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Flashcards in Aquatic Ecology final Deck (324)
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91

reconstruct historic salmon runs with ∂15N

sedimentary ∂15N correlated to number of spawners
250,000spawners ~ 6‰
1mill spawners ~ 8.5‰

92

∂15N sediment signature change in 1900

dramatically drops off, commercial fishing

93

significantly different ∂15N signatures along the river

higher ∂15N signature in root feeders, omnivores, detritivores, predators.. BELOW falls (input of high ∂15N source, salmon)

94

Class 1 lake

lack preferred lake trout prey, pelagic forage fish, causing lake trout to feed on zooplankton and zoobenthos

95

class 2 lake

contain at least one species of pelagic forage fish, resulting in piscivory

96

class 3 lake

pelagic forage fish and glacis-marine relict invertebrate predator Myis relicta - elevates lake trout to fifth trophic level

97

measuring trophic level by ∂15N ratio

gut contents
digestibility highly variable
assumptions made

98

pelagic

Any water in a sea or lake that is neither close to the bottom nor near the shore

99

pelagic zooplankton signatures

variable! needs to be established as a baseline
study found differences in calanoid copepods, Daphnia, Holopedium

100

lake to lake isotope signatures

highly variable depending on inputs (human, animal, fertilizer, salmon)

101

PCB (ng/g wet mass) vs trophic position

liner increasing
class 1 at low end
class 2 in middle
class 3 at top end (most trophic positions)
appears to be due to increased % lipid with increased trophic level

102

PCBs and lipids

lipophilic contaminants, accumulate in fat (lipophilicity)
unnatural, remain in bodies

103

∂15N trophic position vs. dietary trophic position

highly correlated = N good measure of trophic position

104

Hg (µg/g) vs. Lake class

higher in higher class
higher if smelt present in each individual class

105

∂15N vs ∂13C, Arctic Lake System, Lake Trout

LT top predator - highest ∂15N, ~middle of ∂13C spread- consumes pelagic and littoral fish

106

Log Hg (µg/g wet weight) vs. ∂13C

decreasing
terrestrial source has lower level of Hg
if LT feed more on nearshore/benthic than offshore/pelagic they will have lower Hg

107

Hg consumption guideline

0.5µg/g
one meal per week (non pregnant adults)

108

[Hg] (µg/g) vs. ∂15N (‰) in Ontario, Quebec lakes

all Class 2 and 3 fish are above consumption guideline level of Hg
sport fishing species, widely consumed

109

US Hg blood levels

300,000-600,000 children/yr cord blood Hg level > 5.8µg/L, a level associated with loss of IQ

110

cost of methyl mercury toxicity

lost productivity (lower IQ) $8.7bill/yr

111

Daphnia spp. ∂15N (‰) vs levels of land-use (low, high)

low land use (Sooke lake) - 0-5‰
high land use (Shawnigan lake) - 6-13‰

112

Sooke lake

our drinking water
fully protected

113

Shawnigan lake

developed
lots of septic
highly enriched in ∂15N

114

Caffeine (ng/L) vs. ∂15N in Mussel Tissue

linear positive
caffeine from septic contamination
robust indicator of fecal contamination

115

Caffeine (ng/L) vs. Shoreline Development (lots/km^2), Shawnigan lake

linear positive
denser housing = more septic = fecal input = more caffeine

116

∂15N (‰) vs. year, Sooke Lake and Shawnigan lake sediment cores

Shawn. has increased from ~1-3 as a result of human development
Sooke- has some spikes from building new dams/raising the dam- inundating land

117

EBS

Eastern Bering Sea

118

EBS 2002-2005

large-scale warming event
followed by 2yrs cooling event (2006-07)

119

EBS sampling

zooplankton from 186 stations each year
13,000 fish
600 zooplankton

120

change in abundance of juvenile salmon and forage fish

increase in warm years
decrease in cold years
in salmon, juveniles, forage fish