Allochthonous Input

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

Allochtonous Energy Unappreciated Until the 70s May be the main source of energy

What happens to the organics? Allochtonous input primarily detritus Makes it hard to tell Autochtonous from Allochtonous

Size classes of detritus

Coarse particulate organic matter (CPOM)

Fine particulate organic matter (FPOM)

Dissolved organic matter (DOM)

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 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 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

Bear Brook, New Hampshire Famous organic matter budget study (Likens, 1973). Small, forested headwater stream 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

Primarily Allochthonous Energy >99% of the carbon input from allochthonous sources POM slightly greater than DOM Close to 65% of this input was exported downstream 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

Fate of CPOM Best info for autumn-shed leaves Woody material is slower than leaves Other sources little studied Flower parts Feces Carcasses of large animals Macrophyte breakdown like terrestrial leaves

What factors influence leaf breakdown?

Rate of leaf breakdown Determined by Intrinsic differences among leaves Environmental variables Temperature Water chemistry Feeding activity of detritivores

Rate of leaf breakdown Modeled by: Wt= dry mass at time t Wi = initial dry mass t measured in days k is the slope of the plot of loge of leaf mass versus time

What characteristics of leaves might reduce the rate of Microbial Processing?

High [lignin] slows breakdown strengthening material that occurs with cellulose and other polysaccharides in cell walls Second most abundant organic compound on earth Insoluble, high molecular wt., made of 3 aromatic alcohols In living plant also gives resistance to attack by pathogens and consumption by herbivores

Chemical inhibitors in leaves slow breakdown Allelochemics: isoprenoids (= terpenoids or terpenes) Anti-herbivore and allelopathic compounds Tannins bind proteins, make them harder to digest Tannins are anti-microbial (as are many phenolics)

Waxy cuticle inhibits breakdown

Breakdown Rates By Species

Breakdown rates for various woody and non-woody plants 1/2 life in days 596 estimates from field studies Variation due to Site Technique Environmental variables Non-woody woody

Global climate change questions If temperature affects breakdown, what will happen if it gets warmer? If species differ in breakdown time, what will happen as species move north or disappear?

Stages in breakdown of autumn leaves Leaves fall into stream Begin leaching organics & inorganics 25% of initial dry mass lost in 24 hrs Soluble carbohydrates polyphenols

Elm-10oC Elm-20-22 oC Alder-10oC Alder - 20-22oC Time course of leaching of soluble organics (DOM) from elm and alder leaves

Stages in breakdown of autumn leaves Colonization by microbial organisms Bacteria Fungi Fragmentation Mechanical Biotic activity: primarily invertebrates

Processing sequence for a leaf in a temperate stream

What is Succession?

Successional Ecology: Fungi Fungi (aquatic hyphomycetes) dominate in the early fall as leaves enter stream Which ever fungal spores attach first wins

Successional Ecology: Bacteria Bacteria dominate the terminal processing Bacteria benefit by fungal conditioning of leaf

Successional and Feeding Nutritional value of leaf declines after a few weeks in the stream Decomposition and thus nutritional value to a detritivore is variable: good choosers get a better meal

Impact of Microbes on Leaf Breakdown

Influence of Detritivores: fragmentation Why does fragmentation matter?

Influence of Detritivores: fragmentation Leaf packs in mesh bags decomposed more slowly than those without bags Mesh size excluded detritivores Breakdown rates are higher when inverts are more abundant

Up to 25% of degradation due to animals Direct consumption Release of nutrients and DOM Comminution of litter to break or crush into powder Modification of water circulation

Suppression of detrital activity slowed loss in leaf mass

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)

Who are the primary leaf litter detritivores Plecoptera: Stoneflies Pteronarcys sp. From: Merritt & Cummins, 1996

Who are the primary leaf litter detritivores ? From: Wiggins, 1978 Tricoptera: caddis flies Pycnopsyche sp.

Who are the primary leaf litter detritivores? From: Merritt & Cummins, 1996 Diptera: Tipulidae = crane flies Tipula sp.

FPOM: Spores, Feces etc. Even less know than CPOM Comes from both CPOM & DOM Primary source of energy other than leaves In deciduous forest Similar to soil OM Bacteria Dominate decomposition

DOM Typically largest pool of C in lotic systems But often low bioavailability

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)

Water on the Web This presentation includes material from Water on the Web (WoW) WOW. 2004. Water on the Web - Monitoring Minnesota Lakes on the Internet and Training Water Science Technicians for the Future - A National On-line Curriculum using Advanced Technologies and Real-Time Data. http://WaterOntheWeb.org). University of Minnesota-Duluth, Duluth, MN 55812. Authors: Munson, BH, Axler, R, Hagley C, Host G, Merrick G, Richards C. I would also like to thank Dr. Jewett-Smith for her contributions to this presentation