Cycles Part 4

Ecosystems provide the intermediate service of biological fixation, which in turn serves society with food production and soil formation services.

ecosystem disservices (negative impacts on society) of climate change, food scarcity and soil erosion, among others.

nitrogen cycle, damage to ecosystem structure can lead to leaching of nitrogen from the system. This, in turn, can cause food scarcity and soil erosion, and potentially climate change if changes to ecosystem structure lead to losses of N2O to the atmosphere.

Food e.g. crops, fruit, fish • Fibre and fuel e.g. timber, wool • Biochemicals, natural medicines and pharmaceuticals • Genetic resources: genes and genetic information used for animal/plant breeding and biotechnology • Ornamental resources e.g. shells, flowers

Air-quality maintenance: ecosystems contribute chemicals to and extract chemicals from the atmosphere • Climate regulation e.g. land cover can affect local temperature and precipitation; globally ecosystems affect greenhouse gas sequestration and emissions • Water regulation: ecosystems affect e.g. the timing and magnitude of runoff, flooding etc. • Erosion control: vegetative cover plays an important role in soil retention/prevention of land/asset erosion • Water purification/detoxification: ecosystems can be a source of water impurities but can also help to filter out/decompose organic waste • Natural hazard protection e.g. storms, floods, landslides • Bioremediation of waste i.e. removal of pollutants through storage, dilution, transformation and burial

• Spiritual and religious value: many religions attach spiritual and religious values to ecosystems • Inspiration for art, folklore, architecture etc • Social relations: ecosystems affect the types of social relations that are established e.g. fishing societies • Aesthetic values: many people find beauty in various aspects of ecosystems • Cultural heritage values: many societies place high value on the maintenance of important landscapes or species • Recreation and ecotourism

Soil formation and retention • Nutrient cycling • Primary production • Water cycling • Production of atmospheric oxygen • Provision of habitat

concentrations of nutrients in the water, The collective term ‘nutrients’ is used for the elements that are essential for primary production by plants or other photosynthetic organisms.

Macronutrients are those required in relatively high amounts. Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium and magnesium are all macronutrients.

Eutrophication is most often caused by increases in the availability of nitrogen and phosphorus. These elements are common in soil and water in the form of nitrate and phosphate, respectively. However, alterations in the concentration of any plant nutrient may have a recognisable biological effect.

Trophic levels, as applied to a food-chain.

A series of stages were used to describe the trophic state: oligotrophic – mesotrophic – eutrophic – hypertrophic where oligotrophic means ‘low in nutrients’, mesotrophic ‘with intermediate nutrient concentration’, eutrophic ‘high in nutrients’ and hypertrophic ‘very high in nutrients’.

‘Phytoplankton’ is a collective term for the free-floating photosynthetic organisms within the water column. It encompasses both algae and photosynthetic bacteria. Therefore: an oligotrophic lake has clear water with little phytoplankton an eutrophic lake is more turbid and green from dense phytoplankton growth a mesotrophic lake is intermediate between the tw

A further term – dystrophic – describes ‘brown-water lakes’. These have heavily stained water caused by large amounts of organic matter, usually leached from peat soils.

Characteristic Oligotrophic Eutrophic primary production low high

oligotrophic -high species diversity, low population densities Eutrophic - low species diversity, high population densities

oligotrophic - high eutrophic - low

oligotrophic - rare eutrophic - frequent

oligotrophic - low eutrophic - high

oligotrophic - low eutrophic - high

oligotrophic - high eutrophic - low

oligotrophic - salmonid fish (e.g. trout, char) eutrophic - coarse fish (e.g. perch, roach, carp)

The high density of phytoplankton absorbs the light for photosynthesis and prevents it penetrating deeper into the water.

The ready availability of nutrients allows rapid growth. In oligotrophic water, the rate of growth is limited by the nutrient supply. In eutrophic water, often only the availability of light regulates primary production.