Spatio-temporal variation in benthic eukaryotic communities of two tropical coastal lagoons evidenced by eDNA metabarcoding. Spatial and temporal variation in benthic eukaryotic communities in two tropical coastal lagoons

Tropical coastal lagoons are highly important ecosystems due to high biodiversity and the goods and services they provide. Monitoring of lagoon benthic biodiversity and detection of harmful or invasive species is important particularly in relation to seasonal and spatial variation in environmental conditions. However, traditional ecological surveys are time consuming and costly. Here we used eDNA metabarcoding in two tropical coastal lagoons in order to describe the benthic biodiversity and its spatio-temporal dynamics. Samples were collected from Chacahua (CH) and Corralero (CA) lagoons (Southern Mexican Pacific) from March, April (dry season) and September (rainy season) of 2018. Metabarcoding libraries were produced for COI and 18s amplicons. The distribution of biological diversity within the lagoons showed a very particular spatial-temporal pattern evidencing a transition from freshwater to seawater. Our results show that although the two lagoon systems are similar in terms of the species composition of metazoans and micro-eukaryotes, they are different in taxa richness and structure, resulting in regionalization of the diversity for CH especially in the dry season where salinity is the driving factor in community composition. The dominant metazoan phyla in both lagoon systems and both seasons were Arthropods, Chordata, Annelids, Mollusca and Cnidaria; and for microeukaryotes were Ochrophyta, Ciliophora, Cercozoa, Opisthokonta, Archaeplastida and Dinoflagellata. The technique also detected some non-indegenous and bioindicator species that were not previously reported for the area (Amphibalanus eburneus, Alexandrium leei, Amphidinium klebsii and Gyrodinium jinhaense). This study will allow a baseline for a much-needed future monitoring of the diversity dynamics of these tropical ecosystems, since some tropical coastal lagoons are of fishing, commercial and bioprospecting importance.