Recent Change—North Sea

Abstract

This chapter discusses past and ongoing change in the following physical variables within the North Sea: temperature, salinity and stratification; currents and circulation; mean sea level; and extreme sea levels. Also considered are carbon dioxide; pH and nutrients; oxygen; suspended particulate matter and turbidity; coastal erosion, sedimentation and morphology; and sea ice. The distinctive character of the Wadden Sea is addressed, with a particular focus on nutrients and sediments. This chapter covers the past 200 years and focuses on the historical development of evidence (measurements, process understanding and models), the form, duration and accuracy of the evidence available, and what the evidence shows in terms of the state and trends in the respective variables. Much work has focused on detecting long-term change in the North Sea region, either from measurements or with models. Attempts to attribute such changes to, for example, anthropogenic forcing are still missing for the North Sea. Studies are urgently needed to assess consistency between observed changes and current expectations, in order to increase the level of confidence in projections of expected future conditions.

Copernicus Marine Service Ocean State Report, Issue 5

“…While it is well established that the North Sea has warmed substantially in recent decades (e.g. Huthnance et al 2016), with many documented impacts on fish species and the fisheries dependent on these (e.g. Simpson et al 2011;Heath et al 2012;Pinnegar et al 2016), to our knowledge, this is the first study to have systematically identified extreme temperature events and how these may have impacts on key fish and shellfish stocks.…”

Bonamia infection in native oysters (Ostrea edulis) in relation to European restoration projects

“…It is worth noting that B. ostreae exhibited high survival under the full range of pH and temperature conditions tested. Besides, the tested range of temperature and pH is far greater than the actual changes in the variables predicted in Huthnance et al (2016) for the end of this century, so it seems unlikely that the Bonamia parasite will be strongly negatively impacted by climate change in the near to medium term. However, specific research on the interactions between climate change effects and Bonamia is needed to test this hypothesis.…”

“…General effects of climate change include higher temperature and (through dissolution of CO 2 ) lower pH (Huthnance et al, 2016). To our knowledge, there are no specific studies of the impact on the prevalence and/or the mortality caused by Bonamia infection to O. edulis populations under these climate change scenarios.…”

“…While the initial collapse of O. edulis populations was largely driven by overfishing (Gercken & Schmidt, 2014;Houziaux, Kerckhof, Degrendele, Roche, & Norro, 2008;Pogoda, 2019), the emergence of parasites such as Bonamia ostreae and Marteilia refringens during the 20 th century resulted in substantial mortalities, furthering a renewed widespread decline of O. edulis (Laing, Walker, & Areal, 2006), in particular in aquaculture of this species along European coasts. These parasites are still present in several European ecoregions, with varying virulence and impact.…”

Exploring larval phenology as predictor for range expansion in an invasive species

“…Winter seawater temperatures in E England and S Norway (> 7°C: Mathis et al ) are higher than those currently experienced by adults in the German Bight (< 4°C), where populations of H. sanguineus persist over the winter (Geburzi et al ). Such difference in winter temperature is likely to result from coastal waters of E England and S Norway being influenced by the inflow of North Atlantic water, bringing water from the warm north–eastern limb of the Atlantic Meridional Overturning Circulation (Otto et al , Huthnance et al ). Another point is that models are based on records of surface temperature while larvae may occur deeper in the water column.…”