Quantification and characterisation of sediments trapped by Posidonia banquettes: A case study on the southern Catalan coast (Spain).
Authors: Astudillo Gutierrez Carlos , Gracia García Vicente , Sierra Pedrico Joan Pau , Cáceres Rabionet Iván , Sanchez-Arcilla Agustín 
Published: February 2023

&lt;p&gt;Posidonia Oceanica is a phanerogamous species endemic to the Mediterranean. It is characterised by its habitat in sandy and rocky areas at depths of less than 40 m in waters with constant salinity and the necessary clarity for the plant to obtain nutrients (Mar&amp;#237;n Guirao et al., 2011; Ruiz et al., 2009). &amp;#160;In seasonal periods (autumn and winter), part of the Posidonia meadow is dragged by the highest energy waves, mainly associated with storm surges, depositing these remains on the shoreline of the beaches. The constant accumulation of this Posidonia remains can generate vertical growth, transforming it into Posidonia banquettes.&lt;/p&gt;
&lt;p&gt;The Posidonia banquettes accumulation have been continuously found covering the shoreline of the Mediterranean beaches. Over years these accumulations have been retired from the beach mainly by heavy machinery. The movement of these materials has caused an alteration of the beach-dune system, as the removal of banquettes has also removed part of the beach sediment, which is generally not quantified.&lt;/p&gt;
&lt;p&gt;This work will carry out the quantification and characterisation of sediments trapped in the Posidonia banquette of a sandy beach located on the south coast of Catalonia (Spain). For this purpose, several transects perpendicular to the beach line will be sampled. One transects considers a sample of clean sand from the beach and another one from the upper and lower part of the Posidonia banquette.&lt;/p&gt;
&lt;p&gt;For the sediment analysis of the banquette samples, the separation of the sediments from the Posidonia remains by a simplified method will be considered. This method removes the organic matter present by pyrolysis of the samples in an oven at 500&amp;#186;C for 30 minutes. In this way, the amount of sediment by weight per volume of banquette is precisely quantified. The type of sediment retained by these accumulations is characterised with respect to the type of sand present on the beach.&lt;/p&gt;
&lt;p&gt;In addition, the fieldwork considers the measurement of the in-situ compactness of the banquettes using a handheld penetrometer. Thus, the compactness of the accumulations can be related to the amount of sediment retained by the banquette.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;The fields and laboratory experiments to be described in this work have been funded by the Spanish Government within the Research, Development and Innovation Program through a grant to the ECOPLANTS project (REF PID2020-119058RB-I00).&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Mar&amp;#237;n-Guirao, L., Sandoval-Gil, J. M., Ru&amp;#237;z, J. M., and S&amp;#225;nchez-Lizaso, J. L. (2011). &amp;#8220;Photosynthesis, growth and survival of the Mediterranean seagrass Posidonia Oceanica in response to simulated salinity increases in a laboratory mesocosm system&amp;#8221;. Estuarine, coastal and shelf science, 92(2), 286-296.&lt;/p&gt;
&lt;p&gt;Ru&amp;#237;z, J. M., Mar&amp;#237;n-Guirao, L., and Sandoval-Gil, J. M. (2009). &amp;#8220;Responses of the Mediterranean seagrass Posidonia Oceanica to in situ simulated salinity increase&amp;#8221;. 52(5), 459-470.&lt;/p&gt;