Temporary Waters: Ecological Values, Policy, and Management I
Presiding: K Fritz, U.S. Environmental Protection Agency; B Johnson, U.S. Environmental Protection Agency
NB21A-01 INVITED 08:30h
Hydrological and EcologicalConnectivity Under the Clean Water Act: Knowledge Gaps and Research Needs
There is no abstract associated with this presentation.
NB21A-02 INVITED 08:45h
Landscape Ecology Approaches for Detecting, Mapping, and Assessing the Vulnerability of Depressional Wetlands
U.S. EPA is using a landscape ecology approach to assess the ecological/hydrologic functions and related human values of depressional wetlands along coastal Texas, considered to be vulnerable to human disturbance. Many of those wetlands may be at high risk because of recent court rulings and associated jurisdictional interpretations. As a result of these rulings and interpretations, the interpreted area of freshwater depressional wetlands within the study region has been dramatically reduced. It is the general nature of the landscape that many of these wetlands are hydrologically connected via shallow ground swales that provide concentrated directional flow during rainfall events, thereby connecting these depressional wetlands to tributaries. A better understanding of the extent of depressional wetlands, regionally and nationally, is critical to inform policy discussions between federal agencies with joint jurisdiction on these scientific, legal, policy, and regulatory issues. Our approach is to integrate remote-sensing, geospatial information, existing field data, and a priori knowledge of depressional wetland ecology to estimate their extent, connectivity, and ecological/hydrologic functions. Those functions include support for aquatic life use; decreasing the loss of human life and property damage from floods; providing fish and wildlife habitat; and supporting recreational use of the environment.
NB21A-03 INVITED 09:00h
Intermittent Streams and Habitats Function as Refugia for Fish and Crayfish
Drought and summer drying can be important disturbance events in many small streams leading to intermittent or isolated habitats. We examined the influence of stream permanence on fish and crayfish population and community dynamics in multiple streams over several years. We found total crayfish densities and densities of some crayfish species were significantly greater in intermittent than in permanent streams, whereas crayfish species richness did not differ significantly between the two stream types. There was a significant relationship between crayfish relative abundance and abiotic environmental variables for permanent, but not intermittent streams. Fish densities were high in intermittent streams, especially for small species-size classes. Fish moved at large spatial and temporal scales to use intermittent streams, especially for spawning, and fish moved at smaller spatial and temporal scales to avoid drying habitats, especially riffles. During drying events fish survival was greater in pools than in riffles, and pools were more likely to remain permanent habitats. Intermittent streams and permanent pools within dry portions of stream appear to function as refugia for some species and size classes of fish and crayfish. Understanding this relationship will allow natural resource managers to implement effective conservation strategies for fish and crayfish in intermittent streams.
NB21A-04 INVITED 09:15h
Spatial and Temporal Patterns of Aquatic Habitats in a Karstic Environment: Implications for the Stream Biota From Species to Community Level
Due to the specific geohydrological situation, the investigated drainage network of the Paderborner Hochflaeche (North-Rhine Westphalia, Germany) shows typical karst features like sinkholes, dolines, underground caves, dry valleys, and karst springs. Many streams are characterized by spatial and temporal flow intermittency. The objectives of the study were to elucidate temporal and spatial flow patterns, invertebrate distribution and species-specific adaptations. It was hypothesized that different hydrological stream sections are characterized by different lotic communities. It was further assumed that in temporary stream sections a high proportion of the benthic assemblages consists of species adapted to the harsh abiotic conditions either by strategies of resistance or of resilience. Most of the streams are summerdry, and drought duration increases with increasing distance from the perennial upstream sections. However, depending on the precipitation, sudden flash flows may occur. Particularly in small streams permanent springs and springbrook sections can be observed locally. Lotic communites differ in the different hydraulic habitats, and experiments on the species level give evidence for species-dependent plasticity in life history traits or for behavioural adaptations. It can be concluded that temporary karst streams contribute to regional biodiversity, which might be threatened by management practices.
NB21A-05 INVITED 09:30h
Northern Seasonal Woodland Ponds: Distribution, Biota, and Ecological Linkages with the Surrounding Forest
Seasonal woodland ponds are important landscape features across much of eastern and central North America. Learning more about the ecology of these habitats is a pressing need in the US because federal protections are being reduced. Further, the fates of these habitats are not being monitored because most are too small for inclusion in the National Wetland Inventory. In our northern Minnesota study area, the distribution of seasonal woodland ponds is strongly influenced by glacial landform, with most ponds being associated with ground or end moraines. The habitats support an abundance of plants, invertebrates, and amphibians; these organisms are well adapted for the variable environments existing in ponds and they posses a durability that makes them resistant to most natural variation in conditions. Because of the small size of seasonal woodland ponds, input of plant litter and migration of invertebrates from the surrounding forest into ponds is an important ecological link. However, because ponds support an autochthonous growth of wetland trees, the relationship between ponds and the forest differs from that between streams and forests. Like eastern streams, logging of forests around ponds is a concern, but impacts of peripheral logging on theses wetlands appear less dramatic than for streams.
NB21A-06 INVITED 09:45h
Summer-dry Streams in the Temperate Coastal Rainforest
Small streams of the temperate, coastal rainforest can go dry in summer and there is considerable annual variation in the extent of channel lacking surface flow. These small streams provide a special habitat for aquatic and riparian life, supplies of organic matter to downstream reaches, and modulate aspects of water quality. By late summer small streams regularly are reduced to a series of small pools, connected by subsurface flow. These stream beds are cool, but the small volume quickly heats up, potentially affecting downstream reaches. The effects on aquatic organisms are diverse, from isolating fish to maintenance of wetted substrates that support invertebrates. The effects of low flow periods can be persistent across seasons and some species recover slowly. Nevertheless, there are species of multivoltine macroinvertebrates that maintain populations in these systems. Small streams contribute substantial amounts of organic matter to downstream reaches, but most occurs during high flow periods, and not the low flow, warm periods when rates of biological processes are often at their highest. In the Pacific Northwest, many agencies struggle with how to balance the impact on these small streams with the resource values and opportunity costs associated with forest harvesting and other land-uses.