Synopsis Haut de page ↑
During the past two decades marine ecological work increasingly
focused on the role of heterotrophic organisms in remineralization of
nutrients in the sea. In comparison to bacteria and protozoans,
however, little attention has been given to marine fungi. Marine fungi
are of high ecological importance, especially the so-called lower
fungi, which include the exclusively marine thraustochytrids and the
Chytridiomycetes of brackish environments.
These fungi are found in a wide range of environmental conditions,
from inner estuarine waters to the high seas. Thus they can withstand
extreme variabilities of salinity, temperature and irradiance.
As a subject, the ecology of aquatic fungi lags behind because of
difficulties in identifying proper taxa. It has not been possible up to now to
designate an appropriate position of the whole systematic group within the
phylogenetic tree‘of living microbes (GAERTNER, 1972; KARLING, 1960;
MARGULIS, 1980; and others). This book does not aim to settle the question
of evolutionary relationships. Rather, it provides a guide to identification so
that it can be useful in physiological and ecological work.
The fungi are characterized by the following criteria:
- Size of zoosporangia -
- Size of zoospores -
- Flagellation of zoospores -
- Size of resting spores -
- Colour of storage products -
- Shape of sporangial wall -
- Shape of rhizoids -
Additionally, if known, physiological features such as the ability to
survive under oxic or anoxic conditions are given. Life cycles are
demonstrated with photomicrographs which are of special value because
of the extreme morphological variability of these organisms.
Although identification of species often is dependent on electron
microscopy, as is shown by the excellent publications of the working
group on marine fungi in Portsmouth, UK. ((CHAMBERLAIN, 1980; MOSS,
1980; 1985), the information presented in this book should help field
workers who normally are not equipped with EM facilities.
The geographical area covered in this book is mainly restricted to the
North Sea including estuaries and intertidal regions of the Wadden
Sea. Additionally, samples from several tropical mangrove swamps and
the Antarctic Ocean are treated. This poor geographical coverage
indicates the present state of knowledge in the taxonomy of lower
fungi. Nevertheless, it should be possible to identify at least the
genus in other geographical areas by aid of the information provided
here on morphological variance and distribution of the lower fungi.
In the former "Institut für Meeresforschung, Bremerhaven", now
"Alfred-Wegener-Institute of Polar and Marine Research" in
Bremerhaven, FRG, collection and study of marine fungi was initiated
by Dr. W. HOHNK in 1952 and continued by Dr. A. GAERTNER in 1967. He
was the head of the Department of Botany until October 1, 1982. During
this time and later the life cycles of a considerable number of
species of lower fungi have been investigated and documented in the
resulting library of photomicrographs. These micrographs have proved
invaluable for instructions of students in marine mycology
courses. Most of the documented species are stored in liquid nitrogen
and are still available in the live culture collection of marine fungi
of the Institute. This collection was supplemented by samples of newly
described species which have been sent by several colleagues.
Material and Methods
The cultures which had been stored in containers of 'Cryoson' under
liquid nitrogen were thawed by raising the temperature (between -196°
and - 100°C) in small intervals with the aid of a programmable
'Cryoson' freezer. Thereafter, the cultures were kept at room
temperature until they were completely thawed. The cultures then were
immediately transferred to fresh nutrient medium. Good growth occurred
usually within six to eight days. As nutrient medium we used river
water with a salinity of 8-12 8700 enriched with a broth after
OPPENHEIMER & ZOBELL (1952), which was slightly modified regarding the
concentration of nutrients (ULKEN, 1965). The half-strength nutrient
after OPPENHEHVIER & ZOBELL was
Peptone (MERCK) 1.00 g
Yeast extract (MERCK) 2.00 g
Fe(III)-phosphate (MERCK) 0.01 g
agar (DIFCO) 5.00 g
The pH was adjusted to 7.6 - 7.8
The fungi were isolated out of crude cultures with the aid of a
microcapillary. After growth and control of single isolates they were
treated with a solution of antibiotics. From growing pure cultures,
only one zoospore was transferred to the bottom of a 'flow-through
chamber' (HEUNERT, 1974). The 'flow-through chamber' was used to
observe the development of the zoospore under low magnification of a
LEITZ 'Ortholux‘ microscope. Time series of micrographs were prepared
showing the life cycles of these organisms beginning from the settled
zoospore until maturation and sporulation. The time needed for
completion of the life cycles differed with species and culture medium
for each experiment Genera and species are presented alphabetically.