ALBERT

Description: Despite coelacanths, Latimeria chalumnae, being listed as either endangered by CITES or critically endangered by the IUCN, their population size within South Africa is unknown and still needs to be estimated. Their conservation status unfortunately excludes the use of conventional tagging to mark individual animals for a possible mark–recapture experiment. This study shows that because coelacanths have a unique spot patterning it is possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator, the software accurately identified between 56 and 92% of the individuals. Indentification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs, although the percentage of fish correctly identified without operator-intervention decreased rapidly with increasing yaw angle. Computer-aided identification should therefore facilitate future coelacanth research as it is both efficient and accurate while also reducing potential stress on the animals observed.

Description: In this paper, we empirically investigate the robustness of random forests for regression problems. We also investigate the performance of six variations of the original random forest method, all aimed at improving robustness. These variations are based on three main ideas: (1) robustify the aggregation method, (2) robustify the splitting criterion and (3) taking a robust transformation of the response. More precisely, with the first idea, we use the median (or weighted median), instead of the mean, to combine the predictions from the individual trees. With the second idea, we use least-absolute deviations from the median, instead of least-squares, as splitting criterion. With the third idea, we build the trees using the ranks of the response instead of the original values. The competing methods are compared via a simulation study with artificial data using two different types of contaminations and also with 13 real data sets. Our results show that all three ideas improve the robustness of the original random forest algorithm. However, a robust aggregation of the individual trees is generally more profitable than a robust splitting criterion.

Description: Species distribution models (SDMs) are an important tool in biogeography and ecology and are widely used for both fundamental and applied research purposes. SDMs require spatially explicit information about species occurrence and environmental covariates to produce a set of rules that identify and scale the environmental space where the species was observed and that can further be used to predict the suitability of a site for the species. More spatially accurate data are increasingly available, and the number of publications on the influence of spatial inaccuracies on the performance of modelling procedures is growing exponentially. Three main sources of uncertainty are associated with the three elements of a predictive function: the dependent variable, the explanatory variables and the algorithm or function used to relate these two variables. In this study, we review how spatial uncertainties influence model accuracy and we propose some methodological issues in the application of SDMs with regard to the modelling of fundamental and realized niches of species. We distinguish two cases suitable for different types of spatial data accuracy. For modelling the realized distribution of a species, particularly for management and conservation purposes, we suggest using only accurate species occurrence data and large sample sizes. Appropriate data filtering and examination of the spatial autocorrelation in predictors should be a routine procedure to minimize the possible influence of positional uncertainty in species occurrence data. However, if the data are sparse, models of the potential distribution of species can be created using a relatively small sample size, and this can provide a generalized indication of the main regional drivers of the distribution patterns. By this means, field surveys can be targeted to discover unknown populations and species in poorly surveyed regions in order to improve the robustness of the data for later modelling of the realized distributions. Based on this review, we conclude that (1) with data that are currently available, studies performed at a resolution of 1–100 km2 are useful for hypothesizing about the environmental conditions that limit the distribution of a species and (2) incorporating coarse resolution species occurrence data in a model, despite an increase in sample size, lowers model performance.

Description: Cereopsis studeri was described by G. von Koch in 1891 with material from Naples. However, it was subsequently synonymized, erroneously identified, and overlooked in subsequent soft coral literature of the twentieth century. After the original description, this species was not recorded or correctly described for 120 years. The study of newly collected material from the North Western Mediterranean permits the re-description of this forgotten species and its assignation to the genus Nidalia in the family Nidaliidae. The main features of Nidalia studeri com. nov. are: colony torch-like, a capitulum light orange in colour, not laterally flattened, dome-shaped and not distinctly projecting beyond the stalk, introvert with sclerites transversally placed in two longitudinal rows per interseptal space, anthocodial crown with 28–38 sclerite rows, points separated from polyps distally, formed by 6–9 pairs of sclerites, and the presence of intermediate points (secondary points) between principal (interseptal) ones. Nidalia studeri is here compared with its closest congeners, especially with the Indonesian species N. simpsoni, species from the West Indian Region N. dissidens, N.occidentalis, N. deichmannae, and the recently described Nidalia aurantia from the Mid-Atlantic Ocean. This is the first time that the genus Nidalia and the family Nidaliidae have been reported with certainty for the Mediterranean Sea.

Description: Three new compounds, 4′-(4,5-dimethyl-1,3-dioxolan-2-yl)methyl-phenol (1), (3′-hydroxybutan-2′-yl)5-oxopyrrolidine-2-carboxylate (2), and atroviridetide (3), have been isolated from the marine-derived fungus Trichoderma atroviride G 20-12. Their structures were determined on the basis of chemical and spectroscopic methods.

Description: It is well known that random forests reduce the variance of the regression predictors compared to a single tree, while leaving the bias unchanged. In many situations, the dominating component in the risk turns out to be the squared bias, which leads to the necessity of bias correction. In this paper, random forests are used to estimate the regression function. Five different methods for estimating bias are proposed and discussed. Simulated and real data are used to study the performance of these methods. Our proposed methods are significantly effective in reducing bias in regression context.

Description: A histological study of the reproductive cycle of male and female shore crabs, Carcinus maenas (Linnaeus), was performed monthly on the South West coast of Ireland (from December 2006 to July 2008). The calculated sex ratio deviated from equality, 1:0.53, revealing a strong male bias. A system was devised, based on screening of tissue sections, to describe and stage gametogenic development. Histological examinations revealed that ovarian development occurred biannually, with a primary winter cycle in which the larger crabs reproduced and a secondary summer cycle, when smaller crabs reproduced. An association was observed where more of the larger specimens were caught in the summer months and the smaller specimens in the winter months, which inversely correlated with the segregated breeding cycles. There was strong evidence that mature male crabs could potentially copulate year round since all mature specimens, collected throughout the year, contained viable spermatozoa. Developmental stages of oogenesis and spermatogenesis were described to develop a practical gonadal index for this portunid crab, providing information on the biology of this species, which will be of benefit for fisheries management.

Description: There has been debate in the literature about whether jellyfish abundance has increased in the northern Benguela upwelling system, or not, over the past five decades and what impact they are having on pelagic fish. Here we review old expedition literature as well as more recent spatial and temporal patterns in distribution of jellyfish off Namibia at a number of different scales, using both published and previously unpublished data. Specifically, we have used data from fishery-dependent sources of both the demersal (359 638 trawls) and pelagic fisheries (11 324 purse-seine sets) that cover the period 1992–2006, supported by data from fishery-independent demersal (6 109 trawls) and pelagic trawls (1 817 trawls) from 1996 to 2006. Using frequency of capture as an index of abundance, it is clear that jellyfish are not randomly distributed within the northern Benguela ecosystem, but show specific areas of concentration that broadly reflect regional oceanography and the distribution of other zooplankton. Although jellyfish are present throughout the year, peaks in abundance are shown that often coincide with peaks in the spawning activity of fish of commercial importance. Interannual changes in jellyfish abundance observed from all sources do not agree, with some showing increases, others declines, and still others showing no change, which suggests caution should be exercised in their interpretation. Based on the multiple lines of evidence synthesised here, we conclude that jellyfish abundance has increased concomitant with a decline of pelagic fish stocks. We conclude that future recovery of the pelagic fishery off Namibia is likely to be considerably challenged because of significant overlaps in space and time between fish and jellyfish, and through the effects of competition and predation effects of jellyfish on fish.

Description: In this paper, drained behaviour of cemented sand under high pressure is studied. A recently developed high pressure triaxial apparatus is used. The test results indicate the significance of degree of cementation and confining pressure on the isotropic compression, volumetric change, stress-strain behaviour and stress-dilatancy relationship of cemented sand at high confining pressures. The results suggest that the influence of cementation is greater at low confining stresses and it reduces with increasing confining stress where the effect of the confining pressure becomes dominant. A Scanning Electron Microscope analysis has also been included in the paper. It revealed that the particle and cement bonding breakage at high pressure is dependent on the stress level and the cement content. The higher the confining pressure the more significant particle and cement bonding breakage is observed. The higher the cement content the fewer sand particles and cement bonds are broken.

Description: It was demonstrated previously that polar and non-polar surface extracts of the brown alga Fucus vesiculosus collected during winter from the Kiel Bight (Germany) inhibited bacterial attachment at natural concentrations. The present study describes the bioassay-guided identification of the active metabolites from the polar fraction. Chromatographic separation on a size-exclusion liquid chromatography column and bioassays identified an active fraction that was further investigated using nuclear magnetic resonance spectroscopy and mass spectrometry. This fraction contained the metabolites dimethylsulphopropionate (DMSP), proline and alanine. DMSP and proline caused the anti-attachment activity. The metabolites were further quantified on the algal surface together with its associated boundary layer. DMSP and proline were detected in the range 0.12–1.08 ng cm−2 and 0.09–0.59 ng cm−2, respectively. These metabolites were tested in the concentration range from 0.1 to 1000 ng cm−2 against the attachment of five bacterial strains isolated from algae and sediment co-occurring with F. vesiculosus. The surface concentrations for 50% inhibition of attachment of these strains were always 〈0.38 ng cm−2 for DMSP and in four cases 〈0.1 ng cm−2 for proline, while one strain required 1.66 ng cm−2 of proline for 50% inhibition. Two further bacterial strains that had been directly isolated from F. vesiculosus were also tested, but proved to be the least sensitive. This study shows that DMSP and proline have an ecologically relevant role as surface inhibitors against bacterial attachment on F. vesiculosus.

Description: Altered lavas have been dredged from three locations on the Resolution Ridge, west of New Zealand's South Island. On the basis of whole-rock geochemistry, Sr, Nd and Pb isotope data and Ar–Ar ages, they can be divided into two suites: 62–60 Ma enriched mid-ocean ridge basalt (E-MORB), and 57 Ma trachybasalt and trachyandesite of ocean island basalt (OIB) affinity. The E-MORBs from the Resolution Ridge are only the second place from which Tasman Sea abyssal oceanic crust has ever been sampled, they have Indian MORB-like isotope compositions, and their ages support a recent interpretation of a 100 km sinistral offset of the southern part of the Tasman Sea spreading ridge. The slightly younger OIB suite erupted shortly after oceanic crust formation and has FOZO to HIMU source characteristics similar to the well-known SW Pacific Diffuse Alkaline Magmatic Province (DAMP). The close occurrence and isotopic mixing relationships of both Paleocene volcanic suites on the Resolution Ridge may be explained by a heterogeneous upper mantle in which the more fertile OIB component was extracted during a later melting event away from the spreading ridge. The dredged lavas predate formation of Southeast Tasman oceanic crust that borders the Resolution Ridge to the south.

Description: Radiation measurements in the area off Northwest Africa (research cruise, February 2008) and at Mindelo (Cape Verde Islands, May 2009) were used to investigate the impacts of Saharan dust and clouds on solar irradiance and on photosynthetically available radiation, to derive a relationship between dust aerosol optical depth (AOD) and photosynthetically available radiation and to determine the annual variations of photosynthetically available radiation. Three different kinds of atmospheric conditions were considered: cloudy skies, which decreased or increased the irradiance and dusty skies. The reduction by clouds was up to 67.2% at 400 nm and up to 84.4% at 700 nm. Enhancements of up to 21.9% at 400 nm and 34.0% at 700 nm were observed. The decrease by dust was up to 19.7% at 400 nm and up to 4.1% at 700 nm. Clouds decreased or increased the photosynthetically available radiation by up to 79.9% or up to 31.2%. The reduction by dust depended on the dust AOD and was between 3.6% and 12.3%. A linear relationship confirmed a decrease of photosynthetically available radiation of 1.2% by an increase of dust AOD of 0.1.

Description: Bacteria associated with 2 macroalgae growing in the Kiel Fjord (Baltic Sea) were investigated seasonally over two years by scanning electron microscopy and cultivation methods. Seasonal variations and significant differences between both macroalgal species with respect to the associated bacteria were observed. 166 bacterial strains were isolated from the macroalgae and classified by phylogenetic analysis of 16S rRNA gene sequences. The strains formed 82 phylotypes according to sequence similarities of499.0%. Samples from Fucus vesiculosus revealed 43 and from Delesseria sanguinea 57 bacterial phylotypes. They affiliated to Actinobacteria, Alphaproteobacteria, Bacilli, Betaproteobacteria, Flavobacteria, Gammaproteobacteria, and Sphingobacteria. Following the assumption that chemical interactions rule the bacteria-macroalga associations, we tested the biological activity of both macroalgae and isolated bacterial strains against a panel comprising standard and ecologically relevant microorganisms (Gram-positive and Gram-negative bacteria, including macroalgal pathogens and surface associated strains, and a yeast). Both macroalgae presented inhibitory activity against at least one microorganism, but overall the inhibitory activities were low. In contrast, all extracts stimulated growth of many of the tested bacteria. While growth stimulation was common concerning bacteria associated with macroalgae, no stimulation was shown for the standard set of bacteria (with exception of one case of stimulation of the plant pathogen Erwinia amylovora). Regarding the potential biological activity of microorganisms associated with macroalgae, more than 60% of the bacterial phylotypes inhibited the growth of at least one microorganism. A higher proportion of strains showed antimicrobial activity against the set of bacteria associated with macroalgae as compared to standard set of microorganisms. Certain phylotypes are consistently found as epiphytes, suggesting their specific association with macroalgae. The presented positive and negative effects of macroalgal extracts on growth of macroalga-associated bacteria, significant bacterial activity against macroalgal pathogens and competitors, and potential degradative capabilities support the assumption that complex chemical interactions shape the bacteria-macroalga relationships.

Description: Global ocean precipitation is an important part of the water cycle in the climate system. A number of efforts have been undertaken to acquire reliable estimates of precipitation over the oceans based on remote sensing and reanalysis modelling. However, validation of these data is still a challenging task, mainly due to a lack of suitable in situ measurements of precipitation over the oceans. In this study, validation of the satellite-based Hamburg Ocean Atmosphere Parameters and fluxes from Satellite data (HOAPS) climatology was conducted with in situ measurements by ship rain gauges over the Baltic Sea from 1995 to 1997. The ship rain gauge data are point-to-area collocated against the HOAPS data. By choosing suitable collocation parameters, a detection rate of up to about 70% is achieved. Investigation of the influence of the synoptic situation on the detectability shows that HOAPS performs better for stratiform than for convective precipitation. The number of collocated data is not sufficient to validate precipitation rates. Thus, precipitation rates were analysed by applying an interpolation scheme based on the Kriging method to both data sets. It was found that HOAPS underestimates precipitation by about 10%, taking into account that precipitation rates below 0.3 mm h−1 cannot be detected from satellite information.

Description: Investigations of the surface chemistry of marine organisms are essential to understand their chemically mediated interactions with fouling organisms. In this context, the concentration of natural products in the immediate vicinity of algal surfaccs, as well as their biological activity, are of particular importance. Howevcr, due to lack of appropriate methods, the distribution of Compounds within the Chemical sphere around marine algae is unknown. This study demonstrates the suitability of confocal resonance Raman microspcctroscopy for the determination of metabolites around algal surfaces with a micrometer resolution.

Description: A semi-empirical approach was used to quantify the modification of the underwater light field in amplitude (magnitude effect) and spectral distribution (spectral effect) by different atmospheric conditions altering the incident light. The approach based on an optical model in connection with radiation measurements in the area off Northwest Africa. Key inputs of the model were parameterized magnitude and spectral effects. Various atmospheric conditions were considered: clear sky, dusty sky without clouds, cloudy sky without dust and skies with different ratios of dust and clouds. Their impacts were investigated concerning the modification of the downward irradiance and photosynthetically available radiation in the water column. The impact on downward irradiance depended on the wavelength, the water depth, the optical water properties, the dust and cloud properties, and the ratio of clouds to dust. The influence of clouds on the amplitude can be much higher than that of dust. Saharan dust reduced the photosynthetically available radiation in the water column. Ocean regions were more influenced than coastal areas. Compensations of the magnitude and spectral effects were observed at special water depths in ocean regions and at atmospheric conditions with definite cloud to dust ratios

Description: The scintillation index of plane and spherical light waves as well as of a Gaussian beam, propagating in the clear-water weakly turbulent ocean, is revealed. The results are of utmost importance for underwater optical communications and sensing. An analysis of the threshold between the weak and strong regimes of oceanic turbulence is made, with the accent on the contribution from salinity-induced turbulence. It is found that strong oceanic turbulence can occur at distances as short as several meters, in striking contrast with atmospheric studies for which the typical distances are on the order of a kilometer.

Description: This paper introduces new data on Todaropsis eblanae morphology, morphometry and functional aspects of the male reproductive system and hectocotylus. Spermatophores differ in specimens from the Atlantic Ocean (average length, 18.28 ± 1.45 mm, 15.63 ± 0.8% of mantle length; weight, 2.0–12.0 mg) and the Indian Ocean (average length, 24.8 ± 2.85 mm, 16.9 ± 2.1% of mantle length; weight, 35.0–39.6 mg) (t = 3.14; p 〈 0.01 for absolute sizes and t = 0.711; p 〉 001 for relative sizes). An additional important distinctive trait is the form of connection of the cement body with the ejaculatory tube. In recent years, T. eblanae has been regularly caught in the Barents Sea, meaning its range has extended to subarctic waters. The morphology and morphometry of the spermatophoric complex of organs did not vary in investigated parts of its range. Hectocotylus patterns and some important spermatophore traits distinguish Todaropsis from other Ommastrephidae.

Description: We examined the effect of increased copper concentrations (0-10 mu M) on hydrothermal vent microorganisms and the production of copper (Cu)-binding ligands as a response. Hydrothermal vent microbes originated from diffuse fluids at the Lilliput mussel field and the Irina II site in the Logatchev hydrothermal vent field, both on the Mid-Atlantic Ridge. Parallel studies were also conducted with amino acids supplemented to the incubations in order to verify whether dissolved amino acids, present in hydrothermal fluids, can buffer the bioavailable copper and reduce the active production of Cu-binding ligands. In all incubations, ligand concentrations increased with rising copper concentrations, but microbial cell numbers remained constant. This study shows that microbes were able to cope with as much as 10 mu M dissolved copper by buffering the free copper concentration. The presence of amino acids had no significant influence on the active ligand production. Our results imply that mediation of chemical speciation by vent microbes may have an important impact on hydrothermal trace metal fluxes into the ocean.