The invasion of the intertidal canopy-forming alga Fucus serratus L. to southwestern Iceland: Possible community effects

The intertidal serrated wrack, Fucus serratus L. (Fucales: Phaeophyceae), has become an abundant canopy-forming alga along a ca. 100 km stretch of shore in southwestern Iceland in the last century. Its distribution has not changed noticeably since a survey in 1975/1976. Many experimental studies have shown that canopy-forming algae can have profound effects on the community structure. Although such experiments involving F. serratus are few it was decided to test predictions from these experiments on a geographical scale by comparing community compositions within the area where F. serratus is a dominant algae (since at least 1975/1976) with an adjacent area of similar size where F. serratus is absent (with a single exception without consequences). The work is based on measurements on some 372 stations in the F. serratus area, termed region A, and 227 stations from the F. serratus-free area, termed region B. Percentage cover of algae and sessile invertebrates was estimated on 2 m² on each station and animals collected from 800 cm² from each station. The vertical distribution of F. serratus was most similar to that of Fucus distichus and the two species often grew intermingled on the lower part of the shore. F. serratus appeared to have reduced the cover of F. distichus in the lowermost part of the shore, while having little or no effect on other canopy-forming species. The low abundance of Semibalanus balanoides in the F. serratus area (region A) is in line with experiments showing detrimental effect on this barnacle by whiplash of F. serratus. In general algal grazers were more abundant in region A, consistent with the greater attractiveness of F. serratus than other canopy-forming species to grazers, although this may be partly explained by the abundance of understorey algae in region A.     

Support Vector Machines for Classification of?Aggregates by Means of IR-Spectra

The increasing physical and technical demands placed on construction materials, especially as they are being used more and more up to the limits of their mechanical strength, has led the aggregates industry to search for more efficient methods of quality control. Information from theoretical work on rock spectra in near-infrared and mid-infrared light as well as achievements gained in signal processing can all be used to improve quality control in an economically acceptable manner. As engineering properties of aggregates are to a great extent determined by the petrological composition of the rock aggregates, the question is, whether a statistical classification rule for identification of rock aggregates can be developed. However, the classification of rocks is complicated by the fact that the optical behavior of minerals forming the rock often appears muted. In addition, minor constituents may dominate the spectrum. Furthermore, the relevant spectra form high dimensional data that are extremely difficult to analyze statistically, especially when curves are very similar. In this paper, support vector machines for classification of rock spectra are investigated, since they are appropriate in classifying highly dimensional data such as spectra.     

Titanomaghemite in Icelandic basalt: possible clues for the strongly magnetic phase in Martian soil and dust

It is suggested that the strongly magnetic phase found in the soil and dust on Mars, tentatively identified as maghemite, may have been formed in a similar way as titanomaghemite found in the Icelandic basalt. Earlier work has shown that titanomaghemite in Icelandic basalt can be formed upon thermal oxyexolution of titanomagnetite, a process in which water may not have played any significant role. Here, we present further data on how the formation of titanomaghemite takes place in Icelandic basalt, and illustrate how the Mössbauer spectroscopy can be useful in answering fundamental questions related to the possible formation of maghemite on Mars. This might be of special interest for a robotic Mars mission where a ⁵⁷Fe-Mössbauer spectrometer is included.     

Figuring fish and measuring men: the individual transferable quota system in the Icelandic cod fishery

This article discusses inequality in the Icelandic cod fishery, focusing on changes in the actual distribution of fishing quotas and the ways in which Icelanders currently talk about equity and ownership. The individual transferable quota (ITQ) system, introduced in 1984, divided access to an important resource among those who happened to be boat owners at that time. Statistical findings with respect to the cod fishery - based on a database (the ‘Quotabase’) constructed using detailed information on all vessels that have been allotted ITQs from the onset of the system - show that ITQs have been increasingly concentrated in the hands of the biggest companies. Many of the small-scale boat owners that still hold ITQs are increasingly compelled to enter into contracts that involve fishing for larger ITQ holders. It is suggested that the distribution of ITQs, as well as their evaluation in social discourse, represents an important field of research. In Iceland, public discontent with the concentration of fishing rights and the ensuing social repercussions is increasingly articulated in terms of loaded metaphors, including ‘profiteering’, ‘tenancy’ and ‘lords of the sea’. It is argued that the ultimate efficiency of management programs may be jeopardized if managers ignore the history and culture of the fisheries involved and the likely social and ecological consequences of their programs.     

Field characteristics of laterally emplaced dikes: Anatomy of an exhumed Miocene dike swarm in Reydarfjördur, eastern Iceland

Many dikes of the Tertiary Breiddalur dike swarm in Reydarfjördur have a great lateral extent but are vertically (upward and/or downward) discontinuous. Field relationships indicate that they are not the feeders of the lava pile they intrude. Their characteristics can be best interpreted as them constituting the fossil expression of lateral magma emplacement analogous to that occurring in the actively spreading Krafla volcanic center of the neovolcanic zone. Average dike thickness increases clearly with depth and the thickness versus depth relationship is different from that described for other Tertiary dike swarms in eastern Iceland. It is suggested that dikes represent the extent of finite spreading which at higher levels in the crust is expressed by fissures and other extensional structures.     

Statistical Classification of Different Petrographic Varieties of Aggregates by Means of Near and Mid Infrared Spectra

The increasing interest of the construction aggregates industry in reducing production costs and the costs resulting from improper use of construction materials leads to the question whether it is possible to statistically identify some rock variants by their reflectivity of near-infrared and mid-infrared light. Infrared spectroscopy allows quantitative and qualitative analysis of minerals in a reliable manner, whereas the classification of rocks is complicated by the fact that the optic behavior of minerals forming the rock often appears muted. In addition, minor constituents may dominate the spectrum. Furthermore the relevant spectra form high dimensional data, which are extremely difficult to analyse statistically, especially when curves are very similar. Common methods of multivariate statistics for this type of data, used in chemometric studies, followed by linear discriminant analysis, do not lead to acceptable classification error rates. In this paper wavelets are used in order to reduce dimensionality. As wavelets are better able to mirror local behavior of curves, they are more suitable for selecting characteristic features. The approximation is analyzed in terms of its classification properties using Mahalanobis distance or flexible discriminant analysis.     

Modelling the Real World: Conceptual Modelling in Spatiotemporal Information System Design

Throughout the relatively young history of research on spatiotemporal modelling, a substantial number of models have been presented. However, since a spatiotemporal model represents a closer approximation to the real world than is the case for traditional models, such models must be based on a thorough understanding of how objects 'behave' in reality. One way to acquire such knowledge is using conceptual modelling methodologies . In this paper, an overview of different modelling principles and a selection of conceptual modelling languages are presented together with examples related to a selection of spatiotemporal problems.     

Predators on rocky shores in the northern Atlantic: Can the results of local experiments be generalized on a geographical scale?

Experimental manipulations of invertebrate prey and predators on rocky shores have been done by many authors. In the northern Atlantic the predators involved are usually the green crab Carcinus maenas and/or the dogwhelk Nucella lapillus, and the prey species studied are acorn barnacles (balanid Cirripedia), mussels (Mytilus spp.) and winkles (Littorina spp.). Usually the predators are found to have a regulating “top–down” effect on the prey species. In Iceland the acorn barnacle Semibalanus balanoides, the blue mussel Mytilus edulis and the flat periwinkle Littorina obtusata (including to some extent Littorina mariae) are found on rocky shores all around Iceland in what would seem to be near-optimal physical conditions. The predators Carcinus maenas and Nucella lapillus, on the other hand, are relatively southern species that do not thrive on the colder coasts of Iceland. Thus general surveys of different coasts of Iceland would seem to offer opportunities to see whether the results of local experiments can be discerned on a geographical scale (hundreds of km). The roughly 4900 km of the rocky coastline in Iceland was in this study subdivided into four regions, I–IV, according to the commonness or presence of the two predators. With the hope of reducing compounding factors the surveys were confined to sheltered or semi-sheltered fucoid shores, which were further divided into Ascophyllum (more sheltered) and Fucus vesiculosus (less sheltered) shores. Estuaries or other low-salinity environments were avoided. The study was based on 761 stations distributed around the rocky coastline on these two types of shores. The results for barnacles and mussels, being generally more abundant in regions were predators were scarce or absent, and being less common in Ascophyllum than F. vesiculosus shores in contrast to the predatory dogwelks, were in large measure in accord with predictions from experiments indicating “top–down” regulation. The results for the periwinkles, however, suggested that “bottom–up” regulation might be of greater importance, as their density was closely linked to the biomass of macroalgae, while the abundance of predators appeared to have little effect. The periwinkle, although certainly eaten, may not be a preferred prey of the two predators in question in Iceland. This paper forms a link between experimental and observational study approaches.