The Scottish Environment Protection Agency (SEPA) Marine National Environmental Monitoring Buoy Network provides real time, high frequency environmental data from strategic locations around the Scottish coast, as part of SEPA obligations to monitor the marine environment. The monitoring buoy network has been in place in some places from as early as 1996 with more buoys being deployed for ongoing measurements of the marine environment. Continuous monitoring equipment gathers dissolved oxygen, water temperature, salinity and chlorophyll-a data at regular intervals. The data is stored internally and downloaded at regular maintenance intervals. Data is collected by SEPA from monitoring buoys, mostly every 15 minutes. The data was submitted to the British Oceanographic Data Centre (BODC) for "data banking." Data has been removed as part of the SEPA quality control procedure leading to periods of absent data. This also occurs through power failure or lack of deployment. Further quality control by BODC will flag suspect data. The data is used to assess the state of the marine environment at representative locations. Salinity is used to indicate changes in water masses. Salinity decreases as freshwater inputs increase and oxygen is more soluble in freshwater than seawater. Water temperature is closely linked to seasonal changes and oxygen becomes less soluble as the water temperature increases. Chlorophyll-a is an indicator of the biomass of phytoplankton. Phytoplankton blooms are common occurrences at the start and end of the growing season in spring and autumn however excessive phytoplankton is indicated by enhanced abundance throughout the growing season (90 percentile concentration >15 µg/l measured from April to September). Excessive phytoplankton growth may cause an undesirable disturbance to the ecosystem if the decaying algae remove oxygen from the water column and sea bed as a result of microbial breakdown. Dissolved oxygen is one of the most important indicators of the health of a water body and high levels are needed to support a variety of marine life. Dissolved oxygen concentrations are affected by salinity, temperature and phytoplankton growth. Dissolved oxygen produced by photosynthesis may result in supersaturation (>100%) during the growing season. Dissolved oxygen is removed by the microbial breakdown of organic matter.