CRERAN MICROPLANKTON 1979-81 AND 2010-12

The phytoplankton ecology of Loch Creran, a Scottish fjord, has been studied since 1970. For this report, water samples taken from the Loch in 1979-1981 and 2010-2012 were analysed to depict changes in the annual cycles and periodic succession of groups of microplankton. For the most part, the
data in this report refer to larger groupings of organisms than single species. This is for practical reasons as well as the recent ecological theory that functional rather than species-level biodiversity is vital to ecosystem health.
The results indicate that there have been declines or delays in some spring-blooming phytoplankters (especially Skeletonema) but not in the summer-blooming groups. The graphs for Thalassiosira and former Nitschia suggested that the changes in their abundances during spring were counterbalanced in au-
tumn. Overall increased abundances were seen in the groups of medium-sized autotrophic dinoflagellates, heterotrophic dinoflagellates and ciliates. Katodinium and cryptomonads seemed to show increased abundances during the summer that were offset by declines during the start and the end of the year.
One hypothesis for these changes posits an increase of opaque matter in the seawater since 1980s, reducing the amount of light available for photosynthesis.