University of Vienna, Department of Palaeontology, Althanstrasse 14, 1090 Vienna, Austria.
Palaeogeogr Palaeoclimatol Palaeoecol. 2013 Jan 15;370(C):77-91. doi: 10.1016/j.palaeo.2012.11.021.
Life-death (LD) studies of shelly macrofauna are important to evaluate how well a fossil assemblage can reflect the original living community, but can also serve as a proxy for recent ecological shifts in marine habitats and in practice this has to be distinguished using taphonomic preservation pattern and estimates of time-averaging. It remains to be rigorously evaluated, however, how to distinguish between sources of LD disagreement. In addition, death assemblages (DAs) also preserve important information on regional diversity which is not available from single censuses of the life assemblages (LAs). The northern Adriatic Sea is an ecosystem under anthropogenic pressure, and we studied the distribution and abundance of living and dead bivalve and gastropod species in the physically stressful environments (tidal flat and shallow sublittoral soft bottoms) associated with the delta of the Isonzo River (Gulf of Trieste). Specifically we evaluated the fidelity of richness, evenness, abundance, habitat discrimination and beta diversity. A total of 10,740 molluscs from fifteen tidal flat and fourteen sublittoral sites were analyzed for species composition and distribution of living and dead molluscs. Of 78 recorded species, only eleven were numerically abundant. There were many more dead than living individuals and rarefied species richness in the DA was higher at all spatial scales, but the differences are lower in habitats and in the region than at individual stations. Evenness was always higher in death assemblages, and probably due to temporally more variable LAs the differences are stronger in the sublittoral habitats. Distinct assemblages characterized intertidal and sublittoral habitats, and the distribution and abundance of empty shells generally corresponded to that of the living species. Death assemblages have lower beta diversity than life assemblages, but empty shells capture compositional differences between habitats to a higher degree than living shells. More samples would be necessary to account for the diversity of living molluscs in the study area, which is, however, well recorded in the death assemblages. There is no indication of a major environmental change over the last decades in this area, but due to the long history of anthropogenic pressure here, such a potential impact might be preserved in historical layers of the deeper sedimentary record.
有壳大型动物的生死（LD）研究对于评估化石组合能够在多大程度上反映原始生物群落非常重要，但也可以作为海洋栖息地最近生态变化的替代指标，实际上，这需要通过化石化保存模式和时间平均估计来区分。然而，如何区分 LD 不一致的来源仍有待严格评估。此外，死亡组合（DA）还保留了有关区域多样性的重要信息，而这些信息无法从单一的生命组合（LA）普查中获得。亚得里亚海北部是一个受到人为压力的生态系统，我们研究了与伊松佐河三角洲（的里雅斯特湾）相关的物理压力环境（潮滩和浅亚潮带软底）中生活和死亡双壳类和腹足类物种的分布和丰度。具体来说，我们评估了丰富度、均匀度、丰度、栖息地辨别和β多样性的保真度。从 15 个潮滩和 14 个浅亚潮带站点共分析了 10740 个软体动物，以了解生活和死亡软体动物的物种组成和分布。在所记录的 78 种物种中，只有 11 种数量丰富。死亡个体的数量远远超过生活个体，在所有空间尺度上，DA 的稀有物种丰富度都更高，但在生境和区域内的差异低于个别站点。均匀度在死亡组合中总是更高，可能是由于 LA 的时间变化更大，因此在浅亚潮带生境中差异更强。潮滩和浅亚潮带生境的特征分明，空壳的分布和丰度通常与生活物种相对应。死亡组合的β多样性低于生命组合，但空壳比活壳更能捕捉生境之间的组成差异。需要更多的样本才能说明研究区域内生活软体动物的多样性，但这些多样性在死亡组合中记录得很好。在过去几十年中，该地区没有出现重大环境变化的迹象，但由于这里长期受到人为压力的影响，这种潜在影响可能会保存在深层沉积物记录的历史层中。
