When large whales die and sink to the sea floor provide a huge and concentrated food source to the marine ecosystem. Whale falls are mainly known from the deep sea, both in the modern and in the fossil record, where they host a rich and specialized community similar to those living at other deep sea reducing habitats, like hydrothermal vents and hydrocarbon seeps. On the contrary little is known on what happens in shallow waters. This study contributes novel data to our knowledge of shallow water whale fall communities (WFC). Fossil whale falls from the Neogene of Italy were studied in detail, together with a modern analogue ecosystem from the North Sea. A multidisciplinary approach was applied to the study of fossil shelfal WFC, based on a variety of tools, ranging from taphonomy to petrography and isotope analysis, to quantitative benthic paleoecology. Results concern different taxonomic groups that took advantage of the large quantity of energy stored in whale tissues, from the microbial consortium at the base of the food web, to benthic macro-invertebrates, to larger pelagic scavengers. The field excavation of a 10 m long baleen-whale from the Pliocene of Tuscany is at the base of the study. Taphonomy and the position of macrofaunal whale associates with respect to the still articulated bones allowed to reconstruct the main tracts of the ecological succession at the whale fall. Sediment bulk samples collected next to whale bones and from the surrounding sediments were quantitatively analyzed for their mollusc content. Quantitative species-level data on bivalves, gastropods and scaphopods allowed to compare WFC and background communities. A similar approach was applied to the study of the mollusc community associated with a 5 m long minke whale sunk at 125 m depth in the North Sea. To further widen the field of enquiry other twenty-four, more or less complete fossil whales present in Italian museum collections were studied, guided by the experience previously gained during our own field work. The data include taphonomy of fossil bones and qualitative and partial information on the associated fauna. Petrographic microfacies techniques were applied to the study of whale bones. Taphonomy at the microscopic scale was approached through optical and scanning microscopy, Raman spectroscopy and stable isotope geochemistry in order to analyze the signature of microorganisms participating to whale bone degradation, mainly bacteria and fungi, and understand microenvironmental conditions within and around larger bones. Some of the outcrops from which museum specimens had been extracted were studied and sampled to reconstruct local environmental conditions. Bulk samples were analyzed to gather abundance data that were then compared within a larger data set of intertidal to bathyal samples from the literature. As expected, the main factor conditioning the distribution of molluscs around WFC and in other normal settings is water-depth. Absolute depth estimates and considerations based on lithology and paleoecology showed that at least seven whale falls out of twenty-four were located in open shelf settings and possibly associated with high-nutrient conditions. The general results are consistent with the hypothesis that shallow water whale falls are different from their deep counterparts. On the shelf obligate taxa of families typical of deep sea reducing environments are small-sized and rare, possibly occurring only in offshore settings. The organic input concentrated in a large whale sunken to the bottom becomes food for generalist taxa commonly living on the shelf.

Modern and fossil shallow water whale fall communities / S. Danise. - (2010).

Modern and fossil shallow water whale fall communities

DANISE, SILVIA
2010

Abstract

When large whales die and sink to the sea floor provide a huge and concentrated food source to the marine ecosystem. Whale falls are mainly known from the deep sea, both in the modern and in the fossil record, where they host a rich and specialized community similar to those living at other deep sea reducing habitats, like hydrothermal vents and hydrocarbon seeps. On the contrary little is known on what happens in shallow waters. This study contributes novel data to our knowledge of shallow water whale fall communities (WFC). Fossil whale falls from the Neogene of Italy were studied in detail, together with a modern analogue ecosystem from the North Sea. A multidisciplinary approach was applied to the study of fossil shelfal WFC, based on a variety of tools, ranging from taphonomy to petrography and isotope analysis, to quantitative benthic paleoecology. Results concern different taxonomic groups that took advantage of the large quantity of energy stored in whale tissues, from the microbial consortium at the base of the food web, to benthic macro-invertebrates, to larger pelagic scavengers. The field excavation of a 10 m long baleen-whale from the Pliocene of Tuscany is at the base of the study. Taphonomy and the position of macrofaunal whale associates with respect to the still articulated bones allowed to reconstruct the main tracts of the ecological succession at the whale fall. Sediment bulk samples collected next to whale bones and from the surrounding sediments were quantitatively analyzed for their mollusc content. Quantitative species-level data on bivalves, gastropods and scaphopods allowed to compare WFC and background communities. A similar approach was applied to the study of the mollusc community associated with a 5 m long minke whale sunk at 125 m depth in the North Sea. To further widen the field of enquiry other twenty-four, more or less complete fossil whales present in Italian museum collections were studied, guided by the experience previously gained during our own field work. The data include taphonomy of fossil bones and qualitative and partial information on the associated fauna. Petrographic microfacies techniques were applied to the study of whale bones. Taphonomy at the microscopic scale was approached through optical and scanning microscopy, Raman spectroscopy and stable isotope geochemistry in order to analyze the signature of microorganisms participating to whale bone degradation, mainly bacteria and fungi, and understand microenvironmental conditions within and around larger bones. Some of the outcrops from which museum specimens had been extracted were studied and sampled to reconstruct local environmental conditions. Bulk samples were analyzed to gather abundance data that were then compared within a larger data set of intertidal to bathyal samples from the literature. As expected, the main factor conditioning the distribution of molluscs around WFC and in other normal settings is water-depth. Absolute depth estimates and considerations based on lithology and paleoecology showed that at least seven whale falls out of twenty-four were located in open shelf settings and possibly associated with high-nutrient conditions. The general results are consistent with the hypothesis that shallow water whale falls are different from their deep counterparts. On the shelf obligate taxa of families typical of deep sea reducing environments are small-sized and rare, possibly occurring only in offshore settings. The organic input concentrated in a large whale sunken to the bottom becomes food for generalist taxa commonly living on the shelf.
2010
S. Monechi
ITALIA
S. Danise
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/543057
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