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1.
Panos Hadjinicolaou Christos Giannakopoulos Christos Zerefos Manfred A. Lange Stelios Pashiardis Jos Lelieveld 《Regional Environmental Change》2011,11(3):441-457
We present climate change projections and apply indices of weather extremes for the Mediterranean island Cyprus using data
from regional climate model (RCM) simulations driven by the IPCC A1B scenario within the ENSEMBLES project. Daily time-series
of temperature and precipitation were used from six RCMs for a reference period 1976–2000 and for 2026–2050 (‘future‘) for
representative locations, applying a performance selection among neighboring model grid-boxes. The annual average temperatures
of the model ensemble have a ±1.5°C bias from the observations (negative for maximum and positive for minimum temperature),
and the models underestimate annual precipitation totals by 4–17%. The climatological annual cycles for the observations fall
within the 1σ range of the 6-model average, highlighting the strength of using multi-model output. We obtain reasonable agreement
between models and observations for the temperature-related indices of extremes for the recent past, while the comparison
is less good for the precipitation-related extremes. For the future, the RCM ensemble shows significant warming of 1°C in
winter to 2°C in the summer for both maximum and minimum temperatures. Rainfall is projected to decrease by 2–8%, although
this is not statistically significant. Our results indicate the shift of the mean climate to a warmer state, with a relatively
strong increase in the warm extremes. The precipitation frequency is projected to decrease at the inland Nicosia and at the
coastal Limassol, while the mountainous Saittas could experience more frequent 5–15 mm/day rainfall. In future, very hot days
are expected to increase by more than 2 weeks/year and tropical nights by 1 month/year. The annual number of consecutive dry
days shows a statistically significant increase (of 9 days) in Limassol. These projected changes of the Cyprus climate may
adversely affect ecosystems and the economy of the island and emphasize the need for adaptation strategies. 相似文献
2.
Lotfi Rabaoui Sabiha Tlig Zouari Stelios Katsanevakis Oum Kalthoum Ben Hassine 《Marine Biology》2007,152(3):537-548
The variability in absolute and relative growth of Pinna nobilis along the Tunisian coastline was investigated. Five populations of P. nobilis were sampled, three from northern and two from eastern Tunisia. The specimens were aged and ten morphometric characters were
measured on each individual. To test if differences existed in absolute and relative growth patterns among the different populations
an information theory approach was followed. For absolute growth, von Bertalanffy, Gompertz, the logistic and the power models
were fitted in combination with three assumptions regarding inter-population differences in absolute growth patterns: no differences,
differences among all five populations or just between northern and eastern populations. The assumption of common absolute
growth parameters among all five populations had the greatest support by the data, whereas the assumption of different growth
patterns among all five populations had no support. Von Bertalanffy growth model and the power model were both equally supported
by the data (while Gompertz had considerably less support and the logistic model had no support), and thus it may not be definitely
concluded whether P. nobilis grows asymptotically or not. The P. nobilis populations of the Tunisian coastline had a slow growth and up to an age of ∼ 9 years their shells were smaller than from
all other reported populations in the Mediterranean. For relative growth, apart from the classical allometric model Y = aX
b
, relating the size of a part of a body Y to another reference dimension X, more complicated models were used in combination with the three abovementioned assumptions regarding inter-population differences.
Those models, of the form logY = f (logX), either assumed breakpoints in the relative growth trajectories or non-linearities. For most morphometric characters, the
classical allometric model had no support by the data and more complicated models were necessary. In most cases, different
relative growth either among all five populations or between the northern and eastern population groups was supported by the
data. Further investigation is needed to relate the morphological differences observed among different populations of P. nobilis to environmental factors. 相似文献
3.
In-situ bio-remediation is a viable cleanup alternative for aquifers contaminated by hydrocarbons such as BTEX. Transport models of varying complexity and capabilities are used to quantify their degradation. A model that has gained wide acceptance in applications is BIOPLUME II, which assumes that oxygen-limited biodegradation takes place as an instantaneous reaction. In this work we have employed theoretical analysis, using non-dimensional variables, and numerical modelling to establish a quantitative criterion demarcating the range of validity of the instantaneous reaction approximation against biodegradation kinetics. Oxygen was the limiting species and sorption was ignored. This criterion relates (o), the Dahmk?hler number at oxygen depletion, to O(o)*, the ratio of initial to input oxygen concentration, (o) > or = 0.7(O(o)*)(2) + 0.1O(o)* + 1.8. The derived (o) reflects the intrinsic characteristics of the physical transport and of the biochemical reaction, including the effect of biomass density. Relative availability of oxygen and hydrocarbons exerts a small influence on results. Theory, verified and refined via numerical simulations, showed that significant deviations of instantaneous reactions from kinetics are to be expected in the space-time region s相似文献
4.
A complete energy balance equation was estimated for the common octopus Octopus vulgaris at a constant temperature of 20°C, fed ad libitum on anchovy fillet (Engraulis encrasicolus). Energy used for growth and respiration or lost with faeces and excreted ammonia was estimated, along with total energy
consumption through food, for six specimens of O. vulgaris (with masses between 114 and 662 g). The energy balance equation was estimated for the specimens at 10-day intervals. During
each 10-day interval, food consumed, body mass increase and quantity of faeces voided were measured. The calorific values
of octopus flesh, anchovy flesh and faeces were measured by bomb calorimetry. Oxygen consumption and ammonia excretion rates
were monitored for each specimen during three 24-h experiments and daily oxygen consumption and ammonia excretion were estimated.
It was found that 58% of the energy consumed was used for respiration. The amount of energy invested in somatic and gonadal
growth represented 26% of the total energy budget. The energy discarded through faeces was 13% of consumed energy. The estimated
assimilation efficiency (AE) values of O. vulgaris feeding on anchovy (80.9–90.7%) were lower than the AE values estimated for other cephalopod species with different diets
of lower lipid content such as crabs or mussels. Specific growth rates (SGR) ranged 0.43–0.95 and were similar to those reported
for other high-lipid diets (bogue, sardine) and lower than SGR values found for low-lipid, high-protein diets (squid, crab,
natural diet). Ammonia excretion peak (6 h after feeding) followed the one of oxygen consumption (1 h after feeding). The
values of atomic oxygen-to-nitrogen (O:N) ratio indicated a protein-dominated metabolism for O. vulgaris. 相似文献
5.
Stelios Katsanevakis 《Marine Biology》2007,152(6):1319-1331
The temporal patterns and the effect of shell size and depth on growth and mortality rates of the endangered fan mussel Pinna nobilis were investigated in the marine Lake Vouliagmeni (Korinthiakos Gulf, Greece). A total of 160 individuals were tagged and
monitored monthly for a period of 17 months. At each visit, the size of the tagged individuals (shell width, w) was measured in situ and recorded. Any mortality event was also recorded and attributed to natural causes or (illegal) fishing.
Growth and mortality rates were modeled with generalized additive models, which are non-parametric flexible models that free
the researcher from the limiting concept of a strict parametric shape. The use of GAMs allowed the exploration of shapes of
growth and mortality response curves in relation to predictor variables and allowed the fitting of statistical models that
better agree with ecological theory. Growth rates had a seasonal pattern, with an extended period of very slow growth between
late autumn and early spring, i.e., during the cold season, another short period of slow growth during August (when water
temperatures reached their maximum values exceeding 29°C), and a peak in growth rates during late spring–early summer, probably
related to an optimum combination of temperature and food availability. Growth rates varied with shell size, with a peak at
w ∼4.5 cm, followed by a sharp decline to an approximately constant level, with sizes ranging from 9 to 15 cm, and a further
decline with larger sizes down to almost zero for w > 20 cm. Growth rates did not vary substantially with depth. Although P. nobilis is a protected species in the EU and its fishing is strictly prohibited, fishing mortality was very high in Lake Vouliagmeni
(much greater than natural mortality), especially during the hot season when the lake was crowded by summer visitors. The
fan mussels were poached exclusively by free-diving and due to the high turbidity of the lake’s water, fishing mortality was
higher in shallow areas (and mostly for large individuals) and was practically zero at depths >9 m. Due to fishing mortality,
a size segregation of P. nobilis was observed in the lake: large individuals were restricted to deeper areas, while young and small individuals were more
abundant in shallow areas where there was preferential recruitment. Natural mortality was strikingly size dependent and P. nobilis suffered high natural mortality during the first year of life; the probability of death by natural causes quickly diminished
as the fan mussels grew in size. No depth-related differences in natural mortality were found. 相似文献
6.
Classic and centrifugal olive oil mill wastewater volumes of 1.18 and 1.68m3/Mg olives and corresponding polluting loads of 37 and 53 Kg BOD5 and 82 and 121 Kg COD/Mg olives were established in a systematic study of 15 mills. Lime treatment at an optimum pH level near 11 requiring a dose less than 10g/l effected COD removals from 15 to 22% for classic and from 33 to 46% for centrifugal mill waste. The volume of resulting sludge was large and could not be adequately handled by sedimentation; the sludge had good dewatering characteristics and was amenable to simple straining. Excess lime treatment using up to 50 g/l lime offered little additional benefit. 相似文献
7.
Stelios Katsanevakis 《Marine Biology》2009,156(8):1715-1732
A metapopulation, time-invariant, stage-classified matrix model was developed to assess the dynamics of an important Pinna nobilis population in the marine Lake Vouliagmeni (Korinthiakos Gulf, Greece). The main aim of the study was to provide insight on
the life cycle of the fan mussel and reveal influential factors for its population dynamics, with a special focus on the effect
of poaching. The size of the fan mussel shell was selected as a state variable, and the model consisted of five size classes.
The lake was divided in two regions, a shallow region of high (illegal) fishing mortality and high recruitment (region 1)
and a deeper region of low mortality and low recruitment (region 2). The estimation of the transition matrix (stage-specific
growth and mortality probabilities) was based on a tagging survey between 2005 and 2006, while independent annual surveys
for abundance estimation using distance sampling techniques were utilized for the estimation of recruitment and stage-specific
fertilities. The population was found to be increasing with an intrinsic rate of increase r = 0.038; however, r was not statistically different from zero. The life expectancy and expected lifetime offspring production of individuals
in region 1 was markedly lower than that of individuals in region 2. Due to poaching, the life expectancy of a yearling fan
mussel was less than 2.5 years in region 1, while it was almost 12 years in region 2. The highest expected annual natural
mortality of fan mussels occurred on their first year of life after settlement (~43%) and greatly declined at greater sizes.
Perturbation analysis revealed that the population growth rate was most sensitive to the vital rates of the larger size classes
in region 2 and to fertilities corresponding to offspring that settled in the same region. The spatial distribution and abundance
of the species was greatly dependent on the extent of poaching, which caused a size segregation of individuals, with small
and young individuals being abundant in region 1, and larger and older individuals being restricted in region 2. If poaching
ceased, the fan mussel population would be increasing with a significantly higher intrinsic rate of increase (r = 0.186), while if region 2 was also illegally exploited at the same intensity as region 1, the fan mussel population would
be decreasing with r = −0.364 and would eventually collapse. The existence of refuge areas, where fan mussels may grow and reproduce, providing
adjacent areas with offspring, seems crucial for the viability of local populations. Transplantation of fan mussels from high
mortality areas to low mortality refuges might prove to be an effective measure to protect local populations of the species. 相似文献
8.
Stelios Katsanevakis Maria Thessalou-Legaki Constantina Karlou-Riga Eugenia Lefkaditou Evagelos Dimitriou George Verriopoulos 《Marine Biology》2007,151(3):949-959
Allometric growth investigations are usually conducted by fitting the allometric model (L)
(y, x are morphometric characters and b the allometric exponent), which is quite simple both conceptually and mathematically, and its parameters are easy to estimate
by linear regression. However b is not necessarily constant and it may change either continuously or abruptly at specific breakpoints; thus, the simple L
model quite often fails to describe allometric growth successfully. In the current context, a better alternative is proposed,
based on Kullback–Leibler (K-L) information theory and multi-model inference (MMI). Allometric growth was investigated in
eight marine species: the bivalves Pecten jacobaeus and Pinna nobilis, the squids Todarodes sagittatus and Todaropsis eblanae, the crab Pachygrapsus marmoratus (females), the ghost shrimp Pestarella tyrrhena (males), and the fishes Trachurus trachurus and Sparus aurata. In each of the eight species, a pair of body parts was measured and the allometric growth of one body part in relation to
the other (reference dimension) was studied, by fitting five different candidate models including: the simple allometric model,
two models assuming that b changed continuously and two other assuming that b had a breakpoint. For each species, the ‘best’ model was selected by minimizing the small-sample, bias-corrected form of
the Akaike Information Criterion. To quantify the plausibility of each model, given the data and the set of five models, the
‘Akaike weight’ w
i
of each model was calculated; based on w
i
the average model was estimated for each case. MMI is beneficial, more robust, and may reveal more information than the classical
approach. As demonstrated with the given examples, estimation of b from the linear model, when it was not supported by the data, revealed some characteristic pitfalls, such as concluding positive
allometry when there is actually negative or vice versa, or reporting allometry when the data in reality support isometric
growth or vice versa. 相似文献
9.
Towards a framework for assessment and management of cumulative human impacts on marine food webs 下载免费PDF全文
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
10.
Francesca Gatto Stelios Katsanevakis Jochen Vandekerkhove Argyro Zenetos Ana Cristina Cardoso 《Environmental management》2013,51(6):1137-1146
Europe is severely affected by alien invasions, which impact biodiversity, ecosystem services, economy, and human health. A large number of national, regional, and global online databases provide information on the distribution, pathways of introduction, and impacts of alien species. The sufficiency and efficiency of the current online information systems to assist the European policy on alien species was investigated by a comparative analysis of occurrence data across 43 online databases. Large differences among databases were found which are partially explained by variations in their taxonomical, environmental, and geographical scopes but also by the variable efforts for continuous updates and by inconsistencies on the definition of “alien” or “invasive” species. No single database covered all European environments, countries, and taxonomic groups. In many European countries national databases do not exist, which greatly affects the quality of reported information. To be operational and useful to scientists, managers, and policy makers, online information systems need to be regularly updated through continuous monitoring on a country or regional level. We propose the creation of a network of online interoperable web services through which information in distributed resources can be accessed, aggregated and then used for reporting and further analysis at different geographical and political scales, as an efficient approach to increase the accessibility of information. Harmonization, standardization, conformity on international standards for nomenclature, and agreement on common definitions of alien and invasive species are among the necessary prerequisites. 相似文献