Report on the freshwater algae of Cherrapunjee and Mawsynram

by Rohan Nath

Introduction 

The Meghalayan plateau region adjacent to the Indo-Burma biodiversity hotspot is known for  Cherrapunjee and Mawsynram. With the second-highest annual average rainfall of 11,820 to  11,872 mm, these regions are hosting a bountiful of perennial water bodies (Fig 1).

Fig. 1. Overview map of Mawsynram and Cherrapunji. Image Source: qGIS.

The algal diversity of these water bodies remains unexplored. Algae belonging to  Cyanophyta (Cyanoprokaryota/Cyanobacteria) have been reported on the moist soil surfaces  and rice fields of the region. Several other species of algae have been reported from these  locations: 

i. Two species of Lyngbya and one species each of Schizothrix, Spirulina,  Stigonema and Scytonema have been reported by Biswas (1934) from moist soils  of the Khasi and Jaintia hills of the location. 

ii. Oscillatoria variabilis C.B. Rao has been reported from the field soil surface.

iii. One species of Cylindrospermum and two species of Nostoc from the rice  cultivation fields and Stigonema dendroideum Frémy have been reported from the  moist soils of Cherrapunjee. 

iv. Oinam et al. (2010) and Devi et al. (2010) reported five cyanophytes, namely, Phormidium tenue (Menegh.) Gomont, Anabaena doliolum Bharadwaja,  Plectonema nostocorum Bornet ex Gomont, Oscillatoria laevittae Buell and  Calothrix marchica Lemmerm. from the soil surfaces of the area

Locations 

The small town of Cherrapunjee is located in the East Khasi Hills district of Meghalaya at a  distance of 59 km from Shillong and an altitude of 1484 m above mean sea level. It is known  as the wettest place on earth since it receives an average annual rainfall of 11,820 mm along  with the neighbouring village Mawsynram with an average annual rainfall of 11,872 mm. 

Severe deforestation has led to the loss of subtropical forest canopy resulting in soil erosion  due to the heavy rainfall. Grasslands now dominate this area with large trees only present in  protected sacred forests. 

Algal samples were collected from five different fresh waterbodies study sites (Fig 2). 

a. Seven Sister waterfall in Cherrapunjee 

b. Stream in Mawsynram 

c. Fish pond in Cherrapunjee 

d. Nohkalikai waterfall in Cherrapunjee 

e. Mawsynram waterfall

Conclusion 

Forty-eight algal taxa were reported in total from the five different freshwater bodies of  Cherrapunjee and Mawsynram belonging to Chlorophyta (26), Cyanophyta (6), Euglenophyta  (1) and class Bacillariophyceae under Heterokontophyta (15) (Table 1). Most of these algae  occur as planktonic or inside the water as epilithic of the submerged stones.

Table 1.

Phylum	Species	Characteristics
Cyanobacteria	Phormidium chlorinum	No sheath, filaments solitary, cells almost  isodiametric and trichomes straight.
	Oscillatoria jenensis	Trichomes without sheath, thallus dark  bluish-green, filament not constricted and  trichomes shortly attenuated at the ends.
	Oscillatoria limosa	Filamentous, thallus bluish-green,  unsheathed, unbranched.
	Scytonema ocellatum	Short false branches present and thallus  blackish to blackish-green in colour.
	Calothrix marchica	The sheath is very thin, almost invisible and filaments yellowish in colour.
	Stigonema minutum	Yellowish-brown in colour, filaments with  2 – 3 rows of cells and sheath thick.
Chlorophyta	Spirogyra sp.	Chloroplasts spirally arranged and  filaments are straight.
	Cylindrocystis  subpyramidata	Cell apices sub pyramidal with rounded  ends and cells cylindrical.
	Closterium calosporum	Cells gradually attenuated to subacute  apices and cells small.
	Closterium kuetzingii	Cell median part fusiform, single and  attenuated towards each extremity into  long processes.
	Closterium libellula	Cells much longer than broad, single,  large and gradually attenuated from the  middle towards the apices.
	Closterium navicula	Cells are straight, solitary and gradually  narrowed towards both ends.
	Euastrum ansatum	Cells are deeply constricted, small and  sinus narrowly linear with dilated  extremity.
	Euastrum dubium	Cell green, solitary, basal angles broadly  rounded, upper and lower lateral margins  equally rounded.
	Cosmarium awadhense	Cells slightly longer than broad, small and  sinus narrowly linear towards the apex and  slightly open outwards.

	Cosmarium decoratum	Cells deeply constricted, slightly longer  than broad, semi cells semi-elliptic and  sinus narrowly linear.
Euglenophyta	Phacus pleuronectes	Cells posteriorly a stout caudus which is  obliquely turned to the right anterior end and ovoid to suborbicular in outline.
	Aulacoseira granulata	Frustules attached continuously to form  chain-like structures and cylindrical  structures.
	Cyclotella meneghiniana	Frustules rectangular and undulated in  girdle view and discoid in valve view.
	Synedra cyclopum	Frustules slightly bent, linear, the apical  area is attenuated to an obtuse end and the  middle portion is slightly wide.
	Navicula tripunctata	Frustules slightly constricted to form  rostrate apices and are elliptical – lanceolate in shape.

The low algal diversity can be attributed to the temperature at the study site which was  congenial with a range of 20 to 25°C and the pH which was acidic from 5.5 to 6.5. The  surrounding water bodies showed excessive algal growth due to the loading of anthropogenic  wastes. The habitat wise distribution pattern of algal diversity is as follows: waterfall> streams> ponds.  

Reference 1. Das, S. K., & Adhikary, S. P. (2012). Freshwater algae of Cherrapunjee and  Mawsynram, the wettest places on earth. Phykos, 44(2), 29-43.