Abstract
Abstract. In this study we present a comparative quantification of CaCO3 production rates by rhodolith-forming coralline red algal communities situated in high polar latitudes and assess which environmental parameters control these production rates. The present rhodoliths act as ecosystem engineers, and their carbonate skeletons provide an important ecological niche to a variety of benthic organisms. The settings are distributed along the coasts of the Svalbard archipelago, being Floskjeret (78°18' N) in Isfjorden, Krossfjorden (79°08' N) at the eastern coast of Haakon VII Land, Mosselbukta (79°53' N) at the eastern coast of Mosselhalvøya, and Nordkappbukta (80°31' N) at the northern coast of Nordaustlandet. All sites feature Arctic climate and strong seasonality. The algal CaCO3 production rates were calculated from fuchsine-stained, presumably annual growth increments exhibited by the rhodoliths and range from 100.9 g (CaCO3) m−2 yr−1 at Nordkappbukta to 200.3 g (CaCO3) m−2 yr−1 at Floskjeret. The rates correlate to various environmental parameters with geographical latitude being the most significant (negative correlation, R2 = 0.95, p = 0.0070), followed by the duration of the polar night (negative correlation, R2 = 0.93, p = 0.0220), the duration of the sea ice cover (negative correlation, R2 = 0.87, p = 0.0657), and the annual mean temperature (positive correlation, R2 = 0.48, p = 0.0301). This points out sufficient light incidence to be the main control of the growth of the examined coralline red algal rhodolith communities, while temperature is less important. Thus, the ongoing global change with its rising temperatures will most likely result in impaired conditions for the algae, because the concomitant increased global runoff will decrease water transparency and hence light incidence at the four offshore sites. Regarding the aforementioned role of the rhodoliths as ecosystem engineers, the impact on the associated organisms will presumably also be negative.
Highlights
Coralline red algae are the most consistently and heavily calcified group of the red algae, and as such have been elevated to ordinal status (Corallinales Silva and Johansen, 1986)
Rhodoliths and coralline red algae are known as important CaCO3 producers from tropical (Chisholm, 2000) over temperate (Martin et al, 2006) to subpolar environments (Freiwald and Henrich, 1994) and can act as ecosystem engineers sensu Jones et al (1994): they form microhabitats by their own skeletal growth
One sample from Nordkappbukta (714) was collected in significantly shallower waters in order to check the influence of water depth on the CaCO3 production rates
Summary
Coralline red algae are the most consistently and heavily calcified group of the red algae, and as such have been elevated to ordinal status (Corallinales Silva and Johansen, 1986) Their calcification process involves high magnesium calcite precipitation within the cell walls (Kamenos et al, 2009). Rhodoliths and coralline red algae are known as important CaCO3 producers from tropical (Chisholm, 2000) over temperate (Martin et al, 2006) to subpolar environments (Freiwald and Henrich, 1994) and can act as ecosystem engineers sensu Jones et al (1994): they form microhabitats by their own skeletal growth. A variety of methods have been applied to calculate coralline red algal growth rates and CaCO3 production rates, such as in situ growth experiments on living thalli (Adey and McKibbin, 1970; Payri, 1997; Steller et al, 2007), counting of presumed annual growth increments in Published by Copernicus Publications on behalf of the European Geosciences Union
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