LOTIC ECOSYSTEMS Flowing water Moving continuously in one direction. Headwaters- Where the river or streams begin. Rivers are created in two ways: 1. Snow melt 2. Springs that come from underground.

Creation of rivers Watershed - An area of land that water flows across, through, or under on its way to a stream, river, lake, ocean or other body of water. Tributaries - all the creeks/streams that feed into the river to create it.

Parts of a River (draw this) Drainage Divide (separates one watershed from another) Source (snowpack, glaciers, springs, headwater streams) Tributary (small creek or river that runs into a larger one) Mouth (empties into lake or ocean; often forms a delta with extensive wetlands)

Divide Tributary Watershed

Rivers as ecosystems Nutrients in the water are determined by the terrain and vegetation on the land in which the river flows through. Oxygen in water depends on swiftness of river and temp. No stable plankton communities. The base of food chain is algae and rooted plants.

River Zones: 1. Upper reaches- Very fast water, rapids and clean, clear, cold water with a lot of oxygen. Erosion zone. 2. Middle Reaches-more pools and more diversity of plants and animals. Rooted plants development near shoreline. Sediment transfer zone. 3. Lower Reaches- Gentle steady flow. Bottom covered in mud. Environment like that of a pond. Sediment deposition zone

Checkpoint – What part of the river? 1. The erosion zone is in the The sediment deposition zone is in the...

Characteristics of the Different Parts of a River (Young)(Middle-Aged)(Old)

Upper Reaches – fast moving, clear & cold water

Rivers: from Source to Coast Physical Changes: Steep slope; flow swiftly Narrow and shallow channel Bottom of coarse gravel and boulders Drains a small area Lots of shade; less variation in temperature Rivers generally begin in low-lying areas at higher elevations and flow downhill within a channel. Along their length, rivers swell in size, gather tributaries and drain an increasingly larger catchment area. Biological changes also occur along the length of a river. Rivers can be divided into three categories based on these physical and biological characteristics: Upper, Middle, and Lower. UPPER COURSE Biological Changes: Abundant tree canopy Few to no aquatic plants Inputs from land important as food source (decaying organic matter) Lots of aquatic insects Cold water fish that eat insects

Middle Reaches – Wider, some slow areas with rooted plants

Rivers: from Source to Coast Physical Changes: Gentle slope; flow reduced Channel widens and deepens Bottom of small gravel and sand Drains a larger area River begins to meander Little shade; clear water Large variation in temperature MIDDLE COURSE Biological Changes: Less Tree Canopy Lots of aquatic plants and algae Organic matter from upstream important as food source Lots of aquatic insects Warm water fish that eat insects and other fish

Lower Reaches – slow moving, silt deposited

Rivers: from Source to Coast Physical Changes: Slope and flow further reduced Substrate of mud and silt Little to no shade; small variation in temperature Water is turbid due to sediments Delta forms as river deposits sediment LOWER COURSE Biological Changes: Little to no tree canopy Aquatic plants absent from main channel Lots of phytoplankton Low diversity of aquatic insects; more mollusks Fish largely planktivores

Surface Water 191,000 miles of rivers and streams 15 major river basins

Texas has wide, shallow prairie rivers…

…and clear, spring-fed streams creating pristine habitats for unique species.

Slow-moving water in bayous sustain bottomland hardwood forests.

Surface water flows towards the Gulf of Mexico.

Rivers deliver important nutrients and sediment to coastal wetlands.

Pelagic and Benthic Assemblages Organisms relate to the rivers according to flow Benthic types will have some way of attaching themselves to the bottom (helgremites). All of the pelagic species will align themselves with pools and obstructions. Stream flow is not all stress. It also allows for increased oxygen and prey opportunities

Adaptations of benthic animals Small, flat body plan with hooks or suckers to hang on to rocks.

Longitudinal Distribution Patterns Zonation—As the rivers move from headwaters to middle to lowland the types of species will change. There will be more of the small mouth bass, brook trout, and perch at the head waters. In lowland zones there will be more carp and catfish. manversusfish.combouldermountainguide.com

Effect of Water Chemistry Water chemistry also has a large effect on species distribution. Catfish can tolerate a wide variety of water types. Brook trout need clear pure water. There are many of the smaller nymphs and flies that cannot tolerate lowland water chemistry. fishingforbeginners.net

Drift Refers to benthic species that end up in the water column. There are always some individuals there. Drift is a natural phenomenon. These species get swept into areas they do not normally populate. Catastrophic drift occurs when there is a major increase in flow (flood)

Flooding and Flood Refuges During a flood the flood plain is one refuge for critters. Another refuge is in the river channel, in eddys, caves, and behind rocks. Invertebrates usually bury themselves in the dirt.