Ecosystem Processes and the River Continuum Concept Unit 1: Module 4, Lecture 5 The Effect of Current on Organisms Photo: Glenn Merrick

Objectives Students will be able to: classify sources of organic matter. diagram the flow of instream organic matter. factors that influence the storage of organic matter in streams. explain the river continuum concept compare and contrast low order, mid-order, and high order streams.

General organic matter pathway geography.uoregon.edu/ .../SCRfig2-33web.jpg The path energy follows through consumers in a food web and the flux of organic matter through an ecosystem are closely related topics.

Sources of organic matter Autochthonous – instream Allochthonous – out of stream 140.211.62.101/streamwatch/ swm10.html www.landcare.org.nz/SHMAK/ manual/6doing.htm www.bbg.org/sci/blackrock/ veg/brfredmaple.html Autochthonous organic matter – produced within the stream - diatoms; algae; submerged, floating, and emergent macrophytes Allochthonous organic matter – produced outside of the stream and imported into the channel. - includes, but is not limited to leaves, woody debris, dissolved organic compounds, dead organisms

Types of organic matter Dissolved organic matter Soluble organic compounds that leach from leaves, roots, decaying organisms, and other sources Largest pool of organic matter in streams Particulate organic matter Coarse particulate organic matter Woody material & leaves > 1 mm Fine particulate organic matter Leaf fragments, invertebrate feces, and organic precipitates < 1 mm Dissolved Organic Matter Soluble organic compounds that leach from leaves, roots, decaying organisms, and other sources Largest pool of organic matter in streams Particulate Organic Matter Coarse Particulate Organic Matter Woody material, leaves and their fragments > 1 mm in diameter Fine Particulate Organic Matter Leaf fragments, invertebrate feces, and organic precipitates < 1 mm in diameter

Instream organic matter processing This figure depicts the routes carbon follows as it is processed within a stream. Microbes, macro-invertebrates, fish, and other organisms all play roles in the physical and chemical processing of organic matter. Following the fate of organic matter introduced into a stream from its source, through transport, storage, and respiration allows the development of a general understanding of ecosystem function and, possibly, efficiency if organic matter components are quantified. The River Continuum - www.oaa.pdx.edu/CAE/Programs/ sti/pratt/energy.html

Macroinvertebrate functional roles in organic matter processing Shredders Dominant food Vascular macrophyte tissue Coarse particulate organic material (CPOM) Wood Feeding mechanisms Herbivores - Chew and mine live macrophytes Detritivores - Chew on CPOM Representatives Scathophagidae (dung flies) Tipulidae (crane flies) A caddisfly of the family Limnephilidae www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/shredder.html The River Continuum

Macroinvertebrate functional roles Collectors Dominant food Decompose fine particulate organic matter (FPOM) Feeding mechanisms Filterers - Detritivores Gatherers - Detritivores Representatives Filterers Hydropsychidae Simulidae (black flies) Gatherers Elmidae (riffle beetles) Chironomini Baetis Ephemerella Hexagenia A blackfly of the family Simulidae A caddisfly of the family Hydroptilidae www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/collector.html The River Continuum

Macroinvertebrate functional roles Scrapers Dominant food Periphyton (attached algae) Material associated with periphyton Feeding mechanisms Graze and scrape mineral and organic surfaces Representatives Helicopsychidae Psephenidae (water pennies) Thaumaleidae (solitary midges) Glossosoma Heptagenia A dipteran of the family Thaumaleidae www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/scraper.html The River Continuum

Macroinvertebrate functional roles Predators Dominant food Living animal tissue Feeding mechanisms Engulfers - Attack prey and ingest whole animals Piercers - Pierce tissues, suck fluids Representatives Engulfers Anisoptera (dragonflies) Acroneuria Corydalus (hellgrammites) Piercers Veliidae (water striders) Corixidae (water boatmen) Tabanidae (deerflies & horseflies) A stonefly of the family Perlidae A “true bug” of the family Notonectidae www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/predator.html The River Continuum

Seasonal variation in particulate organic carbon Low concentrations in winter and fall High concentrations in summer Particulate organic carbon varies primarily by seasonal changes in biological processes and by discharge. In general: POC is high in summer at low flows POC is low in winter and at high flows Photos by g. merrick

Fate of organic matter Stored within the stream bank or channel (25%) Organic matter that enters streams may be (percent estimates are approximate and variable): Stored within the stream bank or channel (25%) Exported downstream (50%) Metabolized and respired as carbon dioxide by organisms (25%) Photo – g. merrick Organic matter that enters streams may be (percent estimates are approximate and variable): 1) stored within the stream bank or channel (25%) 2) exported downstream (50%) 3) metabolized and respired as carbon dioxide by organisms (25%)

Storage of organic matter Factors that are likely to increase retention time are debris dams, beaver dams, floodplains, and geomorphological features of the stream or river that impede flow. Factors that are likely to increase retention time are debris dams, beaver dams, floodplains, and geomorphological features of the stream or river that impede flow. www.fonz.org/cards/card.html www.minix.ca/pictures/tealake/?42

Net primary production versus litter fall Stream Autotochthonous Allochthonous Bear Brook, NH 0.6 g C/m2/year 251 g C/m2/year Silver Springs, FL 981 g C/m2/year 54 g C/m2/year Net primary production is far greater in open compared to closed canopy streams, but the relative contribution of energy by primary production and litter fall to an ecosystem’s energy is also influenced by climate and nutrient availability. Data from selected from Table 12.5 in Allan, J.D., 1995 www.rijnh.nl/users/bongers/ do/page3.html www.hubbardbrook.org/research/gallery/streams/High/Weir1.jpg

Bear Brook, New Hampshire Bear Brook in New Hampshire is the site of a famous organic matter budget study (Likens, 1973). In the this small, forested headwater stream it was found that greater than 99% of the carbon input to Bear Brook came from allochthonous sources (POM slightly greater than DOM). Close to 65% of this input was exported downstream from the 1700 meter long study site. Input of DOM exceeded exports Due to leaf fall more POM was exported than entered the site Bear Brook in New Hampshire is the site of a famous organic matter budget study (Likens, 1973). In the this small, forested headwater stream it was found that greater than 99% of the carbon input to Bear Brook came from allochthonous sources (POM slightly greater than DOM). Close to 65% of this input was exported downstream from the 1700 meter long study site. Input of DOM exceeded exports Due to leaf fall more POM was exported than entered the site

The River Continuum Concept The River Continuum Concept is an attempt to describe the function of lotic ecosystems from their source to their mouth and explain the variation among sites that result from differences in their terrestrial setting. These differences are manifested in structural and functional differences among stream reaches that can be tied to stream order. Differences between low, middle, and high order streams show up primarily in terms of - geomorphology - energy pathways - diversity and relative abundance of functional groups The differences are a result in changes in percent canopy cover, gradient, substrate type, temperature, and other factors that necessarily change the stream’s physical nature as it increases in size in its path downstream.

Stream order and the RCC Low order streams Shaded headwater streams Coarse particulate matter (CPOM) provides resource base for consumer community http://www.oaa.pdx.edu/CAE/Programs/sti/pratt/streams/low.html

Stream order and the RCC Mid-order streams Energy inputs change as stream broadens Shading and contribution of CPOM decreases Sunlight supports significant periphyton production Upstream processing of CPOM results in input of fine particulate matter (FPOM) Photo by G. Merrick http://www.oaa.pdx.edu/CAE/Programs/sti/pratt/streams/mid.html

Stream order and the RCC High order streams As streams widen even more and flows drop, macrophytes become more abundant In the largest rivers, macrophytes are limited to the river margins because mid-channel conditions are typically too turbid Bottom substrate becomes smaller

Carbon fluxes in a stream ecosystem Figure 12.1 Processing of organic matter in streams, whether autotochthonous or allochthonous, is largely carried out by macroinvertebrates and microbes. Carbon not assimilated is exported and carbon that is respired is exported or evolved back to the atmosphere. Figure 12.1 Simplified model of principal carbon fluxes in a stream ecosystem. Solid lines indicate dominant pathways of transport or metabolism of organic matter in a woodland stream. R-circle denotes mineralization of organic carbon to carbon dioxide respiration. (Modified from Wetzel, 1983)