RESUMO
Globally, conversion of pristine areas to anthropogenic landscapes is one of the main causes of ecosystem service losses. Land uses associated with urbanization and farming can be major sources of pollution to freshwaters promoting artificial inputs of several elements, leading to impaired water quality. However, how the effects of land use on freshwater quality are contingent on properties of the local landscape and climate is still poorly understood. The aim of this study was to evaluate the effects of landscape properties (morphometric measurements of lakes and their catchments), precipitation patterns, and land use properties (extent and proximity of the land use to freshwaters) on water quality of 98 natural lakes and reservoirs in northeast Brazil. Water quality impairment (WQI) was expressed as a composite variable incorporating parameters correlated with eutrophication including nitrogen (N), phosphorus (P) and Chlorophyll-a concentration. Regression tree analysis showed that WQI is mainly related to highly impacted "buffer areas". However, the effects of land use in these adjacent lands were contingent on precipitation variability for 13% of waterbodies and on surface area of the buffer in relation to the volume of waterbody (BA:Vol) for 87% of waterbodies. Overall, effects on WQI originating from the land use in the adjacent portion of the lake were amplified by high precipitation variability for ecosystems with highly impacted buffer areas and by high BA:Vol for ecosystems with less impacted buffer areas, indicating that ecosystems subjected to intense episodic rainfall events (e.g. storms) and higher buffer areas relative to aquatic ecosystem size (i.e. small waterbodies) are more susceptible to impacts of land use. Land use at the catchment scale was important for the largest ecosystems. Thus, our findings point toward the need for considering a holistic approach to managing water quality, which includes watershed management within the context of climate change.
RESUMO
Physical environment of streams present many challenging factors to the organisms living under its influence. Water speed, one of the most important factors affecting such environments, has local influence on substrata, temperature, and oxygen levels. It acts determining species distributions and morphological and behavioral adaptations of organisms. The aim of this study was to assess the relative size of gills of Cloeodes jaragua on two mesohabitats: lentic environment (river dam) and lotic environment (fast flowing area of a stream) in Parque Nacional da Serra dos Órgãos (RJ, Brazil). Twenty individuals were collected on each environment and width of the head and gills were taken. Lentic environment showed nymphs with broader and more constant measurements than the lotic environment. The former, despite being composed of nymphs on different stages of development, presented individuals with narrower gills. Both, head width and environment type explained gills size, showing that streams habitat conditions are important in shaping the morphology of these animals.
O ambiente físico dos rios apresenta diversos desafios para os organismos que vivem sob sua influência. A velocidade da água, um dos fatores mais importantes a atuar nesses ambientes, tem influência local no substrato, temperatura e oxigenação da água. A força da correnteza age determinando a distribuição das espécies e as adaptações morfológicas e comportamentais dos organismos. O objetivo desse estudo foi abordar o tamanho relativo das brânquias de Cloeodes jaragua em dois meso-habitats: um ambiente lêntico (represa) e um ambiente lótico (áreas de correnteza) no Parque Nacional da Serra dos Órgãos - RJ. Um total de 20 indivíduos foi coletado em cada tipo de ambiente e as larguras da cabeça e brânquias foram medidas. O ambiente lêntico apresentou ninfas com medidas mais largas e mais constantes que o ambiente lótico. Este último, apesar de ser composto por ninfas em diferentes estágios de desenvolvimento, apresentou indivíduos com menores larguras de brânquias. Ambos, largura da cabeça e tipo de ambiente, explicaram o tamanho das brânquias, mostrando as condições dos habitats dos rios como importantes modeladores da morfologia desses animais.