Seaweeds are gaining considerable importance in recent times due to the fact of their cosmopolitan
distribution, renewable nature, and wide range of applications.Seaweeds, or marine algae, refer to three taxonomic groups
that have different pigment composition: Chlorophyta (green algae), Rhodophyta (red algae), and
Ochrophyta (brown algae). These groups are non-monophyletic having complex evolutionary life
history strategies. The prevalence of cell wall matrix (sulphated polysaccharides) in their tissue
makes this resource economically important. Its industrial utility essentially cuts across these high
molecular weight polysaccharides also known as phycocolloids and their use as phycosupplement in
nutraceutical market.
Biodiversity in a broad sense includes variation among life forms on this planet and is essential
for human survival, as it sustains the health of the ecosystem, provides biological resources, besides representing culture and identity. The Convention on Biological Diversity (CBD) defines biodiversity
as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and
other aquatic ecosystems and the ecological complexes of which they are part. Further this includes
diversity within species, between species and of ecosystems as well”.
Current Knowledge on Seaweeds of India
History of Seaweed Research in India:
Previous records showed that the first seaweed that had been, perhaps, described from the Indian
Ocean was a specimen of Amphiroa (Rhodophyta) collected by Hermann in 1672. Linnaeus
further recorded Turbinaria turbinate (as Fucus turbinatus) and Sargassum granulatum (as Fucus granulates)
(Ochrophyta, Phaeophyceae) from Indian waters. The authenticated report on seaweed collections
made from Indian shores in 1767 by Köing—who came to this country as a missionary—is available.
Subsequently, in the 19th century, several international expeditions, namely, Novara (1857–1859),
Challenger (1872–1876), Galathea (1890–1892), Investigator (1890–1892), and Siboga (1899–1900)
enriched the seaweed collection in international herbaria. In the early 20th century, seaweeds were
collected from Indian waters by various Europeans, but it was not until 1925 that an Indian phycologist,
M.O.P. Iyengar, worked on the seaweed flora of Krusadai Island. Fredrik Christian Emil Børgesen,
the Danish Prince and a naturalist, visited the coast of the then undivided Hindustan and contributed
substantially to describing the Indian seaweed flora.
Dixit was the first to report a high number of seaweed species in India—411 species. However,
this included records from Pakistan and Sri Lanka as well. Krishnamurthy and Joshi provided the
first comprehensive information on species distribution for Indian waters. They reported the occurrence
of 522 species of seaweeds of which 130 species belong to Chlorophyta, 136 species to Ochrophyta, and
256 species to Rhodophyta. The subsequent checklist by Untawale et al. reported 604 seaweed
species of which 156 species belong to Chlorophyta, 141 species to Ochrophyta, and 307 species to
Rhodophyta. The revised checklist by Oza and Zaidi indicated the occurrence of 841 species of
seaweeds along the Indian coast of which 216 species belong to Chlorophyta, 191 species to Ochrophyta,
and 434 species to Rhodophyta. Nevertheless, the most recent floristic work, compiled by the Botanical
Survey of India, enumerated the occurrence of 865 taxa from Indian waters of which 212 species belong
to Chlorophyta, 211 to Ochrophyta, and 442 to Rhodophyta. When compared to data from
1970, there is an increase of approximately 343 species over the last 45 years.The analysis of data very clearly
shows that red algae are more diverse than green and brown algae. The abundance of red algal taxa,
which inhabits deeper waters, indicates the dominance of subtidal floristics composition along the
Indian coast. However, by considering the fact that red algae are dominant globally, more efforts are
required to decifer the patterns of seaweed composition in India.The regions of Gujarat and Tamil Nadu harbor the highest seaweed diversity. Gujarat,
which is represented by 1600 km coastline, harbours 198 species of which 109 species from 62 genera
belong to Rhodophyta, 54 species from 23 genera to Chlorophyta, and 35 species from 16 genera to
Ochrophyta. Tamil Nadu has a 1076 km coastline. A recent survey encountered 282 species of
which 146 were from Rhodophyta, 80 from Chlorophyta, and 56 from Ochrophyta. A review of the
literature revealed that there are several papers published on the taxonomy of seaweeds of the Indian
coast, but one cannot claim to have sufficiently covered the entire coastline and to be in a position to
compile its seaweed flora.The analysis revealed that there were two
peaks The first, from 1930–1940, can be ascribed to the work carried out by Boergesen. The second peak,
from 1980–1990, was due to the extensive floristic research carried out in the “Flora of India Project”
funded by the Department of Science and Technology, and particularly by the work of Desikachary,
Krishnamurathy, and Balakrishnan. Currently, the rate of new descriptions has decresed considerably,
which can be attributed to the lower funding for taxonomic studies. Furthermore, such information for
neighboring countries is not available in the public domain for comparison of floristic accounts.
Seaweed Biodiversity Research Gaps and Challenges:
Filling Geographic Gaps to Comprehensively Document Species Diversity and Biomass
Although extensive literature exists on the distribution and diversity of seaweeds from Indian
coasts starting from the eighteenth century, not much is known about recent changes. A recent checklist
has reported the occurrence of 841 taxa; however, much of this knowledge is secondary information
coming from various sources published over a vast time period and, therefore, does not confirm
taxonomic validity of taxa nor comment on recent advances. Some of the recent surveys reported on
the number of species from different maritime states, e.g., Ganesan et al.
reported 282 species from Tamil Nadu. Muthuvelan et al.reported 80 species from the Andaman and Nicobar Islands;
Mukhopadhyay and Pal reported 14 species from the West Bengal coast; Sahoo et al.reported
14 species from the Odisha coast; Mantri and Subba Rao reported 70 species from Diu island;
Jha et al.reported 198 species from the Gujarat coast; Sonali reported 240 species from the
Maharashtra coast; Kaladharan et al.reported 78 species from Karnataka; and very recently,
Kamboj et al. reported 151 species from the Gulf of Kutch (Gujarat) current and
precise assessment of the seaweed biodiversity is essential to infer the changes which have taken place
in relation to pollution, overexploitation of natural resources, climate change, recent introductions,
and bio-invasion. The CSIR-CSMCRI performed a seaweed biodiversity assessment program along
the entire Gujarat coast. A total of 15 sampling stations, namely, Gopnath, Navabander, Kotada,
Sutrapada, Veraval, Adri, Porbandar, Dwarka, Shivrajpur, Okha, Kandla, Mandvi, Koteswar, and
Samiyani Island (Gulf of Kutch) were selected along the coastal belt. Each station was visited
monthly during the lowest spring tide from December 2005 to December 2008. The geographical
co-ordinates were recorded while each sampling along with the in situ photographical evidence in its
natural habit for each seaweed taxa collected. In all, 198 taxa belonging to 101 genera were reported.
Of these, 24 species were new to the Gujarat coast and three, namely, Solieria chordalis, Ahnfeltia plicata
(Rhodophyta), and Dictyopteris serrata (Ochrophyta) were reported from Indian coasts for the first
time. The Rhodophycean members outnumbered other groups with a record of 109 species from
62 genera, followed by members of Chlorophyta with 54 species from 23 genera, and Ochrophytawith
with 35 species from 16 genera. This survey confirmed the presence of industrially important
taxa, namely, Gelidiella acerosa, Gelidium micropterum, G. pusillum, Ahnfeltia plicata, Gracilaria dura,
G. debilis, Gracilariopsis longissima (formerly G. verrucosa), Hypnea musciformis, Meristotheca papulosa,
Porphyra sp, Asparagopsis taxiformis (Rhodophyta), Sargassum tenerrimum, S. plagiophyllum, S. swartzii,
Turbinaria ornate (Ochrophyta), Ulva prolifera (formerly Enteromorpha prolifera), Ulva compressa (formerly
Enteromorpha compressa), and Ulva flexuosa (formerly Enteromorpha tubulosa) (Chlorophyta) from the
coastal waters of Gujarat. This study also confirmed the presence of ecologically important species
such as Caulerpa fastigiata f. delicatula, Enteromorpha ovata (Chlorophyta), Sargassum swartzii, Grateloupia
indica, Helminthocladia clavadosii f. indica, Odontothalia veravalensis, and Predaea feldmannii var. indica
(Rhodophyta) which are endemic.
Opportunities to Develop Seaweed Cultivation and Sustainable Exploitation in India:
Seaweeds are the only sources of industrially important thickening agents and gels such as,
agar, carrageenan and alginates, which are of wide commercial value. They are also a source of fine
chemicals such as natural pigments, manitol, iodine and cosmetic and therapeutically active products.
While giving the growing emphasis on utilization of natural materials and the squeeze for land, the
demand for seaweeds will probably increase in the coming years. The seas around India have not been
used for economic gains to the extent possible except for fishing. The marine capture fisheries in India
have been rapidly depleting due to over exploitation and threatening the very livelihood of more than
6 million fishers in India. The CSIR-CSMCRI has considerable expertise on bio-prospecting of Indian seaweeds since the 1960s. The added value work coupled with development of improved cultivation
technologies has opened up renewed employment opportunities in the seaweed based industries in
India in recent years.
The studies have shown that protoplast (cell devoid of cell wall) and tissue culture of seaweed
are the two important micro-propagation techniques employed for multiplication of elite germplasm
(having desired agronomic or economical traits). These techniques are routinely highlighted as the
means to develop elite clones and seedling production strategy for seaweed aquaculture. It would be
rather prudent to develop a seed bank utilising these methods for long term maintenance of some of
these species catering need of elite germplasm for commercial farming. Furthermore, these techniques
will be helpful for immediate conservation attention, such as Gelidiella acerosa which has been locally
become extinct due to high demand. The successful cultivation from tissue culture progeny has
been achieved very recently.
Seaweeds are globally being used for the production of phycocolloids. In India, about 46 seaweed
based industries—21 agar and 25 alginate—form the phycocolloid business.The limited potential
of Indian seaweed industry is partly due to the non-availability of elite germplasm and the absence of
refined cultivation technologies. However, several recent innovative technologies have been developed
by CSIR-CSMCRI of which worth mentioning is the bio-prospecting of Indian agarophytes. The agarose
having gel strength >1900 g/cm2
in 1% gel from Gracilaria dura has been developed by an eco-friendly
method. Simultaneously, the method of mass cultivation from vegetative fragments as well as
spores has also been developed for this algae, by identifying the fast growing tetrasporophytes with
high yield. It is also noteworthy that the cultivation method neither requires any irrigation
water nor any fertilizer. It also helps oxygenate the seawater and functions as a CO2 sink.
Conclusion:
Tropical Indian waters harbor a diversity of habitats which provide excellent support for a myriad
of species. Although the first report of seaweed from India was made in 1672, taxonomy of this
group is neglected. The initial knowledge regarding to diversity of Indian seaweeds came through
the efforts of European Missionaries and naturalists. It may be noted that utilisation aspect has come
much latter, especially during the second world war when the government made serious efforts to use
this neglected renewable marine resource. In reason of the decreasing number of active taxonomists,
seaweed taxonomy has become very rare in the new literature of the last two decades, and there is
therefore an urgent need to strengthen this subject. This review is the first serious effort to synthetically
gather information on seaweed biodiversity of India, as well as to identify gaps and opportunities.
The challenging task of compiling all the relevant information which is currently scattered and not
easily accessible to the research community shall not only help in drawing comprehensive research
program but also aid in policy formulation. Our review clearly highlights the urgent need of mapping
biodiversity at the pan-Indian level by using the latest techniques of remote sensing and geographic
information system. An appropriate collaborative research is absolutely essential to avoid duplication
and to achieve focused reliable goals for tangible outcome. With only ~10% share in global seaweed
diversity and ~0.01% in farming, India still assume significant importance, as more than 20% of its
coastline is occupied by two island territories namely Andaman & Nicobar and Lakshadweep and
largely unexplored for its seaweed diversity. It may also be noted that, establishment of 100 marine
protected areas located in islands and costal union territories of India, coupled with identification
of nine critical habitats provide strong legal frameworks for protection and conservation of this
economically important resource. Subtidal habitats are also important because they can support
seaweed farming activities. Commercial seaweed farming techniques are simple and easy to adopt.
Thus, more focus has been given by government departments on implementing seaweed farming
under rural employment schemes for rejuvenating coastal economy. Seaweed farming that has been
successful in Tamil Nadu and most recently Gujarat it is likely to attract attention by other maritime
states due to the fact of nil agricultural inputs, farmland requirements, and fresh water needed.
Thank you...
