Name: Luiz Eduardo de Oliveira Gomes
Type: MSc dissertation
Publication date: 20/04/2017
Advisor:

Namesort descending Role
Angelo Fraga Bernardino Advisor *

Examining board:

Namesort descending Role
Angelo Fraga Bernardino Advisor *
Jean-Christophe Joyeux Internal Examiner *

Summary: Studies suggest that benthic macroinvertebrates in unconsolidated sediment must respond, by structural changes in their assemblages, to weather events, affecting rainfall, temperature and estuarine primary production. However, few studies have evaluated seasonal and spatial scales of these responses, especially in brazilian tropical estuaries. Thus, this study aimed to: i) analyze changes in benthic assemblages of intertidal mudflats for a year and ii) investigate the relationship between changes in assemblages with salinity, rainfall and temperature in the estuary. Samples were made in Piraquê-Açú Estuary, once a month at two stations located in euhaline and polyhaline areas. Seasonal changes were tested between dry (May to September 2015) and wet (October 2015 to January 2016) seasons. Sediment was predominantly composed of mud/silt in both haline areas, being significantly different seasonally (wet and dry season), with greater variations in wet (36-90%) than dry (62-74%) season. Total organic matter content was significantly different seasonally, ranging from 5 to 28% in wet and 4-11% in dry season. Monthly rainfall (mm) ranged from 13 to 165 mm in dry and 20-106 mm in wet season, dry period had a higher total average rainfall (75.2 and 49, respectively), while salinity was more stable in dry season (26.2 to 33.5) than in wet season (22.4 to 35.5). Macrofaunal density was higher in dry (2191 ± 1061 ind.m-2) than wet (1231 ± 727 ind.m- 2), being significantly different seasonally. Magelonidae (> 35 and> 38% respectively) was the dominant taxon in spatial and temporal scale, dominant taxa composition changes temporally, WHERE, Solecurtidae only occurred in the wet season and Capitellidae showed higher relative abundance in wet than dry season; Spionidae and Paraonidae had higher relative abundance in dry than wet season. Saline areas are similar, according to Principal Component Analysis (PCA). Density (m2), rainfall (mm) and size of the sediment (%) were significant to explain temporal changes in abundance and composition of macrofauna. The estuarine structure contributes to benthic assemblages composition, changes in assemblages structure occur as a result of environmental changes (e.g. Rainfall and sediment), since these variables directly influence salinity and habitat structure. Theses changes can affect ecosystem functions and may have future implications to the environment and near ecosystems.

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