Regime shifts in marine ecosystems

Time scales, and the trophic relations between these scales, are very different in the sea from those on land. In particular, marine systems are much more responsive to decadal scale alterations in their physical environment but are also much more adaptable. Thus it is difficult, and probably counterproductive, to try to define a baseline state for marine ecosystems. Further, regime shifts in fish communities can have major economic consequences without being ecological disasters. Climatic changes at decadal scales, from natural or anthropogenic causes, are likely to produce or enhance regime shifts. There are different management issues in different sectors. The coastal zone demands our intervention to assure integrated management of the land and sea components. At the other extreme, our understanding of open ocean systems is an essential element of climate prediction and so of eventual management. Between these two environments, our use of resources in continental shelf seas requires an ability to distinguish between human and natural causes of long-term change.