|
Northwest North Sea Associated Investigators: Related Time Series: The Stonehaven monitoring site (56 57.8'N 002 06.2'W) has been a part of the Coastal Ecosystem Monitoring Programme operated by Marine Scotland Science (MSS) since 1997. This site acts as a reference site to fulfill the requirements of the EU Water Framework Directive and test the development of tools to identify Good Environmental Status for the Marine Strategy Framework Directive. The Stonehaven monitoring site is 50 m deep and is located 5 km offshore. Samples to measure temperature, salinity, and nutrients are collected using a reversing bottle and digital thermometer from surface (1 m) and bottom (45 m) depths. A 10 m integrated tube sampler is used to collect samples for Chlorophyll and phytoplankton community analysis. Phytoplankton samples are preserved in Lugol s iodine and analysed using the Utermohl method (Utermohl, 1958). Zooplankton samples for community analysis are collected using a 200 µm mesh bongo net. Since 2009, weekly samples have also been taken for total alkalinity and dissolved inorganic carbon measurements. Scanning electron microscopy of selected samples to identify and enumerate the coccolithophores present is also being performed. Samples are collected weekly, weather permitting. Information about the zooplankton community at this site can be found in the ICES Zooplankton Status Report. Seasonal and interannual trends The Stonehaven site is a dynamic site, with strong southerly flow. It is well mixed for most of the year. Temperature and salinity show a strong seasonality. The lowest temperatures are observed during spring (ca. 6 C) and the warmest towards late summer. The temperature at this site rarely exceeds 14 C. Salinity follows a similar pattern, with lowest salinity observed in spring and highest in late summer. Nutrients show a seasonal pattern typical to high latitudes, with the concentration of total nitrates, phosphate, and silicate increasing over winter, when phytoplankton growth is reduced, and decreasing during the phytoplankton growing period. The phytoplankton community observes a strong seasonality at the Stonehaven monitoring site. During winter, phytoplankton growth is reduced. Diatom cells begin to increase in abundance from March, and during most years, there is a strong spring bloom dominated by Diatom genera such as Chaetoceros, Thalassiosira, and Skeletonema. Dinoflagellates such as Ceratium become a more important part of the phytoplankton community during summer. In some years, but not all, an autumn Diatom bloom of larger Diatoms such as Rhizosolenia and Pseudo-nitzschia spp. type cells can be observed. A number of changes have been observed in the phytoplankton community at this site since monitoring began. A period of reduced annual chlorophyll concentrations was observed from 2000 to 2004. This corresponds to a period when the intensity of the spring bloom was reduced. Chlorophyll concentrations increased again in 2005, with Skeletonema observed at high cell densities during the spring bloom. This increase in Skeletonema was also observed at the other monitoring sites in the programme. Since 2000, a decrease has been observed in the large thecate Dinoflagellates, such as Ceratium, that occur during summer, whereas dense blooms of small Prorocentru cf. minimum cells have been observed in early summer. This change in Ceratium has also been observed at other sites in the programme and also in the Continuous Plankton Recorder data (Hinder et al., 2012). A preliminary description of the hydrography, chemistry, and phytoplankton community can be found in Bresnan et al. (2009). A description of a transect survey around this monitoring site can be found in McCollin et al. (2011). Further information and links to the data collected at this site can be found at the Marine Scotland website ( https://www.scotland.gov.uk/Topics/marine/). |