Noise sensitivity of sub- and supercritically bifurcating patterns with group velocities close to the convective-absolute instability

The influence of small additive noise on structure formation near a forwards and near an inverted bifurcation as described by a cubic and quintic Ginzburg Landau amplitude equation, respectively, is studied numerically for group velocities in the vicinity of the convective-absolute instability where the deterministic front dynamics would empty the system.Comment: 16 pages, 7 Postscript figure

Thirty years of research on Crown-of-Thorns Starfish (1986–2016): Scientific advances and emerging opportunities

Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in response to population outbreaks at specific locations. This review considers advances in our understanding of the biology and ecology of CoTS based on the resurgence of research interest, which culminated in this current special issue on the Biology, Ecology and Management of Crown-of-Thorns Starfish. More specifically, this review considers progress in addressing 41 specific research questions posed in a seminal review by P. Moran 30 years ago, as well as exploring new directions for CoTS research. Despite the plethora of research on CoTS ( > 1200 research articles), there are persistent knowledge gaps that constrain effective management of outbreaks. Although directly addressing some of these questions will be extremely difficult, there have been considerable advances in understanding the biology of CoTS, if not the proximate and ultimate cause(s) of outbreaks. Moving forward, researchers need to embrace new technologies and opportunities to advance our understanding of CoTS biology and behavior, focusing on key questions that will improve effectiveness of management in reducing the frequency and likelihood of outbreaks, if not preventing them altogether

A Comparison of Solar Cycle Variations in the Equatorial Rotation Rates of the Sun's Subsurface, Surface, Corona, and Sunspot Groups

Using the Solar Optical Observing Network (SOON) sunspot-group data for the period 1985-2010, the variations in the annual mean equatorial-rotation rates of the sunspot groups are determined and compared with the known variations in the solar equatorial-rotation rates determined from the following data: i) the plasma rotation rates at 0.94Rsun, 0.95Rsun,...,1.0Rsun measured by Global Oscillation Network Group (GONG) during the period 1995-2010, ii) the data on the soft X-ray corona determined from Yohkoh/SXT full disk images for the years 1992-2001, iii) the data on small bright coronal structures (SBCS) which were traced in Solar and Heliospheric Observatory (SOHO)/EIT images during the period 1998-2006, and iv) the Mount Wilson Doppler-velocity measurements during the period 1986-2007. A large portion (up to approximate 30 deg latitude) of the mean differential-rotation profile of the sunspot groups lies between those of the internal differential-rotation rates at 0.94Rsun and 0.98Rsun.The variation in the yearly mean equatorial-rotation rate of the sunspot groups seems to be lagging that of the equatorial-rotation rate determined from the GONG measurements by one to two years.The amplitude of the latter is very small.The solar-cycle variation in the equatorial-rotation rate of the solar corona closely matches that determined from the sunspot-group data.The variation in the equatorial-rotation rate determined from the Mount Wilson Doppler-velocity data closely resembles the corresponding variation in the equatorial-rotation rate determined from the sunspot-group data that included the values of the abnormal angular motions (> 3 deg per day) of the sunspot groups. Implications of these results are pointed out.Comment: 22 pages, 10 figures, accepted by Solar Physic

A Standard Law for the Equatorward Drift of the Sunspot Zones

The latitudinal location of the sunspot zones in each hemisphere is determined by calculating the centroid position of sunspot areas for each solar rotation from May 1874 to June 2011. When these centroid positions are plotted and analyzed as functions of time from each sunspot cycle maximum there appears to be systematic differences in the positions and equatorward drift rates as a function of sunspot cycle amplitude. If, instead, these centroid positions are plotted and analyzed as functions of time from each sunspot cycle minimum then most of the differences in the positions and equatorward drift rates disappear. The differences that remain disappear entirely if curve fitting is used to determine the starting times (which vary by as much as 8 months from the times of minima). The sunspot zone latitudes and equatorward drift measured relative to this starting time follow a standard path for all cycles with no dependence upon cycle strength or hemispheric dominance. Although Cycle 23 was peculiar in its length and the strength of the polar fields it produced, it too shows no significant variation from this standard. This standard law, and the lack of variation with sunspot cycle characteristics, is consistent with Dynamo Wave mechanisms but not consistent with current Flux Transport Dynamo models for the equatorward drift of the sunspot zones.Comment: 12 pages, 7 color figure

Magnetic Field Generation in Stars

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

Disentangling the response of fishes to recreational fishing over 30 years within a fringing coral reef reserve network

Few studies assess the effects of recreational fishing in isolation from commercial fishing. We used meta-analysis to synthesise 4444 samples from 30 years (1987–2017) of fish surveys inside and outside a large network of highly protected reserves in the Ningaloo Marine Park, Western Australia, where the major fishing activity is recreational. Data were collected by different agencies, using varied survey designs and sampling methods. We contrasted the relative abundance and biomass of target and non-target fish groups between fished and reserve locations. We considered the influence of, and possible interactions between, seven additional variables: age and size of reserve, one of two reserve network configurations, reef habitat type, recreational fishing activity, shore-based fishing regulations and survey method. Taxa responded differently: the abundance and biomass inside reserves relative to outside was higher for targeted lethrinids, while other targeted (and non-targeted) fish groups were indistinguishable. Reef habitat was important for explaining lethrinid response to protection, and this factor interacted with reserve size, such that larger reserves were demonstrably more effective in the back reef and lagoon habitats. There was little evidence of changes in relative abundance and biomass of fishes with reserve age, or after rezoning and expansion of the reserve network. Our study demonstrates the complexities in quantifying fishing effects, highlighting some of the key factors and interactions that likely underlie the varied results in reserve assessments that should be considered in future reserve design and assessment

The fish communities and main fish populations of the Jurien Bay Marine Park

The Strategic Research Fund for the Marine Environment funded a range of floral and faunal research projects to determine the characteristics of the marine communities in the Jurien Bay Marine Park (JBMP), which was gazetted in 2003. This project has determined the diversity, density and species compositions of the fishes that occupy reefs, seagrass, unvegetated sand and nearshore surf zone habitats in three different types of management zones in the JBMP. The zones were (1) General use zones, where all types of fishing are allowed. (2) Scientific reference zones, where recreational and commercial rock lobster fishing and selected shore-based fishing activities are allowed. (3) Sanctuary zones, where no boat-based fishing is permitted. Future management of the marine park requires a sound understanding of the relationships among the fish faunas, both within and among the main habitat types in each of the different management zones, and of the variability that occurs at different spatial scales. The vision provided by the management plan for the JBMP was: “In the year 2025, the marine flora and fauna, habitats and water quality of the Jurien Bay Marine Park will be in the same or better condition than in the year 2005. The area will support viable and ecologically sustainable fishing, aquaculture, recreation and nature-based tourism and the marine park will be considered an important asset by the local community” (Anon., 2005). Key performance indicators, described in the management plan, were designed to ensure that this vision is met. This requires data on how estimates of abundance of fishes varied according to the type of sampling method used during this study. The baseline values for different sampling methods can then be used, in the future, to assess whether the vision for the marine park has been achieved. This study used the following complementary sampling methods to survey fishes in the different habitats in the JBMP, i.e. underwater visual census (UVC) and baited remote underwater video stations (BRUVS) over reefs, BRUVS and trawling in seagrass and over unvegetated sand and seine netting in surf zones. The combined results from the different methods demonstrated that the fish fauna of the JBMP is diverse and comprises temperate, sub-tropical and tropical species. Variability in the fish faunas was detected both within and among the main habitat types and was related to the range of physical and biological characteristics present. The compositions of species sampled by each method differed. In particular, whereas the samples obtained using UVC, trawling and seine netting contained a range of trophic groups, those collected employing BRUVS were dominated by carnivorous species. These differences in ichthyofaunal composition within and among habitat types and between sampling methods must thus be taken into account when selecting the methods used both for long-term monitoring of fish communities and for providing the types of data necessary for assessing whether the marine park is achieving its objectives

Growth and mortality in juvenile corals (Goniastrea, Platygyra and Acropora): the first year

Past research on coral growth and mortality in the first year of life has been limited to species which brood their larvae. The larvae of three broadcast-spawning scleractinians, (Goniastrea aspers, Platygyra sinensis, Acropora millepora) were raised in sufficient numbers to obtain data on post-settlement growth and mortality. These are the first data on the growth of post-settlement stages < 1 year) for non-planulating species.\ud \ud Larvae were capable of settlement 3 to 4 days after spawning, at which time they were transferred to aquaria supplied with cut plates of coral. After settlement, these plates were deployed on reefs at Magnetic Island and at Orpheus Island. Zooxanthelae were not present in G. aspera or P. sinensis larvae, or in spat 5 days after settlement on the reef. After 10 days, juveniles of all three species contained zooxanthellae.\ud \ud The growth rates of juvenile G. aspera, P. sinensis and A. millepora (1.5-6.8 mm mean diameter in the first year) are considerably slower than those of juveniles from planulating species (greater than 10 mm diameter).\ud \ud The growth rates of G. aspera and P. sinensis were very similar, (1.6 and 1.4 mm diameter) while A. millepora (6.8 mm diameter) grew much more rapidly than either of the massive species. These growth rates are less than half those reported for the spat of planulating species of scleractinia.\ud \ud Rates of mortality during the first year of life for scleractinian corals in situ are reported for the first time. Mortality of juveniles was calculated between the time of their first measurement (1-2 months old) and their most recent measurement (8-9 months old). The rate of mortality was similar for all three species, however the overall mortality of A. millepora (86%) was slightly higher than that of either of the two massive species, G. aspera (67%) and P. sinensis (73%) over the first 8 months of life