This document summarizes a study that compared the effects of the invasive plant species Lagarosiphon major and the native plant species Ceratophyllum demersum on dissolved oxygen levels, biodiversity, and biomass in simulated pond conditions over 12 weeks. The study found that L. major was least effective at producing oxygen, caused oxygen levels to fall below what is suitable for pond life, and had very low biodiversity. In contrast, C. demersum maintained good oxygen levels and higher biodiversity. Therefore, the study concludes that L. major should not be promoted as an oxygenator for ponds.

1. • Higher pond life
associated with
C. demersum
• L. major = V. low
biodiversity
O2 be, or not to be?
Should Lagarosiphon be promoted as an oxygenator?
Rhiann Mitchell-Holland, Nicola Morris & Peter McGregor
L. major (INNS):
O2 depletion & low biodiversity
• Simulated pond conditions containing
L. major, Ceratophyllum demersum
(200g) or no pond weeds
Measured (over 12 weeks):
• dissolved oxygen
• pond life abundance
• plant biomass
C. demersum (native)
good levels of O2 & biodiversity
The problem
• Invasive in the UK
• rapid growth rate
• high biomass density
• adverse ecological &
economic impacts
• promoted as an ‘oxygenator’
0
2
4
6
8
10
12
14
42 45 49 52 56 59 63 66 70 73 77 80 84 87 91 94 98 101 105 108 112 115 119 122 126
DO(mg/L)
Days since establishment
Dissolved oxygen (mean ± se)
Control
C. demersum
L. major
F-Value P-Value
Days since estab 11.09 0.000
Treatment 53.11 0.000
don’t!
0
2
4
6
8
10
12
42 56 70 84 98 112 126
Biodiversity
Days since establishment
Biodiversity (mean ± se)
L. major
C. demersum
F-Value P-Value
Days since est 3.13 0.013
Treatment 4.55 0.001
L. major C. demersum
0
50
100
150
200
250
300
1 42 56 70 84 98 112 126
Biomass(g)
Days since establishment
Biomass (mean ± se)
L. major
C. demersumF-Value P-Value
Days since est 1.48 0.209
Treatment 70.30 0.000
Take home
The approach
Results
• L. major least
effective at
producing O2
• depleted over time
• caused O2 to fall
below levels suitable
for pond life
• Biomass density
higher in invasive
species = more
invasive
• non-native
maintained steady
growth pace
L. major C. demersum
Before AfterAll L. major
samples
decomposed
by week 14