex interaction of these processes to balance the iron requirements for photosynthesis and carbon demand for sustained growth in iron-limited waters. 相似文献
97.
Sutinee Sinutok Ross Hill Michael Kühl Martina A. Doblin Peter J. Ralph 《Marine Biology》2014,161(9):2143-2154
The impact of elevated CO2 and temperature on photosynthesis and calcification in the symbiont-bearing benthic foraminifer Marginopora vertebralis was studied. Individual specimens of M. vertebralis were collected from Heron Island on the southern Great Barrier Reef (Australia). They were maintained for 5 weeks at different temperatures (28, 32 °C) and pCO2 (400, 1,000 µatm) levels spanning a range of current and future climate-change scenarios. The photosynthetic capacity of M. vertebralis was measured with O2 microsensors and a pulse-amplitude-modulated chlorophyll (Chl) fluorometer, in combination with estimates of Chl a and Chl c 2 concentrations and calcification rates. After 5 weeks, control specimens remained unaltered for all parameters. Chlorophyll a concentrations significantly decreased in the specimens at 1,000 µatm CO2 for both temperatures, while no change in Chl c 2 concentration was observed. Photoinhibition was observed under elevated CO2 and temperature, with a 70–80 % decrease in the maximum quantum yield of PSII. There was no net O2 production at elevated temperatures in both CO2 treatments as compared to the control temperature, supporting that temperature has more impact on photosynthesis and O2 flux than changes in ambient CO2. Photosynthetic pigment loss and a decrease in photochemical efficiency are thus likely to occur with increased temperature. The elevated CO2 and high temperature treatment also lead to a reduction in calcification rate (from +0.1 to >?0.1 % day?1). Thus, both calcification and photosynthesis of the major sediment-producing foraminifer M. vertebralis appears highly vulnerable to elevated temperature and ocean acidification scenarios predicted in climate-change models. 相似文献
98.
Innovation and the dynamics of global warming 总被引:1,自引:0,他引:1
Global warming and the carbon cycle are a dynamic system with positive feedbacks. Fossil fuels are exhaustible resources. These two facts mean that innovation in clean energy technology, rather than mitigating global warming, can lead to a permanently higher temperature path. This paper explores the impact of innovation in the simplest model linking the economic theory of exhaustible resources with positive feedback dynamics in the carbon cycle. 相似文献
99.
In situ seagrass photosynthesis measured using a submersible, pulse-amplitude modulated fluorometer 总被引:8,自引:0,他引:8
Assessments of photosynthetic activity in marine plants can now be made in situ using a newly developed, submersible, pulse-amplitude
modulated (PAM) fluorometer: Diving-PAM. PAM fluorometry provides a measure of chlorophyll a fluorescence using rapid-light curves in which the electron-transport rate can be determined for plants exposed to ambient
light conditions. This technique was used to compare the photosynthetic responses of seagrasses near Rottnest Island, Western
Australia. Several fluorescence parameters were measured as a function of time of day and water depth; electron-transport
rate (ETR), quantum yield, photochemical quenching and non-photochemical quenching and Photosystem II (PSII) photochemical
efficiency (F
v
:F
m
ratio) were measured. Results indicate that recent light-history plays a crucial role in seagrass photosynthetic responses.
Maximum ETR of Posidonia australis, Amphibolis antarctica and Halophila ovalis is influenced by the irradiance during the diurnal cycle, with low rates at dawn and dusk (<10 μmol electron m−2 s−1), highest rates in late morning (40 to 60 μmol electron m−2 s−1) and a mid-day depression. Maximum ETR and PSII photochemical efficiency varied widely between seagrass species and were
not correlated. A comparison of photochemical to non-photochemical quenching indicated that seagrasses in shallow water receiving
high light have a high capacity for non-photochemical quenching (e.g. light protection) compared to seagrasses in deep water.
These results indicate that in situ measurements of photosynthesis will provide new insights into the mechanisms and adaptive
responses of marine plants.
Received: 26 May 1997 / Accepted: 27 May 1998 相似文献
100.
Manfred Niecke Andreas Krüger Peter Hauff Hermann Ellenberg Ralph Labes Susanne Niecke 《Environmental Sciences Europe》1998,10(1):3-14
With the aid of the Hamburg proton micro-probe, we examined the concentration of mercury in sea eagle feathers collected over the course of several decades in the Mecklenburg-Vorpommern area. Based on the sites where these feathers were collected and the data of these findings, it is possible to get a differential picture of mercury contamination related both temporally and regionally to the mercurial pollution of seed mordants used agriculturally. We compared the concentrations found with a basic “geogenic” contamination which was also to be seen in the feather samples from the last century as detected in museum animal specimens. 相似文献