Mudanças em bancos de macroalgas marinhas identificadas em imagens de satélites no Nordeste brasileiro
Seaweeds are vital components of marine ecosystems, supporting a wide diversityandproviding several ecosystem services (environmental, economic and social). Asharpdecline in seaweed beds has been recorded in the last decades in several parts of theworld. The causes of this decline are generally asso...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/49508 |
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| Resumo: | Seaweeds are vital components of marine ecosystems, supporting a wide diversityandproviding several ecosystem services (environmental, economic and social). Asharpdecline in seaweed beds has been recorded in the last decades in several parts of theworld. The causes of this decline are generally associated with climate change andcommercial exploitation of diverse species. In the Rio Grande do Norte state, changes
have been observed over the years, both in algal cover and biomass. These changes
may be caused by seaweed harvesting carried out for decades in the region or changes
in environmental conditions. In this context, this study aimed to analyze the changes
of seaweed cover and biomass in two beaches on the coast of Rio Grande do Nortestate (Rio do Fogo and Baía Formosa). For this study, digital orbital images fromLandsat 5 TM and Landsat 8 OLI satellites were used considering a multitemporal approach of approximately 3 decades (1991-2019). From the digital images, sixenvironments where the seaweeds were found were identified in the two areas. For
this, the isodata classification divided the environments according to seaweed cover
characteristics and flooding level in those areas. Regarding the total cover, there was
an increase of 8% (27.27 ha – 29.34 ha) in Rio do Fogo, whereas there was a decreaseof 30% (12.24 ha – 8.55 ha) in Baía Formosa. As for the change of total biomass, twopeaks occurred in 2003 (3,865 kg) and 2019 (3,967 kg) in Rio do Fogo, which wereinterspersed with a sudden decline in 2010 (1,432 kg). In Baía Formosa, onlyonepeak was observed in 2001 (2,669 kg) with a gradual decrease until reachingminimum values in 2019 (1,438 kg). Based on the analysis of the vegetation dynamics, the biomass reduction occurred more significantly in the middle and lowintertidal zone, particularly in Rio do Fogo beach. In conclusion, the multitemporal studycarried out showed that the use of remote sensing is an effective tool to investigatechanges in seaweed cover and biomass, even in situations where field validation is not possible. |
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