Part A | 2.4
18 Part A Marine Flora and Fauna
nutritional features and persistent nature of the wood of
Avicennia and Rhizophora in mangrove habitats might
be responsible for yielding the rich mycoflora [2.43]. It
is evident from the frequency distribution of fungi from
Malaysian mangroves that driftwood supports a greater
diversity of fungi than exposed test panels, e.g., 26
species on driftwood, 9 species on test blocks, while
104 species have been recorded on mangrove driftwood [2.44], yet only 77 on exposed test blocks of
mangrove wood [2.45].
Differences in fungal counts may be attributed
to a rhizosphere effect, which varies with the mangrove species. The effect of root exudation, which
includes both promoters (sugars, amino acids, etc.)
and inhibitors (phenolic compounds), and the ratio
between the two types of compounds influence the
fungal growth and multiplication [2.46]. It is also inferred that distributions of fungal species within the
mangrove habitat vary with temperature, salinity, humidity, and organic contents [2.47]. Moreover, the
frequency of occurrence and relative abundance of
marine fungi from various mangrove forests of the
world shows variations. This could be attributed to
the difference in the species’ diversity of the mangrove ecosystem, age, and preference of the host
substrate, ecological factors, high temperature, abrasion, desiccation, variation in salinity, and exposure to
UV light [2.48]. Mangrove leaf litter is an important
substratum colonized by a very different fungal community to that of lignocellulosic materials [2.49, 50].
Higher marine fungi are not common on such leaf
material [2.51].
2.4.2 Effects of Salinity
Salinity is an important factor that profoundly influences the abundance and distribution of fungi in the
marine environment [2.52]. There seems to be continuous alterations in the intertidal amplitude and salinity,
which can considerably affect fungal biodiversity. Earlier physiological studies of marine fungi led to the
conclusion that they require sodium chloride at concentrations found in seawater for their growth. In fact,
zoosporic fungi such as Althornia, Haliphthoros and
Thraustochytrium species need sodium for growth at
the macronutrient level [2.53]. Generally, changes in
salinity in brackish water habitats such as estuaries,
backwaters, and mangroves are due to the influx of
freshwater from land run-off, caused by monsoons or
tidal variations. The effects of salinity on fungal growth
have been investigated by various authors, who observed only vegetative growth and depicted that most
freshwater fungi cannot reproduce at salinities above
30% seawater and suggest that this is the major reason that they do not grow in the sea [2.19, 21, 54].
Further, it is interesting to note that the species diversity is much greater at the mangrove site when
compared with the samples from the open ocean site,
and this accounts for the larger number of terrestrial
fungi recorded there [2.55].
In higher salinity, some species like Curvularia lunata, Drechslera sp., A. terreus, Cladosporium herbarum, and Aurobasidium pullulans are isolated [2.55]. This may be due to the fact that all these
species are salt-tolerant fungi, although these species
are mostly found in saltpan and seawater zones [2.56].
These species are mostly isolated from marine zones
and rarely in fresh water and mangrove zones. These
fungal cells employ two main mechanisms for adaptation to salt stress: accumulation of a polyol, glycerol,
and maintenance of ion homeostasis [2.57]. When exposed to NaCl, the cells experience both osmotic stress
and ion toxicity. To respond to a low external osmotic potential, the accumulating glycerol seemingly
compensates for the difference between the extra and
intracellular water potential [2.58]. To reduce sodium
toxicity, fungal cells have to maintain low cytosolic Na
C concentrations, and this is achieved by several mechanisms: by restricting Na
C influx, rapidly
extruding Na
C , and/or efficiently compartmentalizing
sodium into vacuoles [2.59, 60]. Genetic evidence indicates that both mechanisms are essential for yeast salt
tolerance [2.61].
2.4.3 Effects of Temperature
Temperature is the foremost important physical factor influencing the physicochemical characteristics and
also the geographical distribution and abundance of mycoflora [2.52]. This may be due to direct solar heating
and penetration of the warm surface water from the
sea. Generally, the surface water temperature is influenced by the intensity of solar radiation, evaporation,
freshwater influx and cooling, and mix up with ebb
and flow from adjoining neritic waters. In general, marine fungi need high temperatures (usually between
25–30
ı C) to reproduce [2.62]. At higher temperatures,
A. niger, A. terreus and Cladosporium herabrum have
been recorded in the marine zone of the Pichavaram
mangrove forest [2.55]. The abundance of this group
of fungi in the mangrove environment might be due
to their spores, which show adaptation by way of pro-
18 Part A Marine Flora and Fauna
nutritional features and persistent nature of the wood of
Avicennia and Rhizophora in mangrove habitats might
be responsible for yielding the rich mycoflora [2.43]. It
is evident from the frequency distribution of fungi from
Malaysian mangroves that driftwood supports a greater
diversity of fungi than exposed test panels, e.g., 26
species on driftwood, 9 species on test blocks, while
104 species have been recorded on mangrove driftwood [2.44], yet only 77 on exposed test blocks of
mangrove wood [2.45].
Differences in fungal counts may be attributed
to a rhizosphere effect, which varies with the mangrove species. The effect of root exudation, which
includes both promoters (sugars, amino acids, etc.)
and inhibitors (phenolic compounds), and the ratio
between the two types of compounds influence the
fungal growth and multiplication [2.46]. It is also inferred that distributions of fungal species within the
mangrove habitat vary with temperature, salinity, humidity, and organic contents [2.47]. Moreover, the
frequency of occurrence and relative abundance of
marine fungi from various mangrove forests of the
world shows variations. This could be attributed to
the difference in the species’ diversity of the mangrove ecosystem, age, and preference of the host
substrate, ecological factors, high temperature, abrasion, desiccation, variation in salinity, and exposure to
UV light [2.48]. Mangrove leaf litter is an important
substratum colonized by a very different fungal community to that of lignocellulosic materials [2.49, 50].
Higher marine fungi are not common on such leaf
material [2.51].
2.4.2 Effects of Salinity
Salinity is an important factor that profoundly influences the abundance and distribution of fungi in the
marine environment [2.52]. There seems to be continuous alterations in the intertidal amplitude and salinity,
which can considerably affect fungal biodiversity. Earlier physiological studies of marine fungi led to the
conclusion that they require sodium chloride at concentrations found in seawater for their growth. In fact,
zoosporic fungi such as Althornia, Haliphthoros and
Thraustochytrium species need sodium for growth at
the macronutrient level [2.53]. Generally, changes in
salinity in brackish water habitats such as estuaries,
backwaters, and mangroves are due to the influx of
freshwater from land run-off, caused by monsoons or
tidal variations. The effects of salinity on fungal growth
have been investigated by various authors, who observed only vegetative growth and depicted that most
freshwater fungi cannot reproduce at salinities above
30% seawater and suggest that this is the major reason that they do not grow in the sea [2.19, 21, 54].
Further, it is interesting to note that the species diversity is much greater at the mangrove site when
compared with the samples from the open ocean site,
and this accounts for the larger number of terrestrial
fungi recorded there [2.55].
In higher salinity, some species like Curvularia lunata, Drechslera sp., A. terreus, Cladosporium herbarum, and Aurobasidium pullulans are isolated [2.55]. This may be due to the fact that all these
species are salt-tolerant fungi, although these species
are mostly found in saltpan and seawater zones [2.56].
These species are mostly isolated from marine zones
and rarely in fresh water and mangrove zones. These
fungal cells employ two main mechanisms for adaptation to salt stress: accumulation of a polyol, glycerol,
and maintenance of ion homeostasis [2.57]. When exposed to NaCl, the cells experience both osmotic stress
and ion toxicity. To respond to a low external osmotic potential, the accumulating glycerol seemingly
compensates for the difference between the extra and
intracellular water potential [2.58]. To reduce sodium
toxicity, fungal cells have to maintain low cytosolic Na
C concentrations, and this is achieved by several mechanisms: by restricting Na
C influx, rapidly
extruding Na
C , and/or efficiently compartmentalizing
sodium into vacuoles [2.59, 60]. Genetic evidence indicates that both mechanisms are essential for yeast salt
tolerance [2.61].
2.4.3 Effects of Temperature
Temperature is the foremost important physical factor influencing the physicochemical characteristics and
also the geographical distribution and abundance of mycoflora [2.52]. This may be due to direct solar heating
and penetration of the warm surface water from the
sea. Generally, the surface water temperature is influenced by the intensity of solar radiation, evaporation,
freshwater influx and cooling, and mix up with ebb
and flow from adjoining neritic waters. In general, marine fungi need high temperatures (usually between
25–30
ı C) to reproduce [2.62]. At higher temperatures,
A. niger, A. terreus and Cladosporium herabrum have
been recorded in the marine zone of the Pichavaram
mangrove forest [2.55]. The abundance of this group
of fungi in the mangrove environment might be due
to their spores, which show adaptation by way of pro-