Although the carbonate compensation depth (CCD) for calcite, generally located in the depth range 4000–5000 m, is often proposed as a physiological barrier to deep-ocean colonization, many organisms with calcareous exoskeletons are found in the deepest oceanic trenches. Serpulid polychaetes inhabiting unprotected calcareous tubes are unlikely deep-sea inhabitants, yet, they are found at all oceanic depths from intertidal to hadal. Here we review and revise the published and unpublished records of Serpulidae from below 5000 m depth. We also describe tube ultrastructure and mineralogical content of available deep-sea serpulid tubes to obtain insights into their biomineralisation. Species belonging to the genera Bathyditrupa, Bathyvermilia, Hyalopomatus, Pileolaria (spirorbin) and Protis were found at depths from 5020 to 9735 m. However, only specimens of Protis sp. were truly hadal (>6000 m) being found at 6200–9700 m. Hadal specimens of Protis have irregularly oriented prismatic tube microstructure similar to that found in more shallow-water representatives of the genus. Initial EDX analysis suggested a mostly calcitic composition (i.e., the most stable CaCO3 polymorph) on the basis of high Mg levels. Surprisingly, however, tubes of Bathyditrupa hovei and a species of Protis analysed using the more reliable method of laser Raman spectroscopy were found to be composed of aragonite. The compensation depth for this less stable CaCO3 polymorph in the oceans is usually 2000–3000 m. We found no obvious structural adaptations to life at extreme depths in the studied serpulid tubes and how serpulids are able to biomineralise and maintain their tubes below the CCD remains to be explained. 相似文献
Recent years have seen increasing interest in the concepts of compensation and ecosystem services. Regulation systems in the United States dealing with environmental protection (Superfund Act, Oil Pollution Act, National Environment Policy Act, Clean Water Act, Endangered Species Act, etc.) require those responsible for damage to ecosystem services to compensate for it “physically” and restore these services for the benefit of the entire population. This article, using simple indicators of compensation identified in the literature, attempts to analyze what types of ecological compensation are adopted, how performance is assessed, how standards on ecological equivalencies are adopted, and what are the costs of this compensation. To perform this analysis, compensatory measures carried out during the last ten years in the case of coastal and marine ecosystems in Florida have been addressed. The results show that: analysis criteria for the equivalencies between ecosystem services lost due to damage and ecosystem services gained due to compensatory measures are questionable; most compensation monitoring is for a relatively brief period of time and the data obtained during this period may be insufficient for assessing the net effect of the compensatory measure; the weaknesses regarding criteria for the equivalencies and the uncertainty about the relevant time-scale can be counter-balanced by increasing the area of compensation, a problematic solution at best. 相似文献