Abstract Aim Temperature is fundamental to the physiological and ecological performance of marine organisms, but its role in modulating the magnitude of ecological impacts by exotic species remains unresolved. Here, we examine the relationship between thermal regimes in the range of origin of marine exotic species and sites of measured impact, after human‐induced introduction. We compare this relationship with the magnitude of impact exerted by exotic species on native ecosystems. Location Global. Time period 1977–2017 (meta‐analysis). Major taxa studied Marine exotic species. Methods Quantitative impacts of exotic species in marine ecosystems were obtained from a global database. The native range of origin of exotic species was used to estimate the realized thermal niche for each species and compared with the latitude and climatic conditions in recipient sites of recorded impact of exotic species. The difference in median temperatures between recipient sites and the thermal range of origin (i.e., thermal midpoint anomaly) was compared with the magnitude of effect sizes by exotic species on native species, communities and ecosystems. Results Recorded impacts occurred predominantly within the thermal niche of origin of exotic species, albeit with a tendency toward higher latitudes and slightly cooler conditions. The severity of impacts by exotic species on abundance of native taxa displayed a hump‐shaped relationship with temperature. Peak impacts were recorded in recipient sites that were 2.2°C cooler than the thermal midpoint of the range of origin of exotic species, and impacts decreased in magnitude toward higher and lower thermal anomalies. Main conclusions Our findings highlight how temperature and climatic context influence ecological impacts by exotic species in marine ecosystems and the implications for existing and novel species interactions under climate change.
The Novel Coronavirus (COVID-19) daily data of confirmed cases for affected countries and provinces of China reported between 31st December 2019 and 31st May 2020. The data was collected from the European Centre for Disease Prevention and Control (ECDC), and John Hopkin CSSA. The monthly mean temperature of February to May 2020 of capital cities for the various nations.
The Antarctic krill, Euphausia superba is a pelagic crustacean, abundant in high-density swarms (10 000 – 30 000 ind/m2) with a circumpolar distribution and a key role in the food web of the Southern Ocean. Only three EST derived microsatellite markers have been used in previous genetic studies, hence we developed additional highly polymorphic microsatellite markers to allow robust studies of the genetic variability and population differentiation within this species. The microsatellite markers described here were obtained through an enriched genomic library, followed by 454 pyrosequencing. A total of 10 microsatellite markers were tested in 32 individuals from the Antarctic Peninsula. One of the tested loci was fixed for one allele while the other was variable. Of the remaining nine markers, seven showed no departure from Hardy-Weinberg equilibrium. The mean number of alleles was 14.9. These markers open perspectives for population genetic studies of this species to unravel genetic structure, dispersal and population biology, vital information for future conservation.
We used data drawn from the literature to test some basic predictions derived from nutrient limitation theory. Contrary to expectation, nitrogen was not better correlated to chlorophyll in nitrogen limited lakes (as measured by the total nitrogen:total phosphorus (TN:TP) ratio). We also examined whether the variability in published relationships between chlorophyll a (Chla) and nutrient levels in lakes can be explained by differences in the relative concentrations of nitrogen and phosphorus (TN:TP ratio). Our results show that the coefficients and precision of the Chla = f(TP) and Chla = f(TN) regression equations vary systematically and concomitantly with TN:TP ratios, and are highest for lakes with TN:TP ratios of 23–28 (by weight). These findings were confirmed with independent data and explain the variability of published Chla = f(TP) relationships. We propose a model that predicts the coefficients of Chla = f(TP) and Chla = f(TN) equations for lakes with different TN:TP ratios. This model proved useful in predicting the chlorophyll trajectories of lakes over time. The results imply an "optimal" TN:TP ratio beyond which the relative rates of increase in chlorophyll with increasing nutrient concentrations are reduced.
Abstract. Seagrass meadows are autotrophic ecosystems storing carbon in their biomass and sediments, but they have also been shown to be sources of carbon dioxide (CO2) and methane (CH4). Seagrasses can be negatively affected by increasing seawater temperatures, but the effects of warming on CO2 and CH4 fluxes in seagrass meadows have not yet been reported. Here, we examine the effect of two disturbances on air-seawater fluxes of CO2 and CH4 in Red Sea Halophila stipulacea communities compared to adjacent unvegetated sediments using cavity ring-down spectroscopy. We first characterized CO2 and CH4 fluxes in vegetated and adjacent unvegetated sediments, and then experimentally examined their response, along with that of the C isotopic signature of CO2 and CH4, to gradual warming from 25 °C (winter seawater temperature) to 37 °C, 2 °C above current maximum temperature. In addition, we assessed the response to prolonged darkness, thereby providing insights into the possible role of suppressing plant photosynthesis in supporting CO2 and CH4 fluxes. We detected distinct differences between vegetated and unvegetated sediments, with the vegetated sediments supporting 6-fold higher CO2 fluxes, and 10- to 100-fold higher CH4 fluxes. Warming led to an increase in net CO2 and CH4 fluxes, reaching average fluxes of 10,422.18 ± 2,570.12 µmol CO2 m−2 d−1 and 88.11 ± 15.19 µmol CH4 m−2 d−1, while CO2 and CH4 fluxes decreased over time in sediments maintained at 25 °C. Prolonged darkness led to an increase in CO2 fluxes but a decrease in CH4 fluxes in vegetated sediments. These results add to previous research identifying Red Sea seagrass meadows as a significant source of CH4, while also indicating that sublethal warming may lead to increased emissions of greenhouse gases from seagrass meadows, providing a feedback mechanism that may contribute to further enhance global warming.
Abstract The race between pathogens and their hosts is a major evolutionary driver, where both reshuffle their genomes to overcome and reorganize the defenses for infection, respectively. Evolutionary theory helps formulate predictions on the future evolutionary dynamics of SARS-CoV-2, which can be monitored through unprecedented real-time tracking of SARS-CoV-2 population genomics at the global scale. Here we quantify the accelerating evolution of SARS-CoV-2 by tracking the SARS-CoV-2 mutation globally, with a focus on the Receptor Binding Domain (RBD) of the spike protein determining infection success. We estimate that the > 820 million people that had been infected by October 5, 2021, produced up to 10 21 copies of the virus, with 12 new effective RBD variants appearing, on average, daily. Doubling of the number of RBD variants every 89 days, followed by selection of the most infective variants challenges our defenses and calls for a shift to anticipatory, rather than reactive tactics involving collaborative global sequencing and vaccination.
The development of single clones of the seagrass Cymodocea nodosa was analysed using a growth model based on the formation of structures limited by diffusive aggregation. The model implemented the measured clonal growth rules (i.e. rhizome elongation and branching rates, branching angle, and spacer length between consecutive shoots) and shoot mortality rate for C. nodosa at Alfacs Bay (Spain). The simulated patches increased their size nonlinearly with time displaying two different domains of growth. Young patches showed a rapid increase with time of the length of rhizome network and the number of living shoots, which depended on rhizome branching rate, and increased the radial patch size (R g ) algebraically with the number of living shoots as R g ∝ N s 1/Df , being D f the fractal dimension of the patch structure. Patches older than 4 years increased the production of rhizome network and the number of living shoots much more slowly, while their radial patch size behaved as R g ∝ N s 0.5 resulting from an internal patch compactation. Moreover, the linear growth rate of the simulated patches changed up to 30 fold during patch development, increasing with increasing patch size until patches reached an intermediate size. The modelled patch development was found to closely reproduce the observed patch structure for the species at the Alfacs Bay (Spain). Hence, the growth of C. nodosa patches initially proceeds with a growth mode controlled by the branching pattern (branching frequency and angle) of the species, producing sparse and elongated patches. Once patches exceed 4–5 years of age and contained >500 shoots, becoming dense and circular, they shifts to a growth model typical of compact structures. These results explain previously unaccounted evidence of the emergence of nonlinear patch growth from simple clonal growth rules, and highlight the importance of branching frequency and angles as critical determinants of the space occupation rate of seagrasses and probably other clonal plants.
