Macroinvertebrate Resource Utilisation in Upland Streams: Riparian Management Impacts
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Transcript of Macroinvertebrate Resource Utilisation in Upland Streams: Riparian Management Impacts
Macroinvertebrate Resource Utilisation in Upland Streams:
Riparian Management Impacts
Irish Freshwater Biologists Meeting 2012
C. Barry & Y. McElarney
Agri-Environment Branch
Newforge Lane, Belfast
Riparian Management Impacts
RCC – interpretative paradigm for resource utilisation / carbon flow in river food webs
High terrestrial inputsLow nutrient inputsLow PP low P:R
Increasing light and nutrientsgreater PP
P:R increasing
High light & nutrients& C inputs from upstream processing P:R decreasing
But,
● Variation of riparian vegetation at low stream orders
– alters resource availability and quality
● Resource utilisation by functional feeding group
-feeding mechanisms to determine resource
use
-opportunism and generalist feeding
frequent
●To eat is to assimilate?
How to assess macroinvertebrate resource utilisation?
Natural abundance Carbon and Nitrogen Stable Isotope Analysis 13C:12C 15N:14N
Consumer isotopic ratios reflect the isotopic ratios of their diet in a consistent way
► You are what you eat, less what you excrete
Fractionation: stuff happens to lighter isotopes more readily
●Physical: evaporation ●Chemical: respiration
Grass
SeagrassRabbit
Fox
Geese
0
2
4
6
8
10
12
-30 -28 -26 -24 -22 -20 -18 -16
Carbon isotopic signature
(d13C)
Nitr
og
en is
oto
pic
sig
nat
ure
(d15
N)
Ratios unwieldy; reported as signatures-
deviation from standards (δ13C, δ15N)
Measure stable isotope signatures for
● Macroinvertebrates
● Potential dietary sources
Some consumers use several different resources…. Mixing models
SIAR in R … Bayesian mixing model
Methods
No Buffer (n=6)
Natural Upland catchments (n=5)
Unplanted Buffer (n=4)
Broadleaved Buffer (n=4)
Recently Harvested (n=6)
Quantitative estimates of biomass and C & N isotopic analysis for
●macroinvertebrates ●biofilm ●biofilm chl a ●macrophytes ●macroalgae
●benthic organic matter ●riparian vegetation ●seston ●Light penetration
Physico-chemistry sampled seasonally on 3 occasions
25 streams sampled once in summer (50m reach)
Methods: deriving macroinvertebrate dietary reliance
Seratella ignita
Simulium
Baetis rhodani
Ecdyonurus insignis
Elmis aenea
Gammarus duebeni celticus
Leuctra fusca
River conditioned detritus
Scapania undulata
Seston
Biofilm
Ulothrix tenuissima
-3
-2
-1
0
1
2
3
4
-34 -33 -32 -31 -30 -29 -28 -27 -26
δ13C (‰)
δ15N (‰)
Stream with an unplanted riparian buffer
5 potential resources / end members
Resource: River conditioned detritus
1. Baetis 2. Ecdyonurus 3. Elmis 4. Simulium 5. Leuctra 6. Gammarus 7. Seratella
0.0
0.2
0.6
0.8
1.0
0.4
Die
tary
rel
ianc
e (%
)Methods: deriving macroinvertebrate dietary reliance
1. Baetis 2. Ecdyonurus 3. Elmis 4. Simulium 5. Leuctra 6. Gammarus 7. Seratella
0.0
0.2
0.6
0.8
1.0
0.4
Resource: Biofilm
Die
tary
rel
ianc
e (%
)Methods: deriving macroinvertebrate dietary reliance
1. Baetis 2. Ecdyonurus 3. Elmis 4. Simulium 5. Leuctra 6. Gammarus 7. Seratella
0.0
0.2
0.6
0.8
1.0
0.4
Resource: Ulothrix tenuissima(filamentous green alga)
Die
tary
rel
ianc
e (%
)Methods: deriving macroinvertebrate dietary reliance
1. Baetis 2. Ecdyonurus 3. Elmis 4. Simulium 5. Leuctra 6. Gammarus 7. Seratella
0.0
0.2
0.6
0.8
1.0
0.4
Resource: Seston(suspended fine particulate organic matter)
Die
tary
rel
ianc
e (%
)Methods: deriving macroinvertebrate dietary reliance
1. Baetis 2. Ecdyonurus 3. Elmis 4. Simulium 5. Leuctra 6. Gammarus 7. Seratella
0.0
0.2
0.6
0.8
1.0
0.4
Resource: Scapania undulata
(bryophyte)
Die
tary
rel
ianc
e (%
)Methods: deriving macroinvertebrate dietary reliance
Allochthonous
(Terrestrial)%
Autochthonous
(in situ PP) %
Total Invertebrate mass
mg m-2
Allochthonous mass
mg m-2
Autochthonous mass mg m-2
Baetis 15 85 174 26 148
Simulium 61 39 35 21 14
Ecdyonurus 10 90 180 18 162
Elmis 20 80 3 1 2
Gammarus 83 16 342 283 55
Leuctra 89 11 38 34 4
Seratella 47 53 91 43 48
Plectrocnemia 69 31 57 39 18
Total mg m-2465 450
Terrestrial vs. Aquatic
Functional feeding groups
Predator
Shredder
Collector
Grazer/Scraper
C & N stable isotope analysis
Allochthonous
Autochthonous
Methods: Apportioning macroinvertebrate biomass
0
100
200
300
400
500
600
700
800
900
CE
185
CE
0
CE
148
OB
13
CE
133
CM
14
CF
4
CM
15
CE
56
CM
6
CM
1
B20
8
CF
8
CF
2
CF
3
CF
5
B20
9
OB
41
B12
6
CM
2
CE
44
OB
74
CF
6
OB
0
B20
7
Inve
rteb
rate
Bio
mas
s (m
g m
2 Dw
t.)
Autochthonous AllochthonousA
CE = No buffer: Conifers to stream edge OB = Open buffer (unplanted)
CF = Clear felled B = broadleaved buffer CM = Natural upland (control)
Macroinvertebrate Biomass Apportionment by site
Un-skewed distributions
- consumers exploiting a wide variety of resources
- greater niche availability / utilisation
► Clear felled sites, Natural upland sites (control), no buffer sites*
Skewed distributions
-consumers exploiting resources of similar origin
-Suggests high abundance of such resources and/or resources of the same origin present in different forms…. FPOM, CPOM
► Broadleaved buffer & Open buffer sites
Caveat
*Depleted consumer δ13C indicative of methane C
►while terrestrial in origin, the approach regards consumers as utilising an autochthonous resource
100% terrestrial 100% aquatic
Consumer frequency distributions of reliance on terrestrial C
Species Specific Resource utilisation
Sh = shredder Co = Collector Gr = Grazer
0.0
0.2
0.4
0.6
0.8
1.0
Mea
n p
rop
ort
ion
al d
evia
tio
n f
rom
ter
rest
rial
die
t
n = 25 n = 7 n = 2 n = 4n = 4n = 18 n = 20n = 4n = 13n = 13n = 14n = 23n = 23 n = 3 n = 1
Sh Co GrCoGr ShShShSh GrGrCo CoCo Co
Error bars = 1SD
Conclusions
• Light reduction, slope & organic biofilm mass most important variables driving resource utilisation among sites
• Biomass and species richness greater at buffered compared to un-buffered sites
• Invertebrate community structure and resource use at buffered sites show little similarity to unimpacted control sites
• Broadleaved buffer sites show high invertebrate biomass but a community largely specialised for an allochthonous diet
Acknowledgements
AFBI Staff
Lesley Gregg, Rachel Patterson, Alex Higgins
Colm McKenna, Kirsty McConnell,
Louise Davis, Elaine Hamill,
Phil Dinsmore, Brian Stewart
Forest Service, NI
Ian Irwin, Colin Riley
EPA (Strive) for part funding study (project 2007-W-MS-3-S10):
An Effective Framework For assessing aquatic ECosysTem responses to implementation of the Phosphorus Regulations (EFFECT)
Department of Agriculture and Rural Development (DARD) for remainder of project funding.
Results: Isotopic overview
0
10
20
30
40
50
60
-10 -5 0 5 10 15 20
Car
bo
n:N
itro
gen
(m
ola
r)
Coniferous
Deciduous
Grasses
River conditioneddetritusMacro-algae
Bryophyta
Biofilm
Macro-Invertebrates
δ15N (‰)
0
10
20
30
40
50
60
-50 -45 -40 -35 -30 -25
Car
bo
n:N
itro
gen
(m
ola
r)
Coniferous
Deciduous
Bryophyta
Grasses
River conditioned detritus
Macro-algae
Biofilm
Macro-Invertebrates
δ13C (‰)