Wed, May 1, 2019 11:00 AM - 12:00 PM AQUATIC ECOSYSTEMS RESEARCH LABORATORY (AERL). Location: AERL 107/8
Human activities can elevate nutrient levels in coastal waters. Nitrogen loading is of particular concern as it can lead to algal blooms, oxygen depletion, and other indicators of eutrophication. Monitoring aquaculture effluents has therefore developed into an intense area of research as these operations can release considerable amounts of nitrogen and other wastes into the surrounding water. However, most water bodies also receive effluents from other sources such as agriculture and waste water treatment. Hence, there are calls for coastal management to move towards an ‘ecosystem approach to aquaculture’, where the effects of multiple fish farms and other human activities are simultaneously considered at the wider scale.
Monitoring effluents with seaweed ‘bioindicators’ has become a popular way of assessing water quality. This is because seaweeds rapidly absorb and accumulate nutrients within their tissues, meaning their elemental composition (N and C) can better reflect long-term nutrient levels compared to more traditional measures of water chemistry. Furthermore, there is potential that their isotopic composition ( 15N) can distinguish between multiple effluent sources. To test this concept, we translocated several species of seaweed across a bay in Nova Scotia, location to a salmon farm and several other industrial activities. Overall, we found that seaweeds can indeed distinguish and map the footprints of multiple effluent sources but that the results need to be interpreted with caution. Our findings therefore suggest that seaweed bioindicators could play an important role in applying the ecosystem approach to aquaculture.
Speaker: Dr. Leigh Howarth
Post-doctoral Fellow, Dalhousie University