Airborne algae and lichen soredia in Mérida
(Badajoz, SW Spain)
Fernando Henández Trejo1, Adolfo F. Muñoz Rodríguez2, Rafael Tormo Molina3,, Inmaculada Silva Palacios3 1 IES Almendralejo, Badajoz, 2 Universidad de Huelva, 3 Universidad de Extremadura
This work was made possible by the research project s PRI06A190 and PRI BS1008 financed by the Regional Government, Junta de Extremadura (Spain) and the European Regional Development Fund
Introduction
Algae are present everywhere and some of them use air as
dispersion media. Although some airborne algae induce allergy or
other respiratory problems their major concern is contamination of
water tanks as well as attack over surfaces of buildings or outdoor
stone arts, acting as biodeterioration agents (Fig. 1).
Material and Methods
Sampling was taken using a seven day recording spore trap (Burkard) for
two years (1998-1999), it was located 15 meters over the ground level at
the terrace roof of the hospital of Mérida (SW Spain) (Fig. 2). Algae and
lichen soredia were identified and counted using two longitudinal scans
over the slides with x1000 microscope resolution. Meteorological data
and airborne algae and lichen soredia concentrations were analysed
using Spearman correlation coefficient.
Results
Most algae identified are Chlorococcales, forming coenobia of 2-8
cells, with an average concentration of 20 coenobia/m3. June was
the month with the highest concentrations and January with the
lowest. Maximum peak reached a value of 401 coenobia/m3.
Diatoms were found with an average concentration of 0.8 cells/m3,
more often in Summer and most of them were Cyclotella like forms.
Other green algae, including filamentous forms or even Pediastrum
sp. coenobia, were found. Lichen soredia were recorded with an
average concentration of 0.4 soredia/m3, without a clear seasonal
pattern (Fig. 3). Algae concentration showed a statistically
significant positive correlation with temperature and negative with
relative humidity and precipitation, nevertheless lichen soredia did
not showed this relationship. Wind direction affected algae
concentration, with a statistically significant positive correlation with
winds from West and negative from Est, whereas lichen soredia
showed statistically significant positive correlation with wind from
NE and negative from SW (Fig. 4).
Conclusions
Airborne algae and lichen soredia are present in the air along the
year. Algae showed a seasonal pattern affected by temperature,
relative humidity and wind direction. Watercourses are not
considered as the main potential sources of airborne algae
because the main river is located opposite to the predominant wind
direction, nevertheless irrigated crops seems to be their origin and
soilborne algae may constituted the bulk of aeroalgal flora. Lichen
soredia seem to be present in the air when wind blow from holm
oak woods.
Fig. 1. Airborne algae Chlorococcales (upper) and lichen soredia (lower)
Fig. 4. Daily concentration of algae and lichen soredia for the two years studied
Fig. 2. Locaton map of spore trap in Mérida and image on the terrace hospital
0
10
20
30
40
Jan-97 Mar-97 May-97 Jul-97 Sep-97 Nov-97 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98
mm
ra
in
0
50
100
150
200
ce
no
bia
/m3
Chlorococcales algae Rain
0
5
10
15
20
25
30
35
Jan-97 Mar-97 May-97 Jul-97 Sep-97 Nov-97 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98
ºC T
em
p
0
1
2
3
4
5
ce
lls/m
3
Diatoms algae Mean Temperature
0
6
12
18
24
Jan-97 Mar-97 May-97 Jul-97 Sep-97 Nov-97 Jan-98 Mar-98 May-98 Jul-98 Sep-98 Nov-98
Ho
urs
0
2
4
6
8
10
so
red
ia/m
3
Lichen soredia Wind from NE
0
10
20
30
40
50
60
70
80
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Co
en
ob
ia/m
3
Chlorococcales algae 1997 Chlorococcales algae 1998
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ce
lls/m
3Diatoms algae 1997 Diatoms algae 1998
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
So
red
ia/m
3
Lichen soredia 1997 Lichen soredia 1998
Fig. 3. Monthly concentration of airborne algae and lichen soredia
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