Emergent effects of global change on consumption depend on consumers and their resources in marine systems

A better understanding of how environmental change will affect species interactions would significantly aid efforts to scale up predictions of near-future responses to global change from individuals to ecosystems. To address this need, we used meta-analysis to quantify the individual and combined effects of ocean acidification (OA) and warming on consumption rates of predators and herbivores in marine ecosystems. Although the primary studies demonstrated that these environmental variables can have direct effects on consumers, our analyses highlight high variability in consumption rates in response to OA and warming. This variability likely reflects differences in local adaptation among species, as well as important methodological differences. For example, our results suggest that exposure of consumers to OA reduces consumption rates on average, yet consumption rates actually increase when both consumers and their resource(s) are concurrently exposed to the same conditions. We hypothesize that this disparity is due to increased vulnerability of prey or resource(s) in conditions of OA that offset declines in consumption. This hypothesis is supported by an analysis demonstrating clear declines in prey survival in studies that exposed only prey to future OA conditions. Our results illustrate how simultaneous OA and warming produce complex outcomes when species interact. Researchers should further explore other potential sources of variation in response, as well as the prey-driven component of any changes in consumption and the potential for interactive effects of OA and warming.

Numerous studies have demonstrated direct effects of ocean acidification (OA) and warming on organismal physiology and performance (1, 2), yet forecasting the emergent ecological effects of environmental change on communities remains a challenge due to the complexity of interactions between species (3–5) and stressors (1, 2, 6–8) in functioning ecosystems. Species interactions have the potential to drive shifts in communities (5, 9–11) or buffer them (5, 12, 13) from environmental change. For example, environmentally mediated increases in growth of some algal species can lead to ecosystem shifts if they outcompete or overgrow other species (14). However, environmentally mediated increases in consumption rates of key herbivores have the potential to limit this overgrowth of algae and the associated community shift (13). Indeed, authors of several of the studies that have revealed potential emergent effects of OA (14–16) or warming (17, 18) on entire marine communities attributed the observed responses at least in part to changes in species interactions. In addition, pronounced shifts in species assemblages and ecosystems during natural, large-scale warming events are often linked to modified species interactions (19, 20). Establishing general patterns of environmental control on species interactions has thus been proposed as a promising avenue for scaling up the effects of environmental change from individuals to ecosystems (9, 21–24).Environmentally mediated changes in trophic interactions may be especially important in determining the effects of global change on ecosystems, due to their potential to have cascading effects on community structure (25, 26). OA (27, 28) and warming (29–31) are generally predicted to alter consumers’ energetic demands, although the effects on consumption will depend on the shape of the performance curves, how close current environmental temperatures are to their performance optima, the magnitude of the environmental change, and their energy allocation strategies (25). The effects of OA on consumption are more likely to vary among taxa with different traits than the effects of warming, which universally affects metabolism. For example, the effects of OA can vary with the degree of calcification or the level of mobility of a given species (1, 2). However, the ability of consumers in nature to sufficiently compensate for changes in energetic demands associated with either OA or warming through altered consumption will also depend on their prey or resources (32–34). For example, an increase in a consumer’s energetic demand could be met through increased ingestion of a given resource. Shifts in the escape response, production of physical or chemical deterrents, or the size or biomass of the resource species driven by environmental change, however, can mediate the outcome (4). Thus, deciphering the environmental controls on trophic interactions requires analysis of both the consumer- and resource-driven components of predation and herbivory in future conditions.In most studies that assess the effects of OA, warming, or both on the consumption rates of marine species, researchers use controlled laboratory experiments that are amenable to meta-analysis. In these experiments, a consumer or resource is most often exposed to current and future environmental conditions for a period of days to months. Thus, the effects measured are primarily plastic and represent an organism’s ability to acclimate physiologically or behaviorally. Often, the consumer is held in treatment conditions and given prey or a resource that has not been acclimated to the experimental conditions (defined here as consumer-only experiments). In contrast, more complex studies (e.g., multispecies mesocosms or studies focused on species interactions or community-level responses) tend to include both the consumer and its resource(s) in the experimental conditions. While the responses in these experiments still represent the physiological or behavioral acclimation of the species involved, these multispecies experiments capture potential emergent effects of environmental change on species interactions that result from the direct effects on both the consumer and the resource. Prior meta-analyses have shown that there can be important variation in the temperature sensitivity of different ecological rates, such as attack rates and escape rates that can influence the emergent effects based on variation in sensitivity among trophic roles (30). Similarly, OA has been shown to affect both predator and prey detection and behavior (35–37), as well as algal traits that could affect herbivory, such as nutritional status or chemical deterrents (37). Most rare are those studies that expose only prey or resources to experimental conditions and then test their vulnerability to predation using a predator or herbivore that is not acclimated to the experimental conditions being tested. In contrast to the consumer-only experiments, these “resource-only” experiments capture how environmental change may affect the vulnerability or palatability of species that serve as resources.Experiments also vary in the complexity of environmental manipulation. Although OA and warming are happening in concert in nature, many early studies focused on the biological effects of OA or warming in isolation. As global change biology has progressed, the focus has shifted toward multifactor studies that incorporate both OA and warming in combination (e.g., factorial experiments). These studies are critically important for forecasting emergent effects, as the combined effects of OA and warming may not be additive (1, 2). This may be especially important if OA and warming have different modes of action on marine organisms (38). Synergisms, in which the effects of OA and warming exacerbate one another, have gained the most attention because of their potential to cause dramatic ecological shifts. However, even with different modes of action, one environmental-change factor may primarily drive an organism’s overall response, leading to unexpected outcomes.We conducted a systematic review (SI Appendix, Fig. S1 and Dataset S1) to assemble a database of published studies (Dataset S2) and conduct a meta-analysis quantifying the individual and combined effects of OA and warming on consumption rates, testing for variation between predator–prey and herbivore–resource interactions. We also tested for variance in the individual and combined effects of each environmental variable on different trophic roles (i.e., studies that exposed only consumers or only resources to treatment conditions prior to measuring consumption) to provide insight on their relative importance in the overall response of predation and herbivory rates in future conditions. We then tested whether taxonomic groups or life stages of interacting organisms explain any remaining variance among underlying studies to aid interpretation and identify gaps in our knowledge that need to be addressed to move the field forward. We also quantified the effects of OA and warming on prey survival in resource-only experiments, as well as the effects on consumer preference of prey or resources raised in ambient or future conditions. Finally, to quantitatively address the potential for nonadditive effects of the combined exposure to OA and warming, we calculated the individual and interactive effects of OA and warming on consumption rates for the subset of studies that factorially manipulated both variables.     

Concomitant 5-Aminosalicylate Therapy in Moderate-to-Severe Ulcerative Colitis Patients Escalated to Infliximab Is Not Beneficial

Digestive Diseases and Sciences - While there is recent literature to support the discontinuation of 5-aminosalicylate (5-ASA) upon the initiation of biologics, continuing 5-ASA after treatment...     

Sympathetic stimulation and norepinephrine infusion modulate extracellular potassium concentration during acute myocardial ischemia.

The purpose of this study was to investigate whether sympathetic stimulation modulated the rise in extracellular K+ concentration ([K+]o) evoked by acute myocardial ischemia. In 35 alpha-chloralose-anesthetized dogs, we measured changes in [K+]o during acute myocardial ischemia in the presence and absence of sympathetic stimulation or norepinephrine infusion. A series of four 5-minute occlusions of the distal left anterior descending coronary artery (LAD) was completed in 18 dogs. Thirty minutes of reperfusion separated each LAD occlusion. Four to five K(+)-sensitive electrodes were inserted into the left ventricular midmyocardium that was perfused by the distal LAD. Lead II of the electrocardiogram, arterial pressure, and [K+]o were recorded, and the right atrium was paced at a constant cycle length. The first, second, and fourth LAD occlusions were done in the absence of sympathetic stimulation or norepinephrine infusion. The changes in [K+]o evoked by the first LAD occlusion differed (p < 0.05) from those elicited by the second and fourth occlusions. However, the changes in [K+]o during the second and fourth LAD occlusions were similar (p > 0.2) and served as controls for the responses obtained during the third occlusion. Two minutes before the third LAD occlusion, sympathetic stimulation (4 Hz) or norepinephrine infusion (0.25-0.5 micrograms/kg per minute i.v.) was begun and was continued until 2 minutes after reperfusion. We found that sympathetic stimulation and norepinephrine infusion increased (p < 0.05) myocardial blood flow in both normal and ischemic tissue. The mean response recorded by 23 K(+)-sensitive electrodes in 11 dogs showed that sympathetic stimulation increased (p < 0.001) the [K+]o at 1, 2, 3, 4, and 5 minutes after the onset of LAD occlusion compared with the second and fourth occlusions. In contrast, the mean response recorded by 20 K(+)-sensitive electrodes in seven dogs showed that norepinephrine infusion reduced (p < 0.02) the [K+]o at 4 and 5 minutes after the onset of LAD occlusion. These data show that sympathetic stimulation increased the [K+]o evoked by acute myocardial ischemia, an effect that was not mimicked by the intravenous administration of norepinephrine.     

In vivo measurements of NMR relaxation times

A series of solenoidal NMR probes were built to measure T1 and T2 relaxation times in vivo in the mouse, over the frequency range of 5 to 60 MHz, using inversion-recovery and spin-echo pulse sequences. KHT tumors growing in the legs of C3H mice were studied and compared with normal mouse legs. The tumor relaxation times were studied at 10 MHz during the course of tumor growth and as a function of frequency when the tumor had a mass of approximately 0.9 g. Mouse legs with tumors have higher T1 and T2 values than those without tumors over the frequency range of 5 to 60 MHz. Significant changes in both relaxation times were detected before a palpable mass could be detected. T1 contrast between normal and tumor-bearing legs decreased with increasing frequency, while T2 contrast remained nearly constant. A comparison between in vivo and in vitro measurements was done using four different types of sample preparation: live mouse, dead mouse, excised whole mouse leg, and tissue sample. These studies showed small but significant differences between the relaxation times measured in vivo and those measured in vitro.     

Intentional iron overdose: an institutional review.

OBJECTIVE: To document the frequency of admissions and the outcome of patients with a diagnosis of intentional iron overdose to a large urban hospital. DESIGN: Retrospective review of hospital records. SETTING: Health Sciences Centre, Winnipeg, an 1100-bed primary and tertiary care centre serving a regional population of about 1.2 million. PATIENTS: All patients with a discharge diagnosis of iron overdose who were admitted from Jan. 1, 1979, to July 1, 1991. Of these 113 cases 66 (58%) represented an intentional iron overdose on the basis of information derived from the patient, family or friends. MAIN OUTCOME MEASURES: Frequency of admissions, length of hospital stay and survival rate. RESULTS: Most (53 [80%]) of the 66 patients were females. The mean age was 19.8 (standard deviation [SD] 6.1) years (range 9 to 48 years). One third of the cases were associated with excess alcohol intake. The frequency of hospital admissions increased during the study period (1.4 cases per year in the first 5 years and 9.8 cases per year in the last 5; 5.3 cases per year overall). The mean length of hospital stay was 6.8 (SD 12.1) days, and the mortality rate was 10%. CONCLUSIONS: Hospital admissions because of intentional iron overdose are becoming more frequent in this centre and are associated with appreciable morbidity and mortality rates. Prospective studies are required to delineate clearly the signs, symptoms and abnormal laboratory findings associated with this problem.     

Renal cancer staging: Comparison of contrast-enhanced CT and gadolinium-enhanced fat-suppressed spin-echo and gradient-echo MR imaging

Fifty-three consecutive patients with 61 solid or complex non-fat-containing renal masses compatible with renal cancer were examined with contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging with pre- and postcontrast FLASH (fast low-angle shot) and fat-suppressed spin-echo sequences. CT and MR imaging were performed within a 1-month interval. CT and MR images were prospectively interpreted. Tumor detection and staging were determined in all patients. CT and MR imaging enabled detection of 54 and 58 of 61 renal tumors, respectively. CT and MR imaging showed 34 and 35 of 38 histologically proved renal tumors, respectively, in 31 patients. Tumor size on CT and MR images demonstrated good correlation and correlated well with the size of pathologic specimens of 34 of 38 resected tumors detected with CT and MR imaging (r =.99). Of the 31 tumors in 31 patients who underwent surgical resection, 24 were correctly staged with CT and 29 with MR imaging. CT and MR imaging both enabled correct staging of four of five additional tumors with biopsy proof of tumor stage. A moderate difference in staging was observed between CT and MR imaging (P =.05). CT showed 13 and MR imaging 15 of 15 tumor thrombi. CT and MR imaging both showed 11 of 11 cases of adenopathy. The results suggest that MR imaging is moderately better than CT for the detection and staging of renal cancer.     

Antisense treatment of caliciviridae: an emerging disease agent of animals and humans

The Earth's oceans are the primary reservoir for an emerging family of RNA viruses, the Caliciviridae, which can cause a spectrum of diseases in marine animals, wildlife, farm animals, pets and humans. Certain members of this family have unusually broad host ranges, and some are zoonotic (transmissible from animals to humans). The RNA virus replicative processes lack effective genetic repair mechanisms, and, therefore, virtually every calicivirus replicate is a mutant. Hence, traditional therapeutics dependent on specific nucleic acid sequences or protein epitopes lack the required diversity of sequence or conformational specificity that would be required to reliably detect, prevent or treat infections from these mutant clusters (quasi-species) of RNA viruses, including the Caliciviridae. Antisense technology using phosphorodiamidate morpholino oligomers shows promise in overcoming these current diagnostic and therapeutic problems inherent with newly emerging viral diseases.     

Adult liver transplant survey: policies towards eligibility criteria in Canada and the United States 2007

Goals: To assess the current practice patterns of liver transplant centres in Canada and the USA regarding transplant eligibility. Background: Liver transplantation is an evolving field and today remains the only life‐sustaining treatment for end‐stage liver disease. Issues of allocation and transplant eligibility are important factors in the ethical practice of medicine. Study: Questionnaires were mailed to liver transplant programme directors in Canada and the USA inquiring about current practices regarding recipient eligibility. Results: This study demonstrates that there is consensus in the use of other eligibility criteria, including non‐compliance, social status, abstinence from alcohol and methadone and cocaine use. Interestingly, literature is lacking to support the use of these parameters as eligibility criteria with the exception of alcohol. There is a lack in consensus regarding marijuana use, human immunodeficiency virus status, ability to accept blood transfusions and prisoner status. The literature suggests that liver transplantation in select patients who refuse blood transfusions results in good outcomes. Conclusions: Important decisions regarding transplant eligibility still have to be made empirically in the absence of scientific literature about various social issues. While consensus among transplant programmes is useful, it is important that we continue to use the evidence in the literature to revise these eligibility criteria, keeping in mind ethical principles applied to the access and allocation of a scarce resource.