Ecology P3

Primary production of carbon compounds

• production in ecosystems is the accumulation of carbon compounds in the form of biomass

• gross primary productivity is the biomass or energy of carbon compounds per time and area, made in plants by photosynthesis

• net primary productivity is the GPP minus the biomass lost due to respiration of the plant, it is what’s available to consumer

Secondary productivity

• the accumulation of carbon compounds in biomass by heterotrophs

Nutrient cycle

• nutrients enter biosphere via autotrophs, which obtain all of their nutrients from the abiotic environment

• within biotic, heterotrophs obtain most nutrients from their food

• nutrients pass from organisms to organism via feeding

• Atoms return to the abiotic from biotic

• carbon is the most abundant element of life and is continuously cycled between the biotic and abiotic components

Carbon pool

• a location or system that can store or release carbon

Carbon flux

• processes that exchange carbon between pools

• a single carbon pool can often have several fluxes both adding and removing carbon simultaneously

Carbon sink

• anything that absorbs more carbon from the atmosphere than it releases

Carbon source

• anything releasing more carbon into the atmosphere than it absorbs

Carbon cycle

• nutrients in an ecosystem are recycled and reused in form of chemical elements of nutrients circulating between living things and the environment

• carbon is a main nutrient found in proteins, carbs, and lipids

• it cycles continuously between abiotic and biotic environments

Main carbon storage sinks/pools

• Carbon is stored in sinks or pools in form of organic or inorganic compound

• ex: biosphere, oceans and lakes, atmosphere, sediments and soil

• carbon moves between 4 pools by variety of biological or industrial processes called fluxes

Amount of carbon stored in parts of earth

• atmosphere - 750 GT

• Soil - 1580 GT

• Terrestrial Pool - 610 GT

• Aquatic pool - 3 GT

• Ocean surface pool - 970 GT

• Ocean deep pool - 38,000 GT

Lithosphere

• largest amount of carbon on Earth is stored in sedimentary rocks within the planets crust

• these rocks are produced by hardening of mud into shale or by collecting calcium carbonate particles into limestone

• Pool - 1,000,000+ GT

Fossil fuels

• a fossil store in organic matter (coal, oil, natural gas) which formed over millions of years

• normally there would be no flux of this carbon back into the carbon cycle however through human actions, this carbon is introduced into the other carbon pools unnaturally

• Pool - 1200 GT

Fluxes - Photosynthesis

• carbon dioxide diffuses from the atmosphere or water into autotrophs

• CO2 is removed from the atmosphere and moved to the biosphere

• only process that has a net decrease on level of carbon dioxide in atmosphere

Fluxes - respiration

• terrestrial organisms release carbon to the atmosphere whereas aquatic organisms release carbon to the hydrosphere

• CO2 produced by respiration is diffused out of organisms into water or the atmosphere

• CO2 is released from biosphere to the atmosphere during cellular respiration by decomposers

Lithification

• lithification is the process in which sediments compact under pressure, expel fluids, and gradually become solid rock

• moves carbon from the biosphere to the lithosphere

Combustion

• forest fires and fossil fuel combustion releases carbon gases when organic hydrocarbons are burned as a fuel source

• move carbon from fossil fuels and biosphere into atmosphere

Fossilization

• in anaerobic conditions, dead organisms decay slowly or not at all

• these organisms build up and if compressed over millions of years, can form fossil fuels

• moves carbon from soil and biosphere to the geosphere

Keeling curve

• past CO2 concentrations can be collected from ice cores

• annual rhythm shows that the carbon dioxide concentrations is lower in the summer months and higher in the winter months

Ecosystem stability

• the capacity of an ecosystem to maintain its structure, function, and biodiversity over time

• able to withstand environmental changes, recover from disturbances, maintain biodiversity, preserve ecological functions

ecosystem resistance

• the ability to continue functioning without significant change when stressed by disturbance

• forest ecosystem with minimal damage from a minor wildfire

Ecosystem resilience

• ability to recover and return to original state or function after a disturbance

• grassland ecosystem that regrows quickly after a drought/fire

ecosystem stability requirements

• nutrient cycling without leakages

• steady supply of energy

• high genetic diversity so populations can survive selection

• climatic variables within tolerance (temp)

• absence of disruptions with would interfere with sustainability

Disruptions to an ecosystem

• erosion leads to a loss of nutrients

• eutrophication is when nutrient enrichment of water causes population imbalance

• harvesting and removal of materials disrupts nutrient cycles and food webs

• poaching and selective removal disrupts ecosystem structure, especially if keystone species is removed

Amazon rainforest stability - water cycle

• sustains itself through a tight recycling of water and nutrients

• trees release huge amounts of water vapour through transpiration, helping create rainfall that falls back on forest

Amazon rainforest stability - nutrient cycling

• most nutrients are stored in living plants, not soil

• dead leaves and organisms decompose quickly

• roots absorb the released nutrients from decomposition

Amazon rainforest stability - biodiversity balance

• millions of species fill different ecological roles, keeping food webs stable and resources efficiently used

Amazon rainforest stability - climate regulation

• dense vegetation moderates temp and humidity, creating conditions the forest itself depends on

tipping point of ecosystems

• there is so much disturbance that a critical point is reached where a reversal might be difficult or impossible

positive feedback loops (Water cycle)

• positive feedback loops have tendency to amplify the effects and drive a system to a point where new form of stability is reached

Mesocosm

• completely sealed off ecosystems with only light entering as a source of energy, or open but controlled in some way

• used to investigate ecosystem stability and sustainability

Keystone species

• every ecosystem has certain species that are critical to the survival of other species in the ecosystem

• could be a predator, like a wolf or a plant, but without them, the ecosystem may not survive

example of keystone species

• the american beaver is an example of a keystone species in North america

• they perform unique and crucial roles within an ecosystem

sustainability of resource harvesting

• the responsible maintenance of ecological systems so that there is no reduction of conditions for future generations

• ensures long term viability of a system

• depends on the rate of harvesting being lower than rate of replacement

factors affecting the sustainability of agriculture

• soil erosion

• fertilizers

• leaching

• carbon footprint

• monocultures

soil erosion

• caused by tillage, which involves plowing, harrowing, and results in a reduction of soil quality

Fertilizers

• growing crop causes nutrient depletion over time which needs fertilizers to compensate

• excess fertilizers leach into water systems which can lead to eutrophication

leaching

• soil exposure can lead to leaching of nutrients from the soil

• when it rains, nutrients are washed away and not available for plants

carbon footprint

• the use of heavy machines for tillage, harvest, and transport need a lot of energy

• processes large amounts of carbon emissions (diesel engines)

Monocultures

• repeated growth of the same crop results in pests and weeks to become increasingly problematic

• use of pesticides can cause pollution problems and the production of the chemicals needs energy

Eutrophication

• the excessive nutrient enrichment of water

• nutrients like phosphates and nitrates favour the growth of algae, which multiply in big numbers and lead to algae bloom

• can occur naturally through gradual drying up of pools of water

• can be due to leakage of excess chemicals used in agriculture

Algae bloom

• forms a thick, sunlight blocking cover on the surface of water

• prevents oxygen to dissolve and prevents plants to photosynthesis and die

• decomposition by bacteria further depletes oxygen supplies

Biological oxygen demand (BOD)

• amount of dissolved oxygen required to break down organic material in a given volume of water

• aerobic organisms use oxygen in respiration, resulting in higher BOD

• BOD can indirectly measure pollution

BOD measurement technique

• indirect method to determine water quality and aerobic activity by bacteria

• determined by taking a measured volume of water from source and measuring the dissolved oxygen content on day 1

• sample then placed in dark to prevent photosynthesis

• after 5 days, the oxygen level is measured again

• BOD is difference between initial and final oxygen concentration

Bioaccumulation

• increase in the concentrations of a toxin in body tissues during an animal’s lifetime

• usually happens with fat soluble chemicals which cannot be excreted

Biomagnification

• increase in the concentration of a chemical at each successive trophic level in a food chain

• predators tend to accumulate higher chemicals of a toxin than their prey because larger quantities are consumed

effects of plastic pollution of oceans

• main reason plastic accumulation in oceans in a problem is due to their non-biodegradability

• macroplastics (large, visible, more than 5mm in size)

• microplastics (extremely small pieces of plastic debris, less than 5mm)

Ecosystem degradation

• ecosystem degradation by human actions has caused severe consequences such as loss of biodiversity, species extinction and loss of ecosystem services (flood protection)

• efforts are being made to encourage natural ecosystems to return

rewilding

• the process of restoring an area of land to its natural uncultivated state

• ex: distributing seeds of plants, re-introducing apex predators and other keystone species, control of invasive species