8 results for Alfaro, AC

  • Faunal composition within algal mats and adjacent habitats in Likuri, Fiji Islands

    Alfaro, AC; Zemke White, WL; Nainoca, W (2011-06-23)

    Journal article
    Auckland University of Technology

    The faunal composition within three mono-specific algal habitats was investigated at Likuri Island, southern Viti Levu, Fiji Islands. Gracilaria maramae was the dominant alga within algal drift mat, seagrass bed, and rocky substrate habitats at the study site. This algal species exhibits two distinctive morphologies depending on whether it is attached or loose-lying. When attached to seagrass blades or rocky substrates, this alga has long straight branches stemming from a single holdfast, while detached individuals develop curled tendrils that re-attach to adjacent substrates. Re-attachment behaviour and high growth rates result in a dense mat of drift algae, which provides a suitable micro-habitat for macro-invertebrates. The sources of algal fragments that contribute to the algal mat appear to be nearby seagrass beds and rocky substrates, where this species may settle directly from spores. Storm events may detach these algae, although pulling experiments showed that the attachment to rocky substrates is 5 times stronger than the attachment to seagrass blades. Results from the macrofaunal samples indicate that the loose-lying algal mat habitat had the highest abundance and biodiversity of organisms, followed by the seagrass bed, and then the rocky substrate habitat. The ability of loose G. maramae fragments to re-attach, along with their high growth rate, may provide a unique micro-habitat for highly abundant and diverse faunal assemblages, which in turn may sustain adjacent near-shore communities. This study highlights the ecological importance of floating algal mats to coastal ecosystems, which should be considered in future management strategies throughout the Fiji Islands.

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  • Neurophysiological Control of Swimming Behaviour, Attachment and Metamorphosis in Black-footed Abalone (Haliotis Iris) Larvae

    Alfaro, AC; Young, T; Bowden, K

    Journal article
    Auckland University of Technology

    Experiments were conducted to test the effect of a range of chemicals on larval responses in swimming behaviour, attachment and metamorphosis of the black-footed abalone (Haliotis iris). The effect of antibiotics on larval survival was first tested within negative (filtered seawater) and positive (GABA at 10−5, 10−4 and 10−3 mol L−1) control assays over 3 days. This experiment corroborated the effectiveness of using antibiotics to improve survival of larvae without obvious synergistic interactions with the GABA inducer or confounding effects of potential bacterial interactions. Chemical treatments (acetylcholine, potassium chloride, dopamine and glutamine) were then tested at various concentrations for their ability to modulate swimming behaviour and induce larval attachment and metamorphosis over 14 days. Generally, larval state shifted from swimming to attached, and from attached to metamorphosed, in the control and treatments over time. However, the peak percentage of attached and metamorphosed larvae varied in time among chemicals and concentrations. While overall percent metamorphosis was minimally enhanced after 14 days of exposure to some chemical treatments at certain concentrations, all treatments displayed significant capacities to down-regulate larval swimming and induce early attachment and metamorphosis. Mortality was recorded throughout the duration of the experiment, and was generally low (<20%) across controls and most treatments for exposures of less than 12 days. Interpretations of specific results from this study are used to elucidate neurophysiological control of larval activities for this abalone species. Comparisons with other marine invertebrates highlight the specificities of chemical cues and endogenous regulatory mechanisms across relatively closely related taxa.

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  • Induction of Settlement in Larvae of the Mussel Mytilus Galloprovincialis Using Neuroactive Compounds

    Young, T; Sánchez-Lazo, C; Martínez-Pita, I; Alfaro, AC

    Journal article
    Auckland University of Technology

    We investigated the effect on Mytilus galloprovincialis larval settlement, as well as the toxicity, of serial concentrations in filtered seawater of acetylcholine (AC), γ-aminobutiric acid (GABA); 3-isobutyl-1-methylxanthine (IBMX); and the potassium ion in the form of potassium chloride (KCl) and potassium sulfate (K2SO4). All the substances assayed induced larval settlement and peak responses were above 90% in exposures to 10− 2 mol L− 1 (M) AC, 10− 4 and 10− 5 M epinephrine, 10− 3 M GABA and 20, 30 and 40 mM KCl. The optimal concentration of K+ varied depending on the anionic component of the compound assayed, and peak settlement response to KCl was higher (100%) than that achieved with K2SO4 (69.7%). The estimated LC50 of the compounds assayed ranged from 9.4 × 10− 6 M (GABA) to 3.1 × 10− 2 M (KCl). GABA, IBMX and K2SO4 treatments displayed toxic effects in all the active concentrations. In contrast, AC 10− 5 M, epinephrine 10− 4 and 10− 5 M and KCl 20 mM treatments enhanced larval settlement without an acute short-term effect on mortality. These results provide new insights on the molecular mechanisms controlling settlement in M. galloprovincialis larvae, and yield promising outcomes for the mussel industry to find a reliable method to enhance larval settlement in hatcheries.

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  • Two new species of Retiskenea? (Gastropoda: Neomphalidae) from Early Cretaceous hydrocarbon seep-carbonates of California

    Campbell, Kathleen; Peterson, D; Alfaro, AC (2008)

    Journal article
    The University of Auckland Library

    Two new Mesozoic gastropod species, provisionally attributed to the minute (height < 5 mm) coiled neomphalid genus Retiskenea?, are described from three geographically isolated, Early Cretaceous, hydrocarbon seep-carbonate sites at Wilbur Springs, Rice Valley, and Cold Fork of Cottonwood Creek, northern California (USA). A fourth paleo-seep locality at Paskenta, of probable Upper Jurassic age, also yielded a single specimen of a morphologically similar microgastropod that may be a neomphalid with affinities to the Lower Cretaceous specimens described herein. The limestone lenses are ∼2–260 m in length, ∼1–5 m in diameter, and surrounded by forearc siliciclastics of bathyal turbidites or sedimentary serpentinites in the Upper Jurassic to Lower Cretaceous (Tithonian–Albian) Great Valley Group and its equivalents. The Lower Cretaceous microgastropods are tentatively placed in Retiskenea? based on similar shell characters: size, globose shape, inflated reticulate protoconch, number and distinct inflation of the body whorls, and fine, prosocline sculpture of the final body whorl. The fossils occur in carbonate microbialites that formed in seafloor sediments during archaeal anaerobic oxidation of methane in the zone of bacterial sulfate reduction, associated with H2S- and CH4-rich fluid seepage. The California Retiskenea? fossils commonly are found in gregarious clusters, or closely affiliated with thin worm tubes or, in one case, a larger gastropod. These Mesozoic records increase the total known species attributable to this cold-seep endemic genus from two to four. Its spatial and temporal distribution thus may have spanned ∼9,000 km around the Pacific Rim from at least ∼133 m.y. to the present in 10 subduction-related seep sites from California (possibly Upper Jurassic–Lower Cretaceous), Washington (middle Eocene–Upper Oligocene), and modern offshore Oregon, the eastern Aleutians, and the Japan Trench. If the generic placement of these microgastropod fossils is correct, the California records are the oldest-known occurrences of Retiskenea, consistent with an estimated minimum Mesozoic origin for the ‘hot vent’ Neomphalidae, as inferred from molecular analyses published on other living members of the family.

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  • New fossil mussels (Bivalvia: Mytilidae) from Miocene hydrocarbon seep deposits, North Island, New Zealand, with general remarks on vent and seep mussels

    Saether, KP; Little, CTS; Campbell, Kathleen; Marshall, BA; Collins, M; Alfaro, AC (2010-08-26)

    Journal article
    The University of Auckland Library

    Bathymodiolus (sensu lato) heretaunga sp. nov. and Gigantidas coseli sp. nov. are described from Miocene-age hydrocarbon seep carbonates of North Island, New Zealand, adding to only four described fossil hydrocarbon seep mussel species. Both new species are small compared to their modern congeners, and it is suggested that an evolutionary trend toward gigantism occurred in vent and seep mussels since the first known fossil species of the group appeared in the Middle Eocene. Bathymodiolus heretaunga is highly variable in morphology, potentially reflecting population variation over a wide geographic area. Gigantidas coseli is the first named species, fossil or modern, of its genus known from hydrocarbon seeps, although several closely related species in the same group, the Bathymodiolus childressi clade, have been reported from these environments.

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  • Bee and ant burrows in Quaternary "coffee rock" and Holocene sand dunes, Kowhai Bay, Northland, New Zealand

    Gregory, Murray; Campbell, Kathleen; Alfaro, AC; Hudson, Neville (2009-03-01)

    Journal article
    The University of Auckland Library

    Curious. multi-coloured, and pelleted sand mounds (tumuli) constructed by solitary bees, together with similar, but loosely piled white sand mounds made by ants, are a striking feature of deflation and erosion surfaces in coastal sand dune territory of northernmost New Zealand. These native bee and ant mounds (to >20 mounds/m(2)) are found, respectively, on consolidated Quaternary "coffee rock" or atop shifting modern dune sands at Kowhai Bay, Aupouri Peninsula, across an area of several hundred square metres of bare and/or partly vegetated ground, lying some 800 m inland from the open ocean-facing Kowhai Beach. The vicinity is otherwise covered by scrubland vegetation dominated by the local ti tree, kanuka (Kunzea ericoides, var. linaris), and the aggressive introduced alien, Acacia longifolium, which bloom in spring or summer, respectively, attracting bees, ants and other insects to the area. Many of the pelleted bee mounds are connected to simple and open, vertical to steeply inclined cylindrical shafts (cf. Skolithos) that may reach depths approaching one metre. The shafts sometimes terminate in a slightly ovoidal chamber (cell) that is lined with translucent, mucoidal, parchment-like layers and/or stuffed with pollen, and which occasionally contains a single white larva. These biogenic structures are created by solitary endemic colletid bees (Leioproctus (Leioproctus) metallicus) which we observed burrowing vertically through firm "coffee rock" at rates of up to 4 cm/hour. Many of these shafts are plugged near the surface by sand (uppermost 10 cm), or dead-end at shallow depths, suggesting concealment and decoy strategies used to avoid the bees' natural predator, parasitic gasteruptid wasps. In contrast to the pelleted and multi-coloured bee mounds, those made by ants (e.g., Monomorium antarcticum) are uniformly pale grey or white in colour, with a granular and smooth, fine to medium sand surface (i.e., they are non-pelleted). These ant mounds are crescent-shaped to circular, with a conspicuous central entrance hole that lies in a cratered depression, and which opens into irregularly branching burrows and passages that lack a lining other than some weak and discontinuous mucus-like coating (cf. Socialites).Quadrat sampling suggests that bee and ant mound distributions are oppositely related to substrate coherency. Field excavations indicate strong overprinting by bee excavations on consolidated dune fabrics. It is suggested that their burrows may have influenced groundwater movement in these iron-rich, paleosol-bearing strata. They also imply a paleoenvironmental shift from Kauri forest cover to deflationary sand dune episodes in the semi-tropical climate of the late Quaternary of northern New Zealand. The terrestrial deflationary setting can be likened to omission surfaces of marine environments.

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  • Comparison of rose Bengal and Celltracker Green staining for identification of live salt-marsh foraminifera

    Orioli Figueira, Brigida; Grenfell, HG; Hayward, BW; Alfaro, AC (2012)

    Journal article
    The University of Auckland Library

    Modern analog faunal distributions are increasingly being used in fossil foraminiferal studies to provide quantitative estimates of past environmental conditions, requiring an accurate assessment of modern taphonomic assemblages. A fundamental issue with such an approach is the differentiation of live versus dead foraminifera in the modern assemblage. The effectiveness of various biological staining techniques for this purpose has long been debated. In this study, the reliability of the stain rose Bengal, which has been widely used for over 50 years, was compared to that of the modern fluorogenic probe CellTracker™ Green in identifying live agglutinated salt-marsh foraminifera from two locations on the South Island, New Zealand. Cored samples within these locations yielded low diversity assemblages, dominated by Trochamminita salsa, an important high tidal salt-marsh species in the Southern Hemisphere. Parametric statistical analysis of replicate data shows that there is no significant difference between the ability of the two techniques to discriminate between live and dead foraminifera.

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  • Geological imprint of methane seepage on the seabed and biota of the convergent Hikurangi Margin, New Zealand: Box core and grab carbonate results

    Campbell, Kathleen; Nelson, CS; Alfaro, AC; Boyd, S; Greinert, J; Nyman, S; Grosjean, E; Logan, GA; Gregory, MR; Cooke, S; Linke, P; Milloy, S; Wallis, Irene (2010-07-15)

    Journal article
    The University of Auckland Library

    Short box cores (to 30 cm bsf) and seafloor carbonate grab samples were acquired at mapped hydrocarbon seep sites (600-1200 m water depths) during the 2007 RV SONNE SO191 cruise on the Hikurangi Margin offshore eastern North Island, New Zealand, to evaluate the influence of methane seepage on sedimentologic, biotic, mineralogic and stable isotopic attributes of seabed sediments. Sedimentary horizons in the box cores consist of siliciclastic silts and sands, shell beds and nodular, microcrystalline aragonite bands up to 15 cm thick The megafauna is dominated by infaunal to semi-infaunal chemosymbiotic bivalves (Calyptogena, Lucinoma, and Acharax), as well as associated worms and carnivorous and grazing gastropods Burrows in silts, some occupied by worms or juvenile Acharax. mainly have simple morphologies more typical of high-energy, nearshore settings than deep-sea environments, while a few are large and sparsely branched with wall scratch marks inferred to be of decapod crustacean originThe box core silts and nodular carbonate samples vary in TOC content from 0.2 to 09 wt%, carbonate content from 4 to 78%, and delta C-13 and delta O-18 values from -50 3 to -0.6 parts per thousand PDB and + 077 to + 3 2 parts per thousand PDB, respectively Low carbonate content silt samples. have the most enriched delta C-13 values, implying a seawater source for their pore water bicarbonate Negative delta C-13 and positive delta O-18 values typify the nodular, microcrystalline aragonite bands, indicating formation during microbially mediated, sulphate-dependent anaerobic oxidation of methane (AOM) in a cold. near-seafloor environment, as is also supported by lipid biomarker data A clear isotopic mixing trend of decreasing delta C-13 and increasing delta O-18 and carbonate content in the fine (<100 mu m) carbonate fraction of the host silts also has been reported from other methane seep provinces, and suggests a heterogeneous influx of methane-rich seep fluids through the shallow seabed, displacing pore waters of seawater originSeafloor grab carbonate samples show greater textural variability and are divided into two types Fresh-appearing, grey to white blocks yield similar mineralogic. Isotopic and biomarker signatures to the nodular carbonate bands in the cores A largely seep-related epifauna affiliated with these grab samples include chemosymbiotic bathymodiolin mussels. siboglinid tube worms, methanotrophic suberitid sponges and grazing limpets which, in places, are entombed within the carbonate By contrast, some dark reddish to brown, iron-stained, microcrystalline dolomitic slabs and tubular concretions support abundant non-seep epifaunal encrusters from the surrounding deep sea, indicative of long exposure on the seafloor. Distinct stable isotopic signatures of these exhumed dolostones (delta C-13 c. - 20 parts per thousand PDB, delta O-18 up to + 7 parts per thousand PDB) suggest derivation from an oxidised methane pool, and pore fluid freshening by gas hydrate dissociation or from mobilized burial fluids that have undergone clay mineral dehydration (C) 2010 Elsevier B.V. All rights reserved

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