Home Key speaker
Nuisance alga Gonyostomum semen:
Reet Laugaste & Peeter Noges
Vortsjarv Limnological Station, Institute of Zoology and Botany,
Estonian Agricultural University, 61101 Tartu county, Estonia
The large raphidophyte Gonyostomum semen
is a world-wide distributed flagellated that causes allergic reactions to people
swimming in lakes. Its mass development was first recorded by Drouet & Cohen
(1935) in Cedar pond, Massachusetts. Regional reviews of the distribution and
ecology of G. semen are published for
Sweden (Cronberg et al., 1988) and
Finland (Lepistö et al., 1994). We
analysed phytoplankton and water chemistry data collected from 269 Estonian
small lakes since the 1950s. Being not found in Estonian lakes until the 1950s,
this species is now common in 63 lakes with soft (HCO3-<25
mg l-1) brown water and high organic matter content (CODCr>40
mgO l-1). It achieved maximum biomass (> 100 g m-3) in
dystrophic lakes with extremely dark water (Secchi depth < 1 m; CODCr
60-100 mg O l-1). During last years, the species has invaded some
oligo- and semidystrophic lakes. Processes connected with lake acidification are
considered the main reason for the expansion of G. semen. High phosphorus levels favour the alga. The vertical
migration ability gives to the species a certain independence of the phosphorus
deficiency during stratification.
Gonyostomum semen (Ehrb.)
Diesing is a large (length 50-100 µm) raphidophyte with two flagella. The cell
membrane is thin and fragile and brakes easily on physical contacts with other
bodies. Numerous trichocysts (slime bodies) located inside the cell membrane are
characteristic of the species and explode on strong stimulation throwing out up
to 200 µm long slime threads (Cronberg et al., 1988). On stronger physical
forcing cells are totally destroyed and form together a slimy mass that covers
fish nets and bodies of swimmers causing itching and allergic reactions to
people swimming in lakes. Already a G.
semen concentration of 100 ind. ml-1 gives a typical slimy cover
on bathers’ skin (Eloranta
& Palomäki, 1986). With gentle stimulation only few trichocysts eject, the
alga remines alive and can keep attackers at distance. The cells of G.
semen break also on sampling with a plankton net
and on adding formalin or Lugol solution to the samples. As mentioned by Hongve
et al. (1988), bunches of hundreds of spherical chloroplasts remaining in the
preserved sample are often taken for detritus or even identified as Microcystis
colonies. Hard recognizability in preserved samples is probably the main reason
why G. semen has been often
G. semen was first
described by Ehrenberg in 1853 under the name of Monas
semen from a small pond outside Berlin. Up to now, the occurrence of G. semen has been stated from Sweden, Norway, Denmark, Finland,
Austria, Slovakia, Czechia, Russia, USA, Canada, South America (Bourrelly, 1970)
and Africa (Gerrath & Denny, 1980) showing a world-wide distribution of the
species. Mass development of G. semen
was first recorded by Drouet & Cohen (1935) in Cedar pond, Massachusetts and
by Sörensen (1954, cit. Cronberg et al., 1988) in Sweden in 1948. In
Finland G. semen was recorded already in 1894, but the first complaints from
swimmers came in 1978 (Lepistö et al., 1994). The same authors analyse the
distribution of the species in Finland during the period of 1978-1989. Starting
as a small spot in Southeastern Finland, the distribution area expanded and
reached almost the polar circle by the end of the period. Judging upon the
distribution of G. semen by literature
data, the expansion of distribution area during last decades is undisputable. Fast
expansion of G. semen is expressed in
1) extension of the distribution to new areas, 2) occupying new habitats (lake
types) within the distribution area, and 3) achieving mass development in
2. Study site
Estonia is situated in the northeast of Europe, on the east coast of the Baltic Sea, north of Finland. It is the northernmost of the three Baltic states - Estonia, Latvia and Lithuania. Geologically, Estonia lies on the southern slope of the Fennoscandian shield. As Estonia is risen from the seabottom, its surface is mostly flat. The dominating bedrock is Ordovician-Silurian limestone in the northern and Devonian sandstone in the southern
1. Location map of Estonia within Europe.
part of Estonia. The variety of landscapes is due to the retreating ice shield, which changed the appearance of the country completely after the last glaciation period some 10 thousand years ago. At present, Estonia belongs to the temperate climate region. The long-term mean air temperature in January is between -2.4 and -7.4°C and that of July between 16.3 and 17.3°C. There are about 1150 small lakes in Estonia with an aquatory of over 1 hectare. The two largest lakes Peipsi and Võrtsjärv together make up nearly 90% of the total area of lakes. There is a large variety of lake types in Estonia from calcareous to soft water lakes, from uncoloured to dark brown lakes, from alkaline to acidic lakes. The lakes are usually ice-covered from November to April, in summer the water temperature is around 20°C, on average.
3. Material and methods
analysed phytoplankton and water chemistry data collected from 269 small lakes
in Estonia since the 1950s. Sampling was performed mostly in summer (July -
August), spring data were available from less than half of the lakes while whole
year seasonal data were only from Lake Valguta Mustjärv. Biomasses of different
species were determined as direct chamber counts multiplied by cell volumes.
Partly old samples were re-examined for G.
semen. Water transparency was measured using the Secchi disk.
Spectrophotometric light absorbance in filtered (GF-C filters) water at 400 nm
wave length against distilled water was used as an equivalent for water colour.
Two methods were used to determine the concentration of organic matter: the
permanganate and the bichromate methods. Both the total and mineral forms of
nutrients N and P were measured using standard methods. The buffering capacity
was evaluated on the basis of HCO3- concentration and pH.
Using the biomass of G. semen as a
grouping variable, all sets of parameters measured during individual visits to
lakes were divided into four groups: 1 - cases where the species was absent, 2 -
cases where the biomass was less than 2 g m-3, 3 - cases when the
biomass was between 2 and 10 g m-3, and 4 - cases of mass development
of G. semen characterised by a biomass
of more than 10 g m-3.
Distribution in Estonia
For the first time in Estonia, G. semen was found from a small brown water lake (Orava Mustjärv) in South-eastern Estonia in 1983. However, re-examining the old materials, characteristic remains were found from a number of samples taken during earlier decades (Fig. 2). Up to now, G. semen has been found from 63 lakes. More than one half of these lakes (33) are located in Põlva and Võru counties in Southeast Estonia, and 13 in Virumaa county in North Estonia. The alga was found also in two lakes located on the Saaremaa island. The seasonally investigated L. Valguta Mustjärv is still the only lake in Tartu county where G. semen has been found.
2. Number of lakes with G. semen and
the average abundance of the species on a 5-step scale by decades
cases of G. semen absence with those
of its occurrence (Table 1, Fig. 3), we found that the latter cases were
characterised by significantly lower water transparency, higher light absorbance
in the blue region of the spectrum (browner water), lower pH, higher chemical
oxygen demand, at least ten times smaller alkalinity and nitrate nitrogen
content, and at least twice smaller total nitrogen content. As the standard
deviation of several variables (NH4-N, PO4-P, Ptot and N/P
ratio) was very high within the group of cases where G.
semen was absent (this group included data from nearly all lake types), the
between-group differences remained insignificant. With increasing biomass of G.
semen, there occurred continuous increasing trends in water colour and
chemical oxygen demand (both CODMn and CODCr) and
continuous decreasing trends in Secchi depth and nitrate nitrogen content.
Within Gonyostomum lakes, there were
significant differences in COD, total nutrients and their ratio when low biomass
cases (B<2) and high biomass cases (B>10) were compared. Cases of medium
(B=2…10) and high G. semen biomass
(B>10) differed significantly only by total phosphorus concentration.
G. semen was found mainly in softwater lakes (HCO3-<
25 mg l-1) with brown water and high content of dissolved organic
matter (CODCr>40 mg O l-1). It achieved the highest
abundance (maximum biomass > 100 g m-3) in dystrophic lakes with
extremely dark water (Secchi depth < 1 m; CODCr 60-100 mg O l-1).
Most of these lakes are located in sandy areas in Põlva county. In typical bog
lakes and in semidystrophic brown-water lakes the abundance was smaller. G.
semen colonises typical bog pools rather seldom and with low abundance. In
the second half of the1980s, the species occurred with rather high abundance in
four eutrophic soft water lakes. Since the 1990s, G.
semen appeared in two oligotrophic and four semidystrophic soft water lakes.
As a rule, the biomass increases with increasing nutrient content and with
decreasing N/P ratio.
the seasonally studied dyseutrophic forest lake Valguta Mustjärv, G.
semen occurred from may to September and reached its seasonal biomass
maximum usually in July, in some years in June. It was quite rare in August and
September but common in May, although, the biomass remained less than 1 g m-3.
In brown-water lakes the biomass maximum was usually found in the epilimnion, in
non-coloured lakes in the metalimnion or near the bottom when the lakes were
1. Significance (p) of the differences between average values of hydro-optical and
hydrochemical variables in sets of data grouped by the biomass of Gonyostomum
semen (B=0; B<2; B=2…10; and B>10). Significant differences (p<0.05)
are marked in bold
3. Changes of hydro-optical and hydrochemical parameters of lakes grouped by the
biomass of Gonyostomum semen.
in the distribution of G. semen can be followed during the last 15 years. During this
period, the frequency of occurrence as well as the biomass have undoubtedly
increased. We can observe two clear tendencies: 1) the increase of G.
semen biomass in dystrophic lakes around Põlva, especially in the 1990s,
and 2) colonisation of new habitat types in oligotrophic and semidystrophic
softwater lakes where its earlier absence is well documented.
suppose that the actual distribution of G.
semen in Estonia is wider than described by us,
because many of the bog lakes where the species was absent were visited for the
last time in the 1960s. Also we are lacking information about a large number of
big bog pools and some semidystrophic lakes.
occurs mainly in small, shallow, dyseutrophic lakes. For example, in Norway its
distribution is limited by the mean lake depth of 15 m (Hongve
et al, 1988). In Finland G.
semen is numerous in
small brown-water forest lakes. In Sweden it has been found on 70% of occasions
in lakes with an area less than 50 ha and only 10% of lakes have been deeper
than 5 m (Cronberg et al., 1988).
a rule, G. semen requires pH less than
7, but there are different opinions concerning the lower limit. According to Rosén
(1981), G. semen is pH-tolerant,
requiring humus and occurring in lakes with a median water colour value of 60 mg
Pt l-1. Willén
et al. (1990) consider the species typical for humic (dystrophic) lakes with a
median pH of 5.5, but not for very acidified (median pH 4.5) lakes. In Norwegian
lakes G. semen prefers pH ranging from
5 to 7, and is absent at a pH less than 5 (Hongve et al., 1988). Rosenström
& Lepistö (1996) analysing the indicator species for different types of
Finnish lakes, put G. semen among
species typical for dystrophic and eutrophic but not for acidic lakes (acidified
non-coloured lakes with a very low pH). In Finland it occurred in the pH range
of 6.2-7.5 (mean 6.8) and in the
colour range of 12-149 mg Pt l-1 (mean 61). According to Cronberg et
al. (1988), G. semen prefers slightly
acidic or neutral environment but tolerates the pH range of 5-7.5. In two small
lakes in Russia G. semen occurred at
pH 4.5-6.6 (Korneva, 2000); in Japan G.
semen was observed in the pH range of 4-7.5
and it disappeared at pH>8 (Kato, 1991, cit. Korneva, 2000). In Triangle
Lake, a typical Gonyostomum lake in
Ohio, pH is 4.9 (Havens, 1989).
pH is usually coupled with dark colour of water and high content of dissolved
organic matter. Lepistö et al. (1994) divided their lakes into two groups on
the basis of G. semen occurrence. Water colour and the contents of total P and
total N were significantly higher in lakes where G. semen occurred while pH of these lakes was lower. Although the
species prefers brown water, it has been seldom observed also in waters with low
colour levels. Cronberg et al. (1988) point out a tendency of G.
semen to invade less coloured lakes. All Gonyostomum
lakes in Sweden have low buffering capacity (alkalinity < 0.1 meq l-1)
and are therefore vulnerable to acid deposition. Low alkalinity as a main
feature characterizing Gonyostomum lakes
was stressed also by Korneva (2000) and LeCohu et al. (1989). Requirement of low
alkalinity is probably the reason why G.
semen has not spread into some semidystrophic lakes in Estonia having a
nearly neutral pH but where the HCO3-
content is about mg l-1.
a rule, most of the acidic lakes are extremly oligotrophic as a result of Al
precipitation of phosphorus and humic compounds in the lake (Hornström et al.,
1984 cit. Morling & Willén,
1990). The expansion of G. semen
during last decades is undoubtedly related to the tendency of eutrophication
that has touched even the well buffered humic lakes. According to Eloranta &
Palomäki (1986) G. semen occurs in
the Finnish Lake Konnevesi abundantly in the most eutrophic part of the lake
receiving effluent waters from a fish farm and is common and numerous also in
eutrophic brown-water lakes around Konnevesi. Manninen (1988) mentions that the
biggest biomasses of G. semen can be
found in lakes with a high field percentage in their watersheds. Pithart et al.
(1997) showed that the conditions needed to induce a bloom of G. semen in a pond in Czechia were low water level, low content of
oxygen and nitrates, high content of phosphates and the dark colour of water.
Cronberg et al. (1988) found a clear linear relationship between the contents of
chlorophyll a and phosphorus in Gonyostomum
lakes. Lindmark (1984) described a mass development of G.
semen at the depth of 4-5 m in the non-coloured, softwater Lake Lilla Galtsjön
in 1980 and 1981 (biomass 45 mg l-1, chla
105 µg l-1) after liming the lake with sodium carbonate that caused
a rapid phosphorus release from the sediment. Also Hongve et al. (1988)
considered the increasing eutrophication one of the main reasons for the
expansion of G. semen as most of the Gonyostomum
lakes have received at least some extra nutrients. They showed that G.
semen dominated in the total P range of 10-50 µg l-1
and at total N more than1000 µg l-1. The preferred
N/P ratio was less than 30 and the content of inorganic nitrogen forms
(NO3-N + NH4-N) was always less than 10 µgN l-1.
At higher P levels bluegreens started to dominate. As favouring the development
of G. semen, Brettum (1989, cit. Salonen & Rosenberg, 2000)
suggests the N/P ratio of 20-50, Ptot concentration of 7-25 µg l-1
and Ntot concentration of 200-500 µg l-1. The Gonyostomum lakes in Estonia fit well in this range of the N/P
ratio, but phosphorus concentrations are generally higher.
Seasonal dynamics and vertical distribution
Estonia G. semen reaches its biomass
peak usually in July or August, but in other places it has been observed around
midsummer (Havens, 1989; Korneva, 2000), at the end of summer or in early autumn
(Morling & Willén, 1990; Salonen
& Rosenberg, 2000; Pithart et al., 1997), in France even in October-November
(LeCohu et al., 1989). Mostly the species occurs in plankton from May to
September, but Korneva (2000) has found it also in March under the ice.
According to Salonen et al. (2002) G.
semen dominated in Lake Valkea-Kotinen in 1990-1996 from the beginning of
June to the end of September, but in1991 was numerous until November.
investigators have studied the vertical distribution and diel migrations of G.
semen and mention its
avoidance of high light intensities. The vertical biomass maximum has been found
at the quantum irradiadiance of 80 µE m-2
s-1 (LeCohu et al., 1989). A similar limit was pointed out by
Eloranta & Räike (1995), who showed that the upward migration of G.
at a light intensity of ca. 75-95 µE m-2s-1. In
a small artificial stratified water body of dark water (oxygen disappeared at
1.5 m, 1% light penetrated to 1 m) in Texas G.
semen preferred the intermediate incident light levels at the surface at 9
a.m. and migrated to deeper layers with increasing surface irradiance (Van den
Avyle et al., 1982). Avoidance of higher light
intensities explains probably the fact that in non-coloured lakes in Estonia G.
semen colonizes deeper
layers has been never found near the surface. As the
whole biomass may be concentrated within a very thin layer near the bottom, it
may be overlooked already in the sampling phase. For
vertical migration G. semen needs a
light gradient and probably also a nutrient gradient. However, Pithart et al.
(1997) observed a diel migration of G.
semen in a 1.9-m deep nonstratified pool with the biomass maximum located at
the depth of 10 cm at noon and near the bottom at night. A similar migration
pattern was found also by Salonen et al. (2002) in
Finnish dark-water lakes where the biggest biomasses of G.
semen occurred in the
upper 1-m layer in the day time and in the hypolimnion during night. The authors
pointed out the high motility of this large flagellate that enables long
distance vertical migrations to the hypolimnion during night in order to recruit
its cellular nutrient supplies. This gives an
important competitive advantage and can explain its high proportion in
phytoplankton. Migration to the cooler hypolimnion may also help to diminish
respiration losses. Salonen
& Rosenberg (2000) showed that part of G.
semen population remains in the anoxic hypolimnion also during the daytime,
especially near the end of stratification when the nutrient concentration in
these layers has dropped. It could be explained by the increased time required
to reload the nutrient reserves of algae. During this time, the algal uptake of
soluble reactive phosphorus could cause its decrease in the hypolimnion. Staying
in the hypolimnion might be also connected with predator avoidance as G.
semen is seriously threatened by grazing of Holopedium
gibberum and Polyarthra vulgaris.
There are different opinions with regard to the edibility of G.
semen. Havens (1989) explains the domination of G. semen with its inedibility that result from its large size and
ability to discharge trichocysts when contracted by a predator. He relates
vertical migrations mainly with obtaining hypolimnetic nutrients. Sanders
& Wickham (1993), on the contrary, consider G.
semen a favourite food for Diaptomus
oregonensis and Daphnia pulicaria
as this alga made up 27% of the food of Daphnia
in the epilimnion and 94% in the hypolimnion. Hansson (1996) also related
migrations with reducing exposure to grazers. He supposed that the expansion of G.
semen together with the
ongoing acidification might be explained by reduced
abundance of efficient grazers at lower pH. Cronberg
et al.(1988) consider both the nutrient transport and
the avoidance of grazing as
factors stimulating the upward migration of G.
semen in the morning and downward migration in the afternoon.
LeCohu et al. (1989) found no relationship between vertical migration and nutrients. During homothermal periods G. semen was evenly distributed within the water column. During thermal stratification in summer, surface-avoidance by cells was observed, especially between noon and 4 p.m. and the biomass was strongly fluctuating. Maximum population doubling time ranged from 1.5-3.2 days.
strong light avoidance, the incline of G.
semen towards dark water lakes has been explained by its ability of
heterotrophic carbon uptake (Havens, 1989). During a G.
semen bloom located within a 1-m layer (between 0.5 and 1.5 m) in Triangle
Lake (Ohio), light stimulated 3H-glucose uptake. Basing on
autoradiographic method, Buchanan (1982) supposed that it was not necessarily
the direct uptake by algae but could be performed by intracellular bacteria.
Korneva (2000) relates the occurrence of G.
semen with high trophic state and high abundance of bacteria and supposes
that the alga might be bacterivorous. In Triangle Lake Jiang et al. (1993)
studied to what extent G. semen uses
DOC and to what extent bacteria. The lake is rich in both of these potential
food items. Experiments with labelled DOC and bacteria showed that G.
semen is mainly autotrophic getting only a minor part of assimilated carbon
from DOC but having no bactivorous activity.
the observed fast expansion of G. semen, Cronberg et
al. (1988) conclude that the reason for that cannot be
the changes in pH or water colour per
although it might be
related to acidification of lakes. Eloranta & Räike (1995) consider the
expansion partly seeming, caused by more intensive investigation of small lakes
but also being caused by different actions in forestry and peat processing that
have increased water colour and turbidity, and also by agricultural
eutrophication, fish farming and wood processing industry. Hongve et al. (1988)
supposes that the expansion of G. semen
can be also explained by recent implanation of species, or eventually a new
investigation was supported by Estonian Science Foundation grants No. 3689
P. (1970): Les algues d’eau douce. III. N. Boubee et Cie. Paris, 512 pp.
E.L. ( 1982): Planktonic photoheterotrophic and heterotrophic uptake of glucose
in two acid lakes and one eutrophic lake in northeastern Ohio. – A
dissertation submitted to the Kent State University Graduate College.
G., Lindmark, G. & Björk, S. (1988): Mass development of flagellate Gonyostomum
semen (Raphidophyta) in Swedish forest lakes - an effect of acidification?
Hydrobiologia 161: 217-236.
F. & A. Cohen (1935): The morphology of Gonyostomum
semen from Woods Hole, Massachusetts. Biol. Bull. 68: 422-439.
P. & Palomäki, A. (1986): Phytoplankton in Lake Konnevesi with special
reference to eutrophication of the lake by fish farming. – Aqua Fennica 16,
P. & Räike, A. (1995): light as a factor affecting the vertical
distribution of Gonyostomum semen (Ehr.) Diesing (Raphidophyceae) in lakes. – Aqua
Fennica 25: 15-22.
J.F. & P. Denny (1980): Freshwater algae of Sierra Leone III. Cyanophyta,
Chrysophyta, Xanthophyta, Chloromonadophyta, Cryptophyta, Dinophyta. - Nova
Hedwigia 33: 933-947.
L.-A. (1996): Behavioural response in plants: adjustment in algal recruitment
induced by herbivores. Proc. R. Soc. London 263: 1241-1244.
K.E. (1989): Seasonal succession in the plankton of a naturally acidic, highly
humic lake in Northeastern Ohio, USA. – Journal of Plankton Research 11, 6:
D., Løvstad, Ø. & Bjørndalen, K. (1988): Gonyostomum
semen – a new nuisance to bathers in Norwegian lakes. – Verh. Internat.
Verein. Limnol. 23:430-434.
Ping & Heath, R.T. (1993): Carbon sources of the alga Gonyostomum
semen in an acid bog lake. – Ohio J. Sci. 93, 2: 45.
L.G. (2000): Ekologicheskie aspekty massovogo razvitiya Gonyostomum
semen (Ehr.) Dies. (Raphidophyta). - Al’gologiya 10, 3:265-277. Ecological
aspects of mass development of Gonyostomum
semen (Ehr.) Dies. (Raphidophyta), in Russian.
R., Guitard, J., Comoy, N. & Brabet, J. (1989): Gonyostomum
semen (Raphidophycées), nuisance
potentielle des grands réservois
français? L’exemple du lac de Pareloup. – Arch. Hydrobiol. 117, 2: 225-236.
L., Antikainen, S. & Kivinen, J. (1994): The occurrence of Gonyostomum
semen (Ehr.) Diesing in Finnish lakes. - Hydrobiologia 273: 1-8.
G. (1984): Acidified lakes: Ecosystem response following sediment treatment with
sodium carbonate. – Verh. Inter. Verein. Limnol. 22: 772-779.
P. (1988):Gonyostomum semen (Ehr.) Dies. kannan tiheys ja elinolosuhteet
humuspitoisissa lammissa. vesi- ja Ympäristöhallinnon Julkaisuja 14: 55-56.
G. & Willén, T. (1990):
Acidification and Phytoplankton Development in Some West-Swedish Lakes
1996-1983. – Limnologica (Berlin) 20, 2: 291-306.
T., Pechar, L. & Mattsson, G. (1997): Summer blooms of raphidophyte Gonyostomum
semen and its diurnal vertical migration in a floodplain pool. – Algol.
Studies 85: 119-133.
n, G. (1981): Tusen sjöar - växtplanktons miljökrav.
rdsverk. pp. 119.
U. & Lepistö, L. (1996): Phytoplankton indicator species of different types
of boreal lakes. – Algol. Studies 82: 131-140.
K. & Rosenberg, M. (2000): Advantages from diel vertical migration can
explain the dominance of Gonyostomum semen
(Raphidophyceae) in a small, steeply stratified humic lake. – J. Plankton
Research 22, 10: 1841-1853.
K., Holopainen, A.-L. & Keskitalo, J. (2002): regular high contribution of Gonyostomum semen to phytoplankton biomass in a small humic lake.
– Verh. Internat. Verein. Limnol. 28, 488-491.
R.W. & Wickham, S.A. (1993): Planktonic protozoa and metazoa: predation,
food quality and population control. – Marine Microbial Food Webs 7, 2: 197-
den Avyle, M.J., Allard, D.W., Dreier, D.M. & Clark, W.J. (1982): - Texas J.
Science 34, 1: 69-78.
E., Hajdu, S. & Pejler, Y. (1990): Summer phytoplankton in 73 nutrient-poor
Swedish lakes. – Limnologica 20, 3: 217-227.