Given the many services provided by benthic species living in a wide range of freshwater habitats, we must better understand how to maintain and protect these species and their associated processes. We suggest several areas that need more study to improve management of these critical services:
1. Link fisheries production to sustainable models of harvest and management that avoid crashes and long-term breakdown of ecosystem functions. There is an urgent need to strengthen the long-term collection of data on inland fisheries resources if a more complete understanding is to be achieved about the production of benthic invertebrates and determinants of high-quality water. The relationships between safe levels of water quantity and quality that ensure adequate habitats for freshwater species are poorly understood. Too often, minimum values of flow and dissolved oxygen are viewed as sufficient although they are often based on short-term data. In fact, these guidelines do not provide reliable, long-term sustainability. Including margins of error to enhance the "safe minimum levels" will increase reliability and minimize long-term species losses and impairment of benthic ecosystem services.
2. Communicate results of large-scale, long-term monitoring programs to community-based organizations. Major changes in water quantity and quality can encourage governmental agencies and local communities to generate alternative actions such as communities that conserve water for sustaining instream flow needs and fisheries that provide sustainable ecosystem services. Results of water-quality monitoring programs need to be translated into formats that enhance effective and informed responses from a wide range of stakeholders. Management groups need to include wide representation by both professional managers and general consumers of ecosystem services. Community-based ecosystem management approaches will also help to establish systematic data collection on the direct and indirect costs and benefits of fish stocking, introduction, and other "enhancement programs" to determine impacts of nonnative fish species on benthic biodiversity and ecosystem services. Programs such as the European Union's Freshwater Directive, the US Environmental Protection Agency's Community-Based Ecosystem management Program, and the Nature Conservancy's Sustainable Waters Initiative are recent examples of frameworks that are designed to incorporate a wide range of stakeholders in decision making. More of these partnerships and social networks are needed to resolve conflicts regarding evaluations and alternative uses of fresh water.
3. Monitor and restore habitats in rivers, lakes, and wetlands. Information on a wider range of chemical and biological measures is needed to detect changes in both surface water and groundwater that are essential to ecosystem services. Enhanced technologies such as remote sensing, wireless data transmission, and comprehensive modeling to develop spatial data are needed to monitor the connections among groundwater levels, stream and river flows, lake-level changes, and wetland distributions at large scales. This regional and cross-national monitoring can provide up-to-date information on changes in the locations, sizes, and types of lakes and wetlands, especially in response to climate changes and global changes in land use. Extreme fluctuations in runoff and erosion from widespread deforestation and related land uses are rapidly altering sedimentary conditions in many fresh waters that, in turn, will alter benthic habitats and associated ecosystem services. Restoration and establishment of hydrological monitoring stations are needed to improve the water-quality monitoring at the regional level using benthic invertebrates and diatoms. Even though there is increased recognition of the long-term effects of climate changes (global warming, cyclic changes in El Nino—Southern Oscillation and the North Atlantic Oscillation, etc.), the capacity to monitor stream flows and lake levels on large-scales within nested watersheds is limited and even diminishing in many regions. Integrated information on data regarding long-term changes in groundwater resources, including their distribution, quality, capacity, and use, is needed across a wide range of scales in different regions.
4. Restore natural flow regimes. Information on the number and locations of dams, including the thousands of dams less than 15 m in height that are not currently listed in international databanks, must be compiled and made widely available. These small dams greatly influence the peak flows, minimum low flows, and habitats available for benthic species. Additional studies of the effects of dam removal are needed to identify trade-offs for comparisons with more innovative management of water releases from reservoirs. Many small dams are being removed to provide more upstream habitat for fishes, but sediment releases during and after reservoir removal can still degrade benthic habitats for many years. Furthermore, some non-native species can increase their distributions following dam removal if the struc tures previously served as barriers to dispersal. What ecosystem services are lost when dams are removed? How can these relatively short-term losses be minimized and long-term gains maximized? These and many other questions are being investigated as more dams are being phased out and removed.
5. Consider additional measures of diversity. Diversity measures have usually considered just the number of species and/or functional groups in studies of benthic ecosystem processes. This limited approach excludes consideration of the range of diversity elements that potentially affect ecosystem services because different size and age classes within species, as well as their relative abundances, food preferences, and positions within food webs, all can influence rates of processes. Anthropogenic disturbances can substantially change the evenness of species, distributions of abundance, and foraging behavior without associated changes in species richness. The question of whether these changes in evenness, independent of changes in species richness, can influence levels of ecosystem functioning is a necessary focus of future investigation.
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