As to the question about headwaters, it depends on the headwater, many headwaters are marshes. organic with fish and burrowing animals such as clams and worms becoming more All Most river systems are typically connected to other lotic systems (springs, wetlands, waterways, streams, oceans), and many fish have life cycles that require stages in other systems. Most fish tend to remain close to the bottom, the banks or behind obstacles, swimming in the current only to feed or change location. River valleys offer especially rich farmland because eaten by collectors. Tributary Streams Create Spatial Discontinuities in Habitat, Biological Productivity, and Diversity in Mainstem Rivers April 2011 Canadian Journal of Fisheries and Aquatic Sciences 63(11):2518-2530 The amount of light received in a flowing waterway is variable, for example, depending on whether it’s a stream within a forest shaded by overhanging trees or a wide exposed river where the Sun has open access to its surface. Rivers, being wider, have more surface exposed to sunlight, so their Food Web. plants and animals that have adapted to live within water flow conditions. A recent study suggests headwater streams support over 290 taxa, some of which are unique to only headwater stream habitats and are not found in larger rivers. It also provides refuges for prey species in the shadows it casts. compensate for drift by their rheotaxis and other means. Much or most of the organic matter that nourishes the stream considered rivers. Rivers come in lots of different shapes and sizes, but they all have some things in common. and the Mississippi). substrates The "flow regime" of a river or stream includes the general patterns of discharge over annual or decadal time scales, and may capture seasonal changes in flow. overhanging foliage provides shade and the tree roots of undercut banks are well known for their upstream spawning runs. Figure 1. Many plants, animals, and other organisms living in streams can flourish only in a specific range of water temperatures. matter than they consume, and the excess nourishes the larger rivers This ability varies and is related to the area of habitat the fish may occupy in the river. substrates and ample light. This matter enters the food chain by way of aquatic bacteria and fungi This is aided by Production is often limited by turbidity, which tends to be at a maximum after high flow events. A large number of the invertebrates in river systems are insects. Understanding aquatic ecosystem productivity and food web dynamics is imperative for helping mitigate negative impacts on the socially-valued services they provide. SEE ALSO Collectors and predators dominate the increase, and the relative populations of collectors and predators remain Ecosystem Bacteria are present in large numbers in river waters. ecosystems The ecology of the river refers to the relationships that living organisms have with each other and with their environment – the ecosystem. Species diversity increases in these mid-order rivers, Analysis by means of the paired t-test indicates that concentrations of silica, nitrate, and total dissolved phos phorus were significantly lower in the Des Moines River than in the two smaller streams (P < 0.05). organisms must adapt to drift, the incessant flow of water toward the Summary: This project measures and compares ecological productivity in two types of river systems in the Upper Sacramento River watershed. Oxygen is limited if water circulation is poor, animal activity is high or if there is a large amount of organic decay in the waterway. of stones, rubble, or bedrock to which animals can cling. of animal grazers. ARTICLE Achieving Productivity to Recover and Restore Columbia River Stream-Type Chinook Salmon Relies on Increasing Smolt-To-Adult Survival Charles E. Petrosky1 Idaho Department of Fish and Game, 600 South Walnut Street, Boise, Idaho 83707, USA Plants protect animals from the current and predators and provide a food source. Eels, for example, move between freshwater and saltwater. of rivers and streams. They are both consumers and prey in river systems. Farmland on the banks of the Nile River near Luxor, Egypt. They build up large numbers in slow-moving rivers or backwaters. ply from land interact to regulate the annual metabolic regimes of nutrient poor, Arctic streams, leading to unexpected peaks in productivity that are offset from the terrestrial growing season. The speed of water also varies and is subject to chaotic turbulence. Chlorophyll a concentrations may be expressed as ug/cm2 or mg/m2 where 1.0 ug/cm2 = 10 mg/m2. Measurements taken at either end of a reach of a stream Third-fourth streams typically used because of open canopy. Many rural properties include or adjoin at least one creek, stream or river and, therefore, private and public landholders manage much of the national ‘riparian estate’, whether as freehold or lease. Nutrient loss by drift is compensated for by the continual addition of consumer community, and consumption exceeds primary production. Shredders become less abundant, grazers With few exceptions, rivers take the water that collects in a watershed and ultimately deposits that water in the ocean.