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31.
Kasper Elgetti Brodersen Daniel Aagren Nielsen Peter J. Ralph Michael Kühl 《Marine Biology》2014,161(12):2921-2930
We present a new experimental set-up enabling fine-scale examination of how changing environmental conditions affect the below-ground biogeochemical microenvironment of aquatic macrophytes. By means of microsensor and planar optode technology, the influence of plant-mediated radial O2 release on the below-ground chemical microenvironment of Zostera muelleri and Halophila ovalis was determined in high spatio-temporal resolution. The seagrass specimens were cultured in a new split flow chamber with artificial sediment made of a deoxygenated seawater–agar solution with added sulphide. Microelectrode measurements revealed radial O2 release from the root–shoot junction of both Z. muelleri and H. ovalis during both light stimulation and darkness, resulting in a rapid decrease in H2S concentration, and a significant drop in pH was observed within the plant-derived oxic microzone of Z. muelleri. No radial O2 release was detectable from the below-ground tissue of Z. muelleri during conditions of combined water-column hypoxia and darkness, leaving the plants more susceptible to sulphide invasion. The spatial O2 heterogeneity within the immediate rhizosphere of Z. muelleri was furthermore determined in two dimensions by means of planar optodes. O2 images revealed a decrease in the spatial extent of the plant-derived oxic microzone surrounding the below-ground tissue during darkness, supporting the microelectrode measurements. This new experimental approach can be applied to all rooted aquatic plants, as it allows for direct visual assessment of the below-ground tissue surface during microprofiling, while enabling modification of the above-ground environmental conditions. 相似文献
32.
Tommy Kristensen Anders Isberg Nielsen Anders Isak J?rgensen Kim N. Mouritsen Henrik Glenner Jens T. Christensen J?rgen Lützen Jens T. H?eg 《Marine Biology》2012,159(9):2015-2023
Male crabs infected by parasitic barnacles (Rhizocephala) are known to be morphologically feminized. Here, we investigate morphological chances in green crabs, Carcinus maenas, induced by the parasitic barnacle Sacculina carcini. Infected males acquire a broader, longer and segmented abdomen, fringed with marginal setae. Copulatory appendages and pereopods are reduced in length, and the chelae become smaller. The feminization show great individual variation. Males with scars from lost externae, the parasites reproductive organ situated under the abdomen, are less modified than males carrying an externa, and the feminization is more pronounced in smaller than in larger males. No super-feminization is evident in female crabs that remain morphologically unaffected by infection. The protective value of a parasitically induced enlargement of the male abdomen may constitute an adaptation that increases parasite longevity. The additional effects on male morphology are viewed as pleiotropic side effects of the main adaptive value of enlarging the abdomen. 相似文献
33.
The invasive red alga Gracilaria vermiculophylla has quickly spread across Europe, but it is unclear whether its success is based on a high tolerance to variations in environmental conditions or to the absence of native grazers that feed on this alga. We tested whether native invertebrate grazers prefer native algae to G. vermiculophylla. Feeding preferences of three common herbivores were quantified when offered G. vermiculophylla and native Fucus vesiculosus, Ceramium virgatum, and Ulva intestinalis in no-, two- and multiple-choice trials. Herbivore growth was measured when fed each of the algae separately. Grazers consumed G. vermiculophylla in no-choice trials, but avoided generally this alga when having a choice. U. intestinalis was always preferred over G. vermiculophylla, and grazers fed with U. intestinalis grew faster than those fed with G. vermiculophylla. We conclude that grazers avoid G. vermiculophylla to most native algae, which may benefit G. vermiculophylla in northern European estuaries. 相似文献
34.
Patrik Kraufvelin Ann Lindholm Morten Foldager Pedersen Lars Andreas Kirkerud Erik Bonsdorff 《Marine Biology》2010,157(1):29-47
The littoral zone of temperate rocky shores is normally dominated by perennial macroalgae (e.g. Fucus, Ascophyllum, Laminaria), but nutrient enrichment and/or permanently decreased wave action may lead to structural community changes from dominance
of perennials to increased amounts of annual opportunistic species (mainly green algae). Macroalgal biomass, diversity and
production as well as relationships between the two latter were studied using Solbergstrand’s rocky shore mesocosms in SE
Norway in connection with a long-term experimental manipulation of nutrient addition and wave action (high and low levels
of both factors applied in a crossed way to eight outdoor basins). After more than 2 years of experimental treatment, the
total standing stock of macroalgae was larger in low nutrient than in high nutrient treatments as well as in high wave compared
to low wave treatments (in autumn only). For macroalgal functional groups, bushy and filamentous brown and filamentous red
algae were generally favoured by low nutrient concentrations, while annual filamentous and sheet-like green algae were stimulated
by the nutrient enrichment. There was only one significant interaction between nutrient enrichment and wave action (for brown
filamentous algae in autumn) and also only one significant main effect of the wave treatment (for bushy brown algae in autumn).
Surprisingly, the high nutrient treatments supported a higher diversity of macroalgae, whereas the low nutrient treatments
generally showed higher production rates. Moreover, significantly negative correlations were found between macroalgal diversity
and primary productivity in both summer and autumn. This study shows that it is the biological components of the communities
subjected to external forcing (nutrient addition or decreased wave action) that regulate production and this contradicts the
common misperception that resource production in natural systems simply can be fast-forwarded by fertilization. The negative
relationships between diversity and productivity, although a consequence of unexpected results for diversity and production,
are also novel and hint towards species identities having more important functional consequences than general species dominance
patterns and the amount of species per se. These results also emphasise the context dependency of findings within the field
of biodiversity and ecosystem functioning. 相似文献
35.
Manuela Panzacchi Ivar Herfindal John D. C. Linnell Morten Odden John Odden Reidar Andersen 《Behavioral ecology and sociobiology》2010,64(8):1267-1278
The choice of neonatal hiding place is critical for ungulates adopting hiding anti-predator strategies, but the consequences
of different decisions have rarely been evaluated with respect to offspring survival. First, we investigated how landscape-scale
choices made by roe deer fawns and their mothers affected predation risk by red foxes in a forest–farmland mosaic in southeastern
Norway. After, we examined the effect of site-specific characteristics and behaviour (i.e. visibility, mother–fawn distance
and abundance of the predator’s main prey item—small rodents) on predation risk. The study of habitat use, selection and habitat-specific
mortality revealed that roe deer utilised the landscape matrix in a functional way, with different habitats used for feeding,
providing maternal care and as refugia from predation. Mothers faced a trade-off between foraging and offspring survival.
At the landscape-scale decisions were primarily determined by maternal energetic constraints and only secondarily by risk
avoidance. Indeed, forage-rich habitats were strongly selected notwithstanding the exceptionally high densities of rodents
which increased fawn predation. At fine spatial scales, a high visibility of the mother was the major factor determining predation
risk; however, mothers adjusted their behaviour to the level of risk at the bed site to minimise predation. Fawns selected
both landscape-scale refugia and concealed bed sites, but failure to segregate from the main prey of red foxes led to higher
predation. This study provides evidence for the occurrence of spatial heterogeneity in predation risk and shows that energetically
stressed individuals can tackle the foraging-safety trade-off by adopting scale-dependent anti-predator responses. 相似文献
36.
37.
Eva Friis Møller Christian Marc Andersen Borg Sigrún H. Jónasdóttir Suree Satapoomin Cornelia Jaspers Torkel Gissel Nielsen 《Marine Biology》2011,158(3):677-688
The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations
across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during
October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore,
the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest
copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the
lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 μg C m−3 day−1. At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical
export of fecal pellets was low (<0.02 mg m−2 day−1). 相似文献
38.
The physicist Walter M. Elsasser is mostly known for his work on the Earth's magnetism. Less attention has been paid to his efforts toward identifying what are the real differences between physical and biological systems. One essential distinction he recognized was that physical systems are largely homogenous while biological systems always revealed what he called ordered heterogeneity. Calculation of the possible configurations of such heterogeneous systems almost always leads to combinatorial explosions and to what Elsasser referred to as immense numbers. Such calculations have the consequence that any such systems are necessarily unique - mathematically speaking they represent one-sets.Another consequence is that immense numbers automatically introduce enormous uncertainty and indeterminacy into the system. Such systems are said to be ontically open. Applying this perspective to the genome and employing the notion of informational entropy reveals a common drive behind all development. This means that both conventional Darwinian evolution as well as the genomic mistakes that are believed to lie behind processes like aging and diseases can be interpreted against the background of one and the same process.At the same time the approach demonstrates how Darwinian evolution encompasses other notions such as Kauffman's “adjacent possible” (
[Kauffman, 1995] and [Kauffman, 2000]) and Eldrege's and Gould's “evolution via punctuated equilibria” (e.g.,
[Eldredge and Gould, 1972] and [Gould and Eldredge, 1977]). 相似文献
39.
How to Consider the Value of Farm Animals in Breeding Goals. A Review of Current Status and Future Challenges 总被引:1,自引:0,他引:1
H. M. Nielsen I. Olesen S. Navrud K. Kolstad P. Amer 《Journal of Agricultural and Environmental Ethics》2011,24(4):309-330
The objective of this paper is to outline challenges associated with the inclusion of welfare issues in breeding goals for
farm animals and to review the currently available methodologies and discuss their potential advantages and limitations to
address these challenges. The methodology for weighing production traits with respect to cost efficiency and market prices
are well developed and implemented in animal breeding goals. However, these methods are inadequate in terms of assessing proper
values of traits with social and ethical values such as animal welfare, because such values are unlikely to be readily available
from the product prices and costs in the market. Defining breeding goals that take animal welfare and ethical concerns into
account, therefore, requires new approaches. In this paper we suggest a framework and an approach for defining breeding goals,
including animal welfare. The definition of breeding goals including values related to animal welfare requires a multidisciplinary
approach with a combination of different methods such as profit equations, stated preference techniques, and selection index
theory. In addition, a participatory approach involving different stakeholders such as breeding organizations, food authorities,
farmers, and animal welfare organizations should be applied. We conclude that even though these methods provide the necessary
tools for considering welfare issues in the breeding goal, the practical application of these methods is yet to be achieved. 相似文献
40.
E. Steemann Nielsen 《Marine Biology》1978,46(3):185-189
Employing a special batch technique which involves extremely low concentrations of the alga Selenastrum capricornutum, it is shown that a growth rate of ca. 75% of optimum growth occurs at a concentration of 0.02 g-at N(NH4
+) l-1. The low concentrations of this N-source in the oligotrophic parts of the oceans (ca. 0.06 g-at l-1) thus give rise to a borderline deficiency. As the half-saturation constant (K
S) for growth was recorded at 0.05 g-at N(NO3
-), this ion can hardly be of much importance at the low concentrations present in these parts of the oceans. It is wrong to assert that N is the primary limiting nutrient. Phosphate also is found at concentrations giving rise to a borderline deficiency. 相似文献