BIO 3072 ! !Eric L. Peters!

Ecological () Production Earth Area Available to Support Humans : Productive sea and land area  Production of (producer) biomass available to support each  capture and store their own energy and synthesize their own person in Africa: structural materials 1.36 ha  Limited by photosynthetic rates …on Earth: 1.90 ha Secondary Production:!  Production of Used by each W. European/U.S. () biomass citizen:  ’ structural 5.06/5.26 ha materials (and energy) must be World obtained from their food Productive sea and land area needed to produce Wildlife  Limited by primary , number and efficiency of energy the products consumed by each U.S. citizen:" Fund, transfers, and other factors. Many chemical elements (e.g., Ca and P) 9.71 ha (the CSU campus is 64.75 ha: enough to Living Planet must be provided in specific chemical forms or combinations sustain 12.3 U.S. citizens) Report 2002.

Nutrient Requirements of Consumers Energy-bearing Nutrients and Respiration !Edible, adj. good to eat and wholesome to digest, as a worm Cells use many organic molecules as fuel for respiration: to a toad, a toad to a snake, a snake to a pig, a pig to a man, and a man to a worm. –Ambrose Bierce, The Devil’s Dictionary !"

 There is tremendous variability in organismal nutritional requirements, as well as in the adaptations to meet those needs, e.g.,  Insects require a dietary source of cholesterol, mammals manufacture their own  Mammals require iodine for the formation of thyroid hormone  Humans and guinea pigs are the only known mammals that require vitamin C as a dietary supplement  Deficiencies in energy and essential nutrients limit growth, development and reproduction

Energy-bearing Nutrients and Biosynthesis Energy-bearing Nutrient Types !Food molecules are raw materials for biomass production" Carbohydrates (CH O) Energy in the form of ATP used to assemble macromolecules:! 2  Manufactured by autotrophs from CO2 and H2O  Easiest of nutrients to respire  Form the bulk of the diet of many heterotrophs, yet are not essential nutrients for heterotrophs!  Many exist on a carbohydrate-free diet, relying either on lipids or on deaminated amino acids for energy (e.g., vampire bats and other blood parasites, Inuit humans)  Two categories of carbohydrates:  Highly digestible (e.g., starches and sugars) taken up by assimilative digestion  Difficult to digest crude fiber (mostly cellulose): requires digestive symbionts (prokaryotes) to convert cellulose into bacterial biomass (fermentative digestion) before energy-bearing nutrients can be assimilated

Topic 6 !Secondary Productivity and Trophic Structure !1! BIO 3072 !Ecology !Eric L. Peters!

Energy-bearing Nutrient Types Energy-bearing Nutrient Types !Lipids are used as a means of storing energy, and in body Proteins structure. Lipids are not essential, but some of the fatty acids  Are also non-essential nutrients! Yet, protein deficiencies are are, because they cannot be made in animal bodies: most common form of nutritional deficiency! Why?  Necessary for the formation of cell membranes, proper brain/nervous system  Amino acids (which are present in proteins in large quantities) development/function, and for production linoleic acid are essential for heterotrophs. Needed for synthesis of: of hormone-like eicosanoids (which regulate  Structural proteins (skin, bones, muscle, hair, feathers, claws, hooves, numerous physiological functions, horns) including: blood pressure and viscosity, vasoconstriction, immune and inflammatory  Enzymes for regulation of metabolism and development α-linolenic acid responses)  All other proteins (e.g., immunoglobulins, metal-binding and other transport proteins, respiratory pigments, heat shock and antifreeze  Humans have the ability to convert linoleic acid (an ‘omega-6’ fatty acid proteins) found in most animal fats) and α-linolenic acid (an ‘omega-3’ fatty acid common in some fishes, seals, and whales) to longer-chain fatty acids,  Not all amino acids can be synthesized by animals (all can be which in turn serve as precursors for eicosanoids synthesized by plants, but most plants lack all 20)!  Both are also found in plants: linolenic acid is found primarily in seeds,  Many of the 20 required by animals can be synthesized from a single nuts, grains, and legumes, while α-linolenic acid is found in green leaves of dietary amino acid (humans require 9 from their diet) plants, phytoplankton and algae, and in some seeds, nuts and legumes  These amino acids can come from non-protein sources (e.g., nectar)

Other Nutrients Inorganic Nutrients  Vitamins: small organic molecules, from bacterial and plant Essential macronutrients (macroelements) sources. Function as coenzymes or as actual constituents of  Occur in parts per thousand (ppt) or greater quantities enzymes  Function as structural materials as in physiological functions  Lipid-soluble vitamins (e.g., A, E) can be stored in fatty tissues!  Some elements can substitute for others in limited amounts  “ ”  Water-soluble vitamins (e.g., C, B’s) are lost in urine and need to be Some of these nutrient analogs are now known to be essential elements (e.g., Sr is needed in addition to Ca in forming coral skeletons, and in some protozoan continually replaced (unless synthesized by the organism) tests) 137  Inorganic nutrients are also required for life processes  Can influence environmental impacts of human activities (e.g., radioactive Cs and 90Sr can substitute for K and Ca, respectively)  Some required for particular biological functions (e.g., , digestion, reproduction) !Essential micronutrients (microelements, trace elements, and ultratrace elements)  Some are needed to metabolize energy-bearing nutrients  Occur in parts per million (ppm) or lesser quantities All inorganic nutrients needed by autotrophs come from the air  Usually function as enzyme cofactors: work in combination with or (soil) water, sometimes with the aid of symbionts.! coenzymes to activate cellular enzymes (e.g., cobaltamine: vitamin B12) All inorganic nutrients needed by heterotrophs come from their  Include a number of “heavy metals” (e.g., Ni, Cu), which are toxic at food and (to a lesser extent) water, also sometimes with the aid concentrations not much higher than their required levels  Some substances formerly though to be toxicants (e.g., Se, Cr) are now of symbionts.! know to be essential in small quantities

Essential Elements Balancing Nutrient Requirements Essential for all Essential for several Essential for numerous Essential for a few Recently judged Seldom possible to find the ‘perfect’ diet:! plants and classes of plants species in one class of species of plants essential, but animals and/or animals plants and/or animals and/or animals function unknown  Organisms need to optimize energy acquisition while hydrogen (H) silicon (Si) boron (B) lithium (Li) rubidium (Rb) obtaining all needed nutrients to be competitive. carbon (C) vanadium (V) fluorine (F) aluminum (Al) tin (Sn) nitrogen (N) cobalt (Co) chromium (Cr) barium (Ba) lead (Pb) These needs often change during an organism’s oxygen (O) molybdenum (Mo) bromine (Br) lifetime. sodium (Na) iodine (I) nickel (Ni) magnesium (Mg) strontium (Sr)  Some nutrients need to be assimilated at the same phosphorus (P) time (e.g., Ca and P, which also requires vitamin D). sulfur (S) chlorine (C)  Uptake of some elements is hindered by the presence potassium (K) of others (e.g., high N levels can lead to S deficiencies calcium (Ca) manganese (Mn) in plants). iron (Fe)  Some needed nutrients are hard to obtain in some copper (Cu) zinc (Zn) environments. selenium (Se)  Some diets are energy-rich but lack essential nutrients.

Topic 6 !Secondary Productivity and Trophic Structure !2! BIO 3072 !Ecology !Eric L. Peters!

Optimizing Conflicting Dietary Requirements Trophic Levels First tropic level: primary producers" Optimal diet for moose. The (autotrophs) animal’s options (shaded) are limited by digestive capacity  Photosynthetic !Chemo-" (“rumen constraint”) and by prokaryotes !synthetic" daily Na requirements (“sodium constraint”). Na !prokaryotes! comes mostly from aquatic  Photosynthetic" plants. Diagonal lines microalgae: indicate equal energy intake chlorophytes, diatoms, (I) in multiples of metabolic dinoflagellates, etc. rate, and the optimal diet (3) corresponds to the highest I allowed by the model. Moose actually do eat the mixture of  Macroalgae: large green, brown, and red algae plants predicted by this model. (after Belovsky, G.E. 1978. Diet optimization in a  Plants: mosses, ferns, and other vascular plants generalist : the ! moose. Theor. Pop. Biol.  Some fungi (e.g., lichens) and animals (e.g., corals) with algal 14:105-134. endosymbionts serve as ‘primary producers’ in some systems

Trophic Levels Trophic Levels Second tropic level: Third tropic level: primary (1°) consumers! secondary (2°) consumers!  Heterotrophs that feed  Heterotrophs that prey exclusively on 1° directly on autotrophs consumers  Sometimes referred to as  – common usage suggests that grazers, these are the first predator and prey are both heterotrophs, level of predators! and the prey is alive until preyed upon  In predation: one organism (predator) obtains its energy  – eat fishes and/or nutrients from another living organism (prey)  Carnivores – eat muscles, organs  – eat insects and/or other terrestrial arthropods  Many are . Technically, herbivory refers to leaf  Zooplanktivores – eat zooplankton (small floating or drifting aquatic or predators, but can also include: marine animals  Feeders on unicellular algae (phytoplanktivores), and on  – eat the same species fungi and lichens (mycovores)  – most common (most predatory species are parasites). Prey are fed upon while still living, and may be fed upon more than once  Feeders on seeds (granivores) (predator generally does not kill prey)  Feeders on fruits ()  Parasitoidism – predator gradually consumes living prey, but prey eventually dies and is removed from population  Feeders on nectar (nectivores)

Trophic Levels Terrestrial and Marine ‘Food Chains’ Fourth tropic level: tertiary (3°) consumers! 4° (quaternary) consumers Fifth tropic level: quaternary (4°) consumers! red-tailed hawk killer whales  Heterotrophs that prey exclusively on consumers from the trophic levels immediately below 3° (tertiary) consumers " prairie rattlesnakes mackerel " " " ! 2° (secondary) consumers grasshopper mice sardines Omnivory: butter predation on both autotrophs (1° consumer) and heterotrophs: this indicates swordfish 1° (primary) consumers (‘herbivores’) that feeding categories are not (6° consumer) grasshopper zooplankton so simple (more on this later) baked potato, squash, salad 1° (primary) producers green plants phytoplankton (1° producers)

Topic 6 !Secondary Productivity and Trophic Structure !3! BIO 3072 !Ecology !Eric L. Peters!

Detrivory (‘Saprophagy’) ! and  Decomposers are microconsumers (heterotrophic bacteria, are organisms that obtain protists, and fungi) their energy and nutrients  Obtain energy by converting chemical energy in monomers of from dead organisms, organism wastes, or lost once-living macromolecular material back into their original body parts inorganic forms, e.g., nitrogen/sulfur in amino acids into N2 gas/sulfates, etc.  Like detritivores, many decomposers Generally, detritivores are macroconsumers that feed on as-yet undigested material (e.g., hyenas, vultures, earthworms) (e.g., fungi) convert macro molecules back into monomers and use them  A portion of the dead material is digested and a large portion of energy is lost by respiration of these organisms for life processes, but their food source is more ‘biodegraded’  In many terrestrial systems, over 90% of 1° producer energy goes directly through decomposition pathways  Important! All organisms can convert carbon compounds back  Remaining undigested portion and/or simpler molecules present in into inorganic form (CO2) during respiration, but detritivores’ feces, excretions, and other exudates is further final decomposition of many other elements (e.g., N and S) in processed during… organic material back into inorganic forms requires bacteria!

Generalized Energy Budget Ex: energy budget (kJ) of a perch over a 28 d period:!

C = P + R + (U + F) Ingestion = Growth + Metabolism + Wastes! Assimilation (A) = C – F C =consumption (ingestion): gross energy contained in food P =production of biomass: energy deposited in and retained in tissues (all energy for growth and reproduction) Redrawn from Brafield and Llewellyn (1982)! R =respiration: heat loss during ATP production " U=energy absorbed into body and lost in urine (excretion) Note: energy budget does not balance perfectly due to measurement errors in the various techniques used to measure the budget components (animal can also be in F =energy not absorbed from food and lost as feces (egestion) negative energy balance if intake drops below minimum maintenance levels)

Energy budgets can be made for entire populations Ecological Efficiency Ex: energy flow (kJ m-2 y-1) through a population of worms on an intertidal mudflat:!  Energy coefficient of the first order (growth efficiency P/I): estimate of how much energy, consumed by animals within a specific , is available for transfer to the next level P 189  Endotherms less efficient (more energy needed for respiration)  Energy coefficient of the second order (production efficiency, P/A): how efficiently the extracted food energy is converted into biomass C 314  Again, endotherms less efficient (faster digestive passage) R 70  Assimilation efficiency (A/I): the efficiency at which energy U 8 is digested and absorbed from food  Depends on nature of food: herbivore diets w/ high cellulose F 47 result in lower A/I (ca. 50%), diets exceed 80% Redrawn from Kay and  Ectotherms are less efficient (but need less food per unit mass) Brafield (1973)!

Topic 6 !Secondary Productivity and Trophic Structure !4! BIO 3072 !Ecology !Eric L. Peters!

Ecological Efficiencies Energy Transfers and Trophic Levels (Also see Smith and Smith)!  If each trophic level receives all of its energy from the level Individual animal energy efficiencies (as percentages): A = below (i.e., if energy transfers are linear), then the resulting assimilation, P = production, I = intake (consumption) trophic structure is known as a !

 Energy loss due to respiration from each level is about 90%. # Species A/I P/A !P/I Produces ecological pyramids–as trophic level increases, there Ectotherms" are decreasing amounts of: !Herbivores Terrestrial 32 45 52 20  Stored energy in both: Aquatic 15 61 56 34  living matter (biomass) Granivores Terrestrial 4 78 30 24  Nonliving organic matter Carnivores Terrestrial 11 84 58 46 () Aquatic 17 64 48 30  Numbers of organisms Detritivores Terrestrial 6 12 50  Production! Aquatic 6 45 56 25  Less total energy Parasites 3 77 50 42 available Endotherms  Greater respiratory losses by Herbivores Terrestrial 3 66 23 13 (possibly endothermic) Granivores Terrestrial 3 76 29 22 predators Lactivores Terrestrial 2 95 45 43  Turnover (‘recycling rates’ of biomass)

Examples of Ecological Pyramids Livestock and Human Food Chains  Often very short and linear: forage → livestock → human  Livestock are generally ruminants (mammals with specially-adapted fermentative digestion: cattle, sheep, goats, deer, and camels)  Less energy efficient, but can be fed a poor- quality plant diet, converting it into food (meat, milk, blood) that contains all human dietary needs  Availability of ruminants with suitable characteristics for domestication has been a major influence on civilization  Most herding species originated in But Man is a carnivorous production, N. Hemisphere, e.g., sheep, goats, And must have meals, at least one meal a day; cattle, camels, reindeer He cannot live, like woodcocks, upon suction, But, like the shark and tiger, must have prey;  S. Hemisphere ruminants (e.g., Although his anatomical construction antelopes, gazelles, llamas) are Bears vegetables, in a grumbling way, solitary (or have many predators) Your laboring people think beyond all question, and are too fast, agile, nervous, or Beef, veal, and mutton, better for digestion. aggressive to be easily domesticated -George Gordon (Lord Byron), Don Juan

Food Webs General Structure of Food Webs

In most communities and , trophic Heat Heat Heat Heat structure is not linear

 Feeding only from trophic level immediately below is not Secondary Tertiary (3°), Primary (1°) Primary (1°) (2°) energetically advantageous Producers Consumers Quaternary Consumers (4°), etc.  Number of linear transfers is limited by the amount of Consumers energy at the 1° producer base (i.e., more 1° producer Nutrient energy = longer food chain) Detritivores Pool  Numbers and biomass of predatory consumers often low Detritus compared with detritivores and decomposers Heat  Often very complicated trophic interconnections between Energy and Decomposers species: many organisms feed from multiple trophic levels Nutrient Sink  These produce more elaborate trophic structures (food webs) Heat Nutrient Flow

Topic 6 !Secondary Productivity and Trophic Structure !5! BIO 3072 !Ecology !Eric L. Peters!

Determining Trophic Lake Michigan Rocky Reef Relationships 4-5° consumer 4° consumer !Constructing food webs is (parasite) very difficult. Among the 3° many factors that must be consumers considered:  ‘Who eats whom?’ (and how often?) 2° consumers  Many species’ natural histories (including diets) are still poorly known (this is especially true of organisms in the decomposition pathways)  Often, closely related 1° consumers species have very different trophic positions 1° producers

Atlantic Salt Midwestern U.S. Marsh Food Prairie Food Web Web!

Appalachian Forest Litter Detrital Food Web U.S. Riverine Food Web

Topic 6 !Secondary Productivity and Trophic Structure !6! BIO 3072 !Ecology !Eric L. Peters!

Hydrothermic ‘Rift Vent’ Food Webs are Driven by Bacterial Primary Productivity Stable Isotope Analyses of Food Webs Tube worms (e.g., Several stable isotopes of biologically important elements exist in Riftia, Tevnia) also rely nature:! on bacterial endosymbionts in their  Nitrogen: 15N/14N ratios form the basis for determining the gills for their nutrition. They may be up to 1.5 number of ‘trophic transfers’ for organic material in the food m long web  15N/14N ratio increases as the number of trophic transfers increases

Vescomyid clams rely on chemosynthetic bacterial  Carbon: 13C /12C ratios used to determine primary producer symbionts, which live within their gills, for their nutrition origin of organismal carbon The combination of an  13C/12C ratio increases as the number of chemical reaction steps in enhanced ability to filter-feed and the photosynthetic pathways increases (e.g., C3, C4, and CAM presence of multiple photosynthesis all have different numbers of reaction steps) types of symbionts 35 34 enables bathymodiolid  Sulfur: S/ S ratios used to improve identification of primary mussels to survive producer sources of heterotroph energy (e.g., algae vs. farther from the direct sources of vent water terrestrial and aquatic plants) than the clams and the A variety of crabs (some tube worms feed on the tube worms)

Stable Isotope Analyses of Energy Source Stable Isotope Analyses of Trophic Level Diagrammatic representation Diagrammatic representation of carbon and sulfur isotope of carbon and nitrogen isotope ratios in the biota of an ratios in the biota of an estuarine ecosystem (after estuarine ecosystem (after Peterson and Howarth 1987). Peterson and Howarth 1987). The isotopic ratios (‘δ- The isotopic composition (‘δ- values’) of the primary values’) of the 1° producers producers are represented by are again represented by confidence ellipses for δ13C confidence ellipses for δ13C and δ34S .δ-values of consumer and δ15N. The trophic position taxa are represented by circled of individual consumer numbers. In this example, species (circled numbers) can consumer species 1 obtains its be determined from the shift carbon almost entirely from in δ15N relative to their food upland plants, species 2 sources. In this example, the obtains its carbon primarily δ15N enrichments of from macrophytes and consumers 1 and 2 are both partially from upland plants, high relative to their food and species 3, 4, and 5 obtain sources, indicating that these their carbon to a progressively taxa are at a higher trophic greater degree from level than taxa 3, 4 and 5. phytoplankton.

Biomagnification  Some toxicants are very easily absorbed from diet or water, but once taken up, are not easily eliminated from the body, e.g.,  Metals (e.g., Hg, Cd) that are stored in body organs  Organic chemicals (e.g., PCBs and DDT) that are lipid-soluble  An organism’s ‘body burden’ of such substances therefore reflects: DDT increases"  Its own exposure history 10 million times!  The exposure history of all DDT in piscivorous lower trophic levels birds: 25 ppm  The result can be a huge increase in concentration DDT in large with increasing trophic fishes: 2 ppm level (biomagnification), DDT in small eventually producing fishes: 500 ppb toxic effects on organisms at higher trophic levels DDT in zooplankton: 40 ppb DDT in water: 2.5 parts per trillion

Topic 6 !Secondary Productivity and Trophic Structure !7!