Human trampling and vehicle traffic affect meiofauna and Nematoda distribution patterns in Amazonian macrotidal sandy beaches

Recreational activities are important source of disturbance on sandy beaches and have a negative effect on meiofauna communities as they alter species abundance, diversity, and/or distribution. Here, we report for the first time the effects of recreational activities on the distribution patterns of meiofauna communities and Nematoda assemblages of Amazonian sandy beaches. Sampling was performed during four consecutive months with different beach use intensity in 2017 (June – before vacation, July – vacation month, August and September - after vacation months) on two contrasting beaches regarding disturbance (Urban: Atalaia; and Protected: Corvinas). Physical sediment variables remained constant over time in both beaches, whereas differences were found in sediment compaction over the periods. Sediment compaction was considered the most important factor for the differences observed in meiofauna community and Nematoda assemblage structures in the beaches, and it was related to intensity of recreational activities. Overall, variations in density and changes in richness between periods and sampling stations were observed in Atalaia beach. Before the vacation three faunal zones were distinguished in Atalaia beach (upper intertidal, intermediate intertidal, and low-intertidal), whereas in the vacation period only two faunal zones were distinguished (upper-intertidal and intermediate-low intertidal). On the other hand, Corvinas beach remained the same throughout the study. Thus, the initial hypothesis that recreational activities trigger changes in the structure and composition of meiofauna and Nematoda, reducing richness and abundance of the community, was confirmed. Furthermore, the vulnerability of some taxa studied here, particularly Copepoda and Tardigrada, and the Nematoda genera Chromadorita and Daptonema indicates that they might be potential indicators of recreational activities.