An inverse model for the analysis of the Venice lagoon food web

A steady-state model of the Venice lagoon food web was constructed, based on a comprehensive set of data, which were collected in the years 2001-2005. Energy flows were estimated by means of an inverse methodology of constrained optimization based on the Minimum Norm criterion, i.e. on the minimization of both the sum of squares of the residuals and of the sum of squares of energy flows. The solution was constrained by a set inequalities, which were derived from general eco-physiological knowledge and site specific data on energy flows. The trophic network was represented by thirty-two nodes, including single-species compartments for the species of high economical or ecological relevance. Mass balance equations were weighted, in order to obtain meaningful results in presence of large differences, up to 5 orders of magnitude, among biomasses. A perturbation technique was applied, with the purpose of reducing the risk of finding solutions heavily affected by the set of constraints and of obtaining a more robust representation of the energy flows. The main patterns of energy flow are consistent with those obtained in previous attempts at modelling the Venice lagoon food web. Micro- and macro-phytobenthos account for the largest fraction of the primary production. Energy is then transferred towards higher trophic levels by means of two main pathways: the recycling of dead biomass through the detritus compartment and the direct consumption by grazers. The first pathway is the most important and accounts for approximately two/thirds of the energy transferred to the second trophic level.     

Defining and modelling the coastal zone affected by the Po river (Italy)

One of the most important sources of pollution in coastal zones (CZ) is certainly that one produced by human activities in the associated river basin. Understanding the linkage between water quality in CZ and river catchments is important in order to better assess CZ processes and to evaluate different management options aimed at improving the coastal ecosystem state. CZ water quality targets as identified by the Water Framework Directive (EC 2000/60) require an accurate study of the effects of pollutant loads coming from river discharge.In order to evaluate the impacts of human activities in river catchments on the associated coastal zone, a sound definition for this geographic area is needed. Many definitions for this area have been proposed in different contexts. The definition is generally built upon a particular goal, and is henceforth highly variable according to the different purposes. In this paper a general methodology allowing to discern those areas of the sea that are directly influenced by fluvial discharge is presented. The methodology is based on the variation pattern of sea water characteristics, and provides a numerical evaluation of this influence. In particular an analysis based on salinity as tracer, results in a sound definition of this area. The methodology has been applied on the case study of the Po river. Due to the significant nutrient loads discharged by the river, the CZ associated with Po is affected by severe eutrophication phenomena that have important consequences on the ecosystem and on the socio-economy of the area.In order to study the impacts of nutrients loads carried by the river, a water quality model (WASP6) has been implemented. The model simulates the seasonal variability of nutrient concentrations, phytoplankton biomass and dissolved oxygen. Using the CZ model is possible to compare the effects of variations of nutrient loads on the biochemical (short term) and ecological (long term) quality of the coastal environment. This is accomplished by feeding nutrients loads forecasted for different scenarios by the catchment model (MONERIS) as forcing functions to the CZ model. This way the effect of the different catchment management scenarios are propagated to the CZ model, and the trophic conditions of the coastal ecosystem evaluated using TRIX.This study has been developed in the context of the European project EUROCAT.     

Reinvigorating the sustainable development research agenda: the role of the sustainable development goals (SDG)

The United Nations Sustainable Development Goals (UN SDGs) contain a set of 17 measures to foster sustainable development across many areas. It offers a good opportunity to reinvigorate sustainable development research for two main reasons. First, it comprises many areas of SD research, which have become mainstream thanks to the UN SDGs. Second, the fact that the UN and its member countries have committed to attaining SDGs by 2030 has added a sense of urgency to the need to perform quality research on SD on the one hand, and reiterates the need to use the results of this research on the other. Even though the basic concept of sustainability goes back many centuries, it has only recently appeared on the international political agenda. This is partly due to an awakening of the fact that the human ecological pressure on the planet is still much larger than what nature can renew or compensate for. Based on this state of affairs, this paper presents an outline of the process leading to the agreement on the UN SDGs, and looks at some of the ecological aspects as a result of continued pressure of human activities on natural resources. Furthermore, a set of research needs is proposed – also based holistically on updated research trends – discussing the degree of urgency of some measures and explaining why the UN SDGs need to be accorded greater priority in international sustainable development research efforts.     

Forest Management Patterns in the Floodplain of the Amazon Estuary

In the Amazon basin, few studies have focused on environmentally sound land-use alternatives that are linked to markets. This paper analyzes land uses carried out by traditional inhabitants ( ribeirinhos ) on three islands in the Amazon estuary. Management of the native floodplain forest is the most extensive form of land use on these islands. Such management varies in response to local economic and ecological conditions but invariably targets key nontimber forest resources destined for local markets, requires minimal input of labor and capital, and maintains a considerable stock of biotic resources. While restricted to a specific forest type, this form of land use is associated with relatively high population densities and, if supported by appropriate development policies, could provide an environmentally sound land-use alternative for hundreds of thousands of rural inhabitants of Amazonia.     

Notes on the benthic bionomy of the N-NE Brazilian shelf

This paper deals with the bionomy of the sea bottoms of the N-NE Brazilian continental shelf, between Cape Orange and the State of Sergipe, south of São. Francisco River. It is based on data collected by the Instituto Oceanográfico, Recife, Brazil, during several surveys conducted in that area. Special emphasis is placed on the characteristics of the bottom, chiefly surveyed by means of dredging, as well as on the biological populations living on the different substrata. The sector of Recife, investigated in more detail, provides a general scheme of population delimitation. The study is applicable to the rest of the N-NE Brazilian region. The great extent of the mud or muddy sand bottoms gives the Amazonian coasts a very typical aspect. The rest of the area is remarkable for the predominance of calcareous algae of the Melobesiae group. Some biogeographical considerations are presented regarding the northern and southern limits of the NE Brazilian region. Finally, it is attempted to define the bionomical significance of the bottoms studied, comparing them with similar and better knwon biotopes from the Mediterranean Sea and SW Indian Ocean.Based on recent data collected by the Instituto Oceanográfico, Recife, Brazil.     

Multiple mating and the evolution of social behavior in the hymenoptera

Summary The data on the frequency of mating by queens of eusocial Hymenoptera are reviewed.It is pointed out that the issue of sperm clumping is probably irrelevant to the evolution of eusociality.The hypothesis is presented that multiple mating is an adaptation for maintaining large colonies. In ants there is a significant relation between the size of the colony and the frequency of mating.The effect of multiple mating on the spread of a gene for worker behavior is explored. If a female mates twice, the effective number of matings is less than two except in the case of identical sperm contribution by the males.Sperm bias is defined as the contribution of unequal amounts of sperm by the males that mate with a queen. Sperm bias can be produced as a sampling phenomenon, by inter-male competition for females and by sperm competition.The relation between the ergonomic efficiency of the workers at the production of reproductives and the number of matings that is consistent with the evolution of eusociality is derived. If workers are only about 10% more efficient at producing reproductives within a eusocial colony than they are solitarily, then two matings by the queen will still produce a selective advantage to eusocial behavior.     

Effects of Grazing on the Demography and Growth of the Texas Tortoise

Abstract: Considerable effort has been exerted in attempts to understand the complex ecological effects of grazing. North American tortoises, by virtue of their distribution, provide a good model taxon through which to study how grazing effects vary with grazing regime, habitat, and climate. We studied the Texas tortoise (  Gopherus berlandieri ) , which is restricted primarily to privately owned rangelands of southern Texas and northeastern Mexico. Management of this species is hampered by a lack of information on the effects of common land-use practices. We evaluated the effects of moderate grazing by cattle (short-duration, winter-spring rotational grazing regime; 6–28 animal-unit days/ha/year) on this tortoise by comparing two grazed and two ungrazed sites in the Western Rio Grande Plains, Texas ( U.S.A.), from April 1994 to October 1997. We made 132 captures of 106 individuals in the ungrazed pastures and 324 captures of 237 individuals in the grazed pastures. We also radiotracked 22 tortoises in the ungrazed pastures and 25 tortoises in the grazed pastures. Comparisons of relative abundance, body-size distribution, age distribution, body mass, sex ratio, adult survival, proportion of juveniles, and growth rates revealed no differences (  p > 0.05 for all parameters) between tortoises on grazed and ungrazed areas. Based on these results, we suggest that moderate grazing by cattle is not incompatible with maintenance of Texas tortoise populations. Our data were consistent with a general model of tortoise biogeography and tolerance of disturbance which suggests that Texas tortoises are tolerant to intermediate levels of disturbance. Generalities about the effect of cattle grazing on the four North American tortoises should be avoided unless they can be placed in the context of grazing regime, precipitation, habitat quality, and tortoise requirements.     

Assessing the parameterisation of the settling flux in a depth-integrated model of the fate of decaying and sinking particles, with application to fecal bacteria in the Scheldt Estuary

The fate of reactive tracers is often modelled by depth-averaged equations. When integrating the depth-resolved equations, it appears that the term describing the settling of particles is dependent on the concentration just above the bottom. Because in a depth-averaged framework this quantity is not available, the settling term needs to be parameterised. The most natural choice is to make the settling flux dependent on the average concentration. This approximation is acceptable if the water column is well mixed, but these conditions are not necessarily met in real applications. Therefore, this study aims at assessing and understanding the error made by using a depth-averaged model in a range of realistic conditions. For the definition of these conditions, typical values for the Scheldt Estuary and the Dutch-Belgian coast were taken. The realistic inspiration for the reactive tracer in this study is the fecal bacterium Escherichia coli, whose own dynamics are characterised by settling and gradual decay by mortality. In an attempt to understand the relative importance of several factors like settling, mortality, mixing and stratification on the error made by a depth-averaged approach, a number of simplified test cases were investigated. It follows that, as expected, the error is acceptable if the situation is mixing-dominated. However, the effect of mortality and stratification was less obvious in advance. For instance, it appeared that errors can also be significant if settling and mortality have the same characteristic timescales. Stratification often has the effect to increase the error made by the depth-averaged model.     

Reframing the concept of alternative livelihoods

Alternative livelihood project (ALP) is a widely used term for interventions that aim to reduce the prevalence of activities deemed to be environmentally damaging by substituting them with lower impact livelihood activities that provide at least equivalent benefits. ALPs are widely implemented in conservation, but in 2012, an International Union for Conservation of Nature resolution called for a critical review of such projects based on concern that their effectiveness was unproven. We focused on the conceptual design of ALPs by considering their underlying assumptions. We placed ALPs within a broad category of livelihood‐focused interventions to better understand their role in conservation and their intended impacts. We dissected 3 flawed assumptions about ALPs based on the notions of substitution, the homogenous community, and impact scalability. Interventions based on flawed assumptions about people's needs, aspirations, and the factors that influence livelihood choice are unlikely to achieve conservation objectives. We therefore recommend use of a sustainable livelihoods approach to understand the role and function of environmentally damaging behaviors within livelihood strategies; differentiate between households in a community that have the greatest environmental impact and those most vulnerable to resource access restrictions to improve intervention targeting; and learn more about the social–ecological system within which household livelihood strategies are embedded. Rather than using livelihood‐focused interventions as a direct behavior‐change tool, it may be more appropriate to focus on either enhancing the existing livelihood strategies of those most vulnerable to conservation‐imposed resource access restrictions or on use of livelihood‐focused interventions that establish a clear link to conservation as a means of building good community relations. However, we recommend that the term ALP be replaced by the broader term livelihood‐focused intervention. This avoids the implicit assumption that alternatives can fully substitute for natural resource‐based livelihood activities.     

Comparison of exergy found by a classical thermodynamic approach and by the use of the information stored in the genome

It is possible to calculate the exergy for organisms based on classic thermodynamics as already demonstrated by Mejer and Jorgensen [Mejer, H., Jorgensen, S.E., 1979. Exergy and ecological buffer capacity. State-of-the-art in Ecol. Model. 7, 829–846]. The calculation of exergy as eco-exergy, which is based on the information stored in the genome, has lately been proposed by Jørgensen and co-workers. Recently, Ludovisi [Ludovisi, A., 2009. Exergy vs information in ecological successions: interpreting community changes by a classical thermodynamic approach. Ecol. Model. 220, 1566–1577] has put forward a method based on classical thermodynamics, which leads to the calculation of “virtual” values of concentration at equilibrium for a number of organic compounds (VEC) and freshwater organisms (VECE). This paper compares the two approaches by analysing the correlation existing between the VECE- and the β-values derived by Jørgensen et al. [Jørgensen, S.E., Ladegaard, N., Debeljak, M., Marques, J.C., 2005. Calculations of exergy for organisms. Ecol. Model. 185, 165–175]. It was found that there was a good correlation, which can be useful for estimating β-values for organisms whose genome is not known in a sufficient detail. The relationship between VECE- and β-values suggests that two proposed thermodynamic orientors based on these quantities – the eco-exergy index and the structural information – should lead to coherent results when applied to the evaluation of the development state of ecosystems. A numerical simulation shows that this expectation is verified in a major case, but also that different, even opposite, responses can arise, depending on the biological composition of the biocoenosis investigated.     

Modelling the movement and survival of the root-feeding clover weevil,Sitona lepidus,in the root-zone of white clover

White clover (Trifolium repens) is an important pasture legume but is often difficult to sustain in a mixed sward because, among other things, of the damage to roots caused by the soil-dwelling larval stages of S. lepidus. Locating the root nodules on the white clover roots is crucial for the survival of the newly hatched larvae. This paper presents a numerical model to simulate the movement of newly hatched S. lepidus larvae towards the root nodules, guided by a chemical signal released by the nodules. The model is based on the diffusion–chemotaxis equation. Experimental observations showed that the average speed of the larvae remained approximately constant, so the diffusion–chemotaxis model was modified so that the larvae respond only to the gradient direction of the chemical signal but not its magnitude. An individual-based lattice Boltzmann method was used to simulate the movement of individual larvae, and the parameters required for the model were estimated from the measurement of larval movement towards nodules in soil scanned using X-ray microtomography. The model was used to investigate the effects of nodule density, the rate of release of chemical signal, the sensitivity of the larvae to the signal, and the random foraging of the larvae on the movement and subsequent survival of the larvae. The simulations showed that the most significant factors for larval survival were nodule density and the sensitivity of the larvae to the signal. The dependence of larval survival rate on nodule density was well fitted by the Michealis–Menten kinetics.     

Determination of metallic cobalt in the atmosphere

Due to the fact that, among the different chemical species, metallic cobalt is characterized by the highest toxicity, in this paper is proposed a procedure for its determination in the atmospheric paniculate. The air is filtered on a cellulose or glass fiber membrane, to collect the paniculate containing among the other species, metallic cobalt: the determination is based on a selective dissolution of the metallic cobalt possibly present followed by its determination by atomic absorption spectroscopy. The typical interferences that can be present in the matrix are discussed and suggestions for their minimisation are proposed. By the following procedure is also possible to determine separately the sum of the insoluble and water soluble cobalt compounds.     

Conservation of the Northern Spotted Owl under the Northwest Forest Plan

Abstract:  Development of the Northwest Forest Plan (NWFP) was motivated by concerns about the overharvest of late-seral forests and the effects of intensive forest management on the long-term viability of the Northern Spotted Owl ( Strix occidentalis caurina ). Following several years of intense political and legal debates, the final NWFP was approved in 1994. Even though the plan evolved with a broad ecosystem perspective, it remained anchored in the Spotted Owl reserve design proposed in 1990. Based on a criterion of stable or increasing populations, a decade later it remains unclear whether the enactment of the NWFP has improved the conservation status of Spotted Owls. The results of intensive monitoring of several Spotted Owl populations for over a decade suggest a continuing range-wide decline even though rates of timber harvest have declined dramatically on federal lands. The cause of the decline is difficult to determine because the research needed to establish cause and effect relations has not been done. One plausible hypothesis is that the owl's life history greatly constrains its rate of population growth even when habitat is no longer limiting. Since enactment of the NWFP, new threats have arisen, including the movement of Barred Owls ( S. varia ) into the range of the Spotted Owl, political pressure to increase levels of timber harvest, and recent changes to forest laws that eliminate the requirement to assess the viability of wildlife populations on U.S. Department of Agriculture Forest Service lands. At this time is appears that Spotted Owl conservation rests critically on continued implementation of the protections afforded by the NWFP and the U.S. Endangered Species Act.     

Factors affecting the feeding rate of the winkle Littorina littorea

The winkle Littorina littorea (L.) feeds mainly when moistened by the tide and is quiescent when exposed to the drying effects of the wind and sun. Upper shore winkles thus experience a reduced feeding time compared with individuals living lower in the intertidal zone, but are able to completely compensate by an increased rate of radular activity when immersed. The rate of radular activity is influenced by the body size of winkles, by experimental temperature and by acclimation temperature, but is mainly modified by the duration of exposure to air which directly controls the rate of radular activity on immersion.     

The influence of odour on the oviposition behaviour of the cabbage root fly

Summary. Host plant odours are known to be important in long-range host location by the cabbage root fly, whereas at short distances orientation is mainly visual. We show that olfaction also plays a significant role after a fly lands on a plant and before it moves down onto the soil to oviposit. Host plant acceptance by the cabbage root fly seems to result from a synergistic response to simultaneously perceived olfactory and contact chemostimulation. Received 12 May 1999; accepted 24 July 1999     

The role of the cloud optical thickness in the attenuation of the solar ultraviolet radiation reaching the ground: Implications to the human health impacts

Cloud optical depth, as it is derived from the King's method, is compared with that deduced from the simple two stream approximation for the greater Athens, Greece area. The results show that King's method overestimates the cloud optical thickness, in comparison to the two stream approximation. These estimations were also compared with satellite observations provided by the International Satellite Cloud Climatology Project. This comparison showed that there are large deviations between ground‐based and satellite observations. These deviations are probably due to the uncertainty introduced by the integration procedure of the satellite spatial analyzing resolution (distinctness). Furthermore, values of the simple scattering albedo were calculated by employing a recently proposed theoretical method and using the solar ultraviolet irradiance measurements performed at the Athens University on a routine basis. These results are of great importance for the densely populated areas like Athens, in a sense of health impacts, from enhanced incident solar ultraviolet radiation.     

Development and functions of the shell sculpture of the marine snail Ceratostoma foliatum

The shell of the adult Ceratostoma foliatum (Gmelin) is characterized by three varices with foliations, and a tooth on the anterior portion of the outer lip. These features are derived gradually from the markedly different sculpture of shells of small juveniles (a network of fine axial and spiral cords). The sculpture changes as the thin, cord-like basic varix is elaborated, reinforced, and modified by the development of a secondary structure (the tooth) and as the number of varices per whorl decreases. Most muricid shell patterns can be derived from juvenile patterns similar to that of C. foliatum by quantitative variations in these four processes. Likely functions of the complex and varied muricid shell structures include stabilization in shifting substrates, defense against predators, and strengthening of the shell. Different functions and shell-growth patterns are likely for the different types of varices. Shell structures are most elaborate on shells of adults. A structure's functions are likely to change as the structure becomes more complex on each successive whorl. The functional period in an individual's lifespan is consequently restricted by the pattern of growth, the rate of structural development, and the rate of shell erosion.     

Assessing the risk of soil contamination in the Swiss Jura using indicator geostatistics

The probability that the concentrations of toxic substances in soil or other medium exceed tolerablemaxima at any unsampled place can be estimated by indicator geostatistics. The method is developed and used to estimate and map the risk of contamination by cadmium, copper and lead in the topsoil of a 14.5 km 2 region in the Swiss Jura. It combines both direct measurements of metal concentrations and thecalibration of a geological map, and it shows that the risk of toxicity is least on Argovian rocks. Two approaches are proposed to divide a region into safe' and 'hazardous' zones on the basis of probability maps. The first declares as contaminated all places where the risk of contamination exceeds a given threshold. The second approach first evaluates the financial costs that might result from a wrongdeclaration, after which the site is allocated to a class so as to minimize that cost. The risk of exposure for humans and animals is generally greater for contaminated agricultural land than for forest soil, and so land use is taken into account in both procedures.     

Influence of sex and age on the feeding habits of the common soleSolea solea

The lethal concentration of cadmium was determined for the mysidLeptomysis lingvura G.O. Sars, a Mediterranean species from surface coastal waters, and the effect of sublethal doses on respiration, ammonia excretion, and feeding efficiency at different temperatures, and on activities of 19 hydrolases was tested. Experiments were carried out on individuals collected in spring 1987 near Marseille. At 18°C, respiration rate was significantly affected only by concentrations >0.05 mg Cd l^–1. At 0.1 mg Cd l^–1, respiration rate was more significantly depressed at 20°C than at 10°C. There was a concomitant decrease in the Q₁₀ rate (by 23 to 59%, according to the particular experiment), indicating a strong synergistic effect of temperature. Ammonia excretion was likewise affected by cadmium, also with a concomitant decrease in the Q₁₀ rate (by 34%). Daily faecal pellet production was maximum at 18°C; it was inhibited by cadmium at temperatures between 14 and 20°C, and enhanced at extreme temperatures (10 and 22°C). The assimilation efficiency of contaminated individuals was reduced by 9%. These decreases in faecal pellet production and assimilation efficiency reflect a significant decrease in energy (by about 43%) which could rapidly lead to an unbalanced energy budget with a consecutive lowering of the reproductive potential. Generally, hydrolase activities usually increased initially in the presence of 0.2 mg Cd l^–1, but after 48 h they declined, reaching very low values at 72 h. Most physiological processes are therefore affected by exposure to cadmium and the unbalanced energy budget arises from the inability to utilize environmental food. These results are consistent with the literature data on cadmium contamination in marine organisms. Physiological and biochemical changes appear to be very informative in studies of in vitro sublethal effects of micropollutants and in situ environmental modifications.     

Sampling animal association networks with the gambit of the group

Ecologists increasingly use network theory to examine animal association patterns. The gambit of the group (GoG) is a simple and useful assumption for accumulating the data necessary for a network analysis. The gambit of the group implies that each animal in a group is associating with every other individual in that group. Sampling is an important issue for networks in wild populations collected assuming GoG. Due to time, effort, and resource constraints and the difficulty of tracking animals, sampled data are usually a subset of the actual network. Ecologists often use association indexes to calculate the frequency of associations between individuals. These indexes are often transformed by applying a filter to produce a binary network. We explore GoG sampling using model networks. We examine assortment at the level of the group by a single dichotomous trait, along with many other network measures, to examine the effect of different sampling regimes, and choice of filter on the accuracy and precision with which measures are estimated. We find strong support for the use of weighted, rather than filtered, network measures and show that different filters have different effects depending on the nature of the sampling. We make several practical recommendations for ecologists planning GoG sampling.