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Energy Densities of Brown Trout (Salmo trutta) and Its Main Prey Items in an Alpine Stream of the Slizza Basin (Northwest Italy)
No full textThe relative importance of metabolic rate and body size to space use behavior in aquatic invertebrates
Full text linkElucidating the underlying mechanisms behind variations of animal space and resource use is crucial to pinpoint relevant ecological phenomena. Organism's traits related to its energy requirements might be central in explaining behavioral variation, as the ultimate goal of a forager is to fulfill its energy requirements. However, it has remained poorly understood how energy requirements and behavioral patterns are functionally connected. Here we aimed to assess how body mass and standard metabolic rate (SMR) influence behavioral patterns in terms of cumulative space use and time spent in an experimental patchy environment, both within species and among individuals irrespective of species identity. We measured the behavioral patterns and SMR of two invertebrate species, that is, amphipod Gammarus insensibilis, and isopod Lekanesphaera monodi, individually across a range of body masses. We found that species of G. insensibilis have higher SMR level, in addition to cumulatively exploring a larger space than L. monodi. Cumulative space use scaled allometrically with body mass, and it scaled isometrically with SMR in both species. While time spent similarly in both species was characterized by negative body mass and SMR dependence, it was observed that L. monodi individuals tended to stay longer in resource patches compared to G. insensibilis individuals. Our results further showed that within species, body mass and metabolic rate explained a similar amount of variation in behavior modes. However, among individuals, regardless of species identity, SMR had stronger predictive power for behavioral modes compared to body mass. This suggests that SMR might offer a more generalized and holistic description of behavioral patterns that extend beyond species identity. Our study on the metabolic and body mass scaling of space and resource use behavior sheds light on higher-order ecological processes such as species' competitive coexistence along the spatial and trophic dimensions.
Our study explores how metabolic rate and body size are related to space use behavior, using invertebrate as model species. It shows that metabolic rate, encompassing variations related to species-specific characteristics, is associated with behavior beyond mere size.imag
On the potential contribution of microfungi to the decomposition of reed leaf detritus in a costal lagoon.
No full textMacrozoobenthic communities in the regional natural reserve of isonzo river mouth (North-East Italy): First results of a leaf bag technique study
No full textGrazer removal and nutrient enrichment as recovery enhancers for overexploited rocky subtidal habitats
Full text linkIncreasing anthropogenic pressures are causing long-lasting regime shifts from high-diversity ecosystems to low-diversity degraded ones. Understanding the effects of multiple threats on ecosystems, and identifying processes allowing for the recovery of biodiversity, are the current major challenges in ecology. In several temperate marine areas, large parts of rocky subtidal habitats characterised
by high diversity have been completely degraded to barren grounds by overfishing, including illegal date mussel fishing. Bare areas are characterized by the dominance of sea urchins whose grazing perpetuates the impact of overfishing. We investigated experimentally the separate and combined effects of nutrient enrichment and sea urchin exclusion on the recovery of barren grounds. Our results indicate that the two factors have a synergistic effect leading to the re-establishment of erect macroalgal canopies, enhancing the structural complexity of subtidal assemblages. In particular, in the overfished system considered here, the recovery of disturbed assemblages could occur only if sea urchins are removed. However, the recolonization of barren grounds by erect macroalgae is further enhanced under enriched conditions. This study demonstrates that the recovery of dramatically depleted marine habitats is possible, and provides useful indications for specific management actions, which at present are totally lacking, to achieve the restoration of barren grounds caused by human activity
Components of standard metabolic rate variability in three species of gammarids
Full text linkStandard metabolic rate is
a major functional trait with large inter-individual variability in many
groups of aquatic species. Here we present results of an experimental study
to address variation in standard metabolic rates, over different scales of
organisation and environments, within a specific group of aquatic
macro-invertebrates (i.e. gammarid amphipods) that represent the primary
consumers in detritus food webs. The study was carried out using flow-through
microrespirometric techniques on male specimens of three gammarid species
from freshwater, transitional water and marine ecosystems. We examined
individual metabolic rate variations at three scales: (1) at the individual
level, during an 8 h period of daylight; (2) at the within-population level,
along body-size and body-condition gradients; (3) at the interspecific level,
across species occurring in the field in the three different categories of
aquatic ecosystems, from freshwater to marine.
We show that standard metabolic rates vary significantly at all three scales
examined, with the highest variation observed at the within-population level.
Variation in individual standard metabolic rates during the daylight hours
was generally low (coefficient of variation, CV<10 %) and
unrelated to time. The average within-population CV ranged between 30.0 %
and 35.0 %, with body size representing a significant source of overall
inter-individual variation in the three species and individual body condition
exerting only a marginal influence. In all species, the allometric equations
were not as steep as would be expected from the 3∕4 power law, with
significant variation in mass-specific metabolic rates among populations. The
population from the transitional water ecosystem had the highest
mass-specific metabolic rates and the lowest within-population variation.
In the gammarid species studied here, body-size-independent variations in
standard individual metabolic rates were higher than those explained by
allometric body size scaling, and the costs of adaptation to short-term
periodic variations in water salinity in the studied ecosystems also seemed
to represent a major source of variation.</p
Differences in intestinal electrophysiological parameters and nutrient transport rates between eels (Anguilla anguilla) at yellow and silver stages
Full text linkMorphological and physiological characteristics of the European eel (Anguilla anguilla) intestine were analyzed in two different stages (yellow and silver) of the fish ontogenic development. Intestine/body (Wi/Wa) and scraped mucosa/intestine (Wsc/Wi) wet weight ratios were significantly (P < 0.01) reduced in seawater acclimated silver eels compared to yellow ones. Electrogenic, Na+-dependent transport rates of a number of nutrients (D-glucose, L-proline, beta-alanine, L-phenylalanine, L-methylalanine) were indirectly measured in intestinal brush border membrane vesicles of seawater acclimated eels, by monitoring the fluorescence quenching of the electrical membrane potential sensitive dye 3,3'-diethylthiocarbocyanine iodide [Dis-C-2(5)], and were significantly lower (P < 0.05 for L-proline; P < 0.01 for all the others) in silver eels compared to yellow ones. The transepithelial electrical potential difference (Vt) and short-circuit current (Isc), measured by applying the short-circuit current technique to ''in vitro'' isolated intestine, were significantly higher in silver eels compared to yellow ones in both sea- and freshwater. The addition of 10(-5) M bumetanide, inhibitor of the Na+-K+-2Cl(-) cotransporter, to the mucosal bathing solution almost completely abolished Vt and Isc in either yellow or silver eel intestine acclimated to both seawater and freshwater. Further, by using the microelectrode technique, it was shown that the apical membrane potential (Vm) averaged -27.3 +/- 2.3 mV in yellow eels and -42.9 +/- 3.3 mV in silver eels (P = 0.02). It is concluded that the changes in morphological (mucosal weight) and physiological (nutrient transport rates and electrophysiological parameters) characteristics found in silver compared to yellow eel intestine could represent adaptative features preparatory to the onset of the prolonged marine migration of the silver eel
Seasonal dynamics of macrozoobenthic community in the wetland of the Natural Regional Reserve of the Isonzo River mouth, Northeast Italy: a three-years analysis
No full textThis study was seasonally performed over a three year period in a large freshwater temporary pond to investigate (a) seasonal trends of the main abiotic factors, (b) the most important abiotic drivers in shaping macrobenthic invertebrate communities and (c) the structures of these communities among different years. As the study area was placed within a Natural Reserve, the leaf bag technique was used as non invasive sampling method in order to reduce disturbance. The results of chemical and physical investigations point out a clear seasonal trend, while macrobenthic communities differ signifi cantly from year to year, and their main shape drivers were identifi ed to be conductivity, temperature and dissolved oxygen
Variability of Lekanesphaera monodi metabolic rates with habitat trophic status
Full text linkRegulation of metabolism is a common strategy used by individuals to respond to a changing environment. The mechanisms underlying the variability of metabolic rates in macroinvertebrates are of primary importance in studying benthicepelagic energy transfer in transitional water ecosystems. Lekanesphaera monodi is an isopod endemic to transitional water ecosystems that can modify its metabolic rate in response to environmental changes. Therefore it is a useful model in studying the influence of environmental factors on metabolism. This study focused on the interpopulation variability of standard metabolic rates (SMR) in L. monodi populations sampled in three transitional water ecosystems differing in their trophic status. The standard metabolic rates of L. monodi individuals across the same range of body size spectra were inferred from oxygen consumption measurements in a flow-through respirometer in the three populations and a body condition index was assessed for each population. Habitat trophic status was evaluated by monthly measurement of the basic physicalechemical parameters of the water column in the ecosystems for one year. Standard metabolic rates showed high variability, ranging from 0.27 to 10.14 J d^-1. Body size accounted for more than 38% of total variability. In terms of trophic status, individuals from the eutrophic ecosystem had significantly higher standard metabolic rates than individuals from the other ecosystems (SMR 1⁄4 2.3 J d^-1 in Spunderati Sud vs. 1.36 J d^-1 in Alimini and 0.69 J d^-1 in Acquatina). The body conditions index was also higher in the population from the eutrophic ecosystem. Results show that standard metabolic rates and growth rates are directly related to habitat productivity in accordance with the expectations of the food habits hypothesis. A possible extension of this hypothesis to benthic invertebrates is propose
Linking water column perturbations to soft-bottom biological element descriptors: the response of macroinvertebrates
No full textMediterranean lagoons are exposed to natural and anthropogenic disturbances, and the most unlikely
conditions are the dystrophic and hypoxic events. These events determine dis-equilibrium conditions
along temporal and spatial scales, which are linked to metabolism and life cycle of the biotic components.
In summer 2008, Lesina lagoon (SE Italian coastline) was interested by a geographically localized
dystrophic crisis which affected up to 8% of the total lagoon surface.
Temporal dynamics of principal descriptors of abiotic (water, sediment) and biotic (phytoplankton,
benthic macroinvertebrate) compartments have been followed during the 2008 by collecting data inside
stressed and control lagoon areas before a dystrophic event and in the six months after the dystrophic
event. The aim of the study was to analyse the pathways of ecosystem responses to dystrophic
stress, searching for the characteristic scales of ecosystem compartment resistance and resilience.
The characteristic time-scale of abiotic and biotic component time responses varied from days, for the
selected markers of the water column, to year, for the benthic ones. Short-term biotic and abiotic responses
in the water column were strongly coupled while biotic and abiotic responses at the sediment level
were remarkably un-coupled. Dynamics and recovery time of water column and benthic components do not
match in Lesina following the dystrophic crisis, highlighting an intrinsic individualistic behavior
within the lagoon community driving ecosystem processes and ecosystem level responses. Taxonomic
and non-taxonomic descriptors of benthic macroinvertebrates showed different response
patterns as early warning signals and overall resilience. The emphasized differences in the stability
components, i.e., resistance and resilience, of water column and sediment abiotic and biotic
characteristics as well as of taxonomic and nontaxonomic descriptors has key implication in
planning monitoring strategies and programs for transitional waters in the Mediterranean EcoRegion
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