An Analysis of Zooplankton Fauna Associated with Mangrove and Non-Mangrove Ecosystems in Mauritius

Zooplankton are important components of marine food webs, yet very few studies exist on the mangrove plankton of Mauritius. The aim of this study was to analyze the zooplankton fauna and to assess differences between mangrove and non-mangrove ecosystems. Two mangrove ecosystems (Pointe D’Esny and Ferney) and one non-mangrove ecosystem (Bois des Amourettes) were studied for zooplankton abundance, diversity and community structure along the southeast coast of Mauritius. The study was conducted from October to December 2012 and plankton samples were collected using standard plankton nets. Zooplankton fauna of the three ecosystems were representative of the Phyla Arthropoda, Sarcomastigophora, Mollusca, Nematoda, Annelida, Chaetognatha and Ctenophora. Copepods formed the bulk of the zooplankton community (66.44% in Pointe D’Esny mangrove ecosystem and 36.43% in the nonmangrove ecosystem). Cyclopoid Oithona was the most abundant zooplankton in the two mangrove ecosystems with densities of 964 Organisms m-3 and 7760 Organisms m-3 while Foraminiferan Globigerina (329 Organisms m-3) was the most abundant organism in the non-mangrove one. Mangrove sites were found to be more diverse (Margaleff’s Diversity Index: 1.71 and 1.41) in zooplankton than non-mangrove site (Margaleff’s Diversity Index: 1.27). This study supports the view that mangrove ecosystems are a rich habitat and nursery ground.Keywords: Zooplankton, Abundance, Diversity, Mangrove, Copepods, Cyclopoid Oithon

A Preliminary Study on Benthic and Arboreal Fauna Associated with Mangrove Rhizophora Mucronata on the East Coast of Mauritius (Indian Ocean) with Special Reference to the Mollusca

Mangrove ecosystems are important as they harbour a diversity of life forms. This study aimed at studying the benthic and arboreal macrofaunal diversity and abundance associated with three naturally occurring mangrove forests of Mauritius, Western Indian Ocean. The mangrove areas included Roches Noires, Mahebourg and Pointe Maurice, on the east coast of the island. The field study was carried out at low tide during summer season from October 2003 to February 2004. At each of the three sites, the arboreal and benthic macrofauna were sampled separately, using quadrats of 1 m x 1 m and 25 cm x 25 cm, respectively. Sixty-four benthic and 42 arboreal quadrats were collected from Roche Noires, 40 benthic and 41 arboreal quadrats at Mahebourg and 40 benthic and 30 arboreal quadrats at Pointe Maurice. The results showed that benthic habitat is more diverse with regards to molluscan families (24 families) than the arboreal habitat (5 families). Pointe Maurice has a more diverse benthic fauna. Relative percentage abundance and mean density of molluscan families are reported. Highest mean densities and relative abundance were recorded for the Family Littorinidae among arboreal macrofauna. In benthic macrofauna, the highest mean densities and relative abundance were noted in Family Cerithiidae at Roches Noires and Mahebourg

A Study on Assemblage of Invertebrates Inhabiting Rocky Shores Within the Port- Limit of Port- Louis, Mauritius

Rocky shores provide an important habitat for marine organisms. This study aimed at providing baseline data on assemblage of organisms on rocky shores within the port-limit of Port-Louis, Mauritius. Four rocky shores, with three at Pointe aux Sables (La Pointe1, La Pointe2, and Petit Verger) and one at Baie du Tombeau were studied from October 2007 to February 2008. On each site three stations, located at intervals of 2m, with an area of 40m2 each were set up. Intertidal organisms were hand-collected within forty-eight, 1m2 quadrat for invertebrates. Observations of 16,061 specimens led to identification of 30 faunal species belonging mostly to phyla Mollusca and Arthropoda. Mean total abundance of invertebrates per 1m2 varied from 729.22±173.07 at la Pointe2 to 143.97±11.43 at Baie du Tombeau. The gastropod, Planaxis sulcatus was the most abundant species at La Pointe1 and Petit Verger with mean abundance of 196.86±179.71 and 168.10±113.44 per 1m2 respectively. The bivalve, Modiolus auriculatus was the dominant species with mean abundance of 673.33±762.04 per 1m2 at La Pointe2 and Nerita punctata was most abundant (39.41±57.35 per 1m2) at Baie du Tombeau. Lowest Shannon diversity was observed La Pointe 2. The study is useful for future work on port area

The Herschel Virgo Cluster Survey: IV. Resolved dust analysis of spiral galaxies

We present a resolved dust analysis of three of the largest angular size spiral galaxies, NGC 4501 and NGC 4567/8, in the Herschel Virgo Cluster Survey (HeViCS) Science Demonstration field. Herschel has unprecedented spatial resolution at far-infrared wavelengths and with the PACS and SPIRE instruments samples both sides of the peak in the far infrared spectral energy distribution (SED).We present maps of dust temperature, dust mass, and gas-to-dust ratio, produced by fitting modified black bodies to the SED for each pixel. We find that the distribution of dust temperature in both systems is in the range ~19 - 22 K and peaks away from the centres of the galaxies. The distribution of dust mass in both systems is symmetrical and exhibits a single peak coincident with the galaxy centres. This Letter provides a first insight into the future analysis possible with a large sample of resolved galaxies to be observed by Herschel.Comment: Letter accepted for publication in A&A (Herschel special issue

The far-infrared view of M87 as seen by the Herschel Space Observatory

The origin of the far-infrared emission from the nearby radio galaxy M87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We observed M87 with PACS and SPIRE as part of the Herschel Virgo Cluster Survey (HeViCS). We compare the new Herschel data with a synchrotron model based on infrared, submm and radio data to investigate the origin of the far-infrared emission. We find that both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M87.Comment: 4 pages, 2 figures, proceedings IAU Symposium 275 (Jets at all scales

HI Selected Galaxies in the Sloan Digital Sky Survey I: Optical Data

We present the optical data for 195 HI-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically-selected sample. Compared to the optically-selected SDSS sample (in the similar volume), HI-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effects, our sample is bluer, fainter and less massive.Comment: 14 pages, 8 Figures, accepted for publication in AJ. Complete tables will be available in the AJ electronic version and on the Vizier sit

The Herschel Virgo Cluster Survey: I. Luminosity functions

We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data obtained as part of the Science Demonstration Phase (SDP). The data cover a central 4x4 sq deg region of the cluster. We use SPIRE and PACS photometry data to produce 100, 160, 250, 350 and 500 micron luminosity functions (LFs) for optically bright galaxies that are selected at 500 micron and detected in all bands. We compare these LFs with those previously derived using IRAS, BLAST and Herschel-ATLAS data. The Virgo Cluster LFs do not have the large numbers of faint galaxies or examples of very luminous galaxies seen previously in surveys covering less dense environments.Comment: Letter accepted for publication in A&A (Herschel special issue

The Herschel Virgo Cluster Survey: II. Truncated dust disks in HI-deficient spirals

By combining Herschel-SPIRE observations obtained as part of the Herschel Virgo Cluster Survey with 21 cm HI data from the literature, we investigate the role of the cluster environment on the dust content of Virgo spiral galaxies.We show for the first time that the extent of the dust disk is significantly reduced in HI-deficient galaxies, following remarkably well the observed 'truncation' of the HI disk. The ratio of the submillimetre-to- optical diameter correlates with the HI-deficiency, suggesting that the cluster environment is able to strip dust as well as gas. These results provide important insights not only into the evolution of cluster galaxies but also into the metal enrichment of the intra-cluster medium.Comment: Letter accepted for publication in A&A (Herschel special issue

ALMA Observations of Asteroid 3 Juno at 60 Kilometer Resolution

We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of 0.042 arcseconds (60 km at 1.97 AU). The data were obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of ten consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259pm4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215pm13 K, while the median over the whole surface is 197pm15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies across the surface with higher values correlated to the subsolar point and afternoon areas, and lower values beyond the evening terminator. The dominance of the subsolar point is accentuated in the final four images, suggesting a reduction in the thermal inertia of the regolith at the corresponding longitudes, which are possibly correlated to the location of the putative large impact crater. These results demonstrate ALMA's potential to resolve thermal emission from the surface of main belt asteroids, and to measure accurately their position, geometric shape, rotational period, and soil characteristics.Comment: 8 pages, 3 figures, 2 tables, accepted for publication in the Astrophysical Journal Letter