Systematic temporal patterns in the relationship between housing development and forest bird biodiversity.

As people encroach increasingly on natural areas, one question is how this affects avian biodiversity. The answer to this is partly scale-dependent. At broad scales, human populations and biodiversity concentrate in the same areas and are positively associated, but at local scales people and biodiversity are negatively associated with biodiversity. We investigated whether there is also a systematic temporal trend in the relationship between bird biodiversity and housing development. We used linear regression to examine associations between forest bird species richness and housing growth in the conterminous United States over 30 years. Our data sources were the North American Breeding Bird Survey and the 2000 decennial U.S. Census. In the 9 largest forested ecoregions, housing density increased continually over time. Across the conterminous United States, the association between bird species richness and housing density was positive for virtually all guilds except ground nesting birds. We found a systematic trajectory of declining bird species richness as housing increased through time. In more recently developed ecoregions, where housing density was still low, the association with bird species richness was neutral or positive. In ecoregions that were developed earlier and where housing density was highest, the association of housing density with bird species richness for most guilds was negative and grew stronger with advancing decades. We propose that in general the relationship between human settlement and biodiversity over time unfolds as a 2-phase process. The first phase is apparently innocuous; associations are positive due to coincidence of low-density housing with high biodiversity. The second phase is highly detrimental to biodiversity, and increases in housing density are associated with biodiversity losses. The long-term effect on biodiversity depends on the final housing density. This general pattern can help unify our understanding of the relationship of human encroachment and biodiversity response.

Temporal variation in the water quality of ponds and effluent of grow-out ponds of Amazon River prawn Macrobrachium amazonicum

This study was conducted in the Crustacean Sector of the Aquaculture Center (CAUNESP) at the São Paulo State University, Jaboticabal (21°1522”S and 48°1848”W) São Paulo, Brazil, from December 2003 to May 2004. The aim was to examine the water quality parameters of importance to freshwater prawn culture, operated in a semi-intensive system in Amazon River. Nine 0.01-ha earthen ponds were stocked with 20 juveniles.m-2. Prawns were fed commercial diet at a rate of 7 to 9% of biomass until the 14th week. After 145 days of stocking, all ponds were drained and harvested. The following water parameters were determined weekly: dissolved oxygen, oxygen biochemical demand, pH, total alkalinity, electrical conductivity, suspended total solids and turbidity, N-nitrate, N-nitrite, N-nitrogen ammonia, N- total, soluble ortophosphate, total phosphorus, chlorophyll and pheophytin. In the semi-intensive culture system of M. amazonicum, there was no clear pattern of temporal variation in the limnological variables studied. Dissolved oxygen, pH, BOD, ammonia nitrogen and nitrate increased in the afternoon period while, the other variables did not change. In general, water quality is more dependent on the biological processes that occur in the pond than on the characteristics of the renewal water for some variable

Este estudio se llevó a cabo en el Sector de Crustáceos del Centro de Acuicultura (CAUNESP) de la Universidad Estadual Paulista, Jaboticabal (21°15'22”S y 48°18'48”W) en São Paulo, Brasil; entre diciembre de 2003 y mayo de 2004. El objetivo fue evaluar los parámetros de calidad de agua con importancia para los cultivos de camarón de agua dulce, operado en un sistema semi-intensivo de estanques en río Amazonas. Nueve estanques de 0,01 ha, fueron sembrados a una densidad de 20 juveniles.m-2, y alimentados con una dieta comercial a una tasa de 7 a 9% de la biomassa, hasta la semana 14. Después de 145 días de crianza, todos los estanques fueron drenados y cosechados. Se determinaron semanalmente los siguientes: oxígeno disuelto, demanda bioquímica de oxígeno, pH, alcalinidad total, conductividad eléctrica, sólidos totales en suspensión y turbidez, nitrato-N, N-nitrito, amoníaco-nitrógeno N, N-total, ortofosfato soluble, total fósforo, clorofila y feofitina. En el sistema de cultivo semi-intensivo de M. amazonicum, no hubo un patrón claro de variación temporal en las variables limnológicas estudiadas. Oxígeno disuelto, pH, DBO, nitrógeno amoniacal y nitratos aumentaron durante las tardes, mientras que las otras variables no cambiaron. En general, la calidad del agua es más dependiente de los procesos biológicos que se producen en el estanque, que de las características de la renovación del agua para alguna variable