Estimativa das taxas de mortalidade e da contribuição de carcaças do zooplâncton em seis sistemas estuarinos do Nordeste do Brasil

Abstract

To understand the ecological role of zooplankton in the environment, it is also necessary to study the participation of dead and the mortality rate of these organisms, being very difficult to obtain information from traditional methods of study. Prehistoric factors do not have as main factors natural aging, conditional diseases and physical-chemical stress in the non-environment in which they live. This study sought to evaluate and characterize non-predatory mortality rates and the contribution of carcasses from the zooplankton community in tropical estuarine ecosystems with different degrees of urbanization, considering the following hypotheses. different tropical regions within the same tropical region with different percentages of carcasses, varying spatially; ii. estuaries embedded in large urban mortality rates, unanticipated higher degrees of large domestic rates. The study was carried out in six estuarine systems on the east coast of northeastern Brazil. Samples were collected between November 2020 and September 2021, always during the daytime (between 9 am and 12 pm) and during the ebb tide of syzygy. A total of 46 taxa were found, 12 of which were copepod species. The Oithonidae nauplii and the species Oithona oswaldocruzi were the most frequent organisms (35.7%). The mean density of zooplankton considering all the systems studied was 6,900.99 (± 8,674.87) ind. m-3, while that of live copepods was 124,501 ind. M-3. The average percentage of copepod carcasses was 51.34% with values ranging from 4 to 100% and the average mortality rate was 0.113 day-1 (± 0.070 day-1, CV: 62.4%), with the minimum values of 0.016 d-1 and maximum of 0.273 d-1, being the families Paracalanidae (0.545 day-1± 0.255; CV: 47%) and Oithonidae (0.119 ± 0.061 d-1; CV: 51.7%) have the highest values. The average number of days for carcass decomposition was 4.7 days. The present study showed that estuaries can supply the estuarine food web with a significant portion of planktonic copepod carcasses in the tropical Atlantic region (Northeast Brazil), and this contribution may vary in terms of families and environment. Differentiating organisms in terms of living and dead individuals can contribute to a greater understanding of how planktonic copepods actually participate in marine food webs, which is almost always erroneously related only to the route of classical food chains.