The area-to-mass ratio and fractal dimension of marine flocs

publisher: Elsevier articletitle: The area-to-mass ratio and fractal dimension of marine flocs journaltitle: Estuarine, Coastal and Shelf Science articlelink: http://dx.doi.org/10.1016/j.ecss.2017.03.026 content_type: article copyright: © 2017 The Authors. Published by Elsevier Ltd

Titan's cold case files - Outstanding questions after Cassini-Huygens

Abstract The entry of the Cassini-Huygens spacecraft into orbit around Saturn in July 2004 marked the start of a golden era in the exploration of Titan, Saturn's giant moon. During the Prime Mission (2004–2008), ground-breaking discoveries were made by the Cassini orbiter including the equatorial dune fields (flyby T3, 2005), northern lakes and seas (T16, 2006), and the large positive and negative ions (T16 & T18, 2006), to name a few. In 2005 the Huygens probe descended through Titan's atmosphere, taking the first close-up pictures of the surface, including large networks of dendritic channels leading to a dried-up seabed, and also obtaining detailed profiles of temperature and gas composition during the atmospheric descent. The discoveries continued through the Equinox Mission (2008–2010) and Solstice Mission (2010–2017) totaling 127 targeted flybys of Titan in all. Now at the end of the mission, we are able to look back on the high-level scientific questions from the start of the mission, and assess the progress that has been made towards answering these. At the same time, new scientific questions regarding Titan have emerged from the discoveries that have been made. In this paper we review a cross-section of important scientific questions that remain partially or completely unanswered, ranging from Titan's deep interior to the exosphere. Our intention is to help formulate the science goals for the next generation of planetary missions to Titan, and to stimulate new experimental, observational and theoretical investigations in the interim

Species' traits affect the occurrence of birds in a native timber plantation landscape

Many of the world's terrestrial environments are dominated by production land-uses, making the incorporation of production landscapes into conservation strategies critical for halting global biodiversity declines. Two challenges for developing such strategies are: (1) determining species' capacity to survive in production land-uses; and (2) understanding why some species can survive, while others cannot. The interaction between biological traits of organisms and their response to disturbances may assist in resolving these challenges. We compared species and trait composition of 41 lowland rainforest birds among unlogged and forestry production land-uses on New Britain Island, Papua New Guinea. At least 92% of forest species occurred in mature, native Eucalyptus plantation and regrown logged forest. However, composition changes demonstrated successive loss of some species (medium-and large-bodied frugivores, forest specialists) with increasing intensity of disturbance, indicating that forestry management practices can affect the functional composition of forest birds. In contrast to many continental studies where endemism confers susceptibility to disturbance, we found endemic island species widely distributed across all land-uses, reflecting their capacity for colonizing new environments. Ecological traits can help to explain species' responses to landscape management, however, the type and intensity of disturbance and biogeography of the region affect the traits-disturbance interaction. Our study indicates that native plantations may be able to assist with biodiversity conservation while providing production values, but only if they are judiciously managed in concert with unlogged and regrown logged forest reserves

Vive la résistance: reviving resistance for 21st century conservation

Confronted with increasing anthropogenic change, conservation in the 21st century requires a sound understanding of how ecological systems change during disturbance. We highlight the benefits of recognizing two distinct components of change in an ecological unit (i.e., ecosystem, community, population): \u27resistance\u27, the ability to withstand disturbance; and \u27resilience\u27, the capacity to recover following disturbance. By adopting a \u27resistance-resilience\u27 framework, important insights for conservation can be gained into: (i) the key role of resistance in response to persistent disturbance, (ii) the intrinsic attributes of an ecological unit associated with resistance and resilience, (iii) the extrinsic environmental factors that influence resistance and resilience, (iv) mechanisms that confer resistance and resilience, (v) the post-disturbance status of an ecological unit, (vi) the nature of long-term ecological changes, and (vii) policy-relevant ways of communicating the ecological impacts of disturbance processes

Rock removal associated with agricultural intensification will exacerbate the loss of reptile diversity

Rocky environments host rich levels of biodiversity and provide vital habitat for specialised organisms, range-restricted species and a broad range of ectotherms adapted to saxicoline environments. In Australia, rock habitat is being destroyed during soil amelioration practices associated with agricultural intensification. Advances in rock crushing technology, developed to expand or increase crop yields and efficiency, pose an undocumented threat to global biodiversity, especially reptiles dependent on non-renewable rock habitat in agricultural landscapes. Rock removal is a legislated key threatening process in parts of Australia and will accelerate biodiversity loss if not mitigated. We estimated reptile species’ range overlap with dryland cropping and modified pastoral regions within the Australian wheat-sheep zone to assess the potential impacts of rock crushing practices. We examined species- and family-richness within the impact zone and across bioregions within the impact zone, to identify areas where rock removal has the greatest potential to impact terrestrial and fossorial squamates. Our analysis revealed that 159 potentially impacted reptile species occur within the study area, representing 16% of Australian terrestrial squamates. Fourteen of these species, including six threatened species, have more than 50% range overlap with areas of intensive agriculture, and include several endangered pygopodids, scincids and agamids. Bioregions rich in rock and burrow-dwelling reptiles include the Brigalow Belt South, Murray Darling Depression, Darling Riverine Plains, Eyre Yorke Block, Avon Wheatbelt, Nandewar, Flinders Lofty Block and New South Wales South Western Slopes. Synthesis and applications. The conservation of reptiles in agricultural landscapes requires appropriate management and retention of surface rocks. Potential yield increases from destroying rock habitat to intensify or expand cropland will not compensate for the net loss of reptile populations dependent on non-renewable resources. Financial incentives to prevent the expansion and transformation of non-arable landscapes to cropland are required to prevent the ongoing loss of biodiversity

Interpreting LISST-100X measurements of particles with complex shape using digital in-line holography

[1] Measurements of suspended sediment volume concentrations, particle size and number density are routinely collected in marine and fresh-water environments with LISST-100X instruments to understand sediment transport, biological processes and fundamental opto-acoustic problems. A LISST-100X was simultaneously deployed with a novel holographic camera (holocam) in UK coastal waters to assess the performance of the laser diffraction technique when measuring natural suspensions. Volume distributions from the LISST-100X, truncated to exclude non-overlapping size bins with the holocam, exhibit an increase in small particles and median particle size is elevated in comparison to the holocam by 20�40%. We observe positive offsets between LISST-100X and holocam number distributions of up to 2 orders of magnitude for particle sizes between 58�218μm, with discrepancies rising to 4 orders of magnitude for finer and coarser sizes. To explain these differences, a novel multiscale representation of particle size is used. The method quantifies individual dimensions that make up any two-dimensional geometrical structure, it can be used as a metric for particle complexity, and offers a plausible explanation for an apparent increase in small particles (<58μm) reported by the LISST-100X. The results suggest that for non-spherical natural suspensions the LISST-100X may be sensitive to optical scattering from sub-scales within larger particles, reporting them as individual particles regardless of the way in which they may be packaged into particles of larger overall size. We urge caution in over interpretation of LISST size distributions obtained in natural suspensions without verification with independent particle imaging