The goal of the Arctic LTER is to predict the future ecological characteristics of Arctic Alaska based upon our knowledge of the controls of ecosystem structure and function as exerted by physical setting and geologic factors, climatic factors, biotic factors, and the changes in fluxes of water and materials from land to water.

Urbanization is one of the major threats to stream ecosystems worldwide. The phrase “urban stream syndrome” has been coined to describe patterns in degraded streams draining urban land. In Puerto Rico, urbanization now covers 16% of the island. The fully protected Luquillo Experimental Forest (focus of the LUQ-LTER) is only 23 km from the center of San Juan, a city of 1.3 million. Therefore, LUQ is assessing the impacts of urbanization on tropical stream ecosystem structure and function.

Despite substantial changes in climate, sea-ice and glacier extent, and vegetation in much of the Arctic, the area near Toolik Lake, Alaska has experienced no significant trends of increasing temperature, altered precipitation, or increasing active-layer thaw depth. There has been, however, a near doubling of alkalinity in Toolik Lake since 1975 and increases in alkalinity in many lakes of all depths and sizes in the surrounding area. Lake monitoring indicates that in-lake processes such as sulfate or nitrate reduction cannot account for these alkalinity increases.

Lake ice seasonality (freeze day, breakup day, and ice duration) is closely related to climate change and variability. Trends and changes in variability and extreme events are apparent. The shared variance between mean anomalies of ice duration and Northern Hemisphere land air temperature over the last 150 years is r2 = 0.47. Mean trends are in the direction of warming. Ice duration has the steepest decline with mean trends (days/decade) of 1.7 over the last 150 years, 1.1 over the last 100 years, and 6 over the last 30 years.

Two major foundations of ecosystem science are comparative analyses and long-term studies. Here, we explore the capacity of long-term and comparative data to predict lake characteristics (LCs). We ask if a variable is best explained by neighboring lakes (NL; comparative data), lake history (LH; temporal data), or by some combination of the two.

Tropical environments are changing fast due to deforestation and regrowth, urbanization, climate change, and other forces. The consequences are immense for the whole array of ecosystem services people require. The Luquillo Long-Term Ecological Research Program (LUQ) is tackling these issues in Puerto Rico. LUQ began in 1988 and focused on natural disturbances (hurricanes, landslides, droughts, floods) and ecosystem response. That work revealed patterns of resistance and resilience to cycles of natural disturbance.

Suspended solids in streams are important to monitor and manage because high levels of suspended solids have been shown to affect the primary and secondary production of a stream. The loading rate of total suspended solids (TSS) can greatly be influenced by the land management of a stream site’s catchment area. A computer-based geographic information system (GIS) was used to assess what land cover/land use variables were highly correlated to high levels of TSS in Kansas Flinthill streams on a long-term data set collected by the Kansas Department of Health and Environment.

Woody encroachment and its effects on terrestrial ecosystems have been well-studied. However, the effect on riparian and aquatic ecosystems, specifically denitrification, has been lacking. Riparian areas of headwater prairie streams were historically dominated by grasses, but have become increasingly covered by woody vegetation. To determine potential consequences of woody plant invasion on denitrification, three adjacent reaches were delineated from two branches of King’s Creek, which drains Konza Prairie Biological Station.

We have developed an autonomous underwater vehicle (AUV) capable of generating for the first time 3-D biogeochemical datasets in the extreme environment of perennially ice-covered Antarctic dry valley lakes. The ENDURANCE (Environmentally Non-Disturbing Under-ice Robotic ANtarctic Explorer) is in the middle of a two year campaign to map the under-ice lake dimensions of West Lake Bonney in the McMurdo Dry Valleys, and is equipped to measure a comprehensive suite of physical and biogeochemical indices in the water column.

The history of perennially ice covered lakes in the McMurdo Dry Valleys (MCM), Antarctica have been extensively studied under the Long Term Ecological Research (LTER) project. The lakes are formed in endorheic basins enclosed by topographic relief or glaciers. Over the past century, the lakes have experienced an overall trend of continuous lake level rise despite decrease in solar radiation (Doran et al, 2002). Variability/increase of lake levels is caused by the sole water source; melt from nearby glaciers during austral summer months.