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This digital document is a journal article from Journal of Experimental Marine Biology and Ecology, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Canopy-forming algae often coexist with an understorey of encrusting coralline algae that bleach following the loss of canopies. We tested the hypothesis that canopy loss causes a reduction in photosynthetic activity of encrusting coralline algae concomitant with their bleaching. When canopies were experimentally removed, corallines bleached and their photosynthetic activity was rapidly reduced to half their activity observed under canopies. This result prompted us to test, and subsequently accept, the hypothesis that exposure of understorey corallines to enhanced light intensity per se (simulation of canopy loss) acts as a mechanism that causes bleaching and reduced photosynthetic activity. Despite bleaching, encrusting corallines maintained reduced levels of photosynthetic activity, and this may explain why, under certain conditions, bleached corallines can persist in the absence of canopy-forming algae. Nevertheless, our data provide evidence that the positive association between canopy-forming algae and encrusting coralline algae is maintained because of shade provided by the canopy. ... Read more

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This digital document is a journal article from Journal of Experimental Marine Biology and Ecology, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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We evaluated the effect of light intensity and substratum complexity on habitat preference and displacement speed of the ophiuroid Ophiopholis aculeata. The ophiuroid strongly preferred reduced light and to a lesser extent complex substrata. Further, displacement speed increased with light intensity and decreased with substratum complexity (ophiuroids were virtually immobile on darkened complex substrata). In the field, the density of exposed ophiuroids, with the disk out of a crevice, was always low, irrespective of the intensity of solar radiation. However, the extent to which they extended their arms (to feed) was inversely related to light intensity, as the number of suspension-feeding arms was low under direct sunlight, intermediate under indirect light and high at night. Field observations showed that the response to light was not modified when UV radiation was eliminated with a filter, and a laboratory experiment showed that white light intensity alone produced patterns similar to those observed in the field. O. aculeata may reduce arm extension with increasing light intensity to reduce the threat of visual predators, whose foraging efficiency increases with light intensity. However, visual predators are rare in our study site. We hypothesize that the large-scale larval dispersion of O. aculeata (due to the long pelagic phase) prevents ophiuroids from adapting to local conditions so that its response to light reflects adaptation to visual predators in other locations. ... Read more

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This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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The depletion of oxygen and the use of high energy cost electron acceptors for mineralisation processes are considered as one of the main reasons limiting degradation rates in aquatic organic-rich ecosystems. In this research the effect of two different biostimulation oxygen-releasing protocols were investigated using extracellular @b-glucosidase activity rates. Organic-rich sediment and water was collected from the harbour of Genoa (Italy, North-Western Mediterranean) and oxygenation was generated either by positioning air tubes into the overlying water, or by placing oxygen release compounds (ORC) directly into the sediment, in laboratory microcosms. The increase in enzymatic activity was significant in the water compartment of the oxygenated microcosms (ANOVA, p<0.05) and greater for the ORC treatment. In particular, in the water, air tubes caused an increase in the @b-glucosidase activity during the first 24h (from 18.1nmoll^-^1h^-^1 (T=0, before the treatment) to 50.9nmoll^-^1h^-^1 (T=24h)), while ORC induced a @b-glucosidase activity increase over the whole period (from 12.4nmoll^-^1h^-^1 (T=0) to 63.7nmoll^-^1h^-^1 (T=60d)) together with a reduction in carbohydrate (from 1.91mgl^-^1 (T=0) to 0.76mgl^-^1 (T=60d)) and a sedimentary pH increase (from 8.04 (T=0) to 8.22 (T=60d)). The response to ORC treatment in the overlying water was also evident in the potential carbohydrate turnover rate, decreasing from 0.86h (T=0) to 0.06h (T=60d) and cell specific enzymatic activity, increasing from 3.8 (T=0) to 22.8nmoll^-^1h^-^1cell^-^1 (T=60d). A less marked change was observed in the sediment. This research shows that the supply of oxygen directly into the sediment rather than water aeration is a better way of naturally enhancing enzymatic degradation rates in organic-rich marine ecosystems. The marked effect observed in the water following the sediment treatment suggests the occurring of a close association of decomposition processes within water and sediment compartments. ... Read more

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This digital document is a journal article from Journal of Experimental Marine Biology and Ecology, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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Time-lapse digital images can be acquired and archived using web-cameras, allowing non-invasive analysis of behavior patterns of bivalve molluscs at ultradian (sub-daily) time-scales over long intervals. These records can be analyzed directly by a human operator or through properly calibrated image analysis software. Preliminary results using species of marine and freshwater bivalves identify several ultradian biological rhythms of similar duration. Wavelet analysis indicates strong periodicity in mantle and siphon activity in the 3 to 7 min range, with longer duration shell contraction periods at 60-90 min. The recurrence of these rhythms among marine and freshwater bivalve species maintained under constant (but differing) conditions suggests the influence of common intrinsic drivers (chemico-physical mechanisms or biological clocks). Sub-daily growth increments preserved in the shells of rapidly growing bivalve species are potentially related to these biological rhythms, with implications for shell growth, biomineralization, and the temporal resolution of paleoclimate proxy data. ... Read more

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This digital document is a journal article from Journal of Experimental Marine Biology and Ecology, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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In temperate coastal seas, phytodetritus settling from the spring phytoplankton bloom is a potential food source for benthic deposit-feeders. The ability to exploit this seasonally variable resource could be enhanced by sensitivity to chemical cues signalling its arrival at the seabed. The biogenic sulphur compound dimethylsulphide (DMS), a breakdown product of dimethylsulphonioproprionate (DMSP) produced by some phytoplankton species, is a potential candidate for this role. We investigated the behavioural response of a sedentary surface deposit-feeder, the echiuran worm Maxmuelleria lankesteri, to DMS by observations and manipulative experimentation under natural conditions in a Scottish sea loch. Experimental addition of sediment enriched with DMSP-producing phytoplankton caused no significant increase in either the frequency of feeding by M. lankesteri or the rate of sediment ejection from observed burrows. Naturally occurring (DMSP+DMS) content of surface sediment was low during the winter, then peaked in April before declining in May. There was no consistent relationship between this parameter and rate of sediment ejection from M. lankesteri burrows. The results therefore provide no evidence that M. lankesteri uses DMSP or DMS as a stimulus to increased activity. An observed imbalance between the frequency of surface deposit-feeding and sediment ejection from individual burrows remains unexplained. ... Read more

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Chapters: Steller's Sea Cow, Dodo, Thylacine, Great Auk, Passenger Pigeon, Caribbean Monk Seal, Paschalococos. Source: Wikipedia. Pages: 77. Not illustrated. Free updates online. Purchase includes a free trial membership in the publisher's book club where you can select from more than a million books without charge. Excerpt: The thylacine (pronounced , or in Australia , also ) (binomial name: Thylacinus cynocephalus; Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger (because of its striped back), the Tasmanian wolf, and colloquially the Tassie tiger or simply the tiger. Native to continental Australia, Tasmania and New Guinea, it is thought to have become extinct in the 20th century. It was the last extant member of its genus, Thylacinus, although several related species have been found in the fossil record dating back to the early Miocene. The thylacine had become extremely rare or extinct on the Australian mainland before European settlement of the continent, but it survived on the island state of Tasmania along with several other endemic species, including the Tasmanian devil. Intensive hunting encouraged by bounties is generally blamed for its extinction, but other contributory factors may have been disease, the introduction of dogs, and human encroachment into its habitat. Despite its official classification as extinct, sightings are still reported, though none proven. Like the tigers and wolves of the Northern Hemisphere, from which it obtained two of its common names, the thylacine was an apex predator. As a marsupial, it was not closely related to these placental mammals, but because of convergent evolution it displayed the same general form and adaptations. Its closest living relative is thought to be either the Tasmanian devil or numbat. The thylacine was one of only two marsupials to have a pouch in both sexes (the other bein...More: http://booksllc.net/?id=30388 ... Read more

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How Deep Is the Sea? fosters children's knowledge about animal life bothabove and below water with more than 200 interactive pages. Youngchildren can dive into the mysteries of the deep while learning tons ofocean facts through skill-building exercises, such as coloring bynumbers, matching activities, number puzzles, crosswords, mazes, wordsearches, make-and-do crafts, and much, much more!