Problems/threats to aquatic ecosystems

• the biodiversity loss in freshwater has seen an 80% decline since 1970
• saprobicity is the amount of organic matter in a system
• oligosaprobic means low in organic matter
• polysaprobic means high in organic matter
• organic matter comes from waste waters, sewage, overflows, industrial waste
• oxygen depletion occurs through loading of organic matter
• design, construction and maintenance shows trade off between needing construction (dams/canals) and supporting natural way of flow and living within waterways
• chemical threats include chemicals in sunscreen, medicine residues reaching surface waters and pesticide and herbicide uses in agriculture reaching surface waters
• eutrophication describes the loading of nutrients (nitrogen and phosphorous) in ecosystems which can lead to waters becoming swampy (naturally) or covered in algae (due to humans)
• when water become covered in algae, the area underneath becomes anaerobic without sunlight causes living organisms to die off
• eutrophic means high in nutrients while polysaprobic means high in organic matter
• cyanobacteria and cyanotoxins cause blankets of green above the water that produce toxins that impact the nervous system
• the general order of succession of algal groups from spring to autumn is diatoms - green algae - cyanobacteria
• diatoms grow well in low temperatures and low sunlight levels
• green algae grow well in high temperatures and high amounts of sunlight
• lakes with low amounts of nutrients (due to algal growth) leads to the production of cyanobacteria who can obtain oxygen from atmosphere and can thus thrive in anaerobic water conditions
• organic materials are dead plants and animals from water and banks that are dissolved or float in water or accumulate in sediment
• hypereutrophic environments are characterised by murky, highly productive waters in which many clear water species cannot survive