Nutrient Pollution Mitigation Research Articles

Retrospective eDNA assessment of potentially harmful algae in historical ship ballast tank and marine port sediments.

Microalgal bloom events can cause major ecosystem disturbances, devastate local marine economies, and endanger public health. Therefore, detecting and monitoring harmful microalgal taxa is essential to ensure effective risk management in waterways used for fisheries, aquaculture, recreational activity, and shipping. To fully understand the current status and future direction of algal bloom distributions, we need to know how populations and ecosystems have changed over time. This baseline knowledge is critical for predicting ecosystem responses to future anthropogenic change and will assist in the future management of coastal ecosystems. We explore a NGS metabarcoding approach to rapidly identify potentially harmful microalgal taxa in 63 historic and modern Australian marine port and ballast tank sediment samples. The results provide a record of past microalgal distribution and important baseline data that can be used to assess the efficacy of shipping guidelines, nutrient pollution mitigation, and predict the impact of climate change. Critically, eDNA surveys of archived sediments were able to detect harmful algal taxa that do not produce microscopic fossils, such as Chattonella, Heterosigma, Karlodinium, and Noctiluca. Our data suggest a potential increase in Australian harmful microalgal taxa over the past 30years, and confirm ship ballast tanks as key dispersal vectors. These molecular mapping tools will assist in the creation of policies aimed at reducing the global increase and spread of harmful algal taxa and help prevent economic and public-health problems caused by harmful algal blooms.

Impact and Mitigation of Nutrient Pollution and Overland Water Flow Change on the Florida Everglades, USA

A subtropical watershed and wetland covering nearly 47,000 km2 in the southeastern United States, the Florida Everglades is a degraded, human-dominated environment. As a unique and important ecosystem, the Everglades provide a variety of important environmental services for society and nature. Over the past century and a half, anthropogenic actions have severely impacted the Everglades by disrupting the natural water flow and causing water pollution. As a result, the native flora and fauna have been displaced, important habitats have been lost, invasive species have become prevalent, and water contaminant concentrations have increased. Accelerating efforts are being made towards preserving the Everglades ecosystem by restoring water flow and improving water quality. To explore this complex and important aquatic ecosystem, we critically review the relevant environmental history, major terrestrial and aquatic characteristics and dynamics, engineered changes to water flow, major sources and impacts of nutrient pollution, trends in system response to pollution and mitigation actions, and recent regulatory efforts driving restoration.

Seasonal nitrous oxide emissions from different land uses and their controlling factors in a tropical riparian ecosystem

An important ecological service provided by tropical riparian ecosystems is the mitigation of nutrient pollution (e.g. nitrate) from surrounding agricultural areas. However, a negative impact of this nutrient remediation may be that the ecozone also functions as a major emitter of nitrous oxide (N2O). We hypothesized that the high inorganic nitrogen, organic carbon, and soil water content in tropical riparian ecosystems enhances N2O production through rapid nitrification and denitrification processes. This study was therefore designed to quantify the variability in N2O emissions in such an ecosystem in northern Thailand with specific emphasis on (1) different land uses (comparing replicate leguminous reforestation areas with conventional maize agriculture with high rates of nitrogen fertilizer addition), and (2) temporal aspects (comparing wet and dry seasons). Our aim was to quantify N2O emissions and to identify the major drivers controlling these emissions. Using in situ closed chambers the annual average emissions of N2O from the leguminous reforestation area (3.3kgN2ONha−1 y−1) was significantly higher than agricultural areas with maize (2.2kgN2ONha−1 y−1). The seasonal variation results indicated that the rate of N2O flux in the wet season was higher than in the dry season. The variations of N2O emission rates were strongly correlated with water filled pore space (WFPS), denitrification, and microbial biomass C, but not with nitrification. This study indicates that when inorganic N and soil organic C are sufficient, WFPS plays an important role in controlling N2O emissions from denitrification. Comparatively, annual N2O emissions from the tropical riparian reforestation were similar to that reported for temperate riparian forests and other ecosystems. Although the annual N2O emissions from the maize agricultural area were comparable to other crops cultivated in riparian ecosystems, it was higher than the N2O fluxes from crops grown in non-riparian zones. We conclude that agricultural lands located in tropical riparian zones do not represent a major hotspot of N2O emissions and that this does not diminish the positive benefits they provide in relation to other aspects of ecosystem service provision.