Marine biodiversity and climate change: assessing and predicting the influence of climatic change using intertidal rocky shore biota. Occasional Publication of the Marine Biological Association 20

In the last 60 years climate change has altered the distribution and abundance of many seashore species. Below is a summary of the findings of this project. The MarClim project was a four year multi-partner funded project created to investigate the effects of climatic warming on marine biodiversity. In particular the project aimed to use intertidal species, whose abundances had been shown to fluctuate with changes in climatic conditions, as indicator species of likely responses of species not only on rocky shores, but also those found offshore. The project used historic time series data, from in some cases the 1950s onwards, and contemporary data collected as part of the MarClim project (2001-2005), to provide evidence of changes in the abundance, range and population structure of intertidal species and relate these changes to recent rapid climatic warming. In particular quantitative counts of barnacles, limpets and trochids were made as well as semi-quantitative surveys of up to 56 intertidal taxa.Historic and contemporary data informed experiments to understand the mechanisms behind these changes and models to predict future species ranges and abundances.

North Atlantic climatic signals and the plankton of the European Continental Shelf

Climatic variability on the European Continental Shelf is dominated by events over the North Atlantic Ocean, and in particular by the North Atlantic Oscillation (NAO). The NAO is essentially a winter phenomenon, and its effects will be felt most strongly by populations for which winter conditions are critical. One example is the copepod Calanus finmarchicus, whose northern North Sea populations overwinter at depth in the North Atlantic. Its annual abundance in this region is strongly dependent on water transports at the end of the winter, and hence on the NAO index. Variations in the NAO give rise to changes in the circulation of the North Atlantic Ocean, with additional perturbations arising from El Ni (n) over tildeo - Southern Oscillation (ENSO) events in the Pacific, and these changes can be delayed by several years because of the adjustment time of the ocean circulation. One measure of the circulation is the latitude of the north wall of the Gulf Stream (GSNW index). Interannual variations in the plankton of the Shelf Seas show strong correlations with the fluctuations of the GSNW index, which are the result of Atlantic-wide atmospheric processes. These associations imply that the interannual variations are climatically induced rather than due to natural fluctuations of the marine ecosystem, and that the zooplankton populations have not been significantly affected by anthropogenic processes such as nutrient enrichment or fishing pressure. While the GSNW index represents a response to atmospheric changes over two or more years, the zooplankton populations correlated with it have generation times of a few weeks. The simplest explanation for the associations between the zooplankton and the GSNW index is that the plankton are responding to weather patterns propagating downstream from the Gulf Stream system. It seems that these meteorological processes operate in the spring. Although it has been suggested that there was a regime shift in the North Sea in the late 1980s, examination of the time-series by the cumulative sum (CUSUM) technique shows that any changes in the zooplankton of the central and northern North Sea are consistent with the background climatic variability. The abundance of total copepods increased during this period but this change does not represent a dramatic change in ecosystem processes. It is possible some change may have occurred at the end of the time-series in the years 1997 and 1998.

Synchronous response of marine plankton ecosystems to climate in the Northeast Atlantic and the North Sea

Over the last few decades, global warming has accelerated both the rate and magnitude of changes observed in many functional units of the Earth System. In this context, plankton are sentinel organisms because they are sensitive to subtle levels of changes in temperature and might help in identifying the current effects of climate change on pelagic ecosystems. In this paper, we performed a comparative approach in two regions of the North Atlantic (i.e. the Northeast Atlantic and the North Sea) to explore the relationships between changes in marine plankton, the regional physico-chemical environment and large-scale hydro-climatic forcing using four key indices: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the East Atlantic (EA) pattern and Northern Hemisphere Temperature (NHT) anomalies. Our analyses suggest that long-term changes in the states of the two ecosystems were synchronous and correlated to the same large-scale hydro-climatic variables: NHT anomalies, the AMO and to a lesser extent the EA pattern. No significant correlation was found between long-term ecosystem modifications and the state of the NAO. Our results suggest that the effect of climate on these ecosystems has mainly occurred in both regions through the modulation of the thermal regime.