Efeitos da variação sazonal e da heterogeneidade ambiental nas respostas ecológicas de camarões palaemonidae em um reservatório do nordeste médio-oriental brasileiro

Abstract

Seasonal variations alter the water dynamics in reservoirs, directly influencing ecological conditions, resource availability, and the physical structure of the environment. These changes significantly affect aquatic organisms, depending on their intensity and frequency. This analysis evaluated if seasonal variations of abiotic factors and habitat structural complexity affect the ecological responses of two Palaemonidae shrimp species, Macrobrachium amazonicum and Macrobrachium jelskii, in a semi-arid northeastern water reservoir. In Chapter 1, "Ecological responses of two shrimp populations (Palaemonidae) to seasonal variation of abiotic factors in a semi-arid Brazilian reservoir," the influence of abiotic factors (rainfall, depth, temperature, dissolved oxygen, hydrogen potential, ammonia, and electrical conductivity) on the abundance and population structure of M. amazonicum and M. jelskii was scrutinized. Data gathered from October 2016 to September 2017 showed that the abundance of these species was higher during the dry period, with M. amazonicum always being more abundant. The most influential variables for M. amazonicum were rainfall, depth, and ammonia, while temperature and total dissolved solids were more relevant for M. jelskii. In Chapter 2, "Structural complexity and habitat use by two shrimp populations (Palaemonidae) in a water reservoir in the semi-arid region of Northeast Brazil," the relationship between habitat structural complexity, provided by different macrophyte bank compositions, and the abundance, distribution, and population structure of M. amazonicum and M. jelskii was analyzed. It was concluded that the structuring of macrophyte assemblages, mediated by the seasonal variation of abiotic factors, caused indirect variations in shrimp population abundance. The morphology and density of macrophytes were more significant for shrimp abundance than macrophyte banks with complex architecture. Egeria densa and Nymphoides indica were the most important macrophyte species for shrimp abundance. These results highlight that the differences in ecological responses between M. amazonicum and M. jelskii are crucial to ensuring niche opportunities and stable coexistence of these two species.