Is it possible to differentiate between environmental and fishery effects on abundance‐biomass variation? A case study of blackspot seabream (Pagellus bogaraveo) in the Strait of Gibraltar

We assessed the potential for simulation and modelling of the blackspot seabream (Pagellus bogaraveo) population in the Strait of Gibraltar to discriminate the environmental effects of fishery impacts. A discrete biomass–abundance dynamic model was implemented to obtain a simulated monthly time series of blackspot seabream biomass. On this simulated time series, autoregressive integrated moving average (ARIMA) models were fitted. The best ARIMA fit provided a significant correlation of 0.76 and persistence index higher than 0.85. The proportion of variance non‐explained by the ARIMA models was correlated with a time series of sea surface temperature (SST) and North Atlantic Oscillation (NAO). The analysis of global, annual and winter correlation between the proportion of variance not explained by the ARIMA models and environmental variables showed that significant associations were not detected over the full time series. Our analysis therefore suggests that overexploitation is the main factor responsible for the commercial depletion of blackspot seabream in the Strait of Gibraltar.     

Arbuscular mycorrhizas and performance of Polylepis australis trees in relation to livestock density

Polylepis australis trees endemic to Argentina dominate the canopy of subtropical high altitude forests. Here, livestock rearing is the main economic activity and is suspect of the low performance of P. australis trees through direct and indirect effects which could include the reduction in arbuscular mycorrhizal fungi (AMF) and their benefit to trees. To elucidate the role of AMF, we compare plant performance indicators, arbuscular mycorrhizal (AM) colonization and AMF communities in 20 trees distributed in two areas of central Argentina which differed in livestock grazing intensity. The area with high livestock density presented more soil degradation and trees with a lower overall plant performance than the area with reduced livestock density. The AM colonization values of P. australis were considerably higher than reported for other tree species and the area with high livestock density had a lower proportion of arbuscules and higher proportion of hyphae, while vesicles and AM colonization – all structure considered together – did not differ between areas. Overall AMF spore number and of most species when considered separately was significantly higher in the area with high livestock density, suggesting a high tolerance and adaptation of AMF to livestock. We conclude that a reduction in livestock improves the performance of P. australis, that this improvement could be mediated by an increase in the proportion of arbuscules, but there does not appear to be any limitation in AM colonization or AMF spore number which could otherwise be limiting forest restoration.     

Arbuscular mycorrhizal colonization of vascular plants from the Yungas forests, Argentina

In Argentina, the Yungas forests are among the ecosystems most affected by human activity, with loss of biodiversity. To assess the mycorrhizal status in these ecosystems, the roots of 41 native plant species belonging to 25 families were collected throughout the year from two sites of the Yungas forests. Roots were washed and stained to study the presence of arbuscular mycorrhizas (AM). Morphological types of arbuscular mycorrhizas (Arum and Paris-type) and colonization patterns were identified and photographed. All plants presented AM colonization. The AM colonization patterns varied from single intracellular aseptate hyphae, coils, appresoria, to vesicles and/or arbuscules. Among the species studied, the Paris-type colonization showed to be dominant. Results confirmed that AM hosts are predominant in the Yungas of South American forests.     

Ecosystem services from coffee agroforestry in Central America: estimation using the CAF2021 model

The goal of sustainable coffee production requires multiple functions from agroforestry systems. Many are difficult to quantify and data are lacking, hampering the choice of shade tree species and agronomic management. Process-based modelling may help quantify ecosystem services and disservices. We introduce and apply coffee agroforestry model CAF2021 (https://doi.org/10.5281/zenodo.5862195). The model allows for complex systems with up to three shade tree species. It simulates coffee yield, timber and fruit production by shade trees, soil loss in erosion, C-sequestration, N-fixation, -emission and -leaching. To calibrate the model, we used multivariate data from 32 different treatments applied in two long-term coffee agroforestry experiments in Costa Rica and Nicaragua. Without any further calibration, the model was then applied to agroforestry systems on 89 farms in Costa Rica and 79 in Guatemala where yields had been reported previously in farmer interviews. Despite wide variation in environmental and agronomic conditions, the model explained 36% of yield variation in Costa Rica but only 15% in Guatemala. Model analysis quantified trade-offs between yield and other ecosystem services as a function of fertilisation and shading.

     

Antioxidant and anti‐inflammatory activities of Pinus radiata bark extract in salmonid cell lines

A fish meal supply shortage is limiting aquaculture development. Currently, plant‐based proteins, such as soya bean meal, are being used as an alternative protein source, despite that such a diet can adversely affect fish, such as by inducing an inflammatory response. A possible solution is to include dietary additives in farm diets to counteract negative effects. One such solution originates from pine bark extracts, which present bioactive properties. In this study, the antioxidant and anti‐inflammatory properties of Pinus radiata bark extracts were evaluated for the first time in a salmonid cell line. This extract chemically demonstrated antioxidant activity through 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH = 58.4 ± 1.1%) and ferric ion reducing antioxidant power (FRAP = 575 ± 17 mgEqFe(II)·g extract^?1) assays. Additionally, the extract showed high flavonoid and phenolic compound contents. Up to 100 mg mL^?1, the P. radiata extract showed no cytotoxicity in the CHSE‐214 salmonid embryo cell line. Moreover, the antioxidant activity of the extract (50 μg mL^?1) was evaluated by a dichlorofluorescein (DCFH) assay in the SHK‐1 salmon cell line challenged with an oxidant stimulus (H₂O₂), showing 58.9% activity. The extract also protected DNA from oxidative damage, as observed through a comet assay. When assessing anti‐inflammatory properties in an in vitro inflammation model, the extract significantly reduced the relative expression of the pro‐inflammatory cytokines interleukin‐1β (IL‐1β), tumour necrosis factor‐α (TNF‐α) and interleukin‐8 (IL‐8) and of the inducible cyclooxygenase‐2 (COX‐2) enzyme. These results suggest a potential application of P. radiata bark extract in functional foods in aquaculture.     

The relationship of propagule pressure to invasion potential in plants

Summary The invasive potential of a species can be assessed by propagule pressure, which measures the chances for propagules of a species to find a suitable habitat for establishment and reproduction. Seeds, fruits, and vegetative structures that contribute to the propagule pressure are morphologically, physiologically and genetically different from one another, thus each kind should have a specific way of contributing to a successful invasion. In this paper we review plant traits that contribute to the propagule pressure. Seed production provides an estimate of the potential multiplication rate of the weed. However, it is gap-sensing mechanisms of seeds based on dormancy termination and germination requirements, which significantly contribute to the naturalization and invasion processes assuring a successful seedling establishment in environments of high competition. Dispersal of propagules reduces competition, mating with a sibling, and subsequent inbreeding depression, and increases colonization opportunities and range of expansion. Some of those benefits can be achieved in a population by existence of dormancy mechanisms and thus, the existence of a seed bank. Finally, vegetative propagation may ensure expansion of local populations when seedling establishment is low. Broadening the scope of traits that are considered in the breeding programs aimed at commercial production of plant propagules, to include those related to propagule pressure, is essential for adequate evaluation of invasive potential.     

Coriander essential oil composition from two genotypes grown in different environmental conditions

The objective was to study the essential oil composition of coriander fruits in plants growing in environments differing in soil conditions and weediness level. Factorial field experiments were conducted in two locations from the Rolling Pampas, Argentina, and two coriander landraces (European and Argentinean) were tested under two levels of nitrogen fertilization and weediness. Data were evaluated with uni- and multivariate techniques. The variation in the oil composition was related to the relative proportion of the constituents and not to the presence/absence of a particular component. Weather conditions in 1997 favored linalool and camphor in both landraces. Location, fertilization, and weediness also affected the chemical profile. The European landrace showed a more stable concentration of the major components than the Argentinean landrace. These results, which show the relationships between some environmental conditions and the essential oil composition, are useful in the development of innovative strategies aimed to improve oil composition and to manage crop pests.     

Effect of the density on the growth and survival of the Caribbean scallops Argopecten nucleus and Nodipecten nodosus in suspended culture

Juveniles of the Caribbean scallops Argopecten nucleus and Nodipecten nodosus were suspended in pearl nets at densities of 25%, 30% and 50% coverage of the bottom of the net (BC) during days. Additionally, adults of A. nucleus (>35 mm) were placed in lantern nets at densities of 40%, 50% and 65% BC during days. Stocking density affected the growth of animals, with higher growth rates obtained at the lower densities. Although the survival of the two scallops was not influenced at the densities studied, the 15-day net changes, and culture in water of <28 °C produced better survival of A. nucleus and N. nodosus respectively. Predators of the families Cymatiidae, Grapsidae, Portunidae, Majidae and Xanthidae were found in the culture nets of juvenile A. nucleus , but during the adult phase they were absent. Predators exhibited a dense-independent behaviour in relation to scallops. There was not any association between predator frequency and survival of A. nucleus .