ABSTRACT. This study describes the predominantly tropical, subtidal seaweed populations growing on rhodoliths between 4 and 18 m depth in the southern part of Espírito Santo State (Brazil). Qualitative and quantitative sampling revealed species-rich algal communities, comprising 167 species. Three species of rhodophytes represent new records for the Brazilian marine flora (Lithothamnion muelleri, Scinaia aborealis, and Mesophyllum engelhartii). Marked seasonal differences in fleshy algal species composition and abundance were related to seasonal instabilities caused by winter-storm disturbance over the rhodolith beds. In relation to depth, rhodolith density appears to be an important factor for the variation in the abundance of fleshy algae. The rhodolith community is composed of at least seven nongeniculate crustose coralline algal species. Rhodolith beds in southern Espírito Santo State, in an area of 150 km 2 , provide an important habitat for epibenthic communities, supporting 25% of the known macroalgal species richness along the Brazilian coast.Key words: rhodoliths, marine algae of Brazil, benthic algal community, Espírito Santo State, crustose coralline algae. RESUMEN.Se describen las poblaciones de las macroalgas submareales predominantemente tropicales que crecen sobre rodolitos entre 4 y 18 m de profundidad en la parte sur del estado de Espírito Santo (Brasil). Muestreos cualitativos y cuantitativos revelaron comunidades ricas en especies de algas, incluyendo 167 especies. Tres especies de rodofitas son nuevas adiciones a la flora marina de Brasil (Lithothamnion muelleri, Scinaia aborealis y Mesophyllum engelhartii). Las marcadas diferencias estacionales en la composición y abundancia de especies de algas carnosas se relacionaron con la inestabilidad causada por el disturbio de tormentas invernales sobre los mantos de rodolitos. En cuanto a la profundidad, la densidad de rodolitos parece ser un factor importante para la variación en la abundancia de algas carnosas. La comunidad de rodolitos está formada por al menos siete especies de algas coralinas no geniculadas. Se demostró que los mantos de rodolitos, en un área de 150 km 2 , proporcionan un hábitat importante para las comunidades bentónicas, manteniendo 25% de la riqueza de especies de macroalgas conocidas para la costa brasileña.Palabras clave: rodolitos, algas marinas de Brasil, comunidad algal bentónica, estado de Espírito Santo, algas coralinas incrustantes.

Morphological investigations identified 11 Ceramium Roth species, of the 18 previously reported from Brazil. Phylogenetic analyses of sequences of the chloroplast‐encoded rbcL gene confirmed the presence of seven of these species. Three other species are reported from Brazil for the first time. Ceramium affine Setchell & Gardner and C. filicula Harvey ex Womersley were previously known only from the Pacific Ocean (Mexico and Australia, respectively). A new species, C. fujianum Barros‐Barreto et Maggs sp. nov., is described here. Its general habit is similar to that of C. strictum sensu Harvey from Europe but it has one less periaxial cell than C. strictum; its cortical filament arrangement is closest to C. deslongchampsii Chauvin ex Duby, also from Europe, but whorled tetrasporangia partially covered by cortical cells differ strikingly from the naked protruding tetrasporangia of C. deslongchampsii. Ceramium species in which each periaxial cell cuts off transversely only a single basipetal cell formed a robust clade. The genus Ceramium as represented in Brazil is not monophyletic with respect to Centroceras Kützing and Corallophila Weber‐van Bosse; Ceramium nitens, which has axial cells completely covered by rounded cortical cells formed by acropetal and basipetal filaments, did not group with any Ceramium clade but was weakly allied to a species of Corallophila. All three Brazilian Centroceras sequences were attributed to a single species, C. clavulatum.

A B S T R A C TLaje de Santos Marine State Park has been pointed out as a site of high marine diversity. In spite of its importance to conservation of marine biota no results of investigations about its marine biodiversity have been published. The aim of this work was to characterize the subtidal seaweed flora of this Marine Park. Samplings were performed by scuba diving: a qualitative one that included the subtidal zone down to 26 m depth and other quantitative at two pre-determined depths, 10 and 20 m. Among the 129 taxa identified, 5 species were identified for the first time for the São Paulo State, 3 for the Brazilian coast and 1 for the South Atlantic Ocean. The most abundant algae were Sargassum vulgare and turf composed by geniculate coralline and filamentous groups. The frequency of occurrence of taxa revealed that most of species are restricted to frequencies less than 20 % in all samples. The analyses of the subtidal marine benthic algal flora indicate the Marine State Park of Laje de Santos as a site of elevated species richness and that its floristic composition is related to a benthic community structure dominated by turf-forming groups and population of S. vulgare. R E S U M OO Parque Estadual Marinho da Laje de Santos tem sido apontado como local de elevada diversidade marinha. Apesar de sua importância para a conservação da biota marinha não existem resultados efetivamente publicados. O objetivo deste trabalho é o de caracterizar a flora marinha bentônica desse Parque Marinho. Amostragens foram realizadas por mergulho autônomo: uma qualitativa que incluiu a zona do sublitoral até a profundidade de 26 m e outra quantitativa em duas profundidades pré-determinadas, 10 e 20 m.. Dentre os 129 táxons encontrados, foram identificadas pela primeira vez, 5 espécies para o Estado de São Paulo, 3 espécies para o litoral brasileiro e 1 espécie para o Atlântico sul. As algas mais abundantes foram Sargasum vulgare e tufos compostos de coralináceas geniculadas e algas filamentosas. A freqüência de ocorrência dos táxons revelou que a maioria deles ocorreu em menos de 20 % das amostras. A análise da flora marinha bentônica demonstra que o Parque Estadual Marinho da Laje de Santos é um local de elevada riqueza e que sua composição florística esta relacionada a uma estrutura de comunidade bentônica dominada por populações de S. vulgare e grupos formadores de tufos.