The importance of zooplankton in reducing levels of atmospheric CO sub(2) via the biological pump

Zooplankton play a key role in climate change through the transfer of large quantities of CO sub(2) to the deep ocean by a process known as the biological pump. Plankton composition is crucial as associated mineral material facilitates sinking of carbon rich debris and some taxa package faecal and detrital material. Ocean acidification may impact calcareous groups. Zooplankton have also been shown to be highly sensitive indicators of environmental change. Results will be presented to show that ocean temperature, circulation and planktonic ecosystems (using data from the Continuous Plankton Recorder, CPR survey) in the North Atlantic are changing rapidly in concert and that there is evidence to suggest that the changes are an ocean wide response to global warming with potential feedback effects. Given the importance of the oceans to the carbon cycle, even a minor change in the flux of carbon to the deep ocean would have a big impact increasing growth of atmospheric CO sub(2). We have virtually no understanding of the spatial and temporal variability in the efficiency of the biological pump for most of the world's ocean. Establishing new plankton monitoring programmes backed up by appropriate research to help understand processes is needed to address this gap in knowledge. There is little doubt within a global change context and the future of mankind that a potential acceleration in the growth of atmospheric carbon due to a reduction in the efficiency of the biological pump is a key issue for future research in zooplankton ecology.

Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥18ma.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤ ±20% in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20±3; 38±3; 29±6 μmolem-2 d-1 at 15, 18, 27ma.m.s.l.) than during falling tides (14±2; 22±2; 21±5 μmolem-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 μmolem-2 d-1 over hourly timescales (4 μmolem-2 d-1 over 24 h).

Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥18ma.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤ ±20% in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20±3; 38±3; 29±6 μmolem-2 d-1 at 15, 18, 27ma.m.s.l.) than during falling tides (14±2; 22±2; 21±5 μmolem-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 μmolem-2 d-1 over hourly timescales (4 μmolem-2 d-1 over 24 h).

Tidal and wind influences on circulation in the southern mouth of the Ría de Vigo (NW Iberian Peninsula)

Tidal and wind influences on the velocity field in the Ría de Vigo were assessed using atmospheric data from two meteorological stations located at Bouzas port and on an oceanic buoy off Silleiro Cape along with oceanic data from an ADCP moored in the Ría for a 72-day period. A two-layer circulation pattern was observed. Near-surface and near-bottom currents are primarily influenced by wind (especially remote winds), separated by an intermediate layer dominated by tidal variability. At subtidal frequencies, residual currents are well correlated with wind variability. Remote wind forcing exhibited a markedly high correlation with surface layer currents, indicating the major role played by wind in the long-term upwelling-modulated circulation of the Ría.

Tidal and wind influences on circulation in the southern mouth of the Ría de Vigo (NW Iberian Peninsula)

Tidal and wind influences on the velocity field in the Ría de Vigo were assessed using atmospheric data from two meteorological stations located at Bouzas port and on an oceanic buoy off Silleiro Cape along with oceanic data from an ADCP moored in the Ría for a 72-day period. A two-layer circulation pattern was observed. Near-surface and near-bottom currents are primarily influenced by wind (especially remote winds), separated by an intermediate layer dominated by tidal variability. At subtidal frequencies, residual currents are well correlated with wind variability. Remote wind forcing exhibited a markedly high correlation with surface layer currents, indicating the major role played by wind in the long-term upwelling-modulated circulation of the Ría.

Interregional Biological Responses in the North Atlantic to Hydrometeorological Forcing

Using data from the CPR survey seven case studies are described that document different spatial and temporal responses in the plankton to hydroclimatic events. Long-term trends in the plankton of the eastern Atlantic and the North Sea over the last five decades are examined. Two of the examples revisit correlations that have been described between copepod abundance in the eastern Atlantic and North Sea and indices of atmospheric variability, the North Atlantic Oscillation index and the Gulf Stream North Wall index. Evidence for an increase in levels of Phytoplankton Colour (a visual index of chlorophyll) on the eastern and western sides of the Atlantic is presented. Changes in three trophic levels and in the hydrodynamics and chemistry of the North Sea circa 1988 are outlined as a regime shift. Two of the case studies emphasise the importance of variability in oceanic advection into shelf seas and the role of western and eastern margin currents at the shelf edge. The plankton appear to be integrating hydrometeorological signals and reflecting basin scale changes in circulation of surface, intermediate and deep waters in part associated with the NAO. The extent to which climatic variability may be contributing to the observed changes in the plankton is discussed with a forecast of potential future ecosystem effects in a climate change scenario.