Using carbon and nitrogen stable isotope analysis, our research aims to determine how food webs in shallow headwater lakes contribute energy to downstream communities. During spring and summer of 2008/2009 organisms (primary producers to secondary consumers) were collected from 3 lakes and their outflow streams in New Brunswick, Canada. Data were analysed using a one isotope, two-source mixing model to determine contributions of nutrient sources and graphically represented in δ13Cvs.δ15N bi-plots. Lake data indicate the diet of adult cyprinid and salmonid fishes (δ13C=-27.23, -25.04) was predominantly littoral algae-grazing invertebrates (δ13C=-27.71). In comparison, isotopic values of juvenile conspecifics (δ13C=-32.33) suggested a food source based on pelagic algae (δ13C =-34.48) during spring when phytoplankton was abundant. By summer, juvenile fishes showed a dietary shift (δ13C =-29.87) suggestive of a littoral food source. Simuliid larva isotope values (δ13C=-32.77) indicated a downstream lacustrine influence when compared with autochthonous carbon sources (δ13C=-27.42) at 0.5km from the lake. In 2009, we focused our efforts farther downstream (up to 3km) to determine reach of lacustrine influence. These results, along with other spatial comparisons, will be presented.
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Title:Developing a predictive model for brook trout (Salvelinus fontinalis) production in New Brunswick streams
Primary Author:
Murray Somers (Student)
Canadian Rivers Institute / University of New Brunswick
Murray Somers (Student)