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Recruitment is an important demographic bottleneck in the life history of many plant and animal species. Microhabitats provided by surfaces or plants or animals can reduce mortality during this critical life-history period. We investigated how microhabitats influence post-settlement processes on a range of ascidians, bryozoans and barnacles. We compared post-settlement mortality and growth on surfaces that were flat or were covered by artificial barnacle mimics or live adult barnacle microhabitats. We also tested whether the effects of surface type changed under different levels of environmental stress by manipulating the orientation of treatments. Orientation had the strongest influence on survival, growth and recruitment, with individuals on downwards-facing surfaces performing the best and those on upwards-facing surfaces with significantly higher mortality. The bryozoan Watersipora subatra had higher survival in microhabitats, but was not influenced by surface orientation. In contrast, barnacles showed increased mortality in microhabitats on upwards-facing panels, but were not affected by other orientations. The presence of adult barnacles caused decreased growth of barnacle recruits, but had no effect on the bryozoan. In comparison, the ascidians (Botryllus sclosseri and Diplosoma listerianum) were mostly not influenced by microhabitats. The high rates of sedimentation on upwards-facing surfaces provide the most plausible answer for the strong influences of surface orientation on survival and growth. While microhabitats can act as refuges for some species, the same microhabitat type can lead to higher mortality in other species. The response of each species to microhabitats ultimately depends on the source of mortality at each site.

The species composition, density, and frequency of recruitment into any given habitat are highly variable in most biological systems that rely on dispersive propagules (larvae, seeds, spores, etc.). There are few direct experimental studies of how recruitment variation between single species influences the composition and assembly of whole communities in many of these systems. We manipulated recruitment of a variety of single taxa and followed their effects on the subsequent development of hard-substrate communities of sessile animals living in temperate marine waters. The effects of recruitment on communities were complex. Patterns of recruitment of individual species influenced community structure, but these effects varied greatly depending on the identity of species recruits, the time of community development, and location across three different sites. Variable recruitment of arborescent bryozoans and didemnid ascidians had little effect on community structure. At one site, recruitment of the colonial ascidian Botryllus schlosseri had short-lived effects on community structure, while barnacles had more persistent effects. At another site, recruitment of B. schlosseri and the bryozoan Watersipora subtorquata had strong persistent effects on community structure, dominating space where they recruited and influencing the abundances of a variety of different taxa. Differences in the effects of species recruitment on communities appear to be caused by differences between the ecology and life history of recruiting species as well as differences in background processes between sites. These results demonstrate that discrete recruitment events that vary between single species can be important drivers of community composition but are likely to be heavily influenced by the local environment, even within a single species.

For organisms with complex life cycles, longer time spent in the plankton by dispersing propagules can cause reduced survival, growth and fecundity, which could alter interactions between neighbours in the post-dispersal environment. We compared post-settlement performance of bryozoan Watersipora subtorquata colonies that developed from larvae of different natural and experimental planktonic durations over ca. 15 wk of colony growth. Settlers were situated either near established adults of the ascidian Botrylloides leachii or without competition. Increased larval planktonic durations reduced colony growth in the absence of competition; colonies that developed from longer or delayed larval durations were 2 to 3 times smaller than those that developed from shorter durations. Colonies that developed from longer larval periods (natural or experimental) also experienced higher mortality (75 to 100%) than those that settled quickly (20 to 42%), but these effects varied between experiments and seasons. In winter, W. subtorquata colonies of longer larval planktonic durations experienced greater mortality when adjacent to established B. leachii, whereas differences in colony growth due to planktonic duration were reduced by adjacent B. leachii. The influence of B. leachii varied between experiments in different seasons, however, and did not alter colony performance in summer. Our findings demonstrate that while increased larval planktonic duration can be costly for post-dispersal growth and survival, some differences can be mediated by species interactions and environmental variability. This suggests that while connectivity among populations that take longer to disperse may be limited, it may also be influenced in complex ways by the post-recruitment environment and not simply dispersal duration.

In many environments recruitment of dispersive propagules (e.g. seeds, spores and larvae) can vary from situations when particular taxa recruit in relative isolation to times when they recruit simultaneously with other, functionally quite different taxa. Differences in the identity and density of recruiting taxa can have important consequences on community structure, but it is still not clear how the effects of individual taxa on communities are modified when they recruit together with other species. Using an experimental approach we compared early development of a temperate marine sessile community after the recruitment of mixtures of botryllid ascidians and barnacles to that when barnacles or botryllid ascidians recruited alone. Communities exposed to recruitment of botryllid ascidians in isolation differed from those that received barnacles, a mixture of botryllids and barnacles or no recruitment in 2-week-old communities. These early differences were driven by higher abundances of the species that were present as initial recruits in experimental treatments. After 2 months communities also differed between barnacle and mixed recruitment treatments but not mixed and botryllid or botryllid and barnacle treatments. These differences were not directly due to differences in the abundances of our manipulated taxa but occurred because of two abundant arborescent bryozoans, Bugula dentata, which occupied more space in communities that initially received mixed recruitment than in those that received barnacle or no recruitment, and Zoobotryon verticillatum, which occupied more space in communities that initially received only barnacle recruitment than those that initially received botryllid or mixed recruitment. These effects did not persist, and communities did not differ after 6 months. These results suggest that, more generally, species may influence community dynamics differently when they recruit alongside other species than when they recruit in relative isolation.

Variation in patterns of propagule establishment (recruitment) has important effects on population dynamics and the structure of some communities. Most experimental studies have varied recruitment by changing the nature of a single event early in community development, but recruitment can also vary from steady rates of arrival to highly episodic 'pulse' events, causing differences in the temporal spacing of individuals recruiting into patches. We examined whether two different temporal patterns of recruitment of sessile invertebrates affected temperate marine communities in southeastern Australia in two experiments that were run at different times at the same site and that manipulated several different species. Target species entered communities as either a single pulse of recruits within a 2-week period or steady input of the same total number of recruits over a longer time period (5-6 weeks). The pattern of recruitment had variable effects on community structure. The colonial ascidian Botryllus schlosseri did not have a strong influence on community structure whether it recruited in a single pulse or steadily. The cover of B. schlosseri was higher when recruitment occurred as a single pulse. In a second experiment, botryllid ascidians caused changes in the composition of communities when they recruited steadily compared to when they did not recruit or didemnids recruited, but caused no differences in communities when they recruited in a shorter pulse. In contrast, recruitment frequency of didemnid ascidians had little effect, though their presence/absence caused community differences. Though we found that different temporal recruitment patterns can alter community composition, the life history and ecology of particular taxa as well as differences in environmental background processes are likely to influence the strength of these effects.

For marine organisms with complex life cycles, recruitment of dispersive propagules is highly variable in time and space, and can have important consequences for population and community dynamics. Recruitment often occurs in patches already occupied by adults that could alter its effects on communities. Using an experimental approach, we examined the effects of initial recruitment of a common bryozoan (Conopeum seurati) and barnacles in the presence/absence of a large and abundant solitary ascidian (Pyura dalbyi) on the composition of a marine fouling community occurring on artificial substrate. The presence of P. dalbyi and different initial recruitment patterns both influenced overall community composition, but did not interact. The main effect of P. dalbyi on communities was to reduce the amount of available primary space and alter the abundance and cover of other taxa. Different initial recruitment patterns also altered the abundance of a small number of taxa, but the direction of differences was variable. There were interactive effects of P. dalbyi and initial recruitment on 2 species. When there were no initial bryo zoan or barnacle recruits, the colonial ascidian Diplosoma listerianum had a higher cover without P. dalbyi than when P. dalbyi was present, but when we inoculated plates with other recruits, D. listeranium was unaffected by the presence of P. dalbyi. In the first month of community development, C. seurati colonies had an overall higher cover on C. seurati recruitment treatments than on other recruitment treatments. C. seurati also had higher colony cover on the primary space of C. seurati recruitment treatments where P. dalbyi was present than on C. seurati treatments without P. dalbyi, but there was no interaction between other recruitment/P. dalbyi treatment pairs. Differences did not persist beyond one month, or lead to overall changes in community composition. The results of this experiment suggest that any combined effects of recruitment and the presence of established adults on individual taxa are likely to be complex and may not always alter overall community composition.

Predation on newly settled sessile invertebrates is an important process shaping the structure of benthic marine communities in localised areas on the northeastern coast of North America. There are no studies that have tested whether predation acts similarly in other locations, so it is not clear whether generalisations can be made about the effects of predation on different sessile communities. In this study we determined whether predation on newly settled recruits altered the structure of 2 different sessile communities in Port Phillip Bay, Australia. We conducted a series of predator exclusion experiments using full cage, partial cage and no cage treatments at 2 study sites, Williamstown and Queenscliff. Full cage and partial cage treatments of either 1 cm or 2 mm mesh sizes were used to separate the effects of different size classes of predators. At both sites, a variety of colonial and solitary ascidians, bryozoans, sponges and polychaetes settled onto experimental surfaces. Predation had little impact on the recruitment success of taxa present at Williamstown and did not alter community structure. At Queenscliff, didemnid ascidians had higher abundances on completely caged plates (2 mm mesh) after 40 d, suggesting that they may have been preyed upon in treatments exposed to carnivores. However, predation had no effect on the densities of other taxa found on experimental surfaces, and there were no differences in overall community structure between treatments. Recruitment rates were low and predators were never observed on experimental surfaces at Queenscliff, so predation on newly settled recruits may be an uncommon occurrence for most taxa. In contrast, predators were commonly found on experimental surfaces at Williamstown, but recruitment rates were high and predators had little effect on the abundance of newly settled prey. The results of this study show that predators can have weak effects on recent recruits and that predation during early post-settlement is not a major process shaping the structure of all marine sessile communities.

Aim Kelp forests throughout temperate regions of the world serve as foundation species that play a critical role in sustaining the health and function of marine ecosystems but are experiencing declines in abundance due to a loss in resilience as the ocean climate changes. Ocean warming along southeast Australia has already been linked to dramatic losses of kelp species and is contributing to the range expansion and population increases of two species of sea urchin. This research attempts to understand the impact of multiple stressors on the decline in kelps in this region. Location Coastal Waters of Victoria, Southeast Australia. Methods In this study, we use long‐term (>20 years) datasets on biological observations across Victorian waters to determine trends in coverage and the impact of multiple environmental variables (oceanography, habitat, and urchin abundances) on two important kelps that serve as foundation species (Phyllospora comosa and Ecklonia radiata) using boosted regression trees. These models were then used to develop predictive distribution models for each species and also to project abundance distributions into the future. Results We found that both kelp species are decreasing in percent coverage over time with multiple environmental variables contributing to these declines, including increasing temperatures, intensifying wave energy, changes in currents and recruitment patterns, and increases in urchin populations. Additionally, future projections of temperature, wave energy, and urchin populations show that both species will continue to decrease across 62%–94% of their range by 2090. Main conclusions Long‐term biological datasets allowed us to develop maps of the past, current, and future distributions of these important foundation species, providing valuable information to managers for prioritization of areas for targeted urchin management and restoration of kelps. Understanding the environmental factors affecting their distribution helps guide manager restoration investments in regions where kelp populations are most likely to persist in the future.

Patients with rheumatoid arthritis (RA) are at increased risk of infection. In this study, we determined the risk of and risk factors for Staphyococcus aureus ( S. aureus ) sepsis in RA. We assembled a retrospective nested case–control subset of RA patients with S. aureus sepsis from the Barnes-Jewish Hospital Medical Informatics database, confirmed the diagnoses, and collected data electronically and by chart review. We used multivariate logistic regression to identify independent risk factors for S. aureus sepsis, with risk expressed as odds ratios (ORs). We extracted data on the length of hospitalization and 30-day and 1-year mortality from the Medical Informatics database for all cases and controls. There were 48 confirmed S. aureus sepsis cases and 232 confirmed controls in the RA cohort. In multivariate analysis, indwelling central venous catheter (OR 15.97; 95 % CI 5.09–50.10; p  < 0.01) and congestive heart failure (OR 2.89; 95 % CI 1.26–6.63; p  = 0.01) were independently associated with risk of S. aureus sepsis, while treatment with disease-modifying anti-rheumatic drugs (DMARDs), both biologic and non-biologic, was not. S. aureus sepsis was associated with increased 30-day and 1-year mortality (OR 7.37; 95 % CI 2.86–19.0; p  < 0.01 for 30-day and OR 5.24; 95 % CI 2.51–10.94; p  < 0.01 for 1-year mortality) and longer hospitalization ( p  < 0.01). Treatment with biologic DMARDs was not associated with longer hospitalization ( p  = 0.89). Indwelling central venous catheters and congestive heart failure increased the risk of S. aureus sepsis in this observational cohort of patients with RA. Treatment with biologic and non-biologic DMARDs did not increase this risk.

We examined the relationship of development, immunocompetence, and tick burdens to neonatal mortality in an overpopulated herd of white-tailed deer (Odocoileus virginianus) during 1990-1992 in northeastern Oklahoma. Risk of mortality to 21 days of age was inversely related to body mass, body mass/length3, delayed hypersensitivity to phytohemagglutinin, and serum concentrations of gamma globulin and gamma-glutamyl transferase (GGTP) for young ≤3days old. Serum GGTP and gamma-globulin concentrations were the most significant predictors of mortality to 21 days of age using multivariate-logistic regression. Increased probability of mortality was associated with lower serum gamma globulin and concentrations of GGTP, which suggested that inadequate absorption of colostrum leads to a partial failure in the passive process of transferring immunity from mother to offspring, and predisposes young to mortality agents among high-density herds.