Como a carcinicultura afeta a dinâmica de fósforo em solos de manguezais?

Abstract

Mangroves are coastal ecosystems of great ecological and socioeconomic importance, recognized for their high capacity to store carbon and nutrients. However, these environments have been progressively degraded by anthropogenic actions, mainly by shrimp farming, which, in addition to converting extensive areas into nurseries, releases effluents rich in nutrients such as phosphorus (P) and nitrogen (N), which contribute to the process of eutrophication and ecological imbalance. The disposal of these effluents alters the biogeochemical dynamics of the soil, mainly the interactions with organic matter (OM) fractions, and may cause important changes in P dynamics. The objective of this study was to evaluate how effluents from shrimp farming affect P dynamics in semiarid mangrove soils, focusing on the relationship between P and organic matter fractions and enzymatic activity (alkaline and acid phosphatases), which are important for understanding microbial activity and P cycles in the soil. Thus, paired soil samples were collected from impacted and unimpacted areas in three sectors of the Acaraú River estuary (Ceará, NE-Brazil), which were characterized by their physical-chemical conditions and granulometry, in addition to the physical fractionation of soil organic matter (SOM) to determine organic and inorganic P in the SOM fractions (MOP and MOAM). The results obtained indicate an increase in total phosphorus (Pt) content in the affected mangroves, with an average of 143.9±62.3 mg kg-1, while unaffected mangroves had an average of 88.7±37.3 mg kg-1, mainly in its organic forms, with an average of 106.5±48.5 mg kg-1, as well as a higher content of P associated with particulate organic matter (COP; 96.1±105.0 mg kg-1) and associated with minerals (COAM; 86.9±50.7 mg kg-1), despitenot showing a significant increase in the C content in the soil, with emphasis on COP, where it was possible to observe a greater input and lower stabilization of this P. Enzymatic activity, however, did not show significant differences between the areas studied. Thus, it can be observed that effluents from shrimp farming directly impact P dynamics in mangroves, significantly increasing its more bioavailable and less stable forms, in addition to altering the physical-chemical properties of the areas, compromising the natural conditions of this soil.