Indirect paleo-seagrass indicators (IPSIs): A review

Seagrass meadows are marine habitats with high ecological importance. Their detection in the fossil record will contribute to our understanding of the development of patterns of marine biodiversity through time and the response of coastal marine habitats to environmental change. Due to the low probability of fossilization of seagrass macrofossils, the reliable identification of seagrass meadows in the fossil record is often challenging. A wide range of indirect indicators has been applied to infer paleo-seagrass habitats in Late Cretaceous and Cenozoic deposits. The usefulness of those indicators is determined by various factors, such as their stratigraphic range, fossilization potential, habitat restriction, and others. Although they have sometimes been briefly summarized in the literature, a comprehensive review of indirect paleo-seagrass indicators, including an assessment of their value for recognition of this habitat, is not yet available. We summarize them here and explore their usefulness. We aim to assist future workers to identify facies and fossil assemblages associated with seagrass beds. Apart from a few truly diagnostic proxies, combinations of several indicators turn out to be most reliable when aiming to identify the presence of paleo-seagrass habitats. The presence/absence of many potentially seagrass-associated taxa cannot serve as a useful indicator due to a lack of habitat restriction, but statistical evaluations of abundance data are promising to discriminate seagrass beds from neighboring areas. However, such studies are available for only a few commonly seagrass-associated organism groups. Furthermore, the applicability of many indicators is confined by latitude, because their occurrence is restricted to (sub)tropical or at most warm temperate regions.