Seminar

If unabated, the continued anthropogenic release of carbon dioxide is expected to lead to warming
and acidification of ocean waters, with widespread and detrimental impacts on marine ecosystems.
Proxy records stored in biomineralized shells and skeletons of long-lived paleoclimate archives are
essential for understanding long-term climate variability – previously unresolvable due to spatially
and temporally limited instrumental observations in Arctic/Subarctic regions. In this talk, I will present
geochemical and physical proxies from Clathromorphum spp. crustose coralline algae used for
interpreting past climate and environmental changes in the Subarctic North Pacific and North
Atlantic Oceans.

Micro-computed tomography (micro-CT) techniques were used to determine changes in growth,
density, and calcification rates of crustose coralline algae collected from the Aleutian Islands, Alaska –
a region that has undergone a long-term decline of 0.08 ± 0.01 pH units since the late 19th century.
Results indicate that coralline algal skeletal densities have entered a steep and unprecedented
decline since 1980. The exact cause(s) for this decline are uncertain; however, correlations to regional
climate and warming sea surface temperatures indicate that in addition to acidification, sunlight
availability and temperature stress may also be factors that influence the ability of corallines to calcify.

Additionally, barium-to-calcium (Ba/Ca) trace element ratios from crustose coralline algae are utilized
as proxies for phytoplankton productivity related to sea-ice variability in northern Labrador, Canada
that extends well into the Little Ice Age (LIA; 1646 AD). Coralline algal Ba/Ca demonstrate significant
correlations to observational and proxy records of sea-ice variability, and show a persistent pattern of
covariability that is broadly consistent with the timing and phasing of the Atlantic Multidecadal
Oscillation (AMO). The results presented here illustrates the physiological response of coralline algae
to warming and acidification, and provides much needed data for future projections of climate
environmental change.