LME LFG

What is an ecosystem?: 

What is an ecosystem? Concepts to know: founding fathers - Tansley, Lindeman, Odum habitats vs. "biomes" vs. ecosystems; what is what? habitat-based approach vs. regional approach uniting principles - energy flow, elemental cycling trophic cascades and energy transfer equilibrium, dynamic equilibrium, and steady state

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Sir Arthur George Tansley (1871 - 1955) English botanist one of the founders of the British Ecological Society editor of the Journal of Ecology for twenty years. admitted to the Royal Society 1924: resigns from Cambridge and studies with Sigmund Freud 1927-1937: professor of botany at Oxford University knighted in 1950 Ecosystem - Tansley asked his friend Clapham to coin a term that described all of the physical and biological components of an environment (Tansley, A.G. 1935. The Use and Abuse of Vegetational Concepts and Terms. Ecology 16:284-307.).

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Modern usage based upon work by Lindeman (1915-1942) Post doc of Hutchinson Thesis rejected from Ecology Published after death study of Minnesota lake - the lake is the ecological unit (Lindeman, R.L. 1942. The Trophic-Dynamic Aspects of Ecology. Ecology 23:399-418). Emphasizes the “trophic or “energy-available” relationships within the community-unit [and how these relate to] to the process of succession.”  energy flow through the system

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Lindeman, 1942

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H.T.Odum (1924–2002) student of Hutchinson (Dissertation Title: The Biogeochemistry of Strontium: With Discussion on the Ecological Integration of Elements) professor at U. Florida 'father' of Ecosystems Ecology founded the discipline known as Systems Ecology Relies on energetics to explain the interactions between and among organisms and environment. = bioenergetics = ecophysiology Uses concept of homeostasis as applied to the ecosystem and succession. (Odum, E.P., 1969. The strategy of ecosystem development. Science 164:262-270.)

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Howard Thomas “Tom” Odum

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Ecotope: “the particular portion…of the physical world that forms a home for the organisms which inhabit it (Tansley 1939)” "The species relation to the full range of environmental and biotic variables affecting it" (Whittaker et al, 1973) - this is the niche or habitat? "the smallest spatial object or component of a geographical landscape” (Troll, 1945) - used to define “landscape ecology” The smallest ecologically-distinct landscape features in a landscape mapping and classification system. Relatively homogeneous, spatially-explicit landscape units that are useful for stratifying landscapes into ecologically distinct features for the measurement and mapping of landscape structure, function and change. Ecotope classification should stratify landscapes based on a combination of both biotic and abiotic factors, including vegetation, soils, hydrology, and other factors.

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Habitat: The physical conditions that surround a species, or species population, or assemblage of species, or community (Clements and Shelford, 1939). Modern usage often applied to population level description  The habitat of several co-existing populations, or a community, can be referred to as a biotope or biome.

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Biome: The set of flora or fauna within a habitat in a certain geography The intersection of several habitats Forms one basis for defining ecosystems Example aquatic ecosystems: * continental shelf * littoral * riparian * pond * coral reef * kelp forest * pack ice * hydrothermal vents * cold seeps * benthic zone * pelagic zone

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Regional Ecosystems: Defined by larger physical features such as current patterns or geologic features such as coastlines (or interplay between both) Sample Large Marine Ecosystems: * Agulhas Current * Antarctic Sea * Beaufort Sea * Benguela Current * Chukchi Sea * California Current * Eastern Bering Sea * Gulf of Alaska * Gulf of California * Gulf of Mexico * Humboldt Current * Scotian Shelf Region * Tasman Sea

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Majority of energy lost as heat (not conserved) Heat Heat Heat Sun Producers Consumers Decomposers Inorgan. nutrient pool nutrients/chemicals are recycled (are conserved) Dave McShaffrey Flow of Energy Cycling of nutrients

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C = C Energy Photosynthesis: CO2 H2O CO2 H2O O2

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C = C Energy CO2 H2O CO2 H2O Respiration: O2

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Intake Energy

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Intake Energy ~10%

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carnivores herbivores

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Trophic Cascades Top down top predators carnivores herbivores 1° producers typically downward E flow top levels dictate community structure seem to predominate in aquatic systems (Menge and Sutherland, Strong) pop’n predator limited pop’n predator limited pop’n predator limited

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Other possible directions of trophic E transfer Bottom up top predators carnivores herbivores 1° producers resources dictate community structure purely competition driven system examples?? resource limited, pop’n limited by K resource limited, pop’n limited by K resource limited, pop’n limited by K

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Two classic models of trophic E transfer top predators carnivores herbivores 1° producers top predators carnivores herbivores 1° producers predator limited predator limited predator limited predator limited resource limited resource limited resource limited resource limited Hairston, Smith, and Slobodkin Fretwell

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Recent examples of cascades salmon zooplankton phytoplankton orcas otters urchins kelp birds urchins macroalgae wolves moose balsam fir beetles ants insects Piper plants In all cases, abundance of lower level species are increased by the presence & activity of upper level species often conferred keystone species status due to strong effects on lower levels interactions are usually site specific and/or time dependent Pace et al 1999

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zooplank. crustose corallines birds amphi. isopods sea stars herb. gastros abalone sea cucumbers urchins phytoplankton octopi other macroalgae kelp carniv. fishes sessile inverts brittle stars herb. fishes lobsters crabs sharks & rays pinnipeds carniv. gastros phytodetritus orcas otters urchins kelp Aleutians So. California Most systems are very “webby” - theory is that system is resilient An example of site specific applicability:

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(organic) Dave McShaffrey (main C reservoirs) Algae

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(inorganic) Dave McShaffrey

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(inorganic) Dave McShaffrey

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Dave McShaffrey