How robust are observed and simulated precipitation responses to tropical ocean warming?

Robust responses and links between the tropical energy and water cycles are investigated using multiple datasets and climate models over the period 1979-2006. Atmospheric moisture and net radiative cooling provide powerful constraints upon future changes in precipitation. While moisture amount is robustly linked with surface temperature, the response of atmospheric net radiative cooling, derived from satellite data, is less coherent. Precipitation trends and relationships with surface temperature are highly sensitive to the data product and the time-period considered. Data from the Special Sensor Microwave Imager (SSM/I) produces the strongest trends in precipitation and response to warming of all the datasets considered. The tendency for moist regions to become wetter while dry regions become drier in response to warming is captured by both observations and models. Citation: John, V. O., R. P. Allan, and B. J. Soden (2009), How robust are observed and simulated precipitation responses to tropical ocean warming?

Global ocean warming tied to anthropogenic forcing

Observed global ocean heat content anomalies over the past five decades agree well with an anthropogenically forced simulation using the European Center/Hamburg coupled general circulation model (GCM) ECHAM4/OPYC3 considering increasing greenhouse gas concentrations, the direct and indirect effect of sulphate aerosols, and anthropogenic changes in tropospheric ozone. An optimal detection and attribution analysis confirms that the simulated climate change signal can be detected in the observations in both the upper 300 m and 3000 m of the water column and that the observed changes in ocean heat content are consistent with those expected from the anthropogenically forced GCM integration. This suggests that anthropogenic forcing is a likely explanation for the observed global ocean warming over the past five decades.

Escape performance of temperate king scallop, Pecten maximus under ocean warming and acidification

Among bivalves, scallops are exceptional due to their capacity to escape from predators by swimming which is provided by rapid and strong claps that are produced by the phasic muscle interspersed with tonic muscle contractions. Based on the concept of oxygen and capacity-limited thermal tolerance, the following hypothesis was tested: ocean warming and acidification (OWA) would induce disturbances in aerobic metabolic scope and extracellular acid-case status and impair swimming performance in temperate scallops. Following long-term incubation under near-future OWA scenarios [20 vs. 10 °C (control) and 0.112 kPa CO2 (hypercapnia) vs. 0.040 kPa CO2 (normocapnic control)], the clapping performance and metabolic rates (MR) were measured in resting (RMR) and fatigued (maximum MR) king scallops, Pecten maximus, from Roscoff, France. Exposure to OA, either alone or combined with warming, left MR and swimming parameters such as the total number of claps and clapping forces virtually unchanged. Only the duration of the escape response was affected by OA which caused earlier exhaustion in hyper- than in normocapnic scallops at 10 °C. While maximum MR was unaffected, warm exposure increased RMR in both normocapnic and hypercapnic P. maximus resulting in similar Q 10 values of ~2.2. The increased costs of maintenance and the observation of strongly reduced haemolymph PO2 levels indicate that at 20 °C scallops have reached the upper thermal pejus range with unbalanced capacities for aerobic energy metabolism. As a consequence, warming to 20 °C decreased mean phasic force during escape performance until fatigue. The observed prolonged recovery time in warm incubated scallops might be a consequence of elevated metabolic costs at reduced oxygen availability in the warmth.

Impacts of ocean warming and acidification on the larval development of the barnacle Amphibalanus improvisus

The world's oceans are warming and becoming more acidic. Both stressors, singly or in combination, impact marine species, and ensuing effects might be particularly serious for early life stages. To date most studies have focused on ocean acidification (OA) effects in fully marine environments, while little attention has been devoted to more variable coastal ecosystems, such as the Western Baltic Sea. Since natural spatial and temporal variability of environmental conditions such as salinity, temperature or pCO2 impose more complex stresses upon organisms inhabiting these habitats, species can be expected to be more tolerant to OA (or warming) than fully marine taxa. We present data on the variability of salinity, temperature and pH within the Kiel Fjord and on the responses of the barnacle Amphibalanus improvisus from this habitat to simulated warming and OA during its early development. Nauplii and cyprids were exposed to different temperature (12, 20 and 27°C) and pCO2 (nominally 400, 1250 and 3250 µatm) treatments for 8 and 4 weeks, respectively. Survival, larval duration and settlement success were monitored. Warming affected larval responses more strongly than OA. Increased temperatures favored survival and development of nauplii but decreased survival of cyprids. OA had no effect upon survival of nauplii but enhanced their development at low (12°C) and high (27°C) temperatures. In contrast, at the intermediate temperature (20°C), nauplii were not affected even by 3250 µatm pCO2. None of the treatments significantly affected settlement success of cyprids. These experiments show a remarkable tolerance of A. improvisus larvae to 1250 µatm pCO2, the level of OA predicted for the end of the century.

Experiment: Adaptation of a globally important coccolithophore to ocean warming and acidification

Although oceanwarming and acidification are recognized as two major anthropogenic perturbations of today's oceanswe know very little about how marine phytoplankton may respond via evolutionary change.We tested for adaptation to ocean warming in combination with ocean acidification in the globally important phytoplankton species Emiliania huxleyi. Temperature adaptation occurred independently of ocean acidifcation levels. Exponential growth rates were were up to 16% higher in populations adapted for one year to warming when assayed at their upper thermal tolerance limit. Particulate inorganic (PIC) and organic (POC) carbon production was restored to values under present-day ocean conditions, owing to adaptive evolution, and were 101% and 55% higher under combined warming and acidification, respectively, than in non-adapted controls. Cells also evolved to a smaller size while they recovered their initial PIC:POC ratio even under elevated CO2. The observed changes in coccolithophore growth, calcite and biomass production, cell size and elemental composition demonstrate the importance of evolutionary processes for phytoplankton performance in a future ocean. At the end of a 1-yr temperature selection phase, we conducted a reciprocal assay experiment in which temperature-adapted asexual populations were compared to the respective non-adapted control populations under high temperature, and vice versa (1. Assay Data, Dataset #835336). Mean exponential growth rates ? in treatments subjected to high temperature increased rapidly under all high temperature-CO2 treatment combinations during the temperature selection phase (2. time series, Dataset #835339).

Sea urchins in a high CO2 world: partitioned effects of body-size, ocean warming and acidification on metabolic rate

Body-size and temperature are the major factors explaining metabolic rate, and the additional factor of pH is a major driver at the biochemical level. These three factors have frequently been found to interact, complicating the formulation of broad models predicting metabolic rates and hence ecological functioning. In this first study of the effects of warming and ocean acidification, and their potential interaction, on metabolic rate across a broad body-size range (two-to-three orders of magnitude difference in body mass) we addressed the impact of climate change on the sea urchin Heliocidaris erythrogramma in context with climate projections for east Australia, an ocean warming hotspot. Urchins were gradually introduced to two temperatures (18 and 23 °C) and two pH (7.5 and 8.0), and maintained for two months. That a new physiological steady-state had been reached, otherwise know as acclimation, was validated through identical experimental trials separated by several weeks. The relationship between body-size, temperature and acidification on the metabolic rate of H. erythrogramma was strikingly stable. Both stressors caused increases in metabolic rate; 20% for temperature and 19% for pH. Combined effects were additive; a 44% increase in metabolism. Body-size had a highly stable relationship with metabolic rate regardless of temperature or pH. None of these diverse drivers of metabolism interacted or modulated the effects of the others, highlighting the partitioned nature of how each influences metabolic rate, and the importance of achieving a full acclimation state. Despite these increases in energetic demand there was very limited capacity for compensatory modulating of feeding rate; food consumption increased only in the very smallest specimens, and only in response to temperature, and not pH. Our data show that warming, acidification and body-size all substantially affect metabolism and are highly consistent and partitioned in their effects, and for H. erythrogramma near-future climate change will incur a substantial energetic cost.

Effects of ocean warming and acidification on the early stages of marine fishes

Tese de doutoramento, Ciências do Mar, Universidade de Lisboa, Faculdade de Ciências, 2016

Effect of ocean warming and acidification on the early life stages of subtropical Acropora spicifera

This study investigated the impacts of acidified seawater (pCO2 900 µatm) and elevated water temperature (+3 °C) on the early life history stages of Acropora spicifera from the subtropical Houtman Abrolhos Islands (28°S) in Western Australia. Settlement rates were unaffected by high temperature (27 °C, 250 µatm), high pCO2 (24 °C, 900 µatm), or a combination of both high temperature and high pCO2 treatments (27 °C, 900 µatm). There were also no significant differences in rates of post-settlement survival after 4 weeks of exposure between any of the treatments, with survival ranging from 60 to 70 % regardless of treatment. Similarly, calcification, as determined by the skeletal weight of recruits, was unaffected by an increase in water temperature under both ambient and high pCO2 conditions. In contrast, high pCO2 significantly reduced early skeletal development, with mean skeletal weight in the high pCO2 and combined treatments reduced by 60 and 48 %, respectively, compared to control weights. Elevated temperature appeared to have a partially mitigative effect on calcification under high pCO2; however, this effect was not significant. Our results show that rates of settlement, post-settlement survival, and calcification in subtropical corals are relatively resilient to increases in temperature. This is in marked contrast to the sensitivity to temperature reported for the majority of tropical larvae and recruits in the literature. The subtropical corals in this study appear able to withstand an increase in temperature of 3 °C above ambient, indicating that they may have a wider thermal tolerance range and may not be adversely affected by initial increases in water temperature from subtropical 24 to 27 °C. However, the reduction in skeletal weight with high pCO2 indicates that early skeletal formation will be highly vulnerable to the changes in ocean pCO2 expected to occur over the twenty-first century, with implications for their longer-term growth and resilience.

The effects of trans-generational exposure to ocean warming and acidification on life history and physiological traits in a marine polychaete

Human-assisted, trans-generational exposure to ocean warming and acidification has been proposed as a conservation and/or restoration tool to produce resilient offspring. To improve our understanding of the need for and the efficacy of this approach, we characterised life history and physiological responses in offspring of the marine polychaete Ophryotrocha labronica exposed to predicted ocean warming (OW: + 3 °C), ocean acidification (OA: pH -0.5) and their combination (OWA: + 3 °C, pH -0.5), following the exposure of their parents to either control conditions (within-generational exposure) or the same conditions (trans-generational exposure). Trans-generational exposure to OW fully alleviated the negative effects of within-generational exposure to OW on fecundity and egg volume and was accompanied by increased metabolic activity. While within-generational exposure to OA reduced juvenile growth rates and egg volume, trans-generational exposure alleviated the former but could not restore the latter. Surprisingly, exposure to OWA had no negative impacts within- or trans-generationally. Our results highlight the potential for trans-generational laboratory experiments in producing offspring that are resilient to OW and OA. However, trans-generational exposure does not always appear to improve traits, and therefore may not be a universally useful tool for all species in the face of global change.