Nitrogen flows from European watersheds to coastal marine waters

Nitrogen flows from European watersheds to coastal marine waters Executive summary Nature of the problem • Most regional watersheds in Europe constitute managed human territories importing large amounts of new reactive nitrogen. • As a consequence, groundwater, surface freshwater and coastal seawater are undergoing severe nitrogen contamination and/or eutrophication problems. Approaches • A comprehensive evaluation of net anthropogenic inputs of reactive nitrogen (NANI) through atmospheric deposition, crop N fixation,fertiliser use and import of food and feed has been carried out for all European watersheds. A database on N, P and Si fluxes delivered at the basin outlets has been assembled. • A number of modelling approaches based on either statistical regression analysis or mechanistic description of the processes involved in nitrogen transfer and transformations have been developed for relating N inputs to watersheds to outputs into coastal marine ecosystems. Key findings/state of knowledge • Throughout Europe, NANI represents 3700 kgN/km2/yr (range, 0–8400 depending on the watershed), i.e. five times the background rate of natural N2 fixation. • A mean of approximately 78% of NANI does not reach the basin outlet, but instead is stored (in soils, sediments or ground water) or eliminated to the atmosphere as reactive N forms or as N2. • N delivery to the European marine coastal zone totals 810 kgN/km2/yr (range, 200–4000 depending on the watershed), about four times the natural background. In areas of limited availability of silica, these inputs cause harmful algal blooms. Major uncertainties/challenges • The exact dimension of anthropogenic N inputs to watersheds is still imperfectly known and requires pursuing monitoring programmes and data integration at the international level. • The exact nature of ‘retention’ processes, which potentially represent a major management lever for reducing N contamination of water resources, is still poorly understood. • Coastal marine eutrophication depends to a large degree on local morphological and hydrographic conditions as well as on estuarine processes, which are also imperfectly known. Recommendations • Better control and management of the nitrogen cascade at the watershed scale is required to reduce N contamination of ground- and surface water, as well as coastal eutrophication. • In spite of the potential of these management measures, there is no choice at the European scale but to reduce the primary inputs of reactive nitrogen to watersheds, through changes in agriculture, human diet and other N flows related to human activity.

A novel satellite-based ocean monitoring system for Mexico

To analyze patterns in marine productivity, harmful algal blooms, thermal stress in coral reefs, and oceanographic processes, optical and biophysical marine parameters, such as sea surface temperature, and ocean color products, such as chlorophyll-a concentration, diffuse attenuation coefficient, total suspended matter concentration, chlorophyll fluorescence line height, and remote sensing reflectance, are required. In this paper we present a novel automatic Satellite-based Ocean Monitoring System (SATMO) developed to provide, in near real-time, continuous spatial data sets of the above-mentioned variables for marine-coastal ecosystems in the Gulf of Mexico, northeastern Pacific Ocean, and western Caribbean Sea, with 1 km spatial resolution. The products are obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) images received at the Direct Readout Ground Station (located at CONABIO) after each overpass of the Aqua and Terra satellites. In addition, at the end of each week and month the system provides composite images for several ocean products, as well as weekly and monthly anomaly composites for chlorophyll-a concentration and sea surface temperature. These anomaly data are reported for the first time for the study region and represent valuable information for analyzing time series of ocean color data for the study of coastal and marine ecosystems in Mexico, Central America, and the western Caribbean.