1,721,069 research outputs found
Polychaete assemblages of the northwestern Ross Sea shelf: worming out the environmental drivers of Antarctic macrobenthic assemblage composition
No full textWe have limited understanding of which environmental factors structure the distribution patterns and composition of Antarctic macrobenthos assemblages, and the spatial scales on which such factors operate. In 2004, the “BioRoss Survey” was conducted on the northwestern Ross Sea shelf between Cape Adare and Cape Hallett in depths of 50–750 m to describe and quantify the assemblage patterns of benthic macroinvertebrates. In order to determine the influence of primary productivity, disturbance and habitat heterogeneity on the distribution and composition of the macrofaunal assemblages, polychaete data derived from 52 grab samples were analysed. Although differences in the composition of polychaete assemblages among different sampling transects and depth strata were not particularly pronounced (yet statistically significant), the results suggested that large-scale differences in both primary productivity and iceberg disturbance influence distribution patterns. The combination of sediment chl a content, sorting coefficient, sponge spicule content and distance to the nearest iceberg scour best explained polychaete assemblage patterns. This finding supports previous contentions that multiple environmental drivers working at varying scales influence Antarctic shelf assemblages. The results do not supply support for a pronounced decoupling of pelagic and benthic systems, as has been suggested by another study of deeper water benthic assemblages on the Ross Sea shelf
FIGURE 6 in New sponge species from hydrothermal vent and cold seep sites off New Zealand
No full textFIGURE 6. Haliclona (Halichoclona) sonnae sp. nov., holotype NIWA 52859, spicules: A, B. Oxea megascleres with fine, fusiform tips, slightly curved.Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 417, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
FIGURE 12 in New sponge species from hydrothermal vent and cold seep sites off New Zealand
No full textFIGURE 12. Pseudosuberites thurberi sp. nov., holotype NIWA 27044, spicules: A, Choanosomal tylostyle, straight shafted; B, Choanosomal tylostyle, acutely bent in the upper proximal end of the spicule; C, Small, possibly ectosomal tylostyle; D, Choanosomal and ectosomal tylostyles of different lengths.Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 429, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
FIGURE 4 in New sponge species from hydrothermal vent and cold seep sites off New Zealand
No full textFIGURE 4. Haliclona (Soestella) battershilli sp. nov., holotype NIWA 32128, spicules: A. Oxea megascleres, thick, fusiform, slightly curved (lower left to middle), to abruptly, slightly centrally bent (upper right); B. Range of oxeas showing degrees of curvature.Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 407, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
FIGURE 8 in New sponge species from hydrothermal vent and cold seep sites off New Zealand
No full textFIGURE 8. Protosuberites novaezelandiae sp. nov., holotype NIWA 32136, spicules: A, Large choanosomal tylostyle with a slightly sinuous shaft, unevenly thickened along the shaft, thicker in the upper half; B, Small ectosomal tylostyle with a straight shaft; C. Large choanosomal tylostyle with a well-developed, spherical head and slight development of the apex; D, Tylostyles in two size categories.Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 420, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
Suberitidae Schmidt
No full textFamily Suberitidae Schmidt Diagnosis. Globular, ramose, stipitate, massive or encrusting habit. Megascleres usually tylostyles, occasionally styles, strongyloxeas or centrotylote oxeas; microscleres usually absent, when present, confined to microrhabds and trichodragmas. In cross section, megascleres are usually arranged in bouquets at the surface, in more massive species becoming progressively confusedly arranged towards the interior, but overall structure may also be strictly radial or show a strong axial orientation. In one genus, the spicules at the surface are arranged tangentially. There is no recognizable cortex. In thinly encrusting species, spicule orientation is either parallel or perpendicular to the substratum. Modifications of shape and position of the tylostyles heads are common; they can be lobate, pearshaped, drop-shaped or subterminal (Van Soest 2002).Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 418, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
Chalinidae Gray 1867
No full textFamily Chalinidae Gray 1867 <p> <b>Diagnosis.</b> Thickly encrusting, cushion-shaped, ramose or tubular growth forms; cushion-shaped sponges commonly with oscular chimneys or mounds. Consistency soft to rather firm, also spongy. Colour purple, violet, pink, brown, blue or green, occasionally white. Megascleres smooth oxeas or strongyles, microscleres, if present, are sigmas, toxas, raphides or microxeas. Choanosomal skeleton a delicate reticulate choanosomal skeleton of uni-, pausi- or multispicular primary lines, which are regularly connected by unispicular secondary lines. Ectosomal skeleton, if present, a regularly hexagonal, unispicular, tangential reticulation (modified from de Weerdt 2000, 2002).</p> <p> <b>Remarks.</b> De Weerdt (2000) included a definition of family Haplosclerida which was primarily a description of the choanosomal and ectosomal skeletons, important characters lacking from the 2002 diagnosis (de Weerdt 2002). We have expanded the original diagnosis to include these details.</p>Published as part of <i>Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3)</i> on pages 403-404, DOI: 10.11646/zootaxa.4576.3.1, <a href="http://zenodo.org/record/3715654">http://zenodo.org/record/3715654</a>
Haliclona (Soestella) De Weerdt 2000
No full textSubgenus Haliclona (Soestella) De Weerdt, 2000 Haliclona (Soestella) de Weerdt, 2000: 7. Diagnosis. Growth form irregularly massive, thickly encrusting, lobate/cushion-shaped, or digitate. Oscula at the end of oscular chimneys or mounds, alongside the branches of digitate forms, flush with the surface of encrusting forms. Consistency varying from soft to moderately firm. Surface even or somewhat irregular, slightly or rather strongly punctate. Colour varying from light to dark brown, black, green to dark red. Ectosomal skeleton a discontinuous tangential, rather open reticulation, due to many rounded meshes framed by spicule lines of 2–5 spicules thick. Choanosomal skeleton a subanisotropic reticulation consisting of ill-defined pausispicular primary lines, irregularly connected by pausispicular secondary lines. Spongin always present at the nodes of the spicules but never abundant. Oxeas usually slender. Microscleres, if present, sigmas, toxas or raphides (de Weerdt 2000, 2002).Published as part of Kelly, Michelle & Rowden, Ashley A., 2019, New sponge species from hydrothermal vent and cold seep sites off New Zealand, pp. 401-438 in Zootaxa 4576 (3) on page 404, DOI: 10.11646/zootaxa.4576.3.1, http://zenodo.org/record/371565
Recovery of a subtidal soft-sediment macroinvertebrate assemblage following experimentally induced effects of a harmful algal bloom
Get PDFA defaunation experiment mimicking the effects of a harmful algal bloom (HAB) on benthic macroinvertebrate assemblages (>500 µm) was conducted at a hydrodynamically active soft-substrate site in Wellington Harbour, New Zealand, to test the recovery rate (return to pre-disturbance state) of temperate benthic macroinvertebrate assemblages and to elucidate the main factors influencing the recovery process. Tarpaulins were used to create anoxic conditions by smothering the sediment for 65 d. Assemblage recovery in treatment plots was studied for 1 yr and compared with assemblage composition in undisturbed adjacent control plots. Recovery was slow until Day 70, at which time abundance of individuals (N) and number of species (S) increased synchronously in treatments and controls. Within 10 mo, univariate indices (N, S and also species diversity H’ and evenness J’) of treatment assemblages returned to values observed for the control assemblages. Multivariate analyses showed that fluctuations in assemblage composition were most pronounced in the first 100 d in treatment replicates, but decreased thereafter as the recovering assemblage became more similar to the undisturbed one. However, after 1 yr, even though the composition of treatment and control assemblages was converging, differences in composition were still significant. Based on the observed trajectory of recovery, complete assemblage recovery is predicted to take approximately 2 yr. Timing of the disturbance in relation to seasonal recruitment events was identified as an important factor for assemblage recovery
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