IMPACT OF SALINIZATION RATE ON ZOOPLANKTON COMMUNITY DIVERSITY AT TWO LAKES IN SWEDEN

The increasing salinization of freshwater systems is threatening planktonic communities around the globe. However, little is known about how the rate of salinization exposure impacts the response of plankton communities to chloride. Zooplankton can experience ecological and evolutionary rescue when exposed to stress but responses may differ under gradual or abrupt exposure to a toxicant. Further, responses to salinization may be vary across habitats. To assess how differing rates of salinization impact zooplankton community dynamics, and how the responses differ between lakes, we employed in-lake mesocosm experiments at two oligotrophic lakes in northern and southern Sweden. Planktonic communities were exposed to 500 mg Cl-/L in a single dose or at a gradual rate over 22 days. Zooplankton were sampled every 6 days for 36 days by filtering 7-10L of water through 50-um mesh. We found a strong negative effect of salt on zooplankton communities but did not observe an effect of salinization rate. At both sites, total abundance and abundance of taxa decreased in salt treatments relative to controls, but there was no difference between abrupt and gradual treatments. We observed similar results for taxa richness except that at the northern site richness in abrupt treatments was lower than in the gradual treatment. A difference in the dominant species was observed between the gradual and abrupt mesocosms. These findings suggest that local community composition may be more important in determining community response to stress than rate of exposure.

Primary Presenter: Erin Ford, Queen's University (erin.sydney.f@gmail.com)

Authors:

Erin Ford, Queen's University  (ford.e@queensu.ca)

Zorka Dulić, University of Belgrade  (sundjerbaby@gmail.com)

Shelley Arnott, Queen's Univeristy  (arnotts@queensu.ca)

Ingrid Sassenhagen, Uppsala University  (ingrid.sassenhagen@io-warnemuende.de)

Jana Isanta-Navarro, University of Copenhagen  (jana.isanta-navarro@bio.ku.dk)

Jose Luis Rodriguez Gill, IISD - Experimental Lakes Area  (jlrodriguez@iisd-ela.org)

Pablo Urrutia Cordero, Lund University  (pablo.urrutia@imdea.org)

Silke Langenheder, Uppsala University  (silke.langenheder@ebc.uu.se)