Natalia Pirani Ghilardi

The biodiversity characterization of benthic communities in the Brazilian coast is limited to a few works, which studied an area of about 3,400 m2. The objective of this study was to propose a new method, unprecedented in hard bottom marine communities, based in the sampling of landscape heterogeneity units, named physiognomies and settlements, aiming at an increase in sampling speed and covering in this environment. This study was performed in a 260 m infralittoral stretch of Presidio Beach eastern coast (Palmas Bay, Anchieta Island State Park, Ubatuba, SP) and was divided in four approaches: 1) identification e description of settlements and their dominant species; 2) georeferenced spatial repartition mapping of each settlement and determination of maximum vertical amplitude; 3) mean percent cover quantification from digital images; 4) evaluation of specific composition and spatial variation of selected settlements. Thirty settlements, included in Bed, Colony, Crust and Turf categories, besides a non-biological attribute included in Region category, were identified and described and the information will be available in a database in the internet. Mapping was performed in only 6 dives of 50 to 80 minutes in each season. The major part of the settlements occurred punctually. Settlements number and horizontal repartition practically did not change between summer and winter. Sargassum Bed (SGB) was more frequent in the summer (25.3%) and Amphiroa and Jania Turf (AJT) in the winter (21.3%). In relation to vertical repartition, four main zones were delimited based in relative frequencies: a shallower one defined by SGB, another upper intermediary defined by AJT, another lower intermediary defined by Ectoprocta Turf (ECT) and a last one, deeper, defined by variable settlements according to season. Eighty four sampling units were obtained in summer and 100 in winter, from which 26 and 28 settlements could be recognized, respectively. Cluster analysis in R and Q modes and heterogeneity evaluation of the obtained groups were made. SGB showed the highest mean percent cover as much in summer (26.1%) as in winter (32.0%), followed by ECT (19.7% in summer and 24.2% in winter), significantly higher than most of the other settlements (p<0.05). Phytobenthic settlements were the most representative in the area (62.2% of mean cover in summer and 61.8% in winter). When settlements categories were considered, phytobenthic beds were the most representative (31.2% in summer and 37.0% in winter). With animals and algae altogether, the category ?turf? was the most represented (46.3% in summer and 41.4% in winter), with great contribution of AJT and ECT, indicating a possible sedimentation influence in the area. The cluster analysis in R Mode showed the existence of six groups in summer and five in winter, suggesting settlements with the same ecological exigencies. In Q Mode a highly heterogeneous community could be evidenced, showing a patchy pattern. The settlements SGB, Unconsolidated Substrate Region, AJT, ECT (and some of its variations) and Gelidiopsis and Hypnea Turf (GHT) were the responsible for group formation with the use of Morisita-Horn Similarity Index. Specific composition analysis of SGB, AJT, ECT and GHT showed that these settlements can be considered homogeneous or present themselves as facies in the study area and can be consistently used as operational units. However, studies in other areas are necessary in order to give support to the obtained data, mainly regarding ECT and GHT, which lack ecological studies. Spectral analysis made evident sampling sufficiency for all settlements in relation to Calleja points adopted. Richness spectra were diagonal and diversity spectra were rectangular. For the four settlements, Shannon?s Diversity Index was between 1.6 and 2.2 and Simpson?s Dominance Index, between 2.6 and 5.7. GHT was the richest and most diverse settlement. The community studied in the present work can be considered typical of Brazilian south eastern region. Settlements method, through approaches 2 and 3, facilitated community structural characterization in a fast way. Micro-heterogeneity evaluation of four settlements showed that they can be used as consistent ecological units.

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