Thermal Decomposition Kinetics of Humic Substances Extracted from Mid-Rio Negro (Amazon Basin) Soil Samples

In this work humic substances (HS) extracted from non-flooded (Araca) and flooded (Iara) soils were characterized through the calculation of stability and activation energies associated with the dehydration and thermal decomposition of HS using TGA and DTA, electronic paramagnetic resonance and C/H, C/N and C/O atomic ratios. For HS extracted from flooded soils, there was evidence for the influence of humidity on the organic matter humification process. Observations of thermal behaviour, with elemental analysis, indicated the presence of fossilized organic carbon within clay particles, which only decomposed above 800 C. This characteristic could explain the different thermal stability and pyrolysis activation energies for Iara HS compared to Araca HS.

Biologia do caranguejo-uçá, Ucides cordatus (Crustacea: Decapoda: Brachyura), na Baía da Babitonga, Santa Catarina, Brasil

O objetivo deste estudo é caracterizar pela primeira vez alguns aspectos da reprodução do caranguejo-uçá em manguezais da Baía da Babitonga (Santa Catarina). Além disso, a densidade e o tamanho do estoque deste recurso pesqueiro foram também estimados. Os exemplares foram coletados mensalmente, de maio de 2002 a abril de 2003, em duas áreas distintas: Iperoba e Palmital; um total de 2265 espécimes (1623 machos e 642 fêmeas) foi analisado. Os machos com gônadas maturas foram registrados durante todo o ano, enquanto as fêmeas com gônadas maturas ocorreram em apenas cinco meses. As fêmeas ovígeras foram registradas apenas em dezembro e janeiro. O etograma do fenômeno de migração reprodutiva (andada) esteve em concordância com a maior atividade de caranguejos associada às luas cheias e novas, com maior intensidade em dezembro e janeiro, relacionados ao verão austral. A densidade total no Manguezal de Iperoba foi de 2,05 ± 0,97 ind./m², não diferindo significativamente daquela registrada para o Manguezal do Palmital (2,06 ± 1,08 ind./m²) (p < 0,05). A média global para a estimativa de densidade na Baia da Babitonga foi de 2,05 ± 1,00 ind./m², correspondendo a 1,42 ± 0,89 ind./m² com base nas galerias abertas e 0,64 ± 0,63 ind./m² para as galerias fechadas.

Orientation and external morphology of burrows of the mangrove crab Ucides cordatus (Crustacea: Brachyura: Ucididae)

The aim of the present study was to characterize the external morphology and the orientation of burrows constructed by the mangrove crab Ucides cordatus. Data were obtained from two mangrove forests of similar vegetation dominance (Laguncularia racemosa) but differing in flooding heights. These mangroves were located near Barra de Icapara, Iguape City (SP), Brazil, (24 degrees 50'36 '' S-47 degrees 59'53'W). A total of 221 burrows were examined (120 on the high mangrove and 101 on the low mangrove). External morphology of the burrows was recorded by photographs for categorization and description. The directions of the burrow openings were recorded using a geological compass and the declivities of the ducts were measured with a clinometer. Females constructed 70.8% at Site A and 69.4% at Site B of the occupied burrows with the opening facing the margin of the river (P < 0.001), whilst males showed no significant difference in the burrow orientation (P > 0.05) at either site. In females, the tendency for burrow orientation possibly has a reproductive connotation as larval dispersal may be favoured and enhanced by the tides. Four groups of distinct tracks related to the morphotypes and developmental stages of U. cordatus were observed, No sediment constructions associated with the burrows were recorded for this species. Declivity of the burrows from juveniles was lower than from adults (P < 0.05), probably caused by the differential growth of the chelipeds in this species.