Length-weight relationships for some important forage crustaceans from South Africa

The diet of marine animals is usually determined by stomach content analysis. Although partially digested prey fragments can often be identified to species level, it is difficult to estimate the original mass of the prey organism. This information, however, is essential for calculating both the total food intake as well as the relative contribution of each prey item. In this study we present regression equations that can be used to estimate the original mass of 18 common South African crustaceans from various indigestible fragments such as the carapace (length and width), chelae (length and width of left and right dactylus) and eye (length and width)

The relative importance of food and temperature to copepod egg production and somatic growth in the southern Benguela upwelling system

The fecundity and somatic growth rates of Calanus agulhensis and Calanoides carinatus, the dominant large calanoid copepods in the southern Benguela upwelling system, as well as the fecundity of several other common copepods, were measured between September and March of 1993/94 and 1994/95. Mean egg production of most copepods was low at >30 eggs female-1 day-1 {Calanoides carinatus 23.7, Calanus agulhensis 19.0, Neocalanus tonsus 16.1 and Rhincalanus nasutus 26.1), whereas the mean fecundity of Centropages brachiatus was significantly greater (83.6 eggs female-1 day-1). This study also presents the first comprehensive field estimates of the fecundity of Nanno-calanus minor (mean: 26.1 eggs female-1 day-1, range: 0.0–96.2 eggs female-1 day-1) and of somatic growth of N6 and all copepodite stages of Calanoides carinatus (decreasing from 0.58 day-1 for N6 to 0.04 day-1 for C5). Somatic growth rates of Calanus agulhensis also declined with age: from 0.57 day1 for N6 to 0.09 day1 for C5. Data on growth rates were used to assess the relative importance of food [as measured by total chlorophyll (Chi) a concentration], phytoplankton cell size (proportion of cells >10 µm) and temperature to the growth of copepods. Multiple regression results suggested that fecundity and somatic growth rates were positively related to both Chi a concentration and phytoplankton cell size, but not to temperature. Although it was not possible to separate the effects of Chi a concentration and phytoplankton cell size, data from previous laboratory experiments suggest that copepod growth is not limited by small cells per se, but by the low Chi a concentrations that are associated with these particles in the field. Despite growth not being directly related to temperature, a dome-shaped relationship was evident in some species, with slower growth rates at cool (<13°C) and warm (>18°C) temperatures. The shape of this relationship mirrors that of Chi a versus temperature, where poor Chi a concentrations are associated with cool and warm temperatures. It is concluded that the effect of food limitation on growth of copepods outweighs that of temperature in the southern Benguela region. Sources of variability in relationships between growth and Chi a concentration are discussed

Modeling the effect of copper availability on bacterial denitrification

When denitrifying bacteria such as Paracoccus denitrificans respire anaerobically they convert nitrate to dinitrogen gas via a pathway which includes the potent greenhouse gas, nitrous oxide (NO). The copper-dependent enzyme Nitrous Oxide reductase (Nos) catalyzes the reduction of NO to dinitrogen. In low-copper conditions, recent experiments in chemostats have demonstrated that Nos efficiency decreases resulting in significant NO emissions. For the first time, a chemostat-based mathematical model is developed that describes the anaerobic denitrification pathway based on Michaelis-Menten kinetics and published kinetic parameters. The model predicts steady-state enzyme levels from experimental data. For low copper concentrations, the predicted Nos level is significantly reduced, whereas the levels for the non copper-dependent reductases in the pathway remain relatively unaffected. The model provides time courses for the pathway metabolites that accurately reflect previously published experimental data. In the absence of experimental data purely predictive analyses can also be readily performed by calculating the relative Nos level directly from the copper concentration. Here, the model quantitatively estimates the increasing level of emitted NO as the copper level decreases. We have developed a mathematical model for the denitrification pathway based on existing experimental results, Michaelis-Menten kinetics and experimentally obtained kinetic constants. This is the first such model to incorporate the copper concentration in order to predict emissions of the potent greenhouse gas, nitrous oxide (NO), as well as the other nitrogenous compounds in the pathway. The model predicts increasing NO emissions as the copper level is lowered, in agreement with experimental observations in chemostats. © 2013 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Rapid wound healing in a reef manta ray masks the extent of vessel strike

Increasing vessel traffic in the marine environment due to commercial and recreational activities has amplified the number of conflicts with marine animals. However, there are limited multi-year observations of the healing rate of marine animals following vessel strike. Here we document the healing rate of a reef manta ray Mobula alfredi, following lacerations caused by a propeller along the pectoral fin. We demonstrate a high healing capacity, with wound length following a negative exponential curve over time. Lacerations healed to 5% of the initial wound length (i.e. 95% closure) within 295 days. The wounds appeared to stabilise at this point as observed more than three years following the incident and resulted in a distinctive scarring pattern. Examination of an extensive photo-identification catalogue of manta rays from the Ningaloo Coast World Heritage Area showed that the scarring pattern occurs more frequently than previously recognised, as the wounds had been previously attributed to failed predation attempts. This study provides baseline information for wound healing from vessel strike in reef manta rays and indirect evidence for increased vessel strikes on manta rays within the Ningaloo Coast World Heritage Area. We discuss the implication for spatial and behavioural management of vessels around manta rays

Coral species composition drives key ecosystem function on coral reefs

Rapid and unprecedented ecological change threatens the functioning and stability of ecosystems. On coral reefs, global climate change and local stressors are reducing and reorganizing habitat-forming corals and associated species, with largely unknown implications for critical ecosystem functions such as herbivory. Herbivory mediates coral–algal competition, thereby facilitating ecosystem recovery following disturbance such as coral bleaching events or large storms. However, relationships between coral species composition, the distribution of herbivorous fishes and the delivery of their functional impact are not well understood. Here, we investigate how herbivorous fish assemblages and delivery of two distinct herbivory processes, grazing and browsing, differ among three taxonomically distinct, replicated coral habitats. While grazing on algal turf assemblages was insensitive to different coral configurations, browsing on the macroalga Laurencia cf. obtusa varied considerably among habitats, suggesting that different mechanisms may shape these processes. Variation in browsing among habitats was best predicted by the composition and structural complexity of benthic assemblages (in particular the cover and composition of corals, but not macroalgal cover), and was poorly reflected by visual estimates of browser biomass. Surprisingly, the lowest browsing rates were recorded in the most structurally complex habitat, with the greatest cover of coral (branching Porites habitat). While the mechanism for the variation in browsing is not clear, it may be related to scale-dependent effects of habitat structure on visual occlusion inhibiting foraging activity by browsing fishes, or the relative availability of alternate dietary resources. Our results suggest that maintained functionality may vary among distinct and emerging coral reef configurations due to ecological interactions between reef fishes and their environment determining habitat selection

Optical fiber fabrication using novel gas-phase deposition technique

We report a highly versatile chemical-in-crucible preform fabrication technique suitable for gas-phase deposition of doped optical fibers. Aluminosilicate and ytterbium-doped phosphosilicate fibers are presented demonstrating the technique and its potential for realizing complex fiber designs that are suitable for the next generation of high-power fiber devices. The results show aluminum-doped fiber with numerical aperture of 0.28 and ytterbium-doped fiber with a measured slope efficiency of 84% with respect to pump launch power

Chapter 06: Vulnerability of Great Barrier Reef plankton to climate change

Our approach here is to examine potential ways that climate change may alter plankton communities of the GBR in the future, focusing on the physical mechanisms that currently drive plankton productivity and composition. Many of the oceanographic and climatic features of the western Coral Sea and GBR region and the ways in which they may be influenced by climate change are detailed in Steinberg (see chapter 3). Smaller members of the plankton such as the viruses and bacteria are covered by Webster and Hill (see chapter 5). Key reef-associated organisms with planktonic life stages such as crown-of-thorns starfish, corals, fish and jellyfish, as well as the ecosystem-level responses such as their recruitment and patch connectivity, will be covered by Kingsford and Welch (see chapter 18). Since there are no long time series of plankton data for waters of the GBR for assessing climaterelated trends and their drivers, and few detailed studies in the laboratory or in the field, this review necessarily draws on relevant knowledge from other ecosystems, tropical where possible, and others when required.This is Chapter 6 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13

Nano-scale composition of commercial white powders for development of latent fingerprints on adhesives

This is the post-print version of the article - Copyright @ 2010 Elsevier.Titanium dioxide based powders are regularly used in the development of latent fingerprints on dark surfaces. For analysis of prints on adhesive tapes, the titanium dioxide can be suspended in a surfactant and used in the form of a powder suspension. Commercially available products, whilst having nominally similar composition, show varying levels of effectiveness of print development, with some powders adhering to the background as well as the print. X-ray fluorescence (XRF), analytical transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and laser particle sizing of the fingerprint powders show TiO2 particles with a surrounding coating, tens of nanometres thick, consisting of Al and Si rich material, with traces of sodium and sulphur. Such aluminosilicates are commonly used as anti-caking agents and to aid adhesion or functionality of some fingerprint powders; however, the morphology, thickness, coverage and composition of the aluminosilicates are the primary differences between the white powder formulations and could be related to variation in the efficacy of print development.This work is part funded by the Home Office Scientific Development Branch, UK

The toxicity of chlorpyrifos towards differentiating mouse N2a neuroblastoma cells

The aim of this work was to study the effects of chlorpyrifos (CPF) on the outgrowth of axons by differentiating mouse N2a neuroblastoma cells. This was achieved by morphological, Western blotting and enzymatic analyses of cells induced to differentiate in the presence and absence of CPF added either at the same time (co-differentiation) or 16 h after (post-differentiation) the induction of cell differentiation. The outgrowth of axon-like processes was impaired following 4 or 8 h exposure to CPF in both co- and post-differentiation experiments. Western blotting analysis revealed reduced levels of neurofilament heavy chain (NF-H) following 8 h of exposure but no significant effect at 4 h under both co- and post-differentiation conditions. By contrast, levels of the heat shock protein HSP-70 were raised at both time points, but only in co-differentiation experiments. Neuropathy target esterase (NTE) activity was lower than controls following 4 or 8 h of exposure under co-differentiation conditions, but not under any post-differentiation conditions. The results suggest that the inhibition of axon production and maintenance by CPF in differentiating N2a cells may involve multiple targets, which are different under co- and post-differentiation conditions