Transcript RECOLONIZATION OF AZOIC SEDIMENTS BY MEIOFAUNA IN THE HYDROPSAMMON

RECOLONIZATION OF AZOIC SEDIMENTS BY MEIOFAUNA IN THE HYDROPSAMMON
OF OTSEGO LAKE, NEW YORK
1
Cornwell
2
Horvath
Mark D.
& Thomas G.
State University New York, Technical College at Cobleskill1 College at Oneonta2
EPIBENTHIC & ENDOBENTHIC
6
Meiofauna are organisms that pass though a 500m mesh and are retained on a 63m mesh
and live between the grains of the littoral and sublittoral sediments. Freshwater psammolittoral
zones, sediments and their associated meiofauna communities have been classified as either
eupsammon (middle beach), hygropsammon (within 1 m above lake’s edge), and
hydropsammon (submerged) by Pennak (1940). These nearshore zones often experience
physical disturbances, such as wave actions, ice scouring, and lake-level fluctuations, which
can defaunate the sediments. The communities associated with these sediments must
recolonize after such disturbances. Little attention has been given to recolonization dynamics
involving freshwater meiofauna.
Invertebrates per sample (50 ml)
5
50
4
40
3
30
2
20
1
Aeolosoma sp.
Chironomidae
30
20
10
Col 1 vs Ambient
Col 1 vs Control
10
0
0
0
0
2
4
6
8
10
Cyclopoida
8
6
4
2
0
0
2
4
6
0
180
160
140
120
100
80
60
40
20
0
8
SUMMARY
40
60
Harpacticoida
ENDOBENTHIC
2
4
6
Col 1 vs Side
0
8
2
4
6
8
50
20
10
0
2
4
6
8
0
2
4
6
8
Ostracoda
Ambient
Control
20
Endobenthic
15
mesotrophic (12 µg TP/L, 0.8 mg Chl a/L).
inundated with water. Experimental
plot under 0.5m water.
0
150
100
50
0
0
2
4
0
2
4
6
8
2.0
1.5
1.0
6
8
Time in Weeks
Epibenthic
10
Otsego Lake: Deep (50 m max. depth), 1710 hectares,
200
2.5
30
25
5
250
40
35
Hydropsammon: Permanently
300
Oligochaeta
Tardigrada
0
30
Total inverts per sample (50 ml)
EPIBENTHIC
Shannon-Weiner index
INTRODUCTION
All error bars ± 1 standard error.
0
2
4
6
Shannon-Weiner Index based on data
accumulated through time.
8
Time in Weeks
MATERIALS & METHODS
We adapted methods from Palmer & Strayer (1996)
for recolonization of hyporheic invertebrates in lake
sediments.
1) 50-m-mesh panels, 50 ml tubes
2) Sediments defaunated by oven drying at 120C for 4 h
3) Azoic sediment packed into treatment tubes with organic
material intact (2% OM by wt)
4) Randomized block design (treatments randomly assigned),
blocked by time: 0, 1, 4, and 8 week
5) Each time block: 5 replicates for each treatment.
6) Four ambient core samples collected when time block
pulled
7) Sediment separated from organisms by elutriation through
63-m-mesh screen
CONCLUSIONS
Ambient
Epibenthic
Endobenthic
Ambient: Simple core sample
Epibenthic: Open top, closed sides
Endobenthic: Closed top, open sides
Control: Open top, open sides
Control
Colonization complete by week 1:
Invertebrate abundance in treatment and ambient samples not
significantly different
No significant difference among treatments
Harpacticoids and cyclopoids appear to colonize epibenthically:
higher abundance in epibenthic tubes
Oligochaetes and aeolosomatids appear to colonize endobenthically:
higher abundance in endobenthic tubes
Tardigrads, ostracods, and chironomids appear to colonize both
epibenthically and endobenthically:
no difference in colonization between treatments
Meiofauna community in the hydropsammon exhibits both stability
and resilience
Literature Cited
Palmer, M. A. & D. L. Strayer. 1996.
Meiofauna, in Hauer and Lamberti (eds),
Methods in Stream Ecology. Academic
Press.
Pennak, R. W. 1940. The ecology of the
microscopic metazoa. Ecol. Monogr.
10(4):5539-611.
Special thanks to the Biological
Field Station, Cooperstown NY