Time Trends and Excess Mortality Compared to Population Controls after a First-Time Pulmonary Embolism or Deep Vein Thrombosis.

BACKGROUND: Recent data on temporal trends in excess mortality for patients with pulmonary embolism (PE) and deep vein thrombosis (DVT) compared with the general population are scarce. METHODS: A nationwide Swedish register study conducted from 2006 to 2018 including 68,960 PE and 70,949 DVT cases matched with population controls. Poisson regression determined relative risk (RR) for 30-day and 1-year mortality trends while Cox regression determined adjusted hazard ratios (aHRs). A significance level of 0.001 was applied. RESULTS: In PE cases, both 30-day mortality (12.5% in 2006 to 7.8% in 2018, RR: 0.95 [95% CI: 0.95-0.96], p < 0.0001) and 1-year mortality (26.5 to 22.1%, RR: 0.98 [0.97-0.98], p < 0.0001) decreased during the study period. Compared with controls, no significant change was seen in 30-day (aHR: 33.08 [95% CI: 25.12-43.55] to 24.64 [95% CI: 18.81-32.27], p = 0.0015 for interaction with calendar year) or 1-year (aHR: 5.85 [95% CI: 5.31-6.45] to 7.07 [95% CI: 6.43-7.78], p = 0.038) excess mortality. The 30-day excess mortality decreased significantly (aHR: 39.93 [95% CI: 28.47-56.00) to 24.63 [95% CI: 17.94-33.83], p = 0.0009) in patients with PE without known cancer before baseline, while the excess 1-year mortality increased (aHR: 3.55 [95% CI: 3.16-3.99] to 5.38 [95% CI: 4.85-5.98], p < 0.0001) in PE cases surviving to fill a prescription of anticoagulation. In DVT cases, 30-day and 1-year mortality declined, while excess mortality compared with controls remained stable. CONCLUSION: In general, the improved mortality following PE and DVT paralleled population trends. However, PE cases without cancer had decreasing excess 30-day mortality, whereas those surviving to fill a prescription for anticoagulant medication showed increasing excess 1-year mortality.

Airway pressure release ventilation (APRV) versus pressure support ventilation (PSV)-A prospective intervention trial comparing haemodynamic parameters in intensive care patients.

BACKGROUND AND AIM: Assisted mechanical ventilation may alter the pressure profile in the thorax compared to normal breathing, which can affect the blood flow to and from the heart. Studies suggest that in patients with severe lung disease, airway pressure release ventilation (APRV) may be haemodynamically beneficial compared to other ventilator settings. The primary aim of this study was to investigate if APRV affects cardiac index in intubated intensive care patients without severe lung disease when compared to pressure support ventilation (PSV). The secondary aim comprised potential changes in other haemodynamic and ventilatory parameters. METHODS: Twenty patients were enrolled in the intensive care unit (ICU) at Sahlgrenska University Hospital. Eligible patients met the inclusion criteria; 18 years of age or above, intubated and mechanically ventilated, triggering and stable on PSV mode, with indwelling haemodynamic monitoring via a pulse-induced continuous cardiac output (PiCCO) catheter. The study protocol started with a 30-min interval on PSV mode, followed by a 30-min interval on APRV mode, and finally a 30-min interval back on PSV mode. At the end of each interval, PiCCO outputs, ventilator outputs, arterial and venous blood gas analyses, heart rate and central venous pressure were recorded and compared between modes. RESULTS: There was no significant difference in cardiac index (3.42 vs. 3.39 L/min/m2) between PSV and APRV, but a significant increase in central venous pressure (+1.0 mmHg, p = .027). Furthermore, we found a significant reduction in peak airway pressure (-3.16 cmH2O, p < .01) and an increase in mean airway pressure (+2.1 cmH2O, p < .01). No statistically significant change was found in oxygenation index (partial pressure of O2 [pO2]/fraction of inspired oxygen) nor in other secondary outcomes when comparing PSV and APRV. There was no significant association between global end-diastolic volume index and cardiac index (R2 = 0.0089) or central venous pressure (R2 = 0.278). All parameters returned to baseline after switching the ventilator mode back to PSV. CONCLUSION: We could not detect any changes in cardiac index in ICU patients without severe lung disease during APRV compared to PSV mode, despite lower peak airway pressure and increased mean airway pressure.

High-sensitivity troponin T for detection of culprit lesions in patients with out-of-hospital cardiac arrest.

BACKGROUND: Patients with an out-of-hospital cardiac arrest (OHCA) often undergo coronary angiography, although a culprit lesion is found in only 30%-40% of patients. The aim of this study was to investigate high-sensitivity troponin T (hsTnT) levels in post cardiac arrest patients with and without coronary culprit lesions; factors affecting hsTnT levels after return of spontaneous circulation (ROSC); and the diagnostic ability of hsTnT in identifying patients with culprit lesions. We hypothesized that peak hsTnT levels were higher during the initial 48 h after cardiac arrest in patients with a coronary culprit lesion. METHODS: This was a retrospective observational study, which included patients admitted to the Intensive Care Unit after an OHCA and who received a coronary angiography. Peak values and dynamic changes in hsTnT were analyzed in relation to the presence of a culprit lesion at coronary angiography. RESULTS: A total of 238 patients were studied, of whom 140 had a culprit lesion. HsTnT levels during the initial 48 h were higher in patients with culprit lesions, longer time to ROSC and an unwitnessed cardiac arrest. At 6 to 12 h after ROSC, a hsTnT cut-off level of 1690 ng/L had a sensitivity of 64% and specificity of 84% to identify a culprit lesion. In patients without ST-elevations, hsTnT measured between 6 and 12 h after ROSC had a specificity above 90%, with a sensitivity of 46%. CONCLUSION: HsTnT levels after cardiac arrest are higher in patients with coronary culprit lesions. Presence of a culprit lesion, witnessed status and the duration of CPR are important factors affecting hsTnT levels. Repeated measurement of hsTnT within the first 12 h after admission improved diagnostic accuracy but the value of hsTnT as a predictor of culprit lesions early after OHCA is limited.

Donor heart dysfunction and graft survival in liver and kidney transplants-A register-based study from Sweden.

BACKGROUND AND AIM: Stress cardiomyopathy in donors can potentially affect graft function and longevity. This study aims to investigate the association between echocardiographic left ventricular ejection fraction (LVEF) < 50%, and/or the presence of left ventricular regional wall motion abnormalities (RWMA) in organ donors, and short- and long-term liver and kidney graft survival. Our secondary aim was to link graft survival with donor and recipient characteristics. METHODS: All donors considered for liver and kidney donation with echocardiographic records at Sahlgrenska University Hospital between 2006 and 2016 were matched with their recipients through the Scandiatransplant register. The studied outcomes were graft survival, re-transplantation, and recipient death. Kaplan-Meier curves were used to plot time to event. Multivariate Cox-regression was used to test independence. RESULTS: There were 370 liver donors and 312 kidney donors (matched with 458 recipients) with echocardiographic records at Sahlgrenska University Hospital between June 2006 and November 2016. Of patients with LV dysfunction by echocardiography, there were 102 liver- and 72 kidney donors. Univariate survival analyses showed no statistical difference in the short- and long-term graft survival from donors with LV dysfunction compared to donors without. Donor age > 65 years, recipient re-transplantation and recipient liver tumor were predictors of worse outcome in liver transplants (p < .05). Donor age > 65, donor hypertension, recipient re-transplantation, and a recipient diagnosis of diabetes or nephritis/glomerulonephritis had a negative association with graft survival in kidney transplants (p < .05). CONCLUSION: We found no significant association between donor LV dysfunction and short- and long-term graft survival in liver and kidney transplants, suggesting that livers and kidneys from such donors can be safely transplanted.

High-frequency, high-intensity transcutaneous electrical nerve stimulation compared with opioids for pain relief after gynecological surgery: a systematic review and meta-analysis.

OBJECTIVES: Opioids are important for postoperative analgesia but their use can be associated with numerous side effects. Transcutaneous electrical nerve stimulation (TENS) has been used for acute pain treatment and has dose-dependent analgesic effects, and therefore presents an alternative to intravenous (iv) opioids for postoperative pain relief. The aim of this meta-analysis was to compare high-frequency, high-intensity (HFHI or intense) TENS to iv opioids with regard to postoperative pain intensity, recovery time in the Post Anesthesia Care Unit (PACU) and opioid consumption after elective gynecological surgery. METHODS: We searched Medline, Embase, Web of Science, Cochrane, Amed and Cinahl for RCTs and quasi-experimental studies (2010-2022), and WHO and ClinicalTrials.gov for ongoing/unpublished studies. Meta-analysis and subsequent Trial Sequential Analysis (TSA) was performed for all stated outcomes. Quality of evidence was assessed according to GRADE. RESULTS: Only three RCTs met the inclusion criteria (362 participants). The surgical procedures involved surgical abortion, gynecologic laparoscopy and hysteroscopy. The applied TENS frequency was 80 Hz and intensity 40-60 mA. There was no difference in pain intensity according to Visual Analogue Scale (VAS) at discharge from PACU between the TENS and opioid group (MD VAS -0.15, 95 % CI -0.38 to 0.09) (moderate level of evidence). Time in PACU was significantly shorter in the TENS group (MD -15.2, 95 % -22.75 to -7.67), and this finding was manifested by TSA (high-level of evidence). Opioid consumption in PACU was lower in the TENS group (MD Morphine equivalents per patient mg -3.42, 95 % -4.67 to -2.17) (high-level of evidence). CONCLUSIONS: There was no detectable difference in postoperative pain relief between HFHI TENS and iv opioids after gynecological surgery. Moreover, HFHI TENS decreases recovery time and opioid consumption in PACU. HFHI TENS may be considered an opioid-sparing alternative for postoperative pain relief after gynecological surgery. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42021231048.

Validating a Simplified Lung Ultrasound Protocol for Detection and Quantification of Pulmonary Edema in Patients With Chronic Kidney Disease Receiving Maintenance Hemodialysis.

OBJECTIVES: Pulmonary edema is a common clinical problem and lung ultrasound (LUS) presents an efficient method for evaluating this pathology. This study aims to investigate if a clinically efficient LUS protocol can quantify the level of extravascular lung fluid in patients receiving hemodialysis, and to develop a simplified B-line scoring system based on this protocol. METHODS: A simple 8-area LUS approach was used for the assessment of the extravascular fluid status in patients before, during, and after receiving hemodialysis. The LUS assessments were compared to the amount of removed fluid over time. To determine the best B-line score system, different scorings for each zone were tested in a linear mixed model with pseudo R-square model fit against removed fluid. The B-line score was further validated through correlations with changes in oxygen saturation, grade of dyspnea, and body weight over time. RESULTS: A total of 53 patients were included and examined on 108 hemodialysis occasions. Median fluid removal was 2.3 L. The B-line score model with best fit was a score of 0 points in a zone with 0 or 1 B-lines, 1 point with 2 or 3 B-lines, 2 points with 3 or more B-lines, and 3 points with any interstitial confluence. Using this B-line score, we found a significant association with amount of removed fluid, oxygen saturation, grade of dyspnea, and change in body weight. CONCLUSION: A straightforward protocol for LUS and B-line score system was shown valid for quantification of pulmonary edema and fluid removal in hemodialysis patients. The scoring system developed here can be useful also in other patient groups, but this requires further validation.

Surgical treatment of obesity and excess risk of developing heart failure in a controlled cohort study.

AIM: We aim to assess the risk of heart failure in patients with obesity with and without gastric bypass surgery compared with population controls. METHODS AND RESULTS: This cohort study included all patients aged 20-65 years with a first ever registered principal diagnosis of obesity in the Swedish Patient Register in 2001-2013. These patients were matched by age, sex, and region with two population controls from the general Swedish population without obesity diagnosis. The obesity cohort was divided into two groups: 27 882 patients who had undergone gastric bypass surgery within 2 years of obesity diagnosis and 39 564 patients who had not undergone such surgery. These groups were compared with 55 149 and 78 004 matched population controls, respectively. Cox regression provided hazard ratios (HR) with 95% confidence intervals (CI), adjusted for age, education, and sex. During follow-up (maximum 10 years, median 4.4 years, and interquartile range 2.5-7.2 years), 1884 participants were hospitalized for heart failure. Compared with population controls, gastric bypass patients had no excess risk of heart failure during the initial 0-≤4 years of follow-up (HR = 1.35 [95% CI = 0.96-1.91]) but a marked increased risk during the final >4-10 years of follow-up (HR = 3.28 [95% CI = 2.25-4.77]). Non-operated patients with obesity had a marked excess risk of heart failure throughout the study period compared with population controls. CONCLUSIONS: Gastric bypass for obesity seems to reduce the risk of heart failure to levels similar to the general population during the initial 4 years after surgery, but not thereafter.

Opioid consumption in patients undergoing Roux-en-Y bariatric surgery compared with population controls with and without obesity.

BACKGROUND: Patients with obesity are prescribed more opioids than the general population. OBJECTIVES: To compare opioid consumption in patients with obesity who underwent Roux-en-Y bariatric surgery (RYGB) with population controls with and without obesity, not undergoing bariatric surgery, and to identify characteristics associated with opioid use. SETTING: This study included all patients with a principal diagnosis of obesity, aged 18-72 years, with a RYGB surgical code in the Swedish Patient Register between 2007 and 2013. METHODS: RYGB patients (n = 23,898) were age- and sex-matched with 1 control patient with obesity (n = 23,898) and 2 population controls without obesity (n = 46,064). Participants were classified as nonconsumers and consumers based on their opioid dispensations during the 12 months before baseline. Opioid consumption was assessed for 24 months. RESULTS: Nonconsumers. Within 24 months, a significantly higher proportion of RYGB patients (16.6%) started using opioids compared with the controls with obesity (14.3%, P < .0001) and population controls (5.4%, P < .0001). RYGB patients and controls with obesity had higher median daily intake of opioid morphine equivalent (MEQ) (2.8 mg/d) than population controls (2.5 mg/d, P < .0001). Consumers. Within 24 months, the proportion of RYGB patients and controls with obesity that was using opioids were similar (53.1% and 53.4%), but higher compared to population controls (38.0%, P < .0001). The median daily opioid MEQ was higher among RYGB patients than in population controls (10.5 versus 7.8 mg/d, P < .0001). RYGB patients, overall, had higher incidence of bowel surgery and cholecystectomy compared with controls with obesity and population controls, leading to prolonged opioid use in this group. Opioid consumption in general was associated with chronic pain and psychiatric disorder, which were more common in patients with obesity than in the population controls. CONCLUSION: RYGB surgery increased the risk of prolonged opioid use in patients with obesity who were nonconsumers before surgery but had no effect on overall opioid use among prior consumers. RYGB-associated complications requiring surgery influenced opioid use for both nonconsumers and consumers. Regular reassessments of pain mechanisms and specific treatment owing to type of pain could prevent unnecessary opioid use in this patient group.

Total opioid-free general anaesthesia can improve postoperative outcomes after surgery, without evidence of adverse effects on patient safety and pain management: A systematic review and meta-analysis.

BACKGROUND: Opioid-based treatment is used to manage stress responses during surgery and postoperative pain. However, opioids have both acute and long-term side effects, calling for opioid-free anaesthetic strategies. This meta-analysis compares adverse events, postoperative recovery, discharge time from post-anaesthesia care unit, and postoperative pain, nausea, vomiting, and opioid consumption between strict opioid-free and opioid-based general anaesthesia. METHODS: We conducted a systematic review and meta-analysis. We searched PubMed, Embase, Cinahl, Cochrane Library, selected reference lists, and Google Scholar. We included randomised controlled trials (RCTs) published between January 2000 and February 2021 with at least one opioid-free study arm, i.e. no opioids administered preoperatively, during anaesthesia induction, before skin closure, or before emergence from anaesthesia. RESULTS: The study comprised 1934 patients from 26 RCTs. Common interventions included laparoscopic gynaecological surgery, upper gastrointestinal surgery, and breast surgery. There is firm evidence that opioid-free anaesthesia significantly reduced adverse postoperative events (OR 0.32, 95% CI 0.22 to 0.46, I2  = 56%, p < 0.00001), mainly driven by decreased nausea (OR 0.27, (0.17 to 0.42), p < 0.00001) and vomiting (OR 0.22 (0.11 to 0.41), p < 0.00001). Postoperative opioid consumption was significantly lower in the opioid-free group (-6.00 mg (-8.52 to -3.48), p < 0.00001). There was no significant difference in length of post-anaesthesia care unit stay and overall postoperative pain between groups. CONCLUSIONS: Opioid-free anaesthesia can improve postoperative outcomes in several surgical settings without evidence of adverse effects on patient safety and pain management. There is a need for more evidence-based non-opioid anaesthetic protocols for different types of surgery as well as postoperative phases.

Does antifouling paint select for antibiotic resistance?

There is concern that heavy metals and biocides contribute to the development of antibiotic resistance via co-selection. Most antifouling paints contain high amounts of such substances, which risks turning painted ship hulls into highly mobile refuges and breeding grounds for antibiotic-resistant bacteria. The objectives of this study were to start investigate if heavy-metal based antifouling paints can pose a risk for co-selection of antibiotic-resistant bacteria and, if so, identify the underlying genetic basis. Plastic panels with one side painted with copper and zinc-containing antifouling paint were submerged in a Swedish marina and biofilms from both sides of the panels were harvested after 2.5-4weeks. DNA was isolated from the biofilms and subjected to metagenomic sequencing. Biofilm bacteria were cultured on marine agar supplemented with tetracycline, gentamicin, copper sulfate or zinc sulfate. Biofilm communities from painted surfaces displayed lower taxonomic diversity and enrichment of Gammaproteobacteria. Bacteria from these communities showed increased resistance to both heavy metals and tetracycline but not to gentamicin. Significantly higher abundance of metal and biocide resistance genes was observed, whereas mobile antibiotic resistance genes were not enriched in these communities. In contrast, we found an enrichment of chromosomal RND efflux system genes, including such with documented ability to confer decreased susceptibility to both antibiotics and biocides/heavy metals. This was paralleled by increased abundances of integron-associated integrase and ISCR transposase genes. The results show that the heavy metal-based antifouling paint exerts a strong selection pressure on marine bacterial communities and can co-select for certain antibiotic-resistant bacteria, likely by favoring species and strains carrying genes that provide cross-resistance. Although this does not indicate an immediate risk for promotion of mobile antibiotic resistance, the clear increase of genes involved in mobilizing DNA provides a foundation for increased opportunities for gene transfer in such communities, which might also involve yet unknown resistance mechanisms.

Eelgrass (Zostera marina) Food Web Structure in Different Environmental Settings.

This study compares the structure of eelgrass (Zostera marina L.) meadows and associated food webs in two eelgrass habitats in Denmark, differing in exposure, connection to the open sea, nutrient enrichment and water transparency. Meadow structure strongly reflected the environmental conditions in each habitat. The eutrophicated, protected site had higher biomass of filamentous algae, lower eelgrass biomass and shoot density, longer and narrower leaves, and higher above to below ground biomass ratio compared to the less nutrient-enriched and more exposed site. The faunal community composition and food web structure also differed markedly between sites with the eutrophicated, enclosed site having higher biomass of consumers and less complex food web. These relationships resulted in a column shaped biomass distribution of the consumers at the eutrophicated site whereas the less nutrient-rich site showed a pyramidal biomass distribution of consumers coupled with a more diverse consumer community. The differences in meadow and food web structure of the two seagrass habitats, suggest how physical setting may shape ecosystem response and resilience to anthropogenic pressure. We encourage larger, replicated studies to further disentangle the effects of different environmental variables on seagrass food web structure.

Simple growth patterns can create complex trajectories for the ontogeny of constitutive chemical defences in seaweeds.

All of the theory and most of the data on the ecology and evolution of chemical defences derive from terrestrial plants, which have considerable capacity for internal movement of resources. In contrast, most macroalgae--seaweeds--have no or very limited capacity for resource translocation, meaning that trade-offs between growth and defence, for example, should be localised rather than systemic. This may change the predictions of chemical defence theories for seaweeds. We developed a model that mimicked the simple growth pattern of the red seaweed Asparagopsis armata which is composed of repeating clusters of somatic cells and cells which contain deterrent secondary chemicals (gland cells). To do this we created a distinct growth curve for the somatic cells and another for the gland cells using empirical data. The somatic growth function was linked to the growth function for defence via differential equations modelling, which effectively generated a trade-off between growth and defence as these neighbouring cells develop. By treating growth and defence as separate functions we were also able to model a trade-off in growth of 2-3% under most circumstances. However, we found contrasting evidence for this trade-off in the empirical relationships between growth and defence, depending on the light level under which the alga was cultured. After developing a model that incorporated both branching and cell division rates, we formally demonstrated that positive correlations between growth and defence are predicted in many circumstances and also that allocation costs, if they exist, will be constrained by the intrinsic growth patterns of the seaweed. Growth patterns could therefore explain contrasting evidence for cost of constitutive chemical defence in many studies, highlighting the need to consider the fundamental biology and ontogeny of organisms when assessing the allocation theories for defence.

Collapse of a marine mammal species driven by human impacts.

Understanding historical roles of species in ecosystems can be crucial for assessing long term human impacts on environments, providing context for management or restoration objectives, and making conservation evaluations of species status. In most cases limited historical abundance data impedes quantitative investigations, but harvested species may have long-term data accessible from hunting records. Here we make use of annual hunting records for Caspian seals (Pusa caspica) dating back to the mid-19(th) century, and current census data from aerial surveys, to reconstruct historical abundance using a hind-casting model. We estimate the minimum numbers of seals in 1867 to have been 1-1.6 million, but the population declined by at least 90% to around 100,000 individuals by 2005, primarily due to unsustainable hunting throughout the 20(th) century. This collapse is part of a broader picture of catastrophic ecological change in the Caspian over the 20(th) Century. Our results combined with fisheries data show that the current biomass of top predators in the Caspian is much reduced compared to historical conditions. The potential for the Caspian and other similar perturbed ecosystems to sustain natural resources of much greater biological and economic value than at present depends on the extent to which a number of anthropogenic impacts can be harnessed.

Linking climate trends to population dynamics in the Baltic ringed seal: impacts of historical and future winter temperatures.

A global trend of a warming climate may seriously affect species dependent on sea ice. We investigated the impact of climate on the Baltic ringed seals (Phoca hispida botnica), using historical and future climatological time series. Availability of suitable breeding ice is known to affect pup survival. We used detailed information on how winter temperatures affect the extent of breeding ice and a climatological model (RCA3) to project the expected effects on the Baltic ringed seal population. The population comprises of three sub-populations, and our simulations suggest that all of them will experience severely hampered growth rates during the coming 90 years. The projected 30, 730 seals at the end of the twenty-first century constitutes only 16 % of the historical population size, and thus reduced ice cover alone will severely limit their growth rate. This adds burden to a species already haunted by other anthropogenic impacts.

Detecting density dependence in recovering seal populations.

Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.

Competing species in a changing climate: effects of recruitment disturbances on two interacting barnacle species.

1. The climate is changing and data-based simulation models can be a valuable tool for predicting population response to such changes and investigate the mechanisms of population change. In this study, a data-based two-species matrix model was constructed to explore the possible effects of elevated sea surface temperature (i.e. climate change) on the interaction between open populations of the south Atlantic barnacle species Chthamalus montagui and the boreal species Semibalanus balanoides in the north-east Atlantic. 2. First, the model was used to perform an elasticity analysis to determine the relative importance of recruitment and survival in the interaction. Further, three scenarios of changes in recruitment, related to climate change, were investigated with model simulations: (i) increased frequencies of low recruitment for S. balanoides; (ii) increased frequencies of high recruitment for C. montagui; (iii) a combination of (i) and (ii). 3. Model simulations showed that in present environmental conditions, S. balanoides occupied most of the space and dominated the interaction through high recruitment and survival. These results matched independent field observations, which validated the model for further analyses. 4. The elasticity analyses showed that although free space was available there was competition for space during recruitment intervals. It was also shown that both populations were sensitive to changes in recruitment. 5. Introducing the three scenarios of recruitment disturbances led to large changes in species abundance and free space. The most significant changes were found when scenario (i) and (ii) were combined, producing a shift in species dynamics towards C. montagui dominance. This demonstrates that recruitment can be an important mechanism in the interaction between populations and that the population response to changes in recruitment depends on the added response of interacting species. 6. In a more general context, this model shows that increased sea surface temperature could rapidly lead to increased competition from southern species at higher latitudes. This might accelerate the effects of climate change on the species distribution at these latitudes and eventually lead to changes in community dynamics on temperate and subarctic shores.

Population resistance to climate change: modelling the effects of low recruitment in open populations.

Isolated populations or those at the edge of their distribution are usually more sensitive to changes in the environment, such as climate change. For the barnacle Semibalanus balanoides (L.), one possible effect of climate change is that unpredictable spring weather could lead to the mismatching of larval release with spring phytoplankton bloom, hence reducing the recruitment. In this paper, model simulations of a variable open population with space limited recruitment were used to investigate the effects of low and zero recruitment on population abundance in S. balanoides. Data for model parameters was taken from an isolated population in the Isle of Man, British Isles. Model simulations with observed frequencies of years with low recruitment showed only small changes in population dynamics. Increased frequencies of low recruitment had large effects on the variation in population growth rate and free space and on population structure. Furthermore, populations with intermediate to high frequencies of low recruitment appeared more sensitive to additional changes in recruitment. Exchanging low recruitment with zero recruitment severely increased the risk of local extinctions. Simulations with consecutive years of low recruitment showed a substantial increase in free space and an increase in the time taken to recover to normal densities. In conclusion, model simulations indicate that variable populations can be well buffered to changes in the demography caused by introduced environmental noise, but also, that intermediate to high frequencies of disturbance can lead to a swift change in population dynamics, which in turn, may affect the dynamics of whole communities.