Mangrove Crab Ucides cordatus Removal Does Not Affect Sediment Parameters and Stipule Production in a One Year Experiment in Northern Brazil.

Mangrove crabs influence ecosystem processes through bioturbation and/or litter feeding. In Brazilian mangroves, the abundant and commercially important crab Ucides cordatus is the main faunal modifier of microtopography establishing up to 2 m deep burrows. They process more than 70% of the leaf litter and propagule production, thus promoting microbial degradation of detritus and benefiting microbe-feeding fiddler crabs. The accelerated nutrient turn-over and increased sediment oxygenation mediated by U. cordatus may enhance mangrove tree growth. Such positive feed-back loop was tested in North Brazil through a one year crab removal experiment simulating increased harvesting rates in a mature Rhizophora mangle forest. Investigated response parameters were sediment salinity, organic matter content, CO2 efflux rates of the surface sediment, and reduction potential. We also determined stipule fall of the mangrove tree R. mangle as a proxy for tree growth. Three treatments were applied to twelve experimental plots (13 m × 13 m each): crab removal, disturbance control and control. Within one year, the number of U. cordatus burrows inside the four removal plots decreased on average to 52% of the initial number. Despite this distinct reduction in burrow density of this large bioturbator, none of the measured parameters differed between treatments. Instead, most parameters were clearly influenced by seasonal changes in precipitation. Hence, in the studied R. mangle forest, abiotic factors seem to be more important drivers of ecosystem processes than factors mediated by U. cordatus, at least within the studied timespan of one year.

Burrows of the semi-terrestrial crab Ucides cordatus enhance CO2 release in a North Brazilian mangrove forest.

Ucides cordatus is an abundant mangrove crab in Brazil constructing burrows of up to 2 m depth. Sediment around burrows may oxidize during low tides. This increase in sediment-air contact area may enhance carbon degradation processes. We hypothesized that 1) the sediment CO2 efflux rate is greater with burrows than without and 2) the reduction potential in radial profiles in the sediment surrounding the burrows decreases gradually, until approximating non-bioturbated conditions. Sampling was conducted during the North Brazilian wet season at neap tides. CO2 efflux rates of inhabited burrows and plain sediment were measured with a CO2/H2O gas analyzer connected to a respiration chamber. Sediment redox potential, pH and temperature were measured in the sediment surrounding the burrows at horizontal distances of 2, 5, 8 and 15 cm at four sediment depths (1, 10, 30 and 50 cm) and rH values were calculated. Sediment cores (50 cm length) were taken to measure the same parameters for plain sediment. CO2 efflux rates of plain sediment and individual crab burrows with entrance diameters of 7 cm were 0.7-1.3 µmol m(-2) s(-1) and 0.2-0.4 µmol burrows(-1) s(-1), respectively. CO2 released from a Rhizophora mangle dominated forest with an average of 1.7 U. cordatus burrows(-1) m(-2) yielded 1.0-1.7 µmol m(-2) s(-1), depending on the month and burrow entrance diameter. Laboratory experiments revealed that 20-60% of the CO2 released by burrows originated from crab respiration. Temporal changes in the reduction potential in the sediment surrounding the burrows did not influence the CO2 release from burrows. More oxidized conditions of plain sediment over time may explain the increase in CO2 release until the end of the wet season. CO2 released by U. cordatus and their burrows may be a significant pathway of CO2 export from mangrove sediments and should be considered in mangrove carbon budget estimates.

Isolation of microsatellite markers for the red mangrove, Rhizophora mangle (Rhizophoraceae).

PREMISE OF THE STUDY: Three species of the mangrove tree genus Rhizophora are found in the New World and along the west coast of Africa. Of these, R. mangle is the most abundant and has a complex interbreeding relationship with the sympatric R. racemosa and R. harrisonii. The development of additional microsatellite markers would permit paternity analyses and investigation of the hybrid origin of these species. • METHODS AND RESULTS: Using an enriched library method, via hybridization with biotinylated oligonucleotides complementary to repetitive poly AG/TC, primers for 11 microsatellite markers of R. mangle were developed and characterized in populations in Pará and São Paulo (Brazil) and Florida (USA). Ten of these markers were transferable to R. racemosa and R. harrisonii. • CONCLUSIONS: The microsatellite markers presented here will be useful in studies of contemporary and historical gene flow between American and West African Rhizophora species.

Mangrove vegetation in Amazonia: a review of studies from the coast of Pará and Maranhão States, north Brazil / Vegetação de manguezais na Amazônia: uma revisão dos estudos da costa dos Estados Pará e Maranhão, norte do Brasil

The present study is a compilation of the literature about vegetation of mangrove forest of the north coast of Brazil. It synthesizes the knowledge about this important ecosystem and lists the currently available literature. The study focuses on the coast of Pará and Maranhão states, which are covered by a continuous belt of mangroves. The mangrove flora comprises six mangrove tree species and several associated species. Mangrove tree height and stem diameter vary as a function of abiotic local stand parameters. Seasonal variation in rainfall and salinity affect the species' phenology and litter fall. Local population use products derived from mangrove plants for different purposes (e.g. fuel; medicinal; rural construction). The increase in the coastal population has given rise to conflicts, which impact on mangrove forest.

O presente estudo apresenta uma compilação da literatura sobre a vegetação dos manguezais da costa norte do Brasil, apresentando uma síntese do conhecimento e listando a literatura disponível. O estudo se concentra na costa dos estados do Pará e Maranhão que formam um cinturão contínuo de manguezais . Foram contabilizadas seis espécies arbóreas exclusivas de mangue e várias outras associadas. A altura e o diâmetro das árvores de mangue variam em função de parâmetros abióticos locais. As variações sazonais do regime de chuvas e da salinidade afetam a fenologia das espécies e a produção de serapilheira. A população costeira utiliza a flora do manguezal para diferentes fins (ex: combustível, medicinal, construção rural). O aumento da ocupação costeira inicia um processo de impacto para as florestas de mangue e a disponibilidade de seus recursos.