Relevance of mangroves for the production and deposition of organic matter along tropical continental margins

Mangroves are highly complex ecosystems occupying a major part of tropical coastlines. High primary productivity, efficient biological nutrient recyling and a permanent exchange with terrestrial and marine ecosystems are their common features. Despite the high production and export rates of leaf litter, mangrove detritus has been reported to be of minor importance in sustaining marine food webs. The geographical distribution of mangrove-derived organic matter (OM) in marine sediments is found to be restricted to the vicinity of its source. Dissolved nutrient inputs from mangroves and rivers may fuel the production of marine OM. In this paper we assess the relevance of mangroves for the production and sedimentation of OM in the tropical coastal ocean based on data available from the literature and our own research results. We estimate the rates of carbon accumulation in mangrove sediments and of carbon export to the coastal seas. From the rates of litter fall and export we calculate carbon accumulating in mangrove sediments to be in the order of 23᎒¹² g C per year and mangrove carbon introduced into the coastal ocean to be in the order of 46᎒¹² g C per year. They account for about 11% of the total input of terrestrial carbon into the ocean and 15% of the total carbon accumulating in modern marine sediments.     

Triploid fetus: An important consideration in the evaluation of very high maternal serum alpha-fetoprotein

Two patients referred for evaluation of very high maternal serum alpha-fetoprotein (10–20 multiples of the median) were carrying triploid fetuses with placentas showing features of partial hydatidiform mole. The diagnosis of fetal triploidy should be considered when there is a very high maternal serum alpha-fetoprotein and no ultrasound evidence of open neural tube defect, ventral wall defect, or any other explanation. Therefore, chromosomal analysis of amniotic fluid cells in such cases is essential.     

The influence of the physical environment on the self-organised foraging patterns of ants

Among social insects such as ants, scouts that modulate their recruiting behaviour, following simple rules based on local information, generate collective patterns of foraging. Here we demonstrate that features of the abiotic environment, specifically the foraging substrate, may also be influential in the emergence of group-level decisions such as the choice of one foraging path. Experimental data and theoretical analyses show that the collective patterns can arise independently of behavioural changes of individual scouts and can result, through self-organising processes, from the physico-chemical properties of the environment that alter the dynamics of information transfer by chemical trails.