Solar cycle dependence of periodic variations in geomagnetic Kp-index

The geomagnetic K_p-index data for the 1932–1969 period have been investigated by means of a modified power spectrum technique on the basis of overlapping 2-yr intervals. The observed 27-, and 13.5-day periodicities show an obvious solar cycle dependence through the whole period concerned. Also, periodicities in the range of 9?4 days have been observed through years of minimum and decreasing phases of solar activity. The periodicities observed are found to be related to the existence of variations in the interplanetary medium structure which modulates the geomagnetic activity.     

Evidence for discrete subpopulations of sea perch (Helicolenus ercoides) across four fjords in Fiordland,New Zealand

In coastal populations of invertebrates and fishes, the distribution of discrete subpopulations is influenced by adult and larval dispersal, as well as by the effects of habitat heterogeneity on site fidelity or connectivity. Here, we examine evidence for spatial structure of sea perch, Helicolenus percoides, populations among four fjords in the Fiordland region of southwestern New Zealand. We examine patterns in adult morphology, length-at-age, δ¹³C and δ¹⁵N of muscle tissue, and trace elemental composition of whole otoliths as proxies for population isolation among the four inner fjord regions. A multivariate analysis of morphometrics reveals significant differences among populations from each of the four sites, suggesting existence of four distinct subpopulations. These patterns are consistent with observed differences in δ¹³C and δ¹⁵N, and length-at-age estimates among the four subpopulations. Differences in whole otolith concentrations of Sr, Ba, Mg and Li, and high classification scores based on the whole otolith elemental fingerprint are also consistent with significant subdivision among areas. Patterns across all four markers are consistent with discrete subpopulation structure of adult sea perch among the four study sites. These data indicate that the newly implemented network of marine protected areas in Fiordland is likely to contain discrete populations of sea perch.     

Riverine dominance of a nearshore marine demersal food web: evidence from stable isotope and C/N ratio analysis

The Thukela Bank, KwaZulu-Natal, supports a diverse ecosystem and South Africa’s only prawn fishery. Oceanographic studies suggest riverine input is not important for the biology of this system, whereas biological studies suggest the contrary, with prawn catches increasing with increased fluvial run-off. The aim of this study was to determine (i) the importance of riverine and marine organic matter for the Thukela Bank food web; and (ii) whether there are seasonal changes in the Thukela River stable isotope values, and, if so, whether these are reflected in the isotope values of demersal organisms. Estuarine organic matter, sediments and demersal organisms were collected from several sites across the bank in the wet and dry seasons of 2008, 2009 and 2010. Marine particulate organic matter was also collected in 2010 and analysed for δ13C and δ15N, as well as C/N ratios. There were strong seasonal changes in isotopic values of organic matter and fauna, especially faunal δ13C. There was an apparent time-lag in organisms assimilating riverine organic matter isotopic values, with the isotopic signature of demersal organisms reflecting that of riverine organic matter from the previous season, which is likely the result of tissue turnover time. In 2010, Thukela Bank sediment organic matter was of riverine origin and this maintained the demersal food web. We conclude that Thukela River organic matter is an important input to the food web of the Thukela Bank, indicating that any future damming of the catchment area could have serious consequences for this ecosystem.     

The role of sea ice in coastal and bottom dynamics in the Pechora Sea

This article deals with the morpho- and lithodynamic role of ice in shaping the Arctic coasts. Taking the Pechora Sea as an example, the direct and indirect impact of ice on the sea floor and shores is described. Active gouging by ice floes, ice-rafting of sedimentary material, formation of strudel scour depressions and frozen rocks on shallows are all direct impacts. The indirect impact of ice that arrests the coastal zone for most of the year is a considerable reduction of the overall energy of waves and currents. Based on the performed analysis, we plot a schematic zonation of the Pechora Sea according to the probable impact of ice on the shores and seafloor.     

Diet and dietary variation of New Zealand hoki Macruronus novaezelandiae

The diet of hoki was determined from examination of stomach contents of 1992 fish of 26–112 cm total length (TL) sampled at depths of 209–904m on Chatham Rise, New Zealand, from summer research trawl surveys and seasonal commercial fishing trawls, during 2004–2008. Prey was predominantly euphausiids, mesopelagic fishes and natant decapods. Multivariate analyses using distance-based linear models, non-parametric multi-dimensional scaling and similarity percentages indicated that the best predictors of diet variability were the position of the fish in relation to the subtropical front (STF), fish size and longitude. Pasiphaeids were more important to the north of the STF, and sternoptychid fishes and euphausiids more important in the STF convergence area. Euphausiids and sternoptychid fishes were important for smaller hoki (26–55 cm TL), myctophid fishes and natant decapods for larger hoki, and macrourids for the largest hoki (>84 cm TL). The longitudinal effect was characterised by pasiphaeids, euphausiids and sternoptychids to the west, and myctophids in the centre of Chatham Rise. Feeding activity was analysed using generalised additive models, and was found to vary with time of day, sample source (research or commercial), longitude, hoki size and depth. The variability in diet suggested hoki forage opportunistically within their preferred habitat and biological limits.     

Chlorate reduction by dithionite/UV advanced reduction process

Chlorate is one of the disinfection byproducts that are formed when chlorine/chlorine dioxide is used as a primary disinfectant. This study investigated the removal of chlorate by photochemical degradation using an advanced reduction process, which is a treatment method that combines a reducing agent with an activating method to generate reducing radicals. The effectiveness of combinations of reducing agents and three UV light sources having a peak output at 254, 365, and 312 nm were evaluated for chlorate removal. Dithionite irradiated by broad-band UVB lamp having the peak energy at 312 nm showed the highest chlorate removal. In pursuit of finding the optimum advanced reduction process conditions, the environmental process variables including pH, reducing agent dose, and light intensity were investigated. Dithionite/UV-B advanced reduction process was effective in weakly acidic conditions (pH < 5), and chlorate removal occurred in two steps. The first was an initial rapid decrease in chlorate concentration that occurred before initiating UV irradiation and was attributed to reaction with dithionite decomposition products. The second step was a slow decrease during UV irradiation that is caused by radicals produced by photolysis of the products of dithionite decomposition. The major product of chlorate destruction was chloride, with negligible amounts of chlorite produced.     

Epibiotic assemblages on the pen shell Pinna rudis (Bivalvia,Pinnidae) at Matiota Beach,São Vicente Island,Cabo Verde

The rough pen shell Pinna rudis Linnaeus, 1758 (family Pinnidae), a mollusc with an Atlantic–Mediterranean distribution, is able to live in coarse sandy substrates. Considering its shell structure and ecological characteristics, P. rudis can enhance biodiversity by providing a substrate for settlement on its shell. For this reason, we compared the diversity of benthic taxa around P. rudis shells with the species diversity on P. rudis shells, at Matiota Beach, São Vicente Island, Cabo Verde. We sampled an area of 900 m2 and recorded data in situ to estimate the population size of P. rudis and the epibiotic and benthic community diversity. The average density of P. rudis estimated in the sampled area was 6.6 ind. 100 m–2 and the highest density was found at between 2 and 3 m depth, mostly in biogenic and sandy substrates. The epibiotic species diversity on P. rudis shells was significantly higher than the species diversity in the microhabitat around the shells. The P. rudis shell seems to play an important role in increasing the biodiversity of the ecosystem, with some species found only as epibionts on P. rudis.     

Studies on the effect of salinity, drought stress and soil type on nodule activities of Lablab purpureus (L.) sweet (Kashrangeeg)

Lablab purpureus(50 cultivars throughout the world) is a drought-tolerant legume widely grown as a high-protein grain food and forage legume within a wide range of neotropical regions with extensive production in India and similar climatic areas of Asia, Africa, Central and South America. The objective of this work was to study the nitrogen-fixing potentialities of L. purpureus under the effects of the extreme environmental conditions prevailing in the southern part of Egypt aiming at the recommendation of its propagation in areas of the National giant projects.L. purpureusinoculated with Rhizobium sp. Strain I₄ (21 days after planting) grown on Nile valley and Wadi Allaqi soils was relatively tolerant to mild levels of salinity, but the nodule number was reduced to about 35% of the control plants when subjected to a high salt level (120mM NaCl). Lablab plants were similarly affected by different rates of water deficits. This legume was tolerant to moderate levels of drought. The nodule number and weight at 50% of field capacity was about 70% of the control. These values were reduced to 45–55% at a field capacity of 16·5%.Absolute nitrogenase activity, leghaemoglobin content of nodules and protein content of bacteroids and cytosol were moderately affected by mild levels of NaCl and drought but significantly reduced to about 25–35% of the control treatments.The results also indicate that plants grown on the soil of Nile Valley exhibited slightly higher values (nitrogenase, protein, etc.) than those grown on Wadi Allaqi soil. This would encourage the possibility of propagating L. purpureus in the newly reclaimed areas of southern Egypt.     

Asexual origin of brooding in the sea anemones Actinia equina and A. schmidti: molecular evidence from the Portuguese shore

Reproduction by sexual or asexual viviparity is a common phenomenon in some anemone species. In this short communication, the origin of the brooded young of Actinia equina and A. schmidti from the Portuguese shore was investigated. DNA was extracted from 56 brooding adult Actinia sp. and the nuclear gene that codes for the 28S ribosomal subunit was sequenced. Species identity was then assessed using GenBank. In total, 50 individuals were A. schmidti, five were A. equina and one had a hybrid origin. Three adult anemones (the hybrid, one A. equina and one A. schmidti) possessed two different 28S sequences and so their offspring was selected for further analysis using the same molecular procedure. Each brooded polyp was found to possess the exact same sequence as its parent, strongly suggesting the asexual origin of broods in A. equina and A. schmidti.     

Electrochemical oxidation of succinic acid in aqueous solutions using boron doped diamond anodes

In this work, the electrochemical oxidation of succinic acid on boron-doped diamond (BDD) anodes was investigated. Voltammetric study had shown that no peaks appeared in the region of electrolyte stability which indicates that succinic acid oxidation can take place at a potential close to the potential region of electrolyte oxidation. Galvanostatic electrolyses achieved total chemical oxygen demand (COD) removals and high mineralization yields under different operating conditions (initial COD, current density and nature of supporting electrolyte). Oxalic, glycolic and formic acids were the main intermediates detected during anodic oxidation of succinic acid on BDD electrode and carbon dioxide as the final product. The mean oxidation state of carbon reached the value of 4 at the end of electrolysis which is indicative of mineralization of almost all organics present in aqueous solution. The exponential profile of COD versus specific electrical charge has shown that mass transfer is the limiting factor for the kinetics of electrochemical process. A simple mechanism was proposed for the mineralization of succinic acid. First, hydroxyl radicals attack of succinic acid leading to formation of glycolic, glyoxylic, fumaric and maleic acids. Then, theses acids undergo rapid and non-selective oxidation by hydroxyl radicals to be transformed into oxalic and formic acids which leads to further oxidation steps to mineralize these acids into carbon dioxide and water.