Long-term changes in the pelagos, benthos and fisheries of the North Sea

Pronounced changes have occurred in the fisheries, plankton and benthos of the North Sea over the last five decades. Attribution of the relative contribution of anthropogenic versus natural hydrometeorological modulation to these changes is still unclear. As a background a summary history of our understanding of the state of health of the North Sea is outlined. We then focus on two contrasting periods in the North Sea, one between 1978-82 (cold) and the other post 1987 (warm) when pronounced alterations in many ecosystem characteristics occurred. The scale of the changes in the second of these periods is sufficiently large and wide ranging for it to have been termed a regime shift. A combination of local, regional and far field hydrometeorological forcing, and in particular variability in oceanic inflow, is believed to be responsible for the observed changes. Finally attention is drawn to the poor status of North Sea fish stocks where 7 stocks are documented as being fished outside safe biological limits. This situation is primarily believed to be a consequence of overfishing, but may have been exacerbated by environmental change.

A change in the zooplankton of the central North Sea (55 degree to 58 degree N): A possible consequence of changes in the benthos

The mesozooplankton taken in continuous plankton recorder samples from the Central North Sea has changed from being numerically dominated by holoplanktonic calanoid copepod species from 1958 to the late 1970s to a situation where pluteus larvae of echinoid and ophiuroid echinoderms have been more abundant than any single holoplanktonic species in the 1980s and early 1990s. The abundance of the echinoderm larvae as a proportion of the zooplankton taken in the samples has followed a continuous increasing trend over the Dogger Bank, but off the eastern coast of northern England and southern Scotland the increase did not become obvious until the 1980s. This trend is consistent with reported increases in abundance of the macrobenthos. It is proposed that changes in the benthos have influenced the composition of the plankton.

Seasonal Sedimentation Of Phytoplankton To The Deep-Sea Benthos

Until recently the deep sea was considered to be a particularly stable environment1, free from seasonal variations. However, atmospheric storms may cause periodicity in deep-ocean currents2 and nepheloid layers3 while seasonality in the particulate flux to the deep sea is known to occur in the Sargasso Sea4,5 and Panama Basin6. Evidence is presented here of a similar seasonal pulse of detrital material to bathyal and abyssal depths in temperate latitudes; this material seems to be derived directly from the surface primary production and to sink rapidly to the deep-sea benthos. Considerable sedimentation occurs soon after the spring bloom and continues throughout the early summer. This process acts as a pathway for the descent of carbon from the euphotic zone, providing a periodic food source for the deep pelagic and benthic communities.

Climate change and marine benthos: a review of existing research and future directions in the North Atlantic

There is growing evidence that climate change could affect marine benthic systems. This review provides information of climate change‐related impacts on the marine benthos in the North Atlantic. We cover a number of related research aspects, mainly in connection to two key issues. First, is the relationship between different physical aspects of climate change and the marine benthos. This section covers: (a) the responses to changes in seawater temperature (biogeographic shifts and phenology); (b) altered Hydrodynamics; (c) ocean acidification (OA); and (d) sea‐level rise‐coastal squeeze. The second major issue addressed is the possible integrated impact of climate change on the benthos. This work is based on relationships between proxies for climate variability, notably the North Atlantic Oscillation (NAO) index, and the long‐term marine benthos. The final section of our review provides a series of conclusions and future directions to support climate change research on marine benthic systems. WIREs Clim Change 2015, 6:203–223. doi: 10.1002/wcc.330