1,802 research outputs found
The loss of natural habitats and the addition of artificial substrata
No full textLaura Airoldi, Sean D. Connell and Michael W. Bec
Portrait of author Jackson A. Graves, [s.d.]
No full textPhotographic portrait of author Jackson A. Graves, [s.d.]. Graves is shown from his upper torso to his head and is looking to the right. He is wearing a light-colored suit, a light shirt, and a dark tie with a square pattern. He has light-colored hair that is neatly combed and parted at left, a thick light mustache, and light eyebrows. There are large bags beneath his eyes and his ears are very big
What are algal turfs? Towards a better description of turfs
No full textThe use of standardised classifications, or operational definitions, is essential if different researchers are to measure and compare similar entities. In the marine realm, algal 'turfs' are increasingly reported to be globally expanding at the expense of kelps and canopy-forming algae. However, ecological research about the underlying drivers of this shift is limited by a vague and inconsistent definition of what exactly a turf is. In order to stimulate more effective descriptions of 'turfs' and facilitate communication of research outcomes and comparisons across studies, we reviewed the use of the term turf in ecological studies of temperate coasts and coral reefs and (1) identified the main types and distribution of algal assemblages known as 'turfs', (2) examined the descriptions of turfs so that we may recognise some general characteristics, including those contingent on environmental conditions; and (3) offered character descriptions that could improve communication and comparisons. These descriptors centre on reporting information on the morphology, height, density of thalli, the amount of sediment trapped in turfs and a description of the area covered by turfs, including their patchiness and persistence. Our review recognised these as common attributes that could be usefully described across a wide range of circumstances and provide insights into the ecology of turfs and their interactions with other assemblages in a community. The use of common descriptors would provide the term 'turf' with greater scientific valu
Resisting regime-shifts: the stabilising effect of compensatory processes
No full textEcologists seem predisposed to studying change because we are intuitively interested in dynamic systems, including their vulnerability to human disturbance. We contrast this disposition with the value of studying processes that work against change. Although powerful, processes that counter disturbance often go unexplored because they yield no observable community change. This stability results from compensatory processes which are initiated by disturbance; these adjust in proportion to the strength of the disturbance to prevent community change. By recognising such buffering processes, we might also learn to recognise the early warning signals of community shifts which are notoriously difficult to predict because communities often show little to no change before their tipping point is reached.Sean D. Connell and Giulia Ghedin
Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers
No full textIncreasing oceanic uptake of CO₂ is predicted to drive ecological change as both a resource (i.e. CO₂ enrichment on primary producers) and stressor (i.e. lower pH on consumers). We use the natural ecological complexity of a CO₂ vent (i.e. a seagrass system) to assess the potential validity of conceptual models developed from laboratory and mesocosm research. Our observations suggest that the stressor-effect of CO₂ enrichment combined with its resource-effect drives simplified food web structure of lower trophic diversity and shorter length. The transfer of CO₂ enrichment from plants to herbivores through consumption (apparent resource-effect) was not compensated by predation, because carnivores failed to contain herbivore outbreaks. Instead, these higher-order consumers collapsed (apparent stressor-effect on carnivores) suggesting limited trophic propagation to predator populations. The dominance of primary producers and their lower-order consumers along with the loss of carnivores reflects the duality of intensifying ocean acidification acting both as resource-effect (i.e. bottom-up control) and stressor-effect (i.e. top-down control) to simplify community and trophic structure and function. This shifting balance between the propagation of resource enrichment and its consumption across trophic levels provides new insights into how the trophic dynamics might stabilize against or propagate future environmental change.S. Vizzini, B. Martínez-Crego, C. Andolina, A. Massa-Gallucci, S.D. Connell, M.C. Gamb
Reproducibility crisis and gravitation towards a consensus in ocean acidification research
No full textPublished online: 25 September 2023Reproducibility is a persistent concern in science and recently attracts considerable attention in assessing biological responses to ocean acidification. Here we track the reproducibility of the harmful effects of ocean acidification on calcification of shell-building organisms by conducting a meta-analysis of 373 studies across 24 years. The pioneering studies tended to report large negative effects, but as other researchers assimilated this research into understanding their biological systems, the size of negative effects declined. Such declines represent a scientific process by which discoveries are initially assimilated and their limitations are subsequently explored. We suggest that scientific novelties can polarize a discipline where researchers fail to distinguish between different motivations for testing a phenomenon, that is, its existence (theory proposal) versus its influence within ever-widening contexts (theory development). Where context dependency is high, the lack of reproducibility may not represent a crisis but a part of theory development and eventual gravitation towards a consensus position.Sean D. Connell and Jonathan Y. S. Leun
Recovering a lost baseline: missing kelp forests from a metropolitan coast
No full text© 2008 AuthorThere is concern about historical and continuing loss of canopy-forming algae across the world’s temperate coastline. In South Australia, the sparse cover of canopy-forming algae on the Adelaide metropolitan coast has been of public concern with continuous years of anecdotal evidence culminating in 2 competing views. One view considers that current patterns existed before the onset of urbanisation, whereas the alternate view is that they developed after urbanisation. We tested hypotheses to distinguish between these 2 models, each centred on the reconstruction of historical covers of canopies on the metropolitan coast. Historically, the metropolitan sites were indistinguishable from contemporary populations of reference sites across 70 km (i.e. Gulf St. Vincent), and could also represent a random subset of exposed coastal sites across 2100 km of the greater biogeographic province. Thus there was nothing ‘special’ about the metropolitan sites historically, but today they stand out because they have sparser covers of canopies compared to equivalent locations and times in the gulf and the greater province. This is evidence of wholesale loss of canopy-forming algae (up to 70%) on parts of the Adelaide metropolitan coast since major urbanisation. These findings not only set a research agenda based on the magnitude of loss, but they also bring into question the logic that smaller metropolitan populations of humans create impacts that are trivial relative to that of larger metropolitan centres. Instead, we highlight a need to recognise the ecological context that makes some coastal systems more vulnerable or resistant to increasing human-domination of the world’s coastlines. We discuss challenges to this kind of research that receive little ecological discussion, particularly better leadership and administration, recognising that the systems we study out-live the life spans of individual research groups and operate on spatial scales that exceed the capacity of single research providers.Sean D. Connell, Bayden D. Russell, David J. Turner, Scoresby A. Shepherd, Timothy Kildea, David Miller, Laura Airoldi, Anthony Cheshir
Simulation and Control of a Pneumatic Muscle Actuator for a Rehabilitation Robot
No full textThe perfomance of a pneumatic muscle actuator, invented by Jim Hennequin and used in a prototype wheelchair-mounted robot ann designed by the first author is reported. Experimental measurements were made of the output torque versus rotary motion and internal pressure. The torque available for a muscle of size 60 mm width by 90 mm length ranges from 1 to 15 Nm. The rotary stiffness of this muscle is 0.081 Nm/deg. A simulation model of the dynamic behaviour of the muscle attached to the robot arm using one-dimensional flow theory was written in ACSL (Advanced Continuous Simulation Language). The resultant simulation gives good agreement to within ± 5% of the experimental values. Control using proportional and a PID controller is shown to be effective
Painted portrait of Father Geronimo Boscana, O.F.M., author of Chinigchinich, [s.d.]
No full textPhotograph of a painted portrait of Father Geronimo Boscana, O.F.M., author of "Chinigchinich", [s.d.]. The friar is at center, is shown from his upper torso to his head and is looking slightly to the right. He is wearing a light-colored hooded robe with the hood pulled halfway up his head. He has some thin white hair but is mostly bald. Chinigchinich was an account of California Indian life, focused on the Indians near San Juan Capistrano
Portrait of James Laughlin, author of "This Is My Blood," [s.d.]
No full textPhotographic portrait of James Laughlin, author of "This Is My Blood," [s.d.]. A elderly man with smiling eyes turns his face toward the camera. He has a slight smile on his face, and a large nose, bushy eyebrows and slicked-back graying hair. He wears a light-colored suit, striped tie, and undergarment.; The book was to be published March 3, 1989 in a limited edition by The Yolla Bolly Press
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