The origin of the compressibility anomaly in amorphous silica : a molecular dynamics study

We propose an explanation for the anomalous compressibility maximum in amorphous silica based on rigidity arguments. The model considers the fact that a network structure will be rigidly compressed in the high-pressure limit, and rigidly taut in the negative pressure limit, but flexible and hence softer at intermediate pressures. We validate the plausibility of this explanation by the analysis of molecular dynamics simulations. In fact this model is quite general, and will apply to any network solid, crystalline or amorphous; there are experimental indications that support this prediction. In contrast to other ideas concerning the compressibility maximum in amorphous silica, the model presented here does not invoke the existence of polyamorphic phase transitions in the glass phase

30 Cold-Water Corals as Shelter, Feeding and Life-History Critical Habitats for Fish Species: Ecological Interactions and Fishing Impact

This chapter is a review of studies that present the role of cold-water corals as shelter, feeding and life-history critical habitats for fish species in the Mediterranean Sea and world oceans. Studies in the Mediterranean have been carried out both in Madrepora-Lophelia dominated communities and in coral areas characterised by octocorals and black corals. Most studies in the northeast Atlantic regard Lophelia pertusa reefs, while those in the northwest Atlantic refer to Oculina varicosa, L. pertusa and octocoral species. Octocorals and black corals dominated in the studies from the northeast Pacific. Most studies show that the cold-water coral habitats are important for fish species. In fact, a variety of fish species have been observed and suggested to benefit from shelter and productive feeding in the complex heterogeneous habitats built by corals. This is due to the enhanced density of zooplankton as potential prey for planktivorous fish and high density of invertebrates between and around corals as food for benthos feeders and scavengers. Moreover, several fish species use cold-water coral habitats as a spawning area and nursery. The occurrence of gravid individuals frequently observed in the coral habitats, as well as the presence of egg masses found deposited on coral stalks and egg cases attached to corals or found nested in coral colonies are clear evidence that several fish species rely on coral habitats as a place to spawn and protect offspring. The fish species of families Scyliorhinidae, Sebastidae, Serranidae, Berycidae, Zoarcidae, Lotidae, Moridae, Congridae, Liparidae seem to be more tightly associated to cold-water coral habitats. Some fish species of these families obtain multiple benefits from their association with cold-water coral habitats, despite being facultative inhabitants. Regarding the occurrence of many commercial fish species in cold-water coral habitats, it should be take into consideration that these habitats are highly impacted in the Mediterranean and throughout the oceans in general. Studies on this topic have been reviewed shortly focusing on the Mediterranean Sea where longlining and trawling are the main causes of fishing impact

The Impact of Fisheries Discards on Scavengers in the Sea

A scavenger is an animal that feeds on dead animals (carrion) that it has not killed itself. Fisheries discards are often seen as an important food source for marine scavengers so the reduction of discards due to the Landing Obligation may affect their populations. The literature on scavenging in marine ecosystems is considerable, due to its importance in the trophic ecology of many species. Although discards undoubtedly contribute to these species’ food sources, few can be seen to be solely dependent on carrion (including discards). Ecosystem models predicted that discards contributed very little to the diet of scavengers at a regional scale. A reduction in discards through the Landing Obligation may therefore affect populations for a few species in some areas, but generally this is unlikely to be the case. But it is challenging to identify how important discards might be to scavengers, as they are taxonomically diverse and vary in the role they play in scavenging interactions