Occurrence, distribution and characteristics of beached plastic production pellets on the island of Malta (central Mediterranean)

The distribution, abundance and chemical characteristics of plastic production pellets on beaches of the island of Malta have been determined. Pellets were observed at all locations visited and were generally most abundant (>1000 m⁻² at the surface) on the backshores of beaches with a westerly aspect. Most pellets were disc-shaped or flattened cylinders and could be categorised as white, yellow, amber or brown. The polymeric matrix of all pellets analysed by infrared spectroscopy was polyethylene and the degree of yellowing or darkening was associated with an increase in the carbonyl index, hence extent of photo-oxidation or aging. Qualitatively, pellets are similar to those reported for other regions of the Mediterranean in surveys spanning three decades, suggesting that they are a general and persistent characteristic of the region.     

Can we improve the spatial predictions of seabed sediments? A case study of spatial interpolation of mud content across the southwest Australian margin

Spatially continuous data of environmental variables is often required for marine conservation and management. However, information for environmental variables is usually collected by point sampling, particularly for the marine region. Thus, methods generating such spatially continuous data by using point samples to estimate values for unknown locations become essential tools. Such methods are, however, often data- or even variable-specific and it is difficult to select an appropriate method for any given dataset. In this study, 14 methods (37 sub-methods) are compared using samples of mud content with five levels of sample density across the southwest Australian margin. Bathymetry, distance-to-coast, slope and geomorphic province were used as secondary variables. Ten-fold cross validation with relative mean absolute error (RMAE) and visual examination were used to assess the performance of these methods. A total of 1850 prediction datasets are produced and used to assess the performance of the methods and the effects of other factors considered. Considering both the accuracy and the visual examination, we found that a combined method (i.e., random forest and ordinary kriging: RKrf) is the most robust method. This method is novel, with a RMAE up to 17% less than that of the control. No threshold in sample density was detected in relation to prediction accuracy. No consistent patterns are observed between the performance of the methods and data variation. The RMAE of three most accurate methods is about 30% lower than that of the best methods in previous publications, highlighting the robustness of the methods selected in this study. The implications and limitations of this study are discussed and a number of suggestions are provided for further studies.     

Epifaunal worm tubes on Lower Jurassic (Lower Lias) ammonites from Dorset

Over 40 ammonites, mostly Promicroceras, with epifaunal worm tubes are described from the Lower Jurassic, Charmouth Mudstone Formation (Lias Group) of Dorset. Serpulids that were overgrown by the ammonites or responded to the ammonites’ growth attached to juvenile, living ammonites. Some epifaunal serpulids attached post-mortem, indicating oxygenated bottom water, which was rare in the lower Charmouth Mudstone Formation. Other serpulids do not conform to either pre- or post-mortem growth predictions and require individual assessment. The commonest pattern of growth for serpulids on live juvenile ammonites was attachment in the umbilical seam, with later growth onto, and finally around, the venter. Reconstructing this pattern shows that serpulids kept their aperture at 6 o’clock with respect to the orientation of the living ammonite (105-115° behind the ammonite aperture) throughout life. Reorientation of growth lines in serpulid worms just before the aperture suggests some worm tubes were fully grown. The 6 o’clock position of the aperture enabled feeding currents generated by the worms to parallel currents generated by swimming ammonites, thus maximizing food gathering and confirming that ammonites swam backwards. The mid-ventral position enabled the worm to deploy its branchia on both sides of the ammonite. Growth on ammonites was beneficial to the worms, but parasitic to the ammonites. Promicroceras with epifaunal worm tubes died at smaller sizes than unencumbered examples and size at death correlates inversely to extra weight of worm tubes. Uniformitarian comparisons suggest fossil serpulid worms grew in one season and that Promicroceras reached full size in two or three years.     

Mercury in the Southern Ocean

We present here the first mercury speciation study in the water column of the Southern Ocean, using a high-resolution south-to-north section (27 stations from 65.50°S to 44.00°S) with up to 15 depths (0-4440 m) between Antarctica and Tasmania (Australia) along the 140°E meridian. In addition, in order to explore the role of sea ice in Hg cycling, a study of mercury speciation in the “snow-sea ice-seawater” continuum was conducted at a coastal site, near the Australian Casey station (66.40°S; 101.14°E). In the open ocean waters, total Hg (Hg_T) concentrations varied from 0.63 to 2.76 pmol L⁻¹ with “transient-type” vertical profiles and a latitudinal distribution suggesting an atmospheric mercury source south of the Southern Polar Front (SPF) and a surface removal north of the Subantartic Front (SAF). Slightly higher mean Hg_T concentrations (1.35 ± 0.39 pmol L⁻¹) were measured in Antarctic Bottom Water (AABW) compared to Antarctic Intermediate water (AAIW) (1.15 ± 0.22 pmol L⁻¹). Labile Hg (Hg_R) concentrations varied from 0.01 to 2.28 pmol L⁻¹, with a distribution showing that the Hg_T enrichment south of the SPF consisted mainly of Hg_R (67 ± 23%), whereas, in contrast, the percentage was half that in surface waters north of PFZ (33 ± 23%). Methylated mercury species (MeHg_T) concentrations ranged from 0.02 to 0.86 pmol L⁻¹. All vertical MeHg_T profiles exhibited roughly the same pattern, with low concentrations observed in the surface layer and increasing concentrations with depth up to an intermediate depth maximum. As for Hg_T, low mean MeHg_T concentrations were associated with AAIW, and higher ones with AABW. The maximum of MeHg_T concentration at each station was systematically observed within the oxygen minimum zone, with a statistically significant MeHg_Tvs Apparent Oxygen Utilization (AOU) relationship (p < 0.001). The proportion of Hg_T as methylated species was lower than 5% in the surface waters, around 50% in deep waters below 1000 m, reaching a maximum of 78% south of the SPF. At Casey coastal station Hg_T and Hg_R concentrations found in the “snow-sea ice-seawater” continuum were one order of magnitude higher than those measured in open ocean waters. The distribution of Hg_T there suggests an atmospheric Hg deposition with snow and a fractionation process during sea ice formation, which excludes Hg from the ice with a parallel Hg enrichment of brine, probably concurring with the Hg enrichment of AABW observed in the open ocean waters. Contrastingly, MeHg_T concentrations in the sea ice environment were in the same range as in the open ocean waters, remaining below 0.45 pmol L⁻¹. The MeHg_T vertical profile through the continuum suggests different sources, including atmosphere, seawater and methylation in basal ice. Whereas Hg_T concentrations in the water samples collected between the Antarctic continent and Tasmania are comparable to recent measurements made in the other parts of the World Ocean (e.g., Soerensen et al., 2010), the Hg species distribution suggests distinct features in the Southern Ocean Hg cycle: (i) a net atmospheric Hg deposition on surface water near the ice edge, (ii) the Hg enrichment in brine during sea ice formation, and (iii) a net methylation of Hg south of the SPF.     

Impacts of the ‘<Emphasis Type="Italic">Pacific Adventurer</Emphasis>’ Oil Spill on the Macrobenthos of Subtropical Sandy Beaches

Biological impacts of oil on sandy shore ecosystems remain incompletely understood, especially following smaller spills on subtropical beaches. Here we quantified changes to benthic assemblages on a sandy beach following the 270-t spill of heavy fuel oil from the Pacific Adventurer that occurred in March 2009 off Moreton Island in Eastern Australia. Assessments of ecological impacts are based on spatial contrasts between multiple reference and impact sites sampled 1 week and 3 months after the spill. Benthic invertebrate assemblages exposed to oil had significantly fewer individuals of fewer species 1 week after the spill, markedly changing their ecological structure. Biological differences consistent with oil-related mortality were significant on the lower shore and in the swash and remained so 3 months after the spill. This signals a lack of recovery of these communities in the short term, despite the fairly rapid removal of oil. Results show that, despite the relatively small size of the spill, heavy fuel oil contamination can cause substantial impacts on sandy beach ecosystems, and that recovery may be prolonged.     

Identification of alluvial fans susceptible to debris-flow hazards

We describe and test a method for identifying alluvial fans likely to be affected by debris flows. It is based on identifying catchment parameters by geographical information system interrogation of a digital elevation model, using the Melton ratio as the discriminating parameter. The method was calibrated using data from debris-flow-generating catchments in Coromandel and the adjacent Kaimai Ranges, North Island, NZ, and tested against data from the rest of New Zealand. The procedure is remarkably (but not completely) reliable for identifying debris-flow-capable catchments, and thus fans, across the wide range of climates and lithologies in New Zealand mountains. A case study illustrates the potential of the method for avoiding future hazards and emphasises the need for a precautionary approach when field investigations do not detect evidence for past debris flows.     

Collaborative, cross-disciplinary learning and co-emergent innovation in eScience teams

Collaborative eScience research teams are impeded by difficulties defining problems that provide research opportunities for all participants. Problem formulation occurs early in the collaboration process when the demand for ideas is high. However, cross-disciplinary linkages and integrated conceptual frameworks from which strong interdisciplinary ideas emerge do not evolve until later. The process of co-creating interdisciplinary research ideas is fundamentally a learning problem; participants from different disciplines must learn enough about each other’s research interests to construct an integrated conceptual framework from which joint problems of interest can be created. However, participants rarely have the conceptual background needed to easily understand research topics in other disciplines; hence methods for enabling rapid learning in these situations are needed. Team interactions that more effectively generate interdisciplinary ideas can be enabled based on a better understanding the process of cross-disciplinary, collaborative learning. This article postulates several models of collaborative learning in these settings and discusses the implications for orchestrating team activities to achieve better outcomes.