Multiple Processes Regulate Long-Term Population Dynamics of Sea Urchins on Mediterranean Rocky Reefs

We annually monitored the abundance and size structure of herbivorous sea urchin populations (Paracentrotus lividus and Arbacia lixula) inside and outside a marine reserve in the Northwestern Mediterranean on two distinct habitats (boulders and vertical walls) over a period of 20 years, with the aim of analyzing changes at different temporal scales in relation to biotic and abiotic drivers. P. lividus exhibited significant variability in density over time on boulder bottoms but not on vertical walls, and temporal trends were not significantly different between the protection levels. Differences in densities were caused primarily by variance in recruitment, which was less pronounced inside the MPA and was correlated with adult density, indicating density-dependent recruitment under high predation pressure, as well as some positive feedback mechanisms that may facilitate higher urchin abundances despite higher predator abundance. Populations within the reserve were less variable in abundance and did not exhibit the hyper-abundances observed outside the reserve, suggesting that predation effects maybe more subtle than simply lowering the numbers of urchins in reserves. A. lixula densities were an order of magnitude lower than P. lividus densities and varied within sites and over time on boulder bottoms but did not differ between protection levels. In December 2008, an exceptionally violent storm reduced sea urchin densities drastically (by 50% to 80%) on boulder substrates, resulting in the lowest values observed over the entire study period, which remained at that level for at least two years (up to the present). Our results also showed great variability in the biological and physical processes acting at different temporal scales. This study highlights the need for appropriate temporal scales for studies to fully understand ecosystem functioning, the concepts of which are fundamental to successful conservation and management

A novel cause of chronic viral meningoencephalitis: Cache Valley virus.

ObjectiveImmunodeficient patients are particularly vulnerable to neuroinvasive infections that can be challenging to diagnose. Metagenomic next generation sequencing can identify unusual or novel microbes and is therefore well suited for investigating the etiology of chronic meningoencephalitis in immunodeficient patients.MethodsWe present the case of a 34-year-old man with X-linked agammaglobulinemia from Australia suffering from 3 years of meningoencephalitis that defied an etiologic diagnosis despite extensive conventional testing, including a brain biopsy. Metagenomic next generation sequencing of his cerebrospinal fluid and brain biopsy tissue was performed to identify a causative pathogen.ResultsSequences aligning to multiple Cache Valley virus genes were identified via metagenomic next generation sequencing. Reverse transcription polymerase chain reaction and immunohistochemistry subsequently confirmed the presence of Cache Valley virus in the brain biopsy tissue.InterpretationCache Valley virus, a mosquito-borne orthobunyavirus, has only been identified in 3 immunocompetent North American patients with acute neuroinvasive disease. The reported severity ranges from a self-limiting meningitis to a rapidly fatal meningoencephalitis with multiorgan failure. The virus has never been known to cause a chronic systemic or neurologic infection in humans. Cache Valley virus has also never previously been detected on the Australian continent. Our research subject traveled to North and South Carolina and Michigan in the weeks prior to the onset of his illness. This report demonstrates that metagenomic next generation sequencing allows for unbiased pathogen identification, the early detection of emerging viruses as they spread to new locales, and the discovery of novel disease phenotypes. Ann Neurol 2017;82:105-114

Smashing tests? Patterns and mechanisms of adult mortality in a declining echinoid population

Mass mortality of echinoids is well documented, and has potentially profound effects on benthic communities. However, no study to date has quantitatively investigated how regular, predictable events such as winter storms might lead to large mortality events in pivotal echinoid species. Hydrodynamic disturbances can be major drivers of crucial biological processes in benthic communities. For echinoid populations in particular, wave action in shallow waters generated by high winds (winter storms) can cause displacement, damage and even death to individuals. However, evidence for displacement-mediated mortality is scant in the literature, in part because it is so difficult to demonstrate in exposed environments where echinoids are frequently found. In this study, we examined mortality in a sheltered subtidal population of the European purple sea urchin Paracentrotus lividus over a 3-year period, and examined the role that dislodgement by wave action or predation might play in these mortality patterns. Because our study population has been in decline for the past three decades, we considered it important to evaluate its current status in addition to assessing the contribution that adult mortality makes to that decline. We sampled twice per month, using the density of freshly dead echinoid material to assess the extent of adult mortality. The Irish Meteorological Service provided our estimates of wind speed data. We compared historical and recent data on P. lividus size frequency data to investigate change the population structure (Poor recruitment would be caused by failure to spawn over a prolonged period). Our data suggest ongoing declines in this population, and support the theory that the decline of the P. lividus population of Lough Hyne is a result of persistent recruitment failure linked to repeated cool maximum sea surface temperatures. Although we found peaks of P. lividus mortality were coincident with spikes in wind speed, mortality was low, and seems unlikely to have contributed significantly to the dramatic decline in P. lividus in the past three decades

The monopolization of understorey habitat by subtidal encrusting coralline algae: a test of the combined effects of canopy-mediated light and sedimentation

The original publication can be found at www.springerlink.comEncrusting-coralline-algae habitat monopolized the substrata (> 74% cover) under canopies of Ecklonia radiata at four sites (∼1 km apart) within each of four localities (> 100 km apart) spanning > 1000 km of continuous South Australian coastline. This monopolization was analyzed experimentally to test whether canopy-mediated shade and sedimentation account for this canopy-understorey association. I tested the hypothesis that initially different habitat types (turf-forming-algae habitat versus habitat dominated by encrusting coralline algae) will converge to become like those under E. radiata if subjected to lower light and accumulation of sediment in the absence of E. radiata. Convergence in the absence of canopies, but in physically similar environments as under canopies, provides strong evidence that understorey habitats are primarily dependent on the manipulated environments. The experiment was provided with sufficient time (338 days) to adequately test for convergence as evidenced by indistinguishable percentage covers of encrusting coralline algae between canopies and treatments of shade on previously unoccupied rock and between habitat types transplanted to canopies. Convergence of habitat types, however, did not occur under treatments of shade and sedimentation. The effect of lowering light accounted for ∼52% of the effect of canopies on percentage cover of encrusting-coralline-algae habitat. The effect of reducing sediment accumulation under shade was negligible. The magnitude of unaccounted effects (∼48%) highlights a need to assess alternative factors that act to exclude taxa from or include taxa in the understorey assemblage. It is clear that canopies place strong constraints on the presence and abundance of many taxa, but not encrusting-algae habitats which beneficially coexist as understorey. A more complete identification of such positive and negative effects is needed to improve our understanding of the conditions that produce readily recognizable canopy-understorey associations that are repeated with great fidelity on a regional scale