Influence of Physicochemical Parameters on Burrowing Activities of the Fiddler Crab Uca tangeri at the Huelva Coast (Southwest Spain): Palaeoichnological Implications

摘要

Populations of fiddler crabs (Uca tangeri) occupy several marginal-marine environments of the Huelva coast of Southwest Spain. Associated with these organisms are large, open burrows that represent domiciles recognized by numerous circular apertures. Ichnological analysis reveals variations in features of the biogenic structures between and through different marginal-marine environments, including an intertidal sandy beach and a salt-marsh setting into an estuary zone. We hypothesized that the observed variations in burrows of Uca tangeri related to changes in particular physicochemical parameters in the overall habitat. Herein the possible relationship between the ichnological features of burrow crabs (density and diameter of aperture) and selected physicochemical factors (pH, temperature, sediment texture, grain size, firmness, and depth of ground water level) are treated. The obtained results in two selected areas where several transects were conducted suggest a variable relationship, with several parameters showing a weak influence on the burrowing behaviour (e. g., pH, and temperature), while others reveal a major important (e. g., firmness and depth of the ground water level). These results are relevant to palaeoichnological analyses regarding the behavior of trace fossil producers, the relationship between palaeoenvironmental limiting factors and burrow features, and to the improvement of characterizations regarding substrate-controlled ichnofacies.