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Scientists studying the same body of water every week for four years in Nova Scotia have discovered how changes in weather and climate can affect a key microbiological process linked to algae blooms and the health of coastal ecosystems.

PhD students from three research groups in Dalhousie University’s Biology and Oceanography departments joined forces to examine data collected from 2014 to 2017 in the Bedford Basin. The team was studying nitrification -- a key process in the marine nitrogen cycle in which microbes turn ammonium into nitrite and nitrate -- and found that it was influenced by weather and climate. Nitrogen is an important nutrient for algae and a lack of it could deplete the food chain and too much of it can lead to algae blooms.

The researchers discovered that in years with colder winters, the process of nitrification was delayed in the summer because a large share of the microbes responsible for nitrification had been flushed out of the basin by water movement or ‘mixing.’ This water mixing is caused mostly by cold winter temperatures, which cool the surface water of the basin and make it sink.

The team found that the flushing causes notable variations from year to year in the transformation of nitrogen. This sort of process and the influence of weather and climate on microbial growth had not been seen clearly before, solving a mystery that had persisted for years. The findings imply that measuring and modelling of microbial communities are needed to predict the impacts of climate change on coastal ecosystems.

The team’s findings are being published today in the prestigious journal, Proceedings of the National Academy of Sciences.

The researchers used weekly time-series measurements, which have been maintained in the basin by the Bedford Institute of Oceanography since 1992. Dalhousie researchers have used this "scientific infrastructure" to do measurements over the past seven years, taking advantage of the semi-enclosed, accessible nature of the basin which make it an optimal ‘natural laboratory.’

Lead author Sebastian Haas, a PhD candidate in the Oceanography Department, is available to discuss the findings and how our knowledge of this phenomenon could apply to places beyond the Bedford Basin since the same conditions exist in many marine ecosystems.

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Media contact:
Alison Auld
Senior Research Reporter
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca