Macroecology of Calanus finmarchicus and C. helgolandicus in the North Atlantic Ocean and adjacent seas

Abstract

Global climate change is expected to modify the spatial distribution of marine organisms. However, projections of future changes should be based on robust information on the ecological niche of species. This paper presents a macroecological study of the environmental tolerance and ecological niche (sensu Hutchinson 1957, i.e. the field of tolerance of a species to the principal factors of its environment) of Calanus finmarchicus and C. helgolandicus in the North Atlantic Ocean and adjacent seas. Biological data were collected by the Continuous Plankton Recorder (CPR) Survey, which samples plankton in the North Atlantic and adjacent seas at a standard depth of 7 m. Eleven parameters were chosen including bathymetry, temperature, salinity, nutrients, mixed-layer depth and an index of turbulence compiled from wind data and chlorophyll a concentrations (used herein as an index of available food). The environmental window and the optimum level were determined for both species and for each abiotic factor and chlorophyll concentration. The most important parameters that influenced abundance and spatial distribution were temperature and its correlates such as oxygen and nutrients. Bathymetry and other water-column-related parameters also played an important role. The ecological niche of C. finmarchicus was larger than that of C. helgolandicus and both niches were significantly separated. Our results have important implications in the context of global climate change. As temperature (and to some extent stratification) is predicted to continue to rise in the North Atlantic sector, changes in the spatial distribution of these 2 Calanus species can be expected. Application of this approach to the 1980s North Sea regime shift provides evidence that changes in sea temperature alone could have triggered the substantial and rapid changes identified in the dynamic regimes of these ecosystems. C. finmarchicus appears to be a good indicator of the Atlantic Polar Biome (mainly the Atlantic Subarctic and Arctic provinces) while C. helgolandicus is an indicator of more temperate waters (Atlantic Westerly Winds Biome) in regions characterised by more pronounced spatial changes in bathymetry.

Update on the relationship between the North Atlantic Oscillation and Calanus finmarchicus

“…For instance, the population of C. finmarchicus in the northeast Atlantic may have been pushed in one direction by long-term trends in local production that are related to temperature. C. finmarchicus is typically found in lower temperatures and is considered an indicator of the Artic Polar Biome (Helaouet & Beaugrand 2007). C. finmarchicus growth and development are coupled to temperature (Sundby 2000, Campbell et al 2001; therefore, a long-term increasing trend in temperature may explain the long-term decline in C. finmarchicus populations.…”

The North Atlantic Spring-Bloom System—Where the Changing Climate Meets the Winter Dark

“…However, the habitats of C. helgolandicus and C. finmarchicus are to a certain extent overlapping, particularly in the eastern part of the distribution. For example, in the North Sea the two species co-occur (Helaouët and Beaugrand, 2007) with C. finmarchicus dominating in the north and C. helgolandicus in the south, but with overlapping distributions in the thermal range 9-11 • C (Hinder et al, 2014). During the recent warming, i.e., after the 1980s, there has even been observed adults (copepodite stage V) of C. helgolandicus as far north as the in coastal water masses of the southwestern Barents Sea (Dalpadado et al, 2012).…”

Contrasting transcriptome response to thermal stress in two key zooplankton species, Calanus finmarchicus and C. glacialis

“…A striking consequence of climate change is the range expansion of warmwater plankton assemblages in the northeast At lantic, and the corresponding range contraction of coldwater species (Beaugrand et al 2002(Beaugrand et al , 2009). The increase in water temperature and different thermal tolerances of copepods appear to be the major drivers of such shifts in zooplankton communities (Beaugrand et al 2002, Helaouët & Beaugrand 2007.…”