Health status of the coral communities of the northern Galapagos Islands Darwin, Wolf and Marchena

Spatially reduced distributions of Galapagos corals and fragmented habitat, after recent strong El Niño Southern Oscillation events and greatly increased levels of human visitation, fisheries activities and dive tourism, raise important conservation questions as to the effects of compounding stress upon coral communities. A lack of knowledge concerning zooxanthellate coral disease in the Galapagos Marine Reserve, which could be used as an indicator of natural and/or anthropogenic stress prompted this characterisation of Galapagos coral health abnormalities. Colony condition was evaluated during research cruises conducted in September 2005, May 2006 and March 2007 at the northern islands of Wolf and Darwin, and in the north-central archipelago at Marchena. Observations of coral health and associated biota were taken for different coral species and sites, allowing characterisation of health anomalies that may indicate disease. Frequency of occurrence (FOC: the proportion of sites exhibiting a particular symptom) across sites and prevalence (the proportion of colonies presenting symptoms) were determined for six species-specific and three general anomalous health states. Over the eight coral reef communities sampled, the overall prevalence was 23.9 % (n = 973). The massive coral Porites lobata was found to be most affected, with 35 % showing symptoms of parasitism or illness. The most common health anomaly was identified as Porites trematodiasis, with 32 % overall prevalence within sites and found in all surveyed sites (FOC = 100 %)

Establishing reference points to assess long-term change in zooxanthellate coral communities of the northern Galapagos coral reefs

Dramatic reduction in zooxanthellate corals through bleaching during the 1982–3 El Niño event and subsequent bio- erosion have resulted in archipelago-wide loss and fragmentation of coral habitat. Slow natural recovery and the risk to corals from global climate change raise important coral conservation questions in a multi-use reserve. The largest coral reef communities remaining at Wolf, Darwin and Marchena islands were surveyed, to provide information on the conditionof these last persisting reef systems as a basis for future evaluation of the effects of climate change, human use and management upon them. Over the period September 2005 to February 2007, 2250 m of subtidal habitat were surveyed at 15 m and 6 m depth at four study sites. At each site we recorded substrate heterogeneity, zooxanthellate coral diversity and relative abundance, simple measurements of colony size, reef relief and health, and relative abundances and size distributions of the associated subtidal marine community (sessile macroinvertebrates and algae, mobile macro invertebrates and reef fish). Given the high level of tourism visitation, restricted range of the coral reef, considerable small scale between-site differences in coral species composition and associated subtidal assemblages, high subtidal species diversity unique to the northerly islands, and strong frequent climatic stress, appropriate additional protective measures, such as low impact fixed moorings, are recommended. Such measures will help conserve the ecosystem function of these key habitat-forming species both in the north and for the archipelago as a whole

Rapid seafloor mapping of the northern Galapagos Islands, Darwin and Wolf

Darwin and Wolf are the most remote of the Galapagos islands and are famous for their remarkable pelagic and benthic marine species abundance and diversity. However, little is known about their surrounding bathymetry. Rapid surveys were carried out in 2008 and 2009 to collect geo-referenced depth soundings down to 100 m around both islands, as a step towards a better understanding of their habitat and species distribution. Five spatial interpolation methods were tested on the data, to find the most accurate. The Triangular Irregular Network (TIN) was the best interpolator for these data sets with the fewest interpolation errors, and was then used to create contour and three dimensional maps of the seafloor topography of both islands. Darwin has a bigger insular platform with gentle submarine slopes whereas Wolf has very steep slopes with a smaller platform

Structure and Evolution of Star Clusters in the Vicinity of the Magellanic Clouds

This thesis describes the collection, reduction, and analysis of Charge Coupled Detector (CCD) images of star clusters. The objects studied are primarily in the Large Magellanic Cloud (LMC), a nearby galaxy. The study of these groupings can provide information such as the initial dynamic state of Globular Clusters, the heavy-clement enrichment rate of the LMC, the distribution of masses that stars form with, and the validity of given stellar evolution models. The majority of the observations were collected at Mount John University Observatory (NZ). Procedures for the collection and transfer of the data are described, along with an overview of the analysis facility and CCDs. Statistical moment-based ellipse fitting was applied to the observations, confirming that trends are evident in the position angles and ellipticities of the clusters, as had been reported in the literature. Artificial images of clusters with known parameters were generated and subjected to the same analysis techniques, revealing apparent trends caused by stochastic processes. Caution should therefore be exercised in the interpretation of observational trends in the structure of young LMC clusters. Isochrones were used to date the 19 clusters. The resulting ages are in good agreement with the literature, as are results from profile modeling. There is no evidence for tidal truncation of the young clusters. Observations were made of two LMC and two Galactic star clusters in a test of imaging clusters with the Vilnius photometric system and a CCD. The colour-magnitude diagrams, distances and interstellar reddenings of the clusters were derived and found to be in agreement with the literature. This is the first time that the standard Vilnius filter set has been used with a CCD. Use of the system for direct imaging of star clusters appears promising. Johnson BV CCD observations were made of the young LMC cluster NGC 2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence was found from profile fitting or the colour-magnitude diagrams to support this contention. Completeness factors were estimated for the CCD frames. These values were used in conjunction with luminosity functions to estimate the Initial Mass Function (IMF) for NGC 2214. A power-law M-(1+x) was assumed for the IMF (where M is stellar mass relative to that of the Sun Mo), with a good fit being found for x = 1.01 plus-minus 0.09. There is some indication that the low mass end (less than or equal to 3oMo) has a smaller gradient than the high mass end of the derived IMF. The value of x is in reasonable agreement with literature values for other Magellanic IMFs, and not substantially different from the poorly determined Galactic IMFs, suggesting the possibility of a 'universal' IMF over the Magellanic Clouds and our Galaxy in the mass range tilde 1 to tilde 10 Mo

The Discovery of XY Sex Chromosomes in a \u3cem\u3eBoa\u3c/em\u3e and \u3cem\u3ePython\u3c/em\u3e

For over 50 years, biologists have accepted that all extant snakes share the same ZW sex chromosomes derived from a common ancestor [1, 2, 3], with different species exhibiting sex chromosomes at varying stages of differentiation. Accordingly, snakes have been a well-studied model for sex chromosome evolution in animals [1, 4]. A review of the literature, however, reveals no compelling support that boas and pythons possess ZW sex chromosomes [2, 5]. Furthermore, phylogenetic patterns of facultative parthenogenesis in snakes and a sex-linked color mutation in the ball python (Python regius) are best explained by boas and pythons possessing an XY sex chromosome system [6, 7]. Here we demonstrate that a boa (Boa imperator) and python (Python bivittatus) indeed possess XY sex chromosomes, based on the discovery of male-specific genetic markers in both species. We use these markers, along with transcriptomic and genomic data, to identify distinct sex chromosomes in boas and pythons, demonstrating that XY systems evolved independently in each lineage. This discovery highlights the dynamic evolution of vertebrate sex chromosomes and further enhances the value of snakes as a model for studying sex chromosome evolution

The large NcN_c limit of four-point functions in N=4 super-Yang-Mills theory from anti-de Sitter Supergravity

We compute the imaginary part of scalar four-point functions in the AdS/CFT correspondence relevant to N=4 super Yang-Mills theory. Unitarity of the AdS supergravity demands that the imaginary parts of the correlation functions factorize into products of lower-point functions. We include the exchange diagrams for scalars as well as gravitons and find explicit expressions for the imaginary parts of these correlators. In momentum space these expressions contain only rational functions and logarithms of the kinematic invariants, in such a manner that the correlator is not a free-field result. The simplicity of these results, however, indicate the possibility of additional symmetry structures in N=4 super Yang-Mills theory in the large $N_c$ limit at strong effective coupling. The complete expressions may be computed from the integral results derived here.Comment: 23 pages, latex, additional references and comment

Caulerpa chemnitzia in Darwin threatening Galapagos coral reefs

Coral reefs are rare in the Galapagos and there is concern that, like in many areas around the world, they may be degrading due to increasing anthropogenic pressure, which can cause changes and reorganizations of structure and function with associated phase shifts. Algae of the genus Caulerpa J.V. Lamouroux, 1809 are known as widespread and persistent marine invaders. They grow rapidly, particularly in disturbed areas where they can opportunistically monopolize substratum and compete with native species, thus reducing biodiversity. Caulerpa chemnitzia increased in abundance and overgrew corals on the reef since 2012, ultimately raising fears that a phase-shift from coral to algae might be imminent. However, from 2019 onwards algae populations strongly contracted and while not having returned to baseline level, there is currently low risk of corals being displaced. Visual censuses were conducted on a yearly basis since 2004 using sample quadrats (0.5 x 0.5m) every 5 m along a 50-m-long transects at a depth of 6–15 m at 5 permanent subtidal ecological monitoring sites around Darwin. In addition, 10 m photo-transects were taken using a graduated meter-long measuring stick in the centre of the frame in 2012, 2014, 2016, 2017, 2018 and 2021 at a depth of 15m at Wellington reef. The authors hypothesize that this species could have expanded its distribution over Wellington Reef because of its known morphological plasticity due to a response to change in the environment, in this case high temperature and low nutrients. As ENSO events are predicted to increase in intensity and frequency due to the impact of climate change it is important to develop and implement a functional alert system. Early Detection Rapid Response (EDRR) protocols are recommended to avoid climate driven Non-Indigenous Species (NIS) entering the GMR or for native species becoming invasive due to warming-related phase shifts

Posterior Contraction Rates for the Bayesian Approach to Linear Ill-Posed Inverse Problems

We consider a Bayesian nonparametric approach to a family of linear inverse problems in a separable Hilbert space setting with Gaussian noise. We assume Gaussian priors, which are conjugate to the model, and present a method of identifying the posterior using its precision operator. Working with the unbounded precision operator enables us to use partial differential equations (PDE) methodology to obtain rates of contraction of the posterior distribution to a Dirac measure centered on the true solution. Our methods assume a relatively weak relation between the prior covariance, noise covariance and forward operator, allowing for a wide range of applications

Analysis of product distribution and characteristics of bio-oil and bio-char from fast pyrolysis of date palm tree waste

According to recent reports, there are more than 120 million date palm trees worldwide, with the estimated Middle East and North Africa combined share of more than 80%. Date palm trees produce huge amounts of waste amounting to 15-35 kg per tree per year. This represents a challenging environmental problem, since disposal is so far mainly based on landfill and uncontrolled combustion. Please click on the file below for full content of the abstract