Presentation on theme: "Ag 508 Aquatic Biology and Environment F Dr. John A. Finn, F Room I1, TOB2 (Agricultural and Food Economics building, opposite old building of Dept of."— Presentation transcript:
Ag 508 Aquatic Biology and Environment F Dr. John A. Finn, F Room I1, TOB2 (Agricultural and Food Economics building, opposite old building of Dept of Agriculture) F F Please note that you may need to increase the zoom (40% box in upper right corner) to view these on your screen. For those of you unfamiliar with Powerpoint: If you feel the need to print, you have the option of printing six slides on one page. Simply go to: F ‘File’ and ‘Print’. Where it says ‘Print What’, click on the arrow and select the ‘Handouts (six slides per page option)’. F Note that relevant reading material and websites are at the back F Enjoy!
Features of Lotic Environments F Lecture Outline Introduction to aquatic habitats The hydrologic cycle Influences on streamwater chemistry in lotic environments Properties of lotic habitats F Lecture outcomes List and describe the dominant features of stream chemistry Relate the effects of the atmosphere, lithosphere and biosphere to stream chemistry Describe main properties of lotic habitats, and what factors contribute to their variation in time and space.
Why is water important? It is the medium by which plant nutrients are introduced into autotrophic plants It is an essential part of living tissue It serves as a means of thermal regulation for both plants and animals It is the medium by which sediments (a prime source of nutrients) are removed or added to ecosystems It covers a large proportion of the Earth's surface It provides a range of services for humans
Water as a resource F Estimated global demand of freshwater: 1950: 1360 km : 4130 km : 5190 km 3 F Main water uses Domestic supply Industrial abstraction Irrigation Diversion between catchments HEP Transport Flood control and storage water transportation Biological resources Recreation and culture
The Hydrological Cycle F How much water is there? F Whilst estimates vary between 2.5 and 5.8%, only a few percent of Earth's water is fresh. (...take these estimates of fresh water with a pinch of salt...!). F Of global fresh water, about 70% is locked in glaciers, permanent snow and aquifers more than a kilometre deep (such aquifers are generally considered inaccessible). Roughly 30 % of global freshwater remains as accessible groundwater, generally in either groundwater, streams, rivers or lakes. F The average of 30% of accessible freshwater is not stagnant, and is being driven by gravity and solar energy through a continuous cycle of water down from the air as precipitation and back up again through evaporation and transpiration. i.e. The Hydrologic Cycle
The proportion of water that ends up as stream flow depends on: F weather (arid versus temperate regions; evaporation, transpiration, ppt. held as snow or ice) F soil type and development (dry permeable soil vs moist porous soil) F vegetation F slope of the land F properties of aquifers Thus, we see that the boundaries of rivers extend much further beyond the air- water interface and the bed of the river/stream. F Streams and rivers do not just get their water from a number of sources, but the water itself has intimate contact with the atmosphere, vegetation, soil, and rocks before entering the freshwater habitat.
Habitat features of lotic environments F What are important chemical descriptors of freshwater? temperature, pH, dissolved gasses, suspended and dissolved organic matter, suspended solids, dissolved nutrients (N+P) and dissolved ions F What are important physical descriptors of freshwater? bank width, water depth, substrate size, substrate depth, flow rate, bankfull height F What are important biological descriptors of freshwater ? productivity (light penetration, temperature), riparian vegetation, organisms, interrelationships between species (see Allan 1995, Chapter 2; Moss 1998, Chapter 3)
Water in lotic environments F a number of chemical influences act to change the chemical composition to a greater or lesser degree These influences primarily include: F Solute composition of rainwater F Catchment geology F Catchment vegetation F Effects of human activities F Volcanic activity
Solute composition of rainwater Atmospheric CO 2 dissolves to form the weak carbonic acid (natural pH of rainwater = 5.64). Sea spray can increase concentrations of Na and Cl. Atmospheric pollution: Sulphur dioxide, nitrogen oxides, hydrogen fluoride etc. Volcanic emissions
Catchment geology F rocks give most of the inorganic substances that reach freshwaters F about 70% of the surface of the continental crust is covered by sedimentary rocks - they are soluble and readily weather F Extent of chemical change by geology is affected by the amount of precipitation, availability of chemical substances local geology and soils of ecosystems alteration by humans
Alteration of freshwater chemistry by catchment vegetation Contributes to the formation of soil Provides a source of nitrogen (nitrogen fixation provides nitrate for plant uptake, and easily leached into streams Live and dead biomass forms a store of soluble ions (not leached as readily)e.g Hubbard Brook Provide organic matter that reaches the streams Fuller vegetation cover reduces erosion, and entry of silt and suspended solids and provides habitat ‘corridor’ Organic matter may enter waters F Increase in evapotranspiration can reduce the amount of water leaving the stream
F Effects of human activities Agricultural nutrients Agricultural chemicals Human settlement Industry Habitat simplification/modification
Physical properties of the river habitat vegetation linkage between the catchment and terrestrial biogeochemical cycles. catchment size, stream size and order pattern of water movement affected by characteristics such as slope, depth and permeability of soils, and local patterns of precipitation. hierarchical organisation of patterns and processes Physical properties(substrate particulate organic matter) Flows and hydraulics Discharge and current Flow and sheer stress Floods F Spatial and temporal variability in physical properties
F Factors important to biota of streams and rivers (Reference: Allan chapter 3) 1. Current 2. Substrate 3. Temperature 4. Oxygen 5. Light 6. Species interactions We will look at each of these in turn: 1. Current Benefits and risks Organisms can be adapted to fast or slow-water conditions e.g. caddis larvae invertebrates have anatomical features that prevent dislodging velocity affects substrate size resource supply,and other env. factors
F 2. Substrate There are many kinds of substrates Slower currents correlated with finer particle size (as well as others) But it’s not just size that counts! Substrate can display high variability Field surveys indicate importance of substrate to diversity and abundance of biota in lotic habitats F 3. Temperature affects metabolism can often set limits to geographical distribution longitudinal temp change in long rivers variation in temperature is buffered by aquatic medium diel, seasonal and geographical variation; elevation, shading by/removal of vegetation, groundwater
F 4. Oxygen Aquatic organisms have several adaptions for gaseous exchange Solubility of oxygen in water is related to temperature In unpolluted running water, oxygen usually not limiting High temperature, low flow, decomposition of o.m. contribute to oxygen poor conditions. F 5. Light Summary F Rivers and streams arise from that portion of the hydrologic cycle that is surface runoff. Several factors influence the extent of surface runoff: e.g. climate, vegetation F Many factors act to cause considerable variation in water chemistry between running water habitats. e.g. rainwater composition, geology, vegetation, human influences F Water chemistry and other factors can be of importance to the biota of running water habitats (examples include temperature, oxygen, current, substrate type and light) F Next week: Food webs and energy flow in running water habitats
References (for this lecture in brackets) F The biology of streams and rivers Giller and Malmqvist. Oxford University Press. (Chapter 1.) F Stream Ecology. Structure and function of running waters Allen, J.D. (Chapters 1& 2.) F Ecology of fresh waters. Man and medium Moss, B. Blackwell Scientific. (Chapter 3.) F Natural Ecosystems Clapham, Jr., W.B. MacMillan. (Chapter on aquatic habitats.) F How many people can the Earth support? Joel E. Cohen. Chapter 14. Water: a Case Study. F Threats to the World’s Water. Maurits la Riviere. Scientific American, September Pp
Websites F F Institute of Hydrology: F Aquatic life and ecology interests on the internet (lists about thirty websites): /4301/links.html F The Environment Agency (Flood relief scheme, eutrophication, water demand, groundwater contamination): F If you find any other websites that are particularly interesting please send me the address so that I can distribute it. Thanks. F