Determination of the association of species (Ophiocomina nigra and Arbacia lixula), Phylum Echinodermata, based on physical-chemical variables in rocky strata of the Wildlife Refuge, Rio Escalante-Chacocente

Abstract

This study was carried out in the intertidal zone in the Escalante Chacocente River Wildlife Refuge, Santa Teresa municipality. Its main objective is the determination of the association of the species Arbacia lixula and Ophiocomine nigra based on physical-chemical variables in rocky strata. The diversity of the species Arbacia lixula and Ophiocomina nigra was quantified, through indexes of biological diversity, horseback riding, specific wealth and their distribution in rocky ecosystems through Temporal Space distribution patterns. Sampling was carried out at two times (Dry and Rainy), from January to June in 2018, in 5 rocky strata on Chacocente Beach. The samples were collected through a 1 m² metal frame. Physical-chemical variables (Temperature, Salinity, pH and OD) were determined. The community structure of the ecosystems consisted of 3 Phylum: Echinodermata (Class Echinoidea and Ophiuroidea), Mollusca (Class Bivalvia and Gasteropoda) and Arthropoda (Malacostraca Class), having 26485 organisms in the two sampling times. The lowest density was found in the dry season (2.99 ind/m²) and the largest in winter with 3.5 ind/m². The abundance and distribution of species was heterogeneous in the rocky strata. With the Jaccard and Morisita-Horn index, they had high similarity between the rocky strata.  The most abundant species was arbacia lixula, having greater ability to adapt to the different changes that occur in rocky ecosystems than Ophiocomine nigra. As for the composition, distribution and association of species they related to the physicochemical variables of seawater, where variations and fluctuations determine that both species adapt perfectly to changes, allowing them to be associated. As for their ecological importance, these species are good indicators of systemic echo quality, allowing the recruitment of new species in rocky ecosystems.