David K. Mills

The spring bloom in the south western North Sea in 1989

During 1989, the North Sea Community Programme made monthly cruises to study physical, chemical and biological conditions at 110 sites in the southern North Sea. This paper describes events during the spring at two sites differing in their tidal stirring characteristics. In situ fluorometers moored at each site gave daily estimates of chlorophyll concentration in the surface mixed layer. At site CS (55°30′N, 0°55′E) the spring bloom was dominated by diatoms and coincided with the onset of seasonal stratification in late April. The fluorometer record showed that the bloom lasted about a week. At the more strongly stirred site AB (52°42′N, 2°25′E), the bloom was dominated by Phaeocystis and occurred in late May, after the termination of the fluorometer record. It was concluded that the greater optical thickness of the surface mixed layer was responsible for the later bloom at AB. Phaeocystis dominance may be explained by the greater depletion of silicate relative to nitrate at AB. It is suggested that the ending of the blooms depended on several factors, including nutrient limitation, sinking and protozoan grazing.

New approaches to improve the detection of eutrophication in UK coastal waters

Robust assessments of eutrophication are necessary to meet the requirements of a range of international (OSPAR) and EU legislative drivers. To meet these needs EU states have developed marine monitoring programmes designed to allow the application of specified assessment procedures. The UK has reviewed its approach to monitoring eutrophication and has identified a range of future requirements to ensure the evidence base for assessment is robust and the underpinning science is in place. This paper describes the pilot application of in situ monitoring technology (SmartBuoy). Currently, two buoys are deployed in the southern North Sea and a third in Liverpool Bay (Irish Sea). The network of SmartBuoys returns data on physical, chemical and biological variables in near real-time (www.cefas.co.uk/monitoring). The rationale for system and network design will be described. Data from the multi-year time series will be presented and their subsequent use in assessments of eutrophication will be described.

The Liverpool Bay Coastal Observatory - towards the goals

A pilot Coastal Observatory was established in Liverpool Bay (eastern Irish Sea) in 2002 with an anticipated lifespan of at least 10 years. In an evolving process, near realtime measurements are integrated with coupled models in a pre-operational prediction system. The aim is to understand a coastal seas response to natural forcing and the consequences of human activity, providing scientific underpinning for coastal management. The impact of human activity on the worlds oceans and the use made of them by humanity is greatest in coastal seas. The eastern Irish Sea is an excellent study area, affected by all coastal sea processes with tidal forcing dominant and near-shore physical and bio-geochemical processes influenced by estuarine discharge where both vertical and horizontal gradients are important. The sea is subject to a range of human industrial, agricultural, fishing and recreational pressures. The time series measurements enable definition of the seasonal cycle, its interannual variability and quantification of the importance of events relative to the mean. Applications include eutrophication (the region receives significantly elevated levels of nutrient inputs), shoreline management (coastal flooding and beach erosion/accretion), and understanding present conditions to predict the impact of climate change (for instance if the number and severity of storms, or of high or low river flows, change). The integrated, systematic measurement suite, which started in August 2002, covers a range of space and time scales, concentrating on horizontal and vertical gradients, and includes in situ surface waves and vertical profiles of current, temperature, salinity, turbidity, nutrients and chlorophyll; regional water column surveys nine times a year; shore-based phased array HF radar measuring waves and surface currents out to a range of 50 km; instrumented ferries measuring surface properties; coastal tide gauges; satellite data-infrared (for sea surface temperature) and visible (for chlorophyll and suspended sediment). Acoustic telemetry and the Orbcomm satellite system are the primary resource for in situ telemetry. The core measurements and infrastructure also form the basis for process studies, instrument trials, for instance a three week glider deployment, and for the incorporation of new sensors. In cooperation with the UK Met Office, and as a component of the National Centre for Ocean Forecasting, a suite of nested 3-dimensional models (the Proudman Oceanographic Laboratory Coastal Ocean Modelling System-POLCOMS) is run daily, focusing on the Observatory area by covering the ocean/shelf of northwest Europe (at 12 km resolution), the Irish Sea (at 1.8 km) and Liverpool Bay (at ~ 200m resolution). These models simulate the physical (hydrodynamic coupled with wave) environment, nutrient and plankton dynamics, and the processes influencing sediment suspension and transport. The measurements test the models against events as they happen in a truly 3-D context - most is learned when model predictions diverge from reality. The value of some of the observations is enhanced by data assimilation which benefits both the models, keeping them on track, and the observations, augmenting their spatial coverage. All measurements and model outputs are displayed on the Coastal Observatory web-site for an audience of researchers, coastal managers and the public. After nearly 4 years of operation we are beginning to build up a picture, which only continuous monitoring provides, of the interaction between a coastal sea and its major estuaries. As always more detailed measurements indicate that processes are more complicated and distributions can have large variability

The plankton of the North Sea—pelagic ecosystems under stress?

Abstract The classical marine pelagic foodweb description was ascribed to the North Sea in the 1920s; phytoplankton production supports planktonic animals such as the copepod crustacean, Calanus, which in turn feed herring and other pelagic fish. Later studies have shown how organic material not consumed in the water column supplies benthic communities and demersal fish. This paper examines the pelagic ecosystems of the North Sea. They are stressed by: (1) fisheries pressure on higher trophic levels; (2) anthropogenic enrichment with nitrates and phosphates, which encourages the blooming of some types of phytoplankton; (3) climatic change; (4) input of toxins. Difficulties in obtaining and interpreting evidence of change are reviewed. Observational evidence of change can be supplemented by understanding the nature of the pelagic ecosystem and its links with physical conditions in different parts of the North Sea. Two regions of the North Sea are examined and compared.

The Pol Coastal Observatory - Methodology and Some First Results

This paper describes progress with a pilot Coastal Observatory (2002-2006) in Liverpool Bay (Eastern Irish Sea, UK) that integrates (near) real-time measurements with coupled models in a pre-operational coasts prediction system. The aim is to understand a coastal sea�s response to natural forcing and the consequences of human activity. The foci are the impacts of storms, seasonality, and variations in river discharge (freshwater and nutrients) on the functioning of Liverpool Bay. The present measurement suite includes: moorings for high frequency in-situ surface waves, temperature, salinity, turbidity, nutrients and chlorophyll; vertical profiles of current; 4-6 weekly regional surveys with CTD, suspended particulate matter and nutrient measurements; an instrumented ferry measuring surface properties (temperature, salinity, turbidity and chlorophyll; coastal tide gauges; satellite data � infra-red (for sea surface temperature) and visible (for chlorophyll and suspended sediment). A suite of nested 3-dimensional models (the Proudman Oceanographic Laboratory Coastal Ocean Modeling System � POLCOMS) is run daily, focusing on the Observatory area by covering the ocean/shelf of northwest Europe (at 12 km resolution) and the Irish Sea (at 1.8km). All measurements and model outputs are displayed on the Coastal Observatory web-site. Initial ways in which this system is being used to support an ecosystem-based approach to marine management are described.