Effect of marine heatwaves and warming on kelp microbiota influence trophic interactions.

The range-expansion of tropical herbivores due to ocean warming can profoundly alter temperate reef communities by overgrazing the seaweed forests that underpin them. Such ecological interactions may be mediated by changes to seaweed-associated microbiota in response to warming, but empirical evidence demonstrating this is rare. We experimentally simulated ocean warming and marine heatwaves (MHWs) to quantify effects on two dominant temperate seaweed species and their microbiota, as well as grazing by a tropical herbivore. The kelp Ecklonia radiata's microbiota in sustained warming and MHW treatments was enriched with microorganisms associated with seaweed disease and tissue degradation. In contrast, the fucoid Sargassum linearifolium's microbiota was unaffected by temperature. Consumption by the tropical sea-urchin Tripneustes gratilla was greater on Ecklonia where the microbiota had been altered by higher temperatures, while Sargassum's consumption was unaffected. Elemental traits (carbon, nitrogen), chemical defences (phenolics) and tissue bleaching of both seaweeds were generally unaffected by temperature. Effects of warming and MHWs on seaweed holobionts (host plus its microbiota) are likely species-specific. The effect of increased temperature on Ecklonia's microbiota and subsequent increased consumption suggest that changes to kelp microbiota may underpin kelp-herbivore interactions, providing novel insights into potential mechanisms driving change in species' interactions in warming oceans.

Persistence of seaweed forests in the anthropocene will depend on warming and marine heatwave profiles.

Marine heatwaves (MHWs), discrete periods of extreme warm water temperatures superimposed onto persistent ocean warming, have increased in frequency and significantly disrupted marine ecosystems. While field observations on the ecological consequences of MHWs are growing, a mechanistic understanding of their direct effects is rare. We conducted an outdoor tank experiment testing how different thermal stressor profiles impacted the ecophysiological performance of three dominant forest-forming seaweeds. Four thermal scenarios were tested: contemporary summer temperature (22°C), low persistent warming (24°C), a discrete MHW (22-27°C), and temperature variability followed by a MHW (22-24°C, 22-27°C). The physiological performance of seaweeds was strongly related to thermal profile and varied among species, with the highest temperature not always having the strongest effect. MHWs were highly detrimental for the fucoid Phyllospora comosa, whereas the laminarian kelp Ecklonia radiata showed sensitivity to extended thermal stress and demonstrated a cumulative temperature threshold. The fucoid Sargassum linearifolium showed resilience, albeit with signs of decline with bleached and degraded fronds, under all conditions, with stronger decline under stable control and warming conditions. The varying responses of these three co-occurring forest-forming seaweeds under different temperature scenarios suggests that the impact of ocean warming on near shore ecosystems may be complex and will depend on the specific thermal profile of rising water temperatures relative to the vulnerability of different species.

A global assessment of marine heatwaves and their drivers.

Marine heatwaves (MHWs) can cause devastating impacts to marine life. Despite the serious consequences of MHWs, our understanding of their drivers is largely based on isolated case studies rather than any systematic unifying assessment. Here we provide the first global assessment under a consistent framework by combining a confidence assessment of the historical refereed literature from 1950 to February 2016, together with the analysis of MHWs determined from daily satellite sea surface temperatures from 1982-2016, to identify the important local processes, large-scale climate modes and teleconnections that are associated with MHWs regionally. Clear patterns emerge, including coherent relationships between enhanced or suppressed MHW occurrences with the dominant climate modes across most regions of the globe - an important exception being western boundary current regions where reports of MHW events are few and ocean-climate relationships are complex. These results provide a global baseline for future MHW process and prediction studies.

Longer and more frequent marine heatwaves over the past century.

Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Recent prominent marine heatwaves have attracted considerable scientific and public interest. Despite this, a comprehensive assessment of how these ocean temperature extremes have been changing globally is missing. Using a range of ocean temperature data including global records of daily satellite observations, daily in situ measurements and gridded monthly in situ-based data sets, we identify significant increases in marine heatwaves over the past century. We find that from 1925 to 2016, global average marine heatwave frequency and duration increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days globally. Importantly, these trends can largely be explained by increases in mean ocean temperatures, suggesting that we can expect further increases in marine heatwave days under continued global warming.

Elevated CO2 levels affect the activity of nitrate reductase and carbonic anhydrase in the calcifying rhodophyte Corallina officinalis.

The concentration of CO(2) in global surface ocean waters is increasing due to rising atmospheric CO(2) emissions, resulting in lower pH and a lower saturation state of carbonate ions. Such changes in seawater chemistry are expected to impact calcification in calcifying marine organisms. However, other physiological processes related to calcification might also be affected, including enzyme activity. In a mesocosm experiment, macroalgal communities were exposed to three CO(2) concentrations (380, 665, and 1486 µatm) to determine how the activity of two enzymes related to inorganic carbon uptake and nutrient assimilation in Corallina officinalis, an abundant calcifying rhodophyte, will be affected by elevated CO(2) concentrations. The activity of external carbonic anhydrase, an important enzyme functioning in macroalgal carbon-concentrating mechanisms, was inversely related to CO(2) concentration after long-term exposure (12 weeks). Nitrate reductase, the enzyme responsible for reduction of nitrate to nitrite, was stimulated by CO(2) and was highest in algae grown at 665 µatm CO(2). Nitrate and phosphate uptake rates were inversely related to CO(2), while ammonium uptake was unaffected, and the percentage of inorganic carbon in the algal skeleton decreased with increasing CO(2). The results indicate that the processes of inorganic carbon and nutrient uptake and assimilation are affected by elevated CO(2) due to changes in enzyme activity, which change the energy balance and physiological status of C. officinalis, therefore affecting its competitive interactions with other macroalgae. The ecological implications of the physiological changes in C. officinalis in response to elevated CO(2) are discussed.

O processo de memória em jovens: o efeito do uso do computador / The memory process in young people: the effect of use of computer

O objetivo desta pesquisa foi investigar o efeito do uso do computador no processo de memória em participantes da faixa etária de 11 a 14 anos de idade. A condição memória envolveu as fases de aquisição da informação e do relembrar, nos intervalos de tempo (2 min, 24 horas e 1 semana) nas situações de pré e pós-teste (antes e após os participantes terem participado do Curso de Informática Básica). Nesta condição, os participantes estudavam o mapa do Brasil durante 7 minutos e as estimativas das diferentes áreas dos estados do Brasil foram realizadas de acordo com o método de estimação de magnitudes, sem a presença do mapa. Na condição perceptiva, as estimativas foram feitas na presença do mapa do Brasil. Através da análise de variância, os resultados evidenciaram diferenças significativas entre as condições experimentais, sendo que a Condição Experimental Perceptiva se diferenciou das demais condições. A análise da condição memória no intervalo de uma semana apresentou diferença significativa entre a situação do pré e pós-teste. Estes dados poderão contribuir na área educacional, na medida em que possibilita ao educador conhecer a forma como o aluno processa e arquiva as informações, incentivando assim o uso do computador como ferramenta pedagógica para a melhoria do processo de ensino-aprendizagem.

O processo de memória em jovens: o efeito do uso do computador / The memory process in young people: the effect of use of computer

O objetivo desta pesquisa foi investigar o efeito do uso do computador no processo de memória em participantes da faixa etária de 11 a 14 anos de idade. A condição memória envolveu as fases de aquisição da informação e do relembrar, nos intervalos de tempo (2 min, 24 horas e 1 semana) nas situações de pré e pós-teste (antes e após os participantes terem participado do Curso de Informática Básica). Nesta condição, os participantes estudavam o mapa do Brasil durante 7 minutos e as estimativas das diferentes áreas dos estados do Brasil foram realizadas de acordo com o método de estimação de magnitudes, sem a presença do mapa. Na condição perceptiva, as estimativas foram feitas na presença do mapa do Brasil. Através da análise de variância, os resultados evidenciaram diferenças significativas entre as condições experimentais, sendo que a Condição Experimental Perceptiva se diferenciou das demais condições. A análise da condição memória no intervalo de uma semana apresentou diferença significativa entre a situação do pré e pós-teste. Estes dados poderão contribuir na área educacional, na medida em que possibilita ao educador conhecer a forma como o aluno processa e arquiva as informações, incentivando assim o uso do computador como ferramenta pedagógica para a melhoria do processo de ensino-aprendizagem.