Benthic biodiversity record in intertidal death assemblages of Punta Mejillón, Patagonia, Argentina

ARCHUBY, FERNANDO M; LÓPEZ RODAL, LISANDRO; ROCHE, ANDREA

Montevideo

Workshop; Taller de Tafonomía Actualista en América del Sur; 2017

Facultad de Ciencias, Universidad de la República, Uruguay

We present an ongoing Project that is in an early stage of development, concerning the taphonomic fidelity of life and death assemblages in Punta Mejillón locality (coast of Río Negro Province, Argentina; 41º 00? 51?? S). The goals are: 1- evaluate how marine benthic intertidal biodiversity is recorded in death assemblages sampled at four levels (lower, middle and upper intertidal and supratidal or high water mark). 2- How sampled levels differ in terms of species richness and abundance. 3- Evaluate the effect of sampling with and without sieves on diversity and species abundance. Previous research showed that death assemblages sampled by hand from the high tide line in Patagonian coasts resemble faunal composition at the regional scale (faunistic provinces). However, at the locality scale the fidelity was low. During spring tides of November and December of 2013 life and death assemblages of marine benthic invertebrates where sampled together in Punta Mejillón. We present here the results of the analysis of the death assemblages. Sampling of death assemblages at the four levels was performed by means of transects parallel to the coastline, along each level, until filling a 12 litres bucket. Every sample was sieved with two mesh sizes, 1 and 10 mm (side of the square). We expect, by the end of the project to assess the following hypothesis: 1- using sieves to get the samples yield different results than picking by hand (sieved samples show higher levels of fidelity and higher diversity than non-sieved ones); 2- there are differences in the faunal composition amongst the four levels, partly correlated with the composition of the living community and partly explained the time-averaging and biostratinomic agents; 3- there is an association in terms of faunal composition between life and death assemblages in each level. We propose that Punta Mejillón serves as the base level for live-dead comparisons in Patagonia, due to its little or no anthropized nature.