European small pelagic fish distribution under global change scenarios

The spectre of increasing impacts on exploited fish stocks in consequence of warmer climate conditions has become a major concern over the last decades. It is now imperative to improve the way we project the effects of future climate warming on fisheries. While estimating future climate‐induced changes in fish distribution is an important contribution to sustainable resource management, the impacts on European small pelagic fish—representing over 50% of the landings in the Mediterranean and Black Sea between 2000 and 2013—are yet largely understudied. Here, we investigated potential changes in the spatial distribution of seven of the most harvested small pelagic fish species in Europe under several climate change scenarios over the 21st century. For each species, we considered eight Species Distribution Models (SDMs), five General Circulation Models (GCMs) and three emission scenarios (the IPCC Representative Concentration Pathways; RCPs). Under all scenarios, our results revealed that the environmental suitability for most of the seven species may strongly decrease in the Mediterranean and western North Sea while increasing in the Black and Baltic Seas. This potential northward range expansion of species is supported by a strong convergence among projections and a low variability between RCPs. Under the most pessimistic scenario (RCP8.5), climate‐related local extinctions were expected in the south‐eastern Mediterranean basin. Our results highlight that a multi‐SDM, multi‐GCM, multi‐RCP approach is needed to produce more robust ecological scenarios of changes in exploited fish stocks in order to better anticipate the economic and social consequences of global climate change.     

Dynamic use of coastal areas by bull sharks and the conciliation of conservation and management of negative human–wildlife interactions

1. Knowledge about spatial and temporal variability in the distribution and abundance of predators is necessary to adapt measures to mitigate human–wildlife interactions.
2. Acoustic telemetry and network analyses were used to investigate the spatial ecology of bull sharks, the species responsible for most shark bites in Reunion Island, one of the world's shark bite hotspots.
3. The west coast of the island was not used uniformly by every individual, with size predicting the movements of sharks along the coast.
4. Node-based metrics – closeness, node strength, and cumulated continuous residency times – derived from up to 181 monthly movement networks from 20 individuals, revealed that smaller sharks (<250 cm total length) primarily used the south-west coast while larger individuals spent most of their time in the northern region with regular visits to multiple areas along the coast.
5. This study provides essential knowledge on bull shark behaviour and central areas used at different periods of the year, which correlates well with the dynamics of observed shark bites. Our approach provides a non-invasive alternative to help predicting and anticipating human–shark conflicts and avoid shark culling programmes detrimental to the conservation of large predators such as sharks.

     

Use of earthworms Eisenia andrei on the bioremediation of contaminated area in north of Tunisia and microbial soil enzymes as bioindicator of change on heavy metals speciation

Purpose

A better understanding is required of the potential of soil biota in controlling the availability and mobility of heavy metals and ascertaining their toxicity. The objectives of this work are to assess, first, the modification of heavy metal speciation induced by earthworms Eisenia andrei and, second, the consequence of this metal speciation change on soil enzyme activities as an easy bioindicator of stress.

Materials and methods

The experiment was conducted on six sites from Jebel Ressas Mines, which are characterized by a gradient heavy metal contamination (Pb, Zn, and Cd). Earthworms E. andrei were introduced in these six soils for 60 days. We had performed heavy metal speciation both in the presence and absence of worms. Modifications of activities of seven enzymes implicated in C, N, and P biochemical cycles were used as a bioindicator of metal stress. We had used the co-inertia statistical method to evaluate the correlation between change in heavy metal speciation induced by earthworms and the enzyme activities in soils.

Results and discussion

Our results suggested that earthworms modified the heavy metal dynamic and speciation. They decrease the amount of metal associated with the most available fraction, such as exchangeable one, and increase the amount of metal bound to the more stable fraction, like Mn and Fe oxide ones. On the same hand, enzyme activities increased in majority of the soils, following earthworm activity, but this effect is dependent on the amount of soil contamination. Moreover, the co-inertia results denote that change in heavy metal speciation significantly influences the soil enzyme activities in Jebel Ressas soils, especially β-glucosidase, urease, deshydrogenase, and fluorescein diacetate hydrolysis (FDA), and can be considered as bioindicators of metal toxicity and biological quality in the contaminated area.

Conclusions

By reducing the availability of heavy metals, the earthworms are useful in the bioremediation of heavy metal contaminated soils. Soil enzymes β- glucosidase, urease, deshydrogenase, and FDA can be used to assess the changes in metal speciation and can let us, therefore, predict if the soils are bioremediated.

     

Identification et distribution des virus responsables de mosaiques chez les cucurbitacées en Tunisie

Les cucurbitacées sont économiquement importantes en Tunisie, elles sont sujettes à plusieurs maladies virales qui ont des effets néfastes sur les rendements et la valeur marchande de la production. Des symptômes de mosaïques sévères sur les feuilles ont été observés dans toutes les cultures de cucurbitacées de plein champ et sous abris. Des prospections (2000–2001, 2002–2003) ont été réalisées afin de tenter d’identifier les virus responsables de ces symptômes. Les échantillons symptomatiques ont été collectés dans les régions majeures de production des cucurbitacées et testés par DAS‐ELISA pour la présence des virus suivants: ZYMV, WMV, MWMV, PRSV‐W, ZYFV CMV, SqMV et MNSV. Cette étude a confirmé la présence de six virus (WMV, CMV, PRSV‐W, ZYMV, ZYFV et SqMV) déjà décrits avec une évolution très remarquable de la fréquence du ZYMV dans toutes les régions prospectées et sur toutes les espèces testées. Le pourcentage d’infection a atteint les 34% durant les prospections (2002–2003). Par contre le MWMV s’est révélé absent au niveau de tous les échantillons testés. Par ailleurs, nous avons mis en évidence pour la première fois la présence du MNSV dans plus de 9% des échantillons testés et ce sur melon de plein champ et sous abris, sur courge et sur pastèque. En outre, nous rapportons pour la première fois l’infection d’une cucurbitacée sauvage, Ecballium elaterium, par le CMV, PRSV‐W et WMV. Les résultats ont montré aussi qu’un pourcentage d’échantillons montrant des symptômes de mosaïques n’a pas été expliqué par la présence de l’un ou l’autre des virus étudiés. Ceci pourrait s’expliquer par l’existence d’autres virus ou de facteurs abiotiques qui restent à identifier.     

Effects of cadmium and copper on pollen germination and fruit set in pea (Pisum sativum L.)

In this work, pea (Pisum sativum) plants exposed to increasing cadmium and copper concentrations were tested for heavy metals accumulation in flowers and for ‘in vivo’ pollen germination. Based on the Cd and Cu accumulation amounts in the flowers, an evaluation of the same metals effects on ‘in vitro’ pollen germination was achieved. Moreover, the effects of both metals on fruits number and weight and on seed set and yield at individual plant level were examined. While cadmium concentrations did not affect ‘in vivo’ pollen germination, only higher copper concentrations rendered a significant reduction. This is in contrast with the clear negative effect on pollen germination in vitro and might be explained by the different dynamic and bioavailability of both metals. A clear effect of Cd and Cu was observed on two important yield components ie, fruit weight and seed set. Although results obtained herein cannot give a clear cut relationship between the effect of Ca and Cu on reproductive development and its consequences on yields, they represent emerging results on the potential consequences of metals contamination on reproductive development in plants.