icolls - Sustainable Tourism CRC

ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS
Woolgoolga Jerusalem Ainsworth Taylor's Belongil Tallows
Favonigobius
lateralis
Gerres
subfasciatus
Platycephalus
fuscus
Sillago ciliata
Mugil cephalus
Acanthopagrus
australis
Other Verts
Larus
novaehollandiae
Isotopic Analyses
Sillago ciliata Achlyopa nigra
Mugil cephalus
Bufo marinus
Larus
novaehollandiae
Platycephalus
fuscus
Hypseleotris
galii
Philypnodon
grandiceps
Anguilla
anguilla
Pelates
sexlineatus
Gerres
subfasciatus
Arothron
manilensis
Acanthopagrus
australis
Sillago ciliata
Pelates
sexlineatus
Mugil cephalus
Sillago ciliata
Acanthopagrus
australis
Achlyopa nigra
In all sites, isotopic discrimination between major principal carbon sources (namely riparian vegetation including
mangroves, marine algae, filamentous green algae and BFPOM/seston) facilitated analyses of food web structure
and consumer reliance on terrestrial, within-system and/or marine carbon subsidies. Wherever possible, replicate
samples were pooled to attain mean (± S.E.) δ13C and δ 15 N isotope signatures. This approach enables a more
rigorous examination of food web structure and function by facilitating greater understanding of isotopic
variability within sites.
There was considerable variability in carbon isotope signatures for some primary carbon sources among
ICOLLs (Table 3). For example, the δ 13 C signatures of periphyton ranged from 18.98‰ in a site from Belongil
Creek to 28.67‰ in a site in Lake Woolgoolga (Table 3). Despite this variability in algal carbon signatures, the
δ 13 C signatures of riparian vegetation (including mangroves) were generally consistent both within and among
sites (Table 3), ensuring a constant terrestrial end-member in the mixing model analyses.
There was a very large range in δ 15 N isotope signatures of primary carbon sources (and consumers) among
the study ICOLLs (Table 4). All components of the food web were heavily 15 N-enriched in Tallows Creek
(relative to other ICOLLs sampled). For example, whiting (Sillago ciliata) isotopic signatures were typically
around 30‰ in Tallows Creek, yet they rarely rose above 12‰ in the other ICOLLs from which they were
collected. A more detailed appraisal of why Tallows Creek δ 15 N signatures are enriched and the implications of
this enrichment are presented in Chapter 3 of this report.
Table 3: Mean and S.E. δ13C values for all food web components sampled from all study ICOLLs.
(Site Codes are as follows: WOO = Lake Woolgoolga, JER = Jerusalem Creek, AINS = Lake Ainsworth, TALL = Tallows
Creek, BEL = Belongil Creek and TAY = Taylors Lagoon).
WOO 1 WOO 2 WOO 3 JER 1 JER 2 AINS 1 TALL 1 TALL 2 TALL 3 BEL 1 BEL 2 BEL 3 TAY 1
Sample δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e. δ 13 C s.e.
BFPOM -26.03 0.00 -27.23 0.00 -18.40 0.00 -27.97 0.00 -22.87 0.00 -27.32 0.00 -22.32 0.00 -24.09 0.00 -26.86 0.00 -27.93 0.00 -27.51 0.00 -27.20 0.00
BCPOM -27.46 0.00 -29.10 0.00 -28.28 0.00 -29.22 0.00 -22.49 0.00 -27.32 0.00 -28.18 0.00 -29.60 0.00 -28.36 0.00 -27.44 0.00 -30.08 0.00 -28.90 0.00 -27.46 0.00
Periphyton -20.20 0.00 -21.80 0.40 -28.67 0.00 -27.83 0.00 -24.20 0.70 -23.60 1.90 -22.10 0.58 -18.98 1.76 -25.57 0.00 -25.70 0.00
Epilithon -21.63 0.00 -20.74 0.00 -22.70 0.00 -24.48 0.00
Epiphytes -18.89 0.00
Floating Algae -27.02 0.00
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