Effect of biodeposits from mussel culture on macroinvertebrate assemblages at sites of different hydrodynamic regime

The present study examined for differences in macroinvertebrate assemblage composition inside and outside of mussel farm sites experiencing different hydrodynamic regimes. Multivariate analysis revealed that there were significant differences in macroinvertebrate assemblage composition (averaged across seasons) between samples taken inside and outside of the two relatively low energy sites, whilst no such difference was observed for the relatively high energy site. Taxa that best discriminated between the dissimilarities observed in macroinvertebrate assemblage composition inside and outside farms were principally polychaetes (more abundant inside) and ophiuroids (more abundant outside). Sediment total organic matter and number of mussel shells were the parameters that best explained the difference in macroinvertebrate assemblage observed at the two relatively sheltered farm study sites. No taxa or environmental variables were particularly good at discriminating or explaining differences observed inside and outside the relatively high energy farm site. The present study indicates there is a relationship between the hydrodynamic regime of a farm site, organic enrichment of seabed sediments by mussel biodeposits, and a subsequent modification of the macroinverebrate assemblages. This finding has implications for the site selection of mussel farms in coastal environments.     

Are juvenile coral‐trouts (Plectropomus) mimics of poisonous pufferfishes (Canthigaster) on coral reefs?

The juveniles of three species of coral‐trout (Plectropomus) resemble two species of poisonous pufferfish (Canthigaster), one of the latter having two distinct colour morphs. Qualitative data are assembled on the diet, feeding mode, palatability, relative abundance, habitat and geographical range of each species. All observations are consistent with the hypothesis that juvenile coral‐trouts are generalized mimics of pufferfishes. Speciation within Plectropomus is discussed with respect to its mimetic relationships with Canthigaster.     

Garnet morphology distribution in the northern part of the Moine Supergroup,Scottish Caledonides

Garnet is a versatile and useful indicator mineral exploited in numerous geological studies. Despite its utility in providing thermobarometry and geochronology constraints, many difficulties remain in making meaningful interpretations of such data. In this paper, we characterize garnet grains from over 140 garnet‐bearing metasedimentary rock samples collected from the northern part of the Moine Supergroup (Scottish Caledonides). Large, euhedral garnet grains are interpreted to be indicative of prograde metamorphic growth during the most recent (Scandian, c. 430 Ma) phase of orogenesis. Anhedral garnet is largely restricted to the relatively low‐grade (greenschist – lower amphibolite facies) Moine thrust sheet, with an abrupt change in morphology and grain size when traced across the overlying Ben Hope and Sgurr Beag thrusts into the higher grade, more hinterland‐positioned thrust sheets. Our results suggest that caution should be exercised in using anhedral garnet in the Moine thrust sheet to estimate peak P–T conditions associated with low temperature (< ~500 °C) Scandian metamorphism, because in at least some cases garnet growth may have occurred during an earlier metamorphic event. However, chemical and isotopic data from this structurally lower anhedral garnet may still be useful for deconvolving a possible polymetamorphic history for this thrust sheet. In the immediately overlying Ben Hope thrust sheet, garnet has prograde euhedral (Scandian?) rims, indicating that the Ben Hope thrust must represent a significant thermal and/or chemical break. Inclusion distribution and mineral assemblages in garnet have been used to gain further insight on garnet growth conditions and to distinguish garnet that likely contains multiple generations of growth. Although our results are specific to the Caledonides of northern Scotland, this work highlights the general necessity of a comprehensive petrographic assessment in advance of interpreting large suites of garnet‐derived thermodynamic and geochronological data.     

Risk perception in small island developing states: a case study in the Commonwealth of Dominica

Natural Hazards - Small island developing states (SIDS) face high vulnerability to natural hazards; thus, understanding risk perception in SIDS is an essential step toward reducing vulnerability. A...     

Exposure to Hurricane Harvey flooding for subsidized housing residents of Harris County,Texas

Natural Hazards - This article contributes to research on social vulnerability to natural hazards by analyzing the relationship between spatial patterns of flooding caused by Hurricane Harvey and...     

A spring and wooded habitat at FLK Zinj and their relevance to origins of human behavior

The 1959 discovery of the hominin fossil Zinjanthropus boisei brought the world's attention to the rich records at Olduvai Gorge, Tanzania. Subsequent excavations of archaeological level 22 (FLK Zinj) Bed I uncovered remains of Homo habilis and a high-density collection of fossils and Oldowan stone tools. The occurrence of this unusual collection of bones and tools at this specific location has been controversial for decades. We present paleoecological data that provide new insights into the origin of FLK Zinj. Our recent excavations 200 m north of the site uncovered a 0.5-m-thick tufa mound draped by Tuff IC, in the same stratigraphic horizon as level 22. Stable isotope analyses indicate that the carbonates were deposited by a freshwater spring. Phytolith analysis of the waxy clay under Tuff IC revealed abundant woody dicotyledon and palm phytoliths, indicating that the site was wooded to densely wooded. The time equivalency and close physical proximity of the two environments indicate the two are related. This study has provided the first documented evidence of springs in Bed I and these data have important implications for the interpretation of hominin behavior in meat acquisition and the ongoing debate on scavenging versus hunting.     

New insights into hominin lithic activities at FLK North Bed I, Olduvai Gorge, Tanzania

Recent work at FLK North (FLK N) has unearthed a new archaeological assemblage recovered with precise control of its stratigraphic position. In the present work, the technological study of the new lithic sample is described. The results show the co-occurrence in the same site of different technological behaviors. At FLK N, hominins were involved in both percussion/battering activities and, through freehand and bipolar knapping, in core reduction. However, the reconstruction of the operational sequences shows that core reduction was probably a marginal behavior, while percussion/battering activities occurred more regularly throughout the sequence. If hominins were not involved in regular carcass processing, as recent taphonomic studies suggest, then hominins' sporadic and low-impact visits to the site over a long period of time must have been driven by other activities probably linked to the exploitation of alternative resources. Plant processing could have been a plausible explanation for hominin presence at FLK N.     

Chemical characterization of microbial-dominated soil organic matter in the Garwood Valley, Antarctica

Despite its harsh environmental conditions, terrestrial Antarctica contains a relatively large microbial biomass. Natural abundance carbon and nitrogen stable isotope signatures of organic materials in the dry valleys indicate mixed provenance of the soil organic matter (SOM) with varying proportions of contributions from lichens, mosses, lake-derived algae and cyanobacteria. Here we employed two complementary analytical techniques, biomarker measurements by gas chromatography/mass spectrometry and solution-state ¹H nuclear magnetic resonance spectroscopy, to provide further information at a molecular-level about the composition and possible source of SOM in the Garwood Valley, Antarctica. The predominance of branched alkanes and short-chain lipids in the solvent extracts indicates that the primary contribution to the SOM was microbial-derived. Chemical structures in the NaOH extracts from soils were also dominated by amide, peptides, and a CH₃-dominating aliphatic region that were characteristic of microbial signatures. Furthermore, the SOM in the Garwood Valley contained compounds that were different from those in the cyanobacteria-dominated mat from a nearby lake (including monoethyl alkanes and enriched side-chain protons). This observation suggests that easily degradable carbon sources from the nearby lake did not dominate the SOM, which is consistent with a fast turnover of the mat-derived organic matter found in the valley. This study highlights the important role of native soil microbes in the carbon transformation and biogeochemistry in terrestrial Antarctica.