Integrated Ecosystem Assessment: Lake Ontario Water Management

BACKGROUND: Ecosystem management requires organizing, synthesizing, and projecting information at a large scale while simultaneously addressing public interests, dynamic ecological properties, and a continuum of physicochemical conditions. We compared the impacts of seven water level management plans for Lake Ontario on a set of environmental attributes of public relevance. METHODOLOGY AND FINDINGS: Our assessment method was developed with a set of established impact assessment tools (checklists, classifications, matrices, simulations, representative taxa, and performance relations) and the concept of archetypal geomorphic shoreline classes. We considered each environmental attribute and shoreline class in its typical and essential form and predicted how water level change would interact with defining properties. The analysis indicated that about half the shoreline of Lake Ontario is potentially sensitive to water level change with a small portion being highly sensitive. The current water management plan may be best for maintaining the environmental resources. In contrast, a natural water regime plan designed for greatest environmental benefits most often had adverse impacts, impacted most shoreline classes, and the largest portion of the lake coast. Plans that balanced multiple objectives and avoided hydrologic extremes were found to be similar relative to the environment, low on adverse impacts, and had many minor impacts across many shoreline classes. SIGNIFICANCE: The Lake Ontario ecosystem assessment provided information that can inform decisions about water management and the environment. No approach and set of methods will perfectly and unarguably accomplish integrated ecosystem assessment. For managing water levels in Lake Ontario, we found that there are no uniformly good and bad options for environmental conservation. The scientific challenge was selecting a set of tools and practices to present broad, relevant, unbiased, and accessible information to guide decision-making on a set of management options

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

Tidal oscillations systematically flood salt marshes, transporting water, sediments, organic matter, and biogeochemical elements such as silica. Here we present a review of recent studies on these fluxes and their effects on both ecosystem functioning and morphological evolution of salt marshes. We reexamine a simplified model for the computation of water fluxes in salt marshes that captures the asymmetry in discharge between flood and ebb. We discuss the role of storm conditions on sediment fluxes both in tidal channels and on the marsh platform. We present recent methods and field instruments for the measurement of fluxes of organic matter. These methods will provide long-term data sets with fine temporal resolution that will help scientists to close the carbon budget in salt marshes. Finally, the main processes controlling fluxes of biogenic and dissolved silica in salt marshes are explained, with particular emphasis on the uptake by marsh macrophytes and diatoms

The impact of dune stabilisation on the conservation status of sand dune systems in Wales

Sand dunes in Wales are becoming increasingly stable, reducing their biodiversity value, particularly for obligate and near obligate dune species. A case study shows that in the 1950s, 75 % of one dune site consisted of mobile dunes and embryonic dune slacks with open vegetation, but by the 1990s only about 6 % of the site could be classed as mobile or open, and embryonic dune slacks were virtually non-existent. This is now considered to be a trend that has affected all dune systems in Wales and most in north-west Europe. As a result, certain plant and fungus species associated with early successional stages and invertebrates that rely on open sandy areas may be facing local extinction. Drivers influencing stabilization can be external, such as sediment supply, nutrient enrichment, climate change, and predicted sea-level rise, and internal, such as soil development, grazing management, and scrub control together with recent measures to counter stabilization. The latter includes the new restoration technique of topsoil inversion or deep ploughing, with early results suggesting success in rejuvenating sand movement. Mobilization will also enable landward migration, providing a mechanism to help conserve the overall sand body in the face of sea-level rise