Sustainability implications of honouring the Code of Conduct for Responsible Fisheries

The Code of Conduct for Responsible Fisheries developed in 1995 by the Food and Agriculture Organization (FAO) of the United Nations includes a set of recommendations for reducing the negative impacts of fishing activities on marine ecosystems. The Code is widely believed to be an important tool for fisheries management and, although the Code is voluntary, all stakeholders concerned with the management and development of fisheries, and conservation of fishery resources, are actively encouraged to implement it. Previous analysis at global scale showed widespread low compliance with the Code of Conduct that may be partly due to a lack of empirical support for the overall ecological benefits of adhering to the Code. Here we evaluated these ecological effects by comparing compliance with the Code to changes in five ecological indicators that quantify the ecosystem effects of fishing. We used the loss in production index and the related probability of sustainable fishing index, the mean trophic level of the catch, total catches, and the primary production required to sustain the catch. We also tested if regional differences and development status of countries influenced the results of ecological indicators. Results indicate that countries with higher levels of compliance with the FAO Code of Conduct in 2008 experienced a decrease in the Loss in Production index and an increase in fisheries sustainability from the 1990s to 2000s. We conclude that better implementation of the Code of Conduct may have had overall positive ecological effects with time. A significant decrease in total catch and primary production required with higher compliance was also observed. While a significant increase in ecosystem sustainability was observed after a decade of adoption of the Code at high levels of compliance, further ecosystem degradation had taken place where compliance with the Code was below a given threshold (4, from a ranking of 0–10). Therefore, since compliance with the Code is still low or very low worldwide, these results may encourage individual countries to adopt well-established fishery management measures in order to increase the ecological sustainability of marine resources.     

Effects of melt percolation on highly siderophile elements and Os isotopes in subcontinental lithospheric mantle: A study of the upper mantle profile beneath Central Europe

The effects of melt percolation on highly siderophile element (HSE) concentrations and Re-Os isotopic systematics of subcontinental lithospheric mantle are examined for a suite of spinel peridotite xenoliths from the 4 Ma Kozákov volcano, Bohemian Massif, Czech Republic. The xenoliths have previously been estimated to originate from depths ranging from ∼32 to 70 km and represent a layered upper mantle profile. Prior petrographic and lithophile trace element data for the xenoliths indicate that they were variably modified via metasomatism resulting from the percolation of basaltic melt derived from the asthenosphere. Chemical and isotopic data suggest that lower sections of the upper mantle profile interacted with melt characterized by a primitive, S-undersaturated composition at high melt/rock ratios. The middle and upper layers of the profile were modified by more evolved melt at moderate to low melt/rock ratios. This profile permits an unusual opportunity to examine the effects of variable melt percolation on HSE abundances and Os isotopes.Most HSE concentrations in the studied rocks are significantly depleted compared to estimates for the primitive upper mantle. The depletions, which are most pronounced for Os, Ir and Ru in the lower sections of the mantle profile, are coupled with strong HSE fractionations (e.g., Os_N/Ir_N ratios ranging from 0.3 to 2.4). Platinum appears to have been removed from some rocks, and enriched in others. This enrichment is coupled with lithophile element evidence for the degree of percolating melt fractionation (i.e., Ce/Tb ratio).Osmium isotopic compositions vary considerably from subchondritic to approximately chondritic (γ_Os at 5 Ma from -6.9 to +2.1). The absence of correlations between ¹⁸⁷Os/¹⁸⁸Os and indicators of fertility, as is common in many lithospheric mantle suites, may suggest significant perturbation of the Os isotopic compositions of some of these rocks, but more likely reflect the normal range of isotopic compositions found in the modern convecting mantle. Osmium isotopic compositions correspondingly yield model Re-depletion (T_RD) ages that range from essentially modern to ∼1.3 Ga.Our data provide evidence for large-scale incompatible behavior of HSE during melt percolation as a result of sulfide dissolution, consistent with observations of prior studies. The degree of incompatibility evidently depended on melt/rock ratios and the degree of S-saturation of the percolating melt. The high Pt contents of some of these rocks suggest that the Pt present in this pervasively metasomatized mantle was controlled by a phase unique to the other HSE. Further, high Os concentrations in several samples suggest deposition of Os in a minority of the samples by melt percolation. In these rocks, the mobilized Os was characterized by similar to the ¹⁸⁷Os/¹⁸⁸Os ratios in the ambient rocks. There is no evidence for either the addition of Os with a strongly depleted isotopic composition, or Os with suprachondritic isotopic composition, as is commonly observed under such circumstances.     

Separation of core and intact polar archaeal tetraether lipids using silica columns: Insights into living and fossil biomass contributions

Intact polar lipids (IPLs) are frequently used as biomarkers for living microbial cells and can be separated from core lipids (i.e. lipids without polar headgroups), which are mainly derived from fossil (i.e. dead) cell material, using column chromatography. We have compared the effect of various silica column conditions on the separation and recovery of archaeal glycerol dialkyl glycerol tetraether (GDGT) core lipids, glycolipids and phosphoglycolipids using authentic standards and direct analysis with various high performance liquid chromatography-mass spectrometry (HPLC-MS) techniques. The commonly used procedure to separate these compound classes using dichloromethane, acetone and methanol as eluents, respectively, did not separate core GDGTs from glyco- and phosphoglyco-GDGTs. In contrast, a recently described procedure using hexane:ethyl acetate (3:1, v:v), ethyl acetate and methanol achieved both high recovery and successful separation of core GDGTs from the other IPLs. Application of the method to a geothermally heated soil and suspended particulate matter from the North Sea showed that it separates most of the core GDGTs from the other IPLS and that considerable qualitative and quantitative differences can occur between core and IPL-GDGTs. We conclude that the method is therefore appropriate for the separation of intact archaeal IPLs and their fossil analogues.     

Nearshore currents on the southern Namaqua shelf of the Benguela upwelling system

Nearshore currents of the southern Namaqua shelf were investigated using data from a mooring situated three and a half kilometres offshore of Lambert's Bay, downstream of the Cape Columbine upwelling cell, on the west coast of South Africa. This area is susceptible to harmful algal blooms (HABs) and wind-forced variations in currents and water column structure are critical in determining the development, transport and dissipation of blooms. Time series of local wind data, and current and temperature profile data are described for three periods, considered to be representative of the latter part of the upwelling season (27 January–22 February), winter conditions (5–29 May) and the early part of the upwelling season (10 November–12 December) in 2005. Differences observed in mean wind strength and direction between data sets are indicative of seasonal changes in synoptic meteorological conditions. These quasi-seasonal variations in wind forcing affect nearshore current flow, leading to mean northward flow in surface waters early in the upwelling season when equatorward, upwelling-favourable winds are persistent. Mean near-surface currents are southward during the latter part of the upwelling season, consistent with more prolonged periods of relaxation from equatorward winds, and under winter conditions when winds were predominantly poleward. Within these seasonal variations in mean near-surface current direction, two scales of current variability were evident within all data sets: strong inertial oscillations were driven by diurnal winds and introduced vertical shear into the water column enhancing mixing across the thermocline, while sub-inertial current variability was driven by north–south wind reversals at periods of 2–5 days. Sub-inertial currents were found to lag wind reversals by approximately 12 h, with a tendency for near-surface currents to flow poleward in the absence of wind forcing. Consistent with similar sites along the Californian and Iberian coasts, the headland at Cape Columbine is considered to influence currents and circulation patterns during periods of relaxation from upwelling-favourable winds, favouring the development of a nearshore poleward current, leading to poleward advection of warm water, the development of stratification, and the creation of potentially favourable conditions for HAB development.     

Overview and status of estuarine microphytobenthos ecological research in South Africa

This article presents a historical overview of estuarine microphytobenthos (MPB) research in South Africa published over the period 1950 to the present, highlighting major milestones, challenges and estuarine management problems, as well as future research needs within the South African context. The studies that were covered comprise peer-reviewed books and journal articles on relevant research conducted in any estuarine environment during the period reviewed. There was a general increase in MPB research outputs over the decades, from only two publications in the 1950s, to over 20 outputs between 2010 and the present. Whereas the MPB studies in South Africa cover a broad spectrum of themes, the research priorities in these works have changed from taxonomically biased studies to those of ecologically based research. Research in the 1950s and 1960s was exclusively taxonomic in nature, with the first ecological investigation incorporating MPB being produced in the 1970s. By the 1980s, ecological studies dominated the research outputs and this trend has persisted to the present. The 1990s and 2000s saw the rise of research into the role of fresh water as a driver of MPB dynamics, whereas the period 2010 to the present saw an increase in more diverse ecological themes, ranging from an autecological investigation to food-web studies and the assessment of multiple drivers of MPB dynamics. However, the majority of studies have focused on either diatoms or estimates of overall MPB biomass. Moreover, there is a regional underrepresentation that runs broadly along biogeographic lines, with the bulk of the work having been conducted in the warm-temperate and subtropical zones of South Africa. Challenges and future research needs for the region are outlined, as is the need to expand MPB research to include other aspects of the biology and ecology of this flora.     

An evaluation of progress in implementing ecosystem-based management of fisheries in 33 countries

The performance of 33 countries was evaluated for ecosystem-based management (EBM) of fisheries in three fields (principles, criteria and implementation) using quantitative ordination including uncertainty. No country rated overall as ‘good’, only four countries were ‘adequate’, while over half received ‘fail’ grades. A few developing countries performed better than many developed nations. Two case studies test the method. In Indonesia, Raja Ampat and Papua, rated similar to the national evaluation, but better performance might follow successful implementation of a planned EBM initiative. A workshop in Australia rated regional fisheries managed by New South Wales 20% lower for EBM than federally managed fisheries.     

Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii

Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35 years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9 wt.%, with temperatures prior to quench ranging from 1140 °C to ambient (110 °C). Five eruption samples were also analyzed.Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006–1.40 ppb for Os and 0.0006–2.01 ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF₆ in some of the most magnesian samples.Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values in both eruption and lava lake samples suggest the presence of unevenly distributed, unidentified Pt-rich trace phases in some Kilauea Iki materials.Estimated mineral (olivine + chromite)/melt D values for Os, Ir, Ru and Pt for equilibrium crystallization for samples from ~ 7 to 27 wt.% MgO are 26, 8.2, 19 and 0.55, respectively. These Os, Ir and Ru estimates are somewhat higher than previous estimates for similar systems. If fractional crystallization is instead assumed, D values are much more similar.Results confirm many prior observations in other mafic systems that olivine (together with included phases) has a major effect on absolute and relative abundances of Re and the PGE. The relatively linear correlations between these elements and MgO potentially permit accurate estimation of the concentrations of these elements in the primary melts of comparable systems, especially in instances where the MgO content of the primary melt is well constrained.