|Where is the climate?|
Belgrano, A. (2002). Where is the climate? Trends Ecol. Evol. 17(1): 13-14
In: Trends in Ecology and Evolution. Elsevier Science: Amsterdam. ISSN 0169-5347, more
As part of their recent review in TREE, Danovaro et al. discuss how some recent changes in the physicochemical characteristics of the eastern Mediterranean deep-sea ecosystem might be related to the eastern Mediterranean Transient (EMT) and climate change. Their consideration of climatic forcing that might induce changes in the structure and function of the ecosystem was limited to El Niño Southern Oscillation (ENSO) events only. However, wintertime variability in the Mediterranean Sea is also strongly related to two other major climatic oscillations, the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). Furthermore, during the summer, teleconnections have been observed with the Indian monsoon. The strengthening of the NAO from the late 1980s to the 1990s has been linked to the influx of fresh water into the eastern Mediterranean basin, as well as to the appearance of the EMT. The formation of deep water in the Aegean Sea during the EMT event might also have been related to fluctuations in the AO, because positive anomalies appear to co-occur with the strengthening of the northerly winds over the Aegean Sea. Changes in the salinity of the Modified Atlantic Water (MAW), observed in 1990 at the Strait of Sicily, could also be related to the NAO , and could be an important factor in altering the salt budget for the eastern Mediterranean Sea. Changes in the thermohaline in the eastern Mediterranean have been simulated in a recent model that provides a better understanding of the deep-water renewal in the eastern Mediterranean Sea and potentially links climatic oscillations to changes in ecosystem processes. There is a need for a better understanding of the role that nutrient dynamics and new production might play in the deep-sea ecosystem processes of the eastern Mediterranean Sea . Hence, consideration must also be given to the climatic variability associated with the NAO and AO. With regards to the ecology of the eastern Mediterranean Sea, the community structure of free-living bacteria in the Aegean Sea (referred to as operational taxonomic units), suggests the presence of a distinct deep-water, compositionally complex, free-living (and to a lesser extent attached) bacterial community in the absence of temperature as a potential regulating factor. Recently, bacteria¯phytoplankton coupling in the eastern Mediterranean Sea has been related to changes therein of the trends of bacterial and phytoplankton production. How can these changes be related to biogeochemical cycles and climatic variability? A longer time series of data is needed if we expect to draw robust statistical inferences linking the ongoing decadal variability that characterizes climatic oscillations, such as the NAO and the AO, to the ecosystem dynamics in the eastern Mediterranean deep-sea, the Mediterranean basin and the adjacent North Atlantic.