Structure of rhodolith beds from 4 to 55 meters deep along the southern coast of Espírito Santo State, Brazil

Rhodoliths are one of the most extensive benthic communities of the Brazilian continental shelf, but their structure is poorly known. The richest marine flora of Brazil’s coastal zone is found in Espírito Santo State and its diversity has been partly associated with the presence of extensive areas of rhodoliths, extending from the intertidal zone to 120 m across the continental shelf. One species of kelp, Laminaria abyssalis, is endemic to this area and occurs between 45 and 120 m depth. Our objective was to determine the density and physical dimensions of the superficial rhodoliths between 4 and 55 m depth in the southern region of Espírito Santo State. The study area was 3 to 45 km offshore. Samples were obtained in 2004 and 2005 by Scuba diving in three depth zones: 4–18 m, 25–30 m and 50–55 m. Transect lines and video images were used to determine rhodolith density. The diameter and sphericity of at least 60 individuals from each zone were measured. Rhodolith size increased and density decreased from the shallow to the deeper zones. Spheroidal was the typical shape throughout the depth zones. Five rhodolith-forming genera were identified: Lithothamnion, Lithophyllum, Hydrolithon, Neogoniolithon and Sporolithon. Epibenthic biomass and species richness over the rhodolith bed in the shallow zone was lowest in winter, likely the result of disturbance caused by typical winter storms. Changes in light and temperature are probably the most important factors in the changes observed in the rhodolith beds from the deepest zones.Web of Scienc

Structure of rhodolith beds from 4 to 55 meters deep along the southern coast of Espírito Santo State, Brazil

Rhodoliths are one of the most extensive benthic communities of the Brazilian continental shelf, but their structure is poorly known. The richest marine flora of Brazil’s coastal zone is found in Espírito Santo State and its diversity has been partly associated with the presence of extensive areas of rhodoliths, extending from the intertidal zone to 120 m across the continental shelf. One species of kelp, Laminaria abyssalis, is endemic to this area and occurs between 45 and 120 m depth. Our objective was to determine the density and physical dimensions of the superficial rhodoliths between 4 and 55 m depth in the southern region of Espírito Santo State. The study area was 3 to 45 km offshore. Samples were obtained in 2004 and 2005 by Scuba diving in three depth zones: 4–18 m, 25–30 m and 50–55 m. Transect lines and video images were used to determine rhodolith density. The diameter and sphericity of at least 60 individuals from each zone were measured. Rhodolith size increased and density decreased from the shallow to the deeper zones. Spheroidal was the typical shape throughout the depth zones. Five rhodolith-forming genera were identified: Lithothamnion, Lithophyllum, Hydrolithon, Neogoniolithon and Sporolithon. Epibenthic biomass and species richness over the rhodolith bed in the shallow zone was lowest in winter, likely the result of disturbance caused by typical winter storms. Changes in light and temperature are probably the most important factors in the changes observed in the rhodolith beds from the deepest zones.Web of Scienc

Dinâmica do carbono da biomassa microbiana em cinco épocas do ano em diferentes sistemas de manejo do solo no cerrado Microbial biomass carbon dynamics in different soil management systems in the cerrado

Em um Latossolo Vermelho argiloso, na Embrapa Cerrados, em Planaltina, Distrito Federal, foram selecionadas uma área com vegetação de Cerrado (CE) e seis parcelas de um experimento de longa duração (20 anos): arado de discos pré-plantio (ADPP); arado de discos pós-colheita (ADPC); plantio direto a partir do segundo ano em área preparada com arado de discos em 1979, primeiro ano de cultivo (PDAD); arado de aivecas pré-plantio (AVPP); arado de aivecas pós-colheita (AVPC); e plantio direto a partir do segundo ano em área preparada com arado de aivecas em 1979, primeiro ano de cultivo (PDAV). Foram estimados o carbono da biomassa microbiana e o carbono orgânico do solo (Csolo) em cinco profundidades: 0-5, 5-10, 10-20, 20-30 e 30-40 cm; e em cinco épocas do ano: na época da colheita da soja (abril/2000); no final do período chuvoso, após aração pós-colheita da soja (maio/2000); no período seco, sem nenhuma cultura no campo (agosto/2000); no início do período chuvoso, no plantio do milho (novembro/2000); e na floração da cultura do milho (fevereiro/2001). Considerando todo o período de estudo, os teores de C da biomassa microbiana (Cmic) e de Csolo foram menores nas camadas mais profundas em todos os sistemas de manejo e no Cerrado. No solo sob sistema plantio direto, os teores de Cmic e Csolo decresceram das camadas mais superficiais para as mais profundas e de forma mais acentuada que no solo sob sistemas convencionais. No CE, a biomassa microbiana constituiu-se em maior percentagem do carbono orgânico total do solo, em comparação aos sistemas cultivados, que não apresentaram diferenças entre si.<br>Microbial biomass carbon and organic carbon were measured in a long-term field experiment (20 years) in Planaltina, DF, Brazil, under corn-soybean crop rotation. Six management systems were selected: disk plow before planting (ADPP); disk plow after harvesting (ADPC), no-till after disk plowing in the first year (PDAD); moldboard plow before planting (AVPP); moldboard plow after harvesting (AVPC), no-till after moldboard plowing in the first year (PDAV) and an undisturbed area of Savanna type vegetation, Cerrado (CE) as a reference. Soil samples were collected five times a year: 1- April, at soybean harvesting; 2- May, after soybean harvesting; 3- August, in the dry season with no crop on the field; 4- November, in the beginning rainfall season, at corn planting; 5- February, at corn tasseling. The samples were taken from five depths: 0-5, 5-10, 10-20, 20-30 and 30-40 cm of a clayey Red Latosol (Oxisol). Considering the whole study period, soil microbial carbon (Cmic) and soil organic carbon (Csoil) concentration were lower as soil profile depth increased for all management systems as well as in the Cerrado. Cmic and Csoil decreases under no-till system from superficial layers to the deeper ones were more pronounced than in the conventional systems. In the Cerrado, the microbial biomass represented a higher percentage of the total soil organic carbon in comparison to the management systems; there was no difference between conventional and no-till systems