OBSERVATIONS
OF THERMOPHILIC
ALGAL
COMMUNITIES
IN MOUNT RAINIER AND
YELLOWSTONE
NATIONAL
PARKS
John G. Stockner
Department
of Zoology,
University
of Washington,
Seattle
98105
ABSTRACT
Observations
on thcrmophilic
algal communities
during a three-year
period at Mount
Rainier National
Park and during January 1965 and 1966 in Yellowstone
National
Park
have been analyzed to evaluate the distribution
of species in thermal streams relative to
temperature
and competitive
interaction.
Although
temperature
appears to bc the most
important
physical factor affecting
the distribution
in alkaline springs, interspecific
competition for space also influences the distribution.
Diatom species commonly occurring above
3% are noted, along with the apparent tolerance by certain species of temperatures in
excess of 45C. The diversity
of the diatom flora increases as the water cools. Despite
thermal and chemical constancv. the growth rate pf the algae is negligible during the winter
months when light is minimal: ’
INTRODUCTION
Hot springs afford an cxcellcnt opportunity to investigate the dynamics of a relativcly simple ecosystem subjected to a minimum of variation. Few species can grow
and reproduce at the high tcmpcratures,
and the complexity, thcrcfore, is greatly reduced. The annual chemical and thermal
uniformity of the environments simulate a
“laboratory in the field” situation.
The literature regarding hot springs is
sparse, and most of the publications have
been descriptive. The work of Brues (1927)
on the animal lift and of Copeland ( 1936)
and Nash ( 1938) on the thermal Myxophyceac arc the major contributions to the biological literature on American hot springs.
Tuxen (1944) did a comprehensive study of
the hot springs of Iceland, and Molisch
( 1926)) Emoto ( 1942), and Yoneda ( 1942)
carried out detailed investigations of the
flora of the hot springs of Japan. Other less
detailed investigations have dealt with the
hot springs in India, China, Algeria, Malaya,
Germany, and Java. There has been some
recent experimental work on the biochemical ecology of hot springs (Brock and Brock
1966), but more work is needed before the
dynamics can bc fully understood.
Since 1963, I have been studying the
ecology of the Ohanapccosh Hot Springs,
Mount Rainier National Park, Washington,
These are all alkaline, travertine-depositing
springs. Similar springs were examined in
January 1965 and 1966 in the Upper Geyser
Basin of the Old Faithful area, Yellowstonc
National Park. Winter observations of hot
spring communities are lacking in previous
reports, leaving some question as to the scasonal effects of light and its relation to the
more constant environmental
conditions
characteristic of hot springs. This article
prcscnts observations of diatom and filamcntous algal distributions
in thermal
streams. The habitable tcmpcrature range
and possible competitive interactions among
the species in streams with a uniform temperaturc gradient arc evaluated.
I am grateful to Drs. Ruth Patrick and
Francis Drouet of the Academy of Natural
Sciences of Philadelphia
for making and
confirming species identifications.
Dr. Vincent J. Schaefer provided the opportunity to
participate in the V. and VI. Yellowstone
Field Research Expedition,
under a National Science Foundation grant to the State
of New York, Atmospheric Science Rcscarch
Center, Albany.
Fruitful
discussion with
H. S. IIorn and W. W. Benson along with
constructive criticism of the manuscript by
Drs. R. T. Paine and W. T. Edmondson is
gratefully acknowledged. This investigation
was in part supported by a Public IIcalth
Service Fellowship
l-Fl-WP-26,042-01,02
from the Federal Water Pollution Control
Administration.
13
JOHN
Temperature
Proflies
C. STOCKNER
o
FIG. 1. The distribution of algae relative to
temperature in Stream A, January 1965, Upper
Geyser Basin, Old Faithful area, Yellowstone National Park.
THE RELATIONSHIP
OF THE
FLORA
BETWEEN
AND
THE DISTRIBUTION
TEMPERATURE
Water emerges from active springs and
geysers in the Upper Geyser Basin at a temperaturc near the boiling point ( 9OC or
higher), loses heat rapidly, and becomes
progressively cooler until it empties into the
Firehole River. Thermal streams of ten have
a source temperature above 9OC and a
mouth temperature near IOC, a change of
80C in a few hundred yards. Temperatures
represent those recorded during January
1965 and 1966 and should not be interpreted
as means of an annual temperature range.
Two
thermal streams were studied in
some detail, here designated as Stream A
and Stream B. Two boiling springs at the
base of Castle Geyser are the source of
Stream A and provide a relatively constant
flow of water. The streambed is solid and
presumably stable. Fig. 1 illustrates the
distribution of algae relative to the means
of four temperature
observations made
within each species range along the transect
line. The variation was never more than
-c-~C. The species and their observed maximum temperature tolerances are: Filamentous bacteria, 7OC, Schixothrix
calcicola
(Cyanophyta)
62C, and Mougeotia
sp.
( Chlorophyta ) 47C. Filamentous bacteria,
presumably with the highest temperature
tolcrancc, occur closest to the source and
are common until the water cools to approximately 56C, 25 m from the source. At
56C, S. calcicoka becomes the dominant
form and the filamentous bacteria are no
longer present. S. calcicola begins to grow
about 6 m from the source and increases in
abundance as the water cools. It attains its
greatest density at 50C and completely disappears where the water has cooled below
42C (46 m from the source). Mougeotia
sp. arc contiguous with the stream margin
.for most of its length and become quite
conspicuous where the water tcmperaturc
falls below 35C.
To infer that temperature is the sole environmental factor affecting the distribution
of algae in thermal streams would be hazardous, for closer examination would probably show that a number of factors interact
to produce the distribution.
One factor
could be interspecific competition for space.
This could be tested by selecting a scgmcnt
of the stream w!hcre two species are contiguous, forming a conspicuous boundary
Zinc, removing a portion of one of the species, for example:, S. calcicola, from an area
of specified size, preventing its recolonization of the area, and observing whether the
other species can colonize the area in the
absense of S. ca2’cicola. This could not bc
done at Yellowstone, but in such an expcriment at Mount Rainier, S. cabcicola grew
into the Oscillatoria
terebriformis
zone
when 0. terebriformis was kept out by continuous removal of any regrowth around
a dcnudcd area ( 100 cm2) but not when
0. terebriformis ‘was allowed to recolonize.
Thus, it appears that S. calcicola can tolcrate temperatures lower than its observed
minimum, but is prevcntcd from colonizing
a greater area by 0. terebriformis, which
has a competitive advantage at lower tcmperatures. Examination of optimum temperature Eor maximum growth would probably show S. calcicola to have a higher optimum than 0. terebriformis.
Peary and
Castenholz (1964), working with a strain
of 0. terebriformis
Ag. from Oregon hot
springs, found that in laboratory cultures
maximum growth rates occurred at 45 and
TEIERMOPHILIC
ALGAL
15
COMMUNITIES
G ORG./
(-----)
G / M’
(-)
M
2
JFMAMJJASOND
FIG.
1964,
2. Total radiation
(Bclfort,
series 059 solariIncter)
Mount Rainier National
Park, Washington.
50C; under field conditions 0. terebriformis
forms a dense mat where the temperatures
are from 48 to 52C. Strain I (clones 45, 48,
and 53) of Synechococcus sp. grew at maximal and very rapid rates at 45 and 50C in
the laboratory;
however, they are completely dominated by 0. terebriformis
at
these temperatures in the field. Pcary and
Castenholz suggested that the constant motility of the 0. terebri;formis filaments probably expels most unicells and results in a
poor substrate for the Synechococcus sp.
Stream B receives the runoff water from
a number of hot springs behind Old Faithful Inn, and appears to bc stable with a
solid streambed and constant volume of
water. Table 1 lists the diatom species and
temperature
at four sample sites along
Stream B during January 1966. These diatoms grow in close association with their
subs tratc-filamentous
green and blucgreen algae. Samples were taken at 45C
and at intervals along the stream until the
water had cooled to 30C. Additional, comparable samples were obtained from cooler
waters and from the Firehole River. For tax-
and net
growth
OF Schixo~h~ix
cnlcicola,
onomic purposes, it is necessary to examine
maccratcd material, permanently mounted
on glass slides, but it is important to examinc living material definitely to establish
diatom viability
at these temperatures.
Only preserved material from Yellowstone
could be observed, but living material from
the hot springs at Mount Rainier was cxamincd. The tables refer only to those diatoms
observed to have cdlular contents-empty
frustules wcrc disregarded.
The thermal
streams of Ycllowstone and Mount Rainier
afford an opportunity to observe the maximum tcmperaturc tolerated by a species.
By sampling throughout the temperature
gradient on a seasonal basis, rather precise
“limits” can bc dctermincd for the species in
question. It should be noted that variation
occurs along the tempcraturc gradient depending on seasonal variations of ambient
air temperatures and on rate of flow. Both
of these factors can markedly affect the
rate of heat loss from the thermal streams.
Table 2 shows that as temperature decreases there is a marked increase in the
number of species and a decrease in each
16
JOHN
G. STOCKNER
TABLE
1. Diatom species distribution
relative to
temperature
in Stream B. (Upper Geyser Basin,
Old Faithful
area, Yellowstone
National Park)
_____
Temperature
Species
2.
TABLI~
Number
of living
species
each sample site
---
Sample
location*
found
at
Diatom
genera
___I_-
45c
Pinnularia microstrauron
Gomphonema parvulum
Achnanthes grimmi
39c
Pin&aria
microstrauron
Gomphonema parvulum
Achnanthes grimmi
Navicula cincta
36C
Pinnrclaria microstrauron
Gomphonema parvulum
Achnanthes grimmi
Navicula cincta
Rhopalodia gibberula
Amphora coffeaeformis
33c
Pinnularia microstrauron
Gomphonema parvulum
Achnanthes grimmi
Navicula cincta
Rhopalodia gibberula
Amphora coffeaeformis
Denticula elegans
species’ population size as judged subjectively. Conversely, at the higher temperatures there are fewer species in greater
abundance.
Although in general diatoms are not considcred thermophilic (Round 1965), it is cvident (Table 3) that a few spccics can tolerate temperatures above 40C. Whether these
is not
species are obligate thermophiles
known, but knowledge of optimal temperature for maximum growth would partially
Brock and Brock
answer this question.
(1966) have shown that the maximum
growth rates of certain blue-green algae
were attained between 50 and 55C. Peterson (1946) observed chloroplasts in diatoms from preserved material taken from
waters at temperatures as high as 70C in
collections taken by Eric Hulten from Hot
Springs on the Kamchatka Peninsula, Siberia, Interpretation
of these data is difficult because of the problems already mentioned. Observation of living material is
the best procedure for correctly interpreting
diatom distribution in thermal streams.
FR
FRB
OF1
OF1
FRB
SG
OF1
FR
OF1
OF1
4
24
33
36
36
37
39
41
42
45
-_
* F-R: Firehole
River.
(Hot spring runoff).
OFI:
Solitary Geyser.
LIG‘IIT
LIMITATION
29
18
8
I:
6
10
10
4
3
3
FRB :
Behind
Fireholc
River bank.
Old Faithful Inn. SG:
OF ALGAL
GROWTH
Another important factor affecting the
growth of algae :in hot springs is the seasonal variation of solar radiation.
During
winter, the algae do not appear qualitatively different than in summer. Squares
(9 cm2) were removed from a number of
algal mats growing around the margins of
springs at Yellowstone in an attempt to mcasure rates of growth when length of daylight
and solar radiation were minimal, The temperature at the quadrats ranged from 42 to
58C. After 15 days there was no visible sign
of growth in the denuded areas, Similar results were obtained from experiments on the
hot springs at the Mount Rainier site (46” 44’
N lat, 121” 34’ W long). During winter (Fig.
2)) growth did not exceed 1 g organic matter mm2 month-l, but in summer, growth
often exceeded 6 g organic matter m-2
month-l. These values were obtained by
removing S. caZ&oZa at monthly intervals
from a wooden trough extending from the
spring source. The source was covered
with heavy black polyethylene, thereby excluding algae from the spring source. Thus,
the possibility of recolonization by S. calcicola from an upstream inoculum was eliminated and a good approximation
of the
growth rate was #obtained. Grazing by herbivores was negligible because of the periodic removal of the algae from the trough.
Samples were brought back to the laboratory for analysis of organic and ash frac-
TIIEl~MOPIIILIC
TABLE 3. Diatom species commonly
temperatures
above 3%
occurring
ALGAL
at
Mount Rainier
Biraphidineae
Rhopalodia gibber&
Rhopalodia gibberula
Denticula elegans
Denticula elegans
Mastogloia elliptica
Mastogloia elliptica
Amphora coffeaeformb
Amphora coffeaeformis
Navicula cincta
Navicula cincta
Nitzschia parvula
Nitzschia frustulum
Nitzschia ignorata
Nitzschia obtusa
Pinnularia microstrauron
Nitzschia thermalis
Gomphonema parvulum
Caloneis bacillum
Diploneis interrupta
Navicula cuspidata var.
ambigua
Yellowstone
Monoraphidineae
Achnanthes
Achnanthes
Achnanthes
grimmi
lanceolata
gibber&
Achnanthes
Achnunthes
var. dubia
Achnanthes
Achnanthes
Achnanthes
grimmi
lanceoluta
exigua
pinnata
minutissima
tions, and caloric content. These results
suggest that during winter, growth is negligiblc because maintenance
(respiration)
and grazing by the conspicuous herbivore
populations equal or exceed primary production, although respiration rates were not
measured. IIowever, grazing by Ephydra
brusei and several species of stratiomyid
larvae has been observed during the winter.
From stomach contents analyzed and estimates of population
density, it appears
that the “grazing effect” is substantial-to
the point of complete denudation where aggregates of larvae have grazed. This often
produced a checkerboard appearance on
17
COMMUNITIES
the mat during the winter months. Filamcntous bacteria, apparently obtaining their
energy by the oxidation of I-I&, are probably not affected by the seasonal variation in
light.
REFERENCES
BROCIC, T. D., AND E. BROCK. 1966. Temperature
optima for algal dcvelopmcnt
in Yellowstone
and Iceland hot springs. Nature, 209: 733734.
BRUES, C. T. 1927. Animal life in hot springs.
Quart. Rev. Biol., 2: 181-201.
COPELAND, J. J.
1936.
Yellowstone
thermal
Ann. N.Y. Acad. Sci., 36:
Myxophyceae.
l-232.
E1v~ro, Y. 1942. Studies on the thermal flora of
Japan XVI.
Bacteria and algae of Onikobe
Botan. Mag. Tokyo,
56:
thermal
springs.
120-136.
MOLISCII, 1% 1926.
Pflanzenbiologie
in Japan.
Gustav Fisher, Jena.
NASH, A. 1938. The Cyanophyceae
of the thermal regions of Yellowstone
National
Park,
U.S.A., and of Rotorua and Whakarewarewa,
New Zealand; with some ecological data. Ph.D.
Thesis, University
of Minnesota, Minneapolis,
Unpaged.
PEAIIY, J. A., AND R. W. CASTENHOLZ.
1964.
Temperature
strains of a thermophilic
bluegreen alga. Nature, 202: 720-721.
PETERSON, J. B. 1946. Algae collected by Eric
II&en
on the Swedish Kamchatka Expedition,
1920-22,
especially
from hot springs.
Kgl.
Danske
Videnskab.
Selskab.,
Biol.
Medd.,
20: 3-122.
ROUND, F. E. 1965. The biology of the algae.
St. Martin’s, New York. 269 p.
TUXEN, S. L. 1944. The hot springs of Iceland,
p. 1-216. In The zoology of Iceland, v. 1.
Einer Munksgard,
Copenhagen.
YONEDA, Y. 1942. Thermal algae of Isihawa Prefecture.
Acta Phytotaxon.
Geobotan., 2 ( 3 ) :
211-215.