Guest post by David Middleton
“Part of NASA’s mission is pioneering scientific discovery, and this is like finding the Amazon rainforest in the middle of the Mojave Desert,” said Paula Bontempi, NASA’s ocean biology and biogeochemistry program manager in Washington.
Or maybe it’s more like finding a lot of trees in a part of the Amazon rainforest where you never bothered to look for trees before. Sub-ice phytoplankton blooms are not exactly “unprecedented.”
Dense sub-ice bloom of dinoflagellates in the Baltic Sea, potentially limited by high pH
Finnish Environment Institute, PO Box 140, 00251 Helsinki, Finland
Tvärminne Zoological Station, University of Helsinki, 10900 Hanko, Finland
Received February 27, 2007.
Accepted June 27, 2007.
Final version accepted August 15, 2007
The phytoplankton community, carbon assimilation, chlorophyll a (Chl a), pH, light and attenuation and inorganic nutrients were monitored under the ice in the coastal Gulf of Finland, Baltic Sea. Maximum ice and snow thickness was 40 and 15 cm, respectively. Freshwater influence had created a halocline 1–2 m below the ice–water interface, and above this halocline, a dense bloom of dinoflagellates developed (max: >300 μg Chl a L−1). The photosynthetic uptake of carbon dioxide by this “red tide” increased the pH to a maximum of 9.0. The sub-ice phytoplankton community was dominated by the dinoflagellate Woloszynskia halophila (max: 3.6 × 107 cells L−1). The pH tolerance of this species was studied in a monoculture and the results indicate that pH >8.5 limits growth of this species at ambient irradiance. This study shows that primary productivity may raise the pH to growth limiting levels, even in marine, low-light environments where pH normally is not considered important.
The Baltic Sea is a semi-enclosed, brackish ocean where ice is an important element of the ecosystem during winter. In the northern part of Baltic Sea and western part of Gulf of Finland, the probability of freezing is >90% and ice coverage normally lasts for 2–6 months (Mälkki and Tamsalu, 1985). There have been observations of dense, dinoflagellate dominated blooms under the ice in the Baltic Sea, but there is relatively little information about this phenomenon (Larsen et al., 1995; Haecky et al., 1998; Kremp and Heiskanen, 1999). These types of blooms are often called red tides because of the obvious discoloration of the water, but a cold-water red tide is very much in contrast to the main distribution and bloom patterns of dinoflagellates, which typically avoid winter and spring in temperate areas (Smayda and Reynolds, 2001).
For an even earlier discussion of phytoplankton blooms under Arctic pack ice, see Gradinger, 1996.
Maybe NASA should stick to Aeronautics and Space.