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International Journal of Fisheries and Aquatic Studies 2015; 2(4): 81-84
ISSN: 2347-5129
IJFAS 2015; 2(4): 81-84
© 2015 IJFAS
www.fisheriesjournal.com
Received: 19-01-2015
Accepted: 06-02-2015
Ivaylo Sirakov
Department of Biology and
aquaculture, Faculty of
Agriculture, Trakia University,
Students campus, 6000 Stara
Zagora, Bulgaria.
Katya Velichkova
Department of Biology and
aquaculture, Faculty of
Agriculture, Trakia University,
Students campus, 6000 Stara
Zagora, Bulgaria.
Stefka Stoyanova
Department of Biology and
aquaculture, Faculty of
Agriculture, Trakia University,
Students campus, 6000 Stara
Zagora, Bulgaria.
Yordan Staykov
Department of Biology and
aquaculture, Faculty of
Agriculture, Trakia University,
Students campus, 6000 Stara
Zagora, Bulgaria.
Correspondence
Katya Velichkova
Department of Biology and
aquaculture, Faculty of
Agriculture, Trakia University,
Students campus, 6000 Stara
Zagora, Bulgaria.
The importance of microalgae for aquaculture
industry. Review.
Ivaylo Sirakov, Katya Velichkova, Stefka Stoyanova, Yordan Staykov
Abstract
The aquaculture is a fast growing sector and constantly increasing its production. This review was done
in order to establish the positive and negative importance of microalgae for the aquaculture due to the
growing significance of this sector. The review is divided into four sections: (1) microalgae – a valuable
additive in feeding in aquaculture, (2) colloring and biologically active compounds, (3) purification of
water, (4) algal toxins.
Keywords: Aquaculture, microalgae, toxins, water purification.
1. Introduction
Algae are photosynthetic organisms and they are the ultimate source of both cellular carbon
and chemical energy for other organisms. Therefore, they often called primary producers.
Generally they categorized as macroalgae (seaweed) and microalgae (unicellular). For the
growth of microalgae need light, carbon dioxide and nutrients. The microalgae are cultivated
and use for food, for production of useful compounds, as biofilters to remove nutrients and
other pollutants from wastewaters, in cosmetic and pharmaceutical industry and in aquaculture
purpose. Also microalgae are potentially good sources for biofuel production because of their
high oil content and rapid biomass production [1, 2, 3].
The aquaculture is a fast growing sector and constantly increasing its production. The most
frequently used microalgae genus in aquaculture are Chlorella, Tetraselmis, Scenedesmus,
Pavlova, Phaeodactylum, Chaetoceros, Nannochloropsis, Skeletonema and Thalassiosira. They
have rapid growth rates and are stable in culture to possible variation in temperature, light and
nutrients as may occur in hatchery systems. Microalgae must have a good nutrient
composition, including an absence of toxins that might be transferred up the food chain [4].
The main application of microalgae in aquaculture is connected with their usage for feed
purposes. Currently 30 per cent of the world algal production is used for animal feed [5] but the
use in aquaculture is mainly for larval fish, molluscs and crustaceans [6]. Waste water from
intensive fish farms are enriched with solid particles and dissolved nutrients, mainly in the
form of inorganic nitrogen and phosphorus. The use of live microalgae to remove excess
dissolved nutrients from aquaculture effluents is an efficient and cost effective waste water
treatment method [7]. Microalgae contain numerous bioactive compounds that can be harnessed
for commercial use. The pigment responsible for the pink color of salmon and trout is the
carotenoid astaxanthin and one of the natural astaxanthin sources is the freshwater green alga
Haematococcus pluvialis [8].
On the other hand, although a small number of some microalgae release toxins which can
cause problems in the freshwater aquaculture of both vertebrates (fish) and invertebrates
(shellfish). Severe blooms of even non-toxic algae can spell disaster for cultured hydrobionts,
because the blooms deplete the oxygen in the shallow waters of many aquaculture systems.
This review was done in order to establish the positive and negative importance of microalgae
for the aquaculture due to the growing significance of this sector.
2. Microalgae – A valuable additive in feeding in aquaculture
Increasing the needs for protein and the high cost of fish meal in the recent years has led to the
need to search for new alternatives, as animal and plant sources of protein for the needs of
aquaculture. One such accessible and relatively inexpensive food component that could
respond successfully the challenge question raised by aquaculture is algae.
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International Journal of Fisheries and Aquatic Studies
Concerning the usage of algae meal (Spirulina sp.) for the
replacement of fish meal in the feed for hydrobionts,
experiments were conducted with the following species – fish
from genera Oreochromis [9], Siganus canaliculatus [10],
Oncorhynchus mykiss [11].
Microalgae are utilized in aquaculture as live feeds for all
growth stages of bivalve molluscs (eg. oysters, scallops, clams
and mussels), for the juvenile stages of abalone, crustaceans
and some fish species, and for zooplankton used in aquaculture
food chains [4]. Microalgal species can vary significantly in
their nutritional value, and this may also change under
different culture conditions [12, 13]. Microalgae have good
nutritional properties as monospecies or within a mixed diet
which include C. calcitrans, C. muelleri, P. lutheri, Isochrysis
sp., T. suecica, S. costatum and Thalassiosira pseudonana [13,
14, 15].
Genera of microalgae for larval feeds include Chaetoceros,
Thalassiosira, Tetraselmis, Isochrysis, and Nannochloropsis.
These organisms are fed directly or indirectly to the cultured
larval organism. Indirect means of providing the algae are
through artemia, rotifers, and daphnia, which are, in turn, fed
to the target larval organisms.
Combination of different algal species provides better
balanced nutrition and improves fish growth better than a diet
composed of only one algal species [16]. For use in aquaculture
a microalgae strain has to ease of culturing, lack of toxicity,
high nutritional value with correct cell size and shape and a
digestible cell wall to make nutrients available [17].
Protein and vitamin content is a major factor determining the
nutritional value of microalgae, also polyunsaturated fatty
acid. Different methods are practiced to improve the
polyunsaturated fatty acid content in microalgae: manipulation
of conditions such as light intensity, nutrient status or
temperature allows the modulation of the lipid composition
and consequent optimization of their overall yield and
productivity [18].
The use of algae as an additive in aquaculture has received a
lot of attention due to the positive effect it has on weight gain,
increased triglyceride and protein deposition in muscle,
improved resistance to disease, decreased nitrogen output into
the environment, increased fish digestibility, physiological
activity, starvation tolerance and carcass quality [19, 20].
3. Colloring and biologically active compounds
Microalgae such as Dunaliella salina, Haematococcus
pluvialis and Spirulina sp. are also used as a source of natural
pigments for the culture of prawns, salmonid fish and
ornamental fish. Dunaliella sp., Chlorella sp. and Spirulina sp.
are three major type that have been used successfully to
produced high concentrations of valuable compounds such as
lipids, protein and pigments [21, 22, 23]. Chlorella sp. and
Spirulina sp. are commonly included into feeds for ornamental
fish, where colouration and healthy appearance is the main
market criterion [24, 25, 26].
Some microalgae are organisms that live in complex habitats
with change conditions of salinity, temperature, nutrients, UV-
Vis irradiation, therefore, they must adapt rapidly to the new
environmental conditions to survive, producing a great variety
of secondary (biologically active) metabolites, which cannot
be found in other organisms [27]. Rønnestad et al. [28]
demonstrated that microalgae pigments transferred through to
zooplankton may contribute to nutritional value. The pigment
lutein is common in "green" microalgae (Tetraselmis spp.)
which could be used to improve the nutritional value of
Artemia. The lutein could be converted into the vitamin A
from halibut larvae when aquatic crustaceans were used as a
feed. Dunaliella salina is grown for a source of the
photosynthetic pigment, beta-carotene. Beta-carotene is used
as an orange dye and as a vitamin C supplement.
According Li et al. [29] some high-value bioproducts extracted
from microalgae are: astaxanthin and leutin produce
Haematococcus pluvialis, phycocyanin - Spirulina platensis,
polyunsaturated fatty acids – Chlorella sp., Schizochytrium
sp., biotin and vitamine E - Euglena gracilis.
The potential of micro-algae as a source of food coloring is
limited. The algal-derived food coloring is not photo stable
and the color tends to bleach with cooking.
4. Purification of water
Cultivation of microalgae is usually carried out in suitable
nutrient media to aggregate a biomass used for food or biofuel
production /1, 30/. Except in a nutrient medium for the
cultivation of microalgae are used and waste waters from
recirculation systems in aquaculture, as they are rich in
inorganic and organic substances. Thus establishing that
certain types of algae have a potential for integrated use - in
water purification from aquaculture and biomass production
[31]. Such species are C. vulgaris, N. oculata, T. chuii which
show high potential of accumulation in terms of nitrogen and
phosphorus compounds contained in the wastewater from
aquaculture and could be used for their treatment /32, 33/. The
microalgal bioremediation systems in terms of wastewater
aquaculture treatment and recycling have received an impetus
over the past few years. They are designed to meet specific
treatment and wastewater specifications, and may
simultaneously solve environmental and sanitary problems
along with economic feasibility. The microalgal genera, which
have a role like a treatment plant in aquaculture wastewater are
Chlorella, Ankistrodesmus, Scenedesmus, Euglena,
Chlamydomonas, Oscillatoria, Micractinium and Golenkinia
[34], where wastewater-born nutrients are converted into
biomass protein. Their morphology as unicellular
microorganisms could enable absorbing nutrient more
effective compared to terrestrial plant.
In Chile, for example, has some experience to be growing
salmon with a specific type of algae that remove phosphorus
and nitrogen waste and enrich the water with oxygen, which
could also serve as a supplement in the diet of fish [35].
Nowadays are creating a complex aquaculture consisting of
microalgae, which could be used for water treatment in fish
farming. Wastewater remediation by microalgae is an
ecological process without any secondary pollution and the
biomass produced is reused [36]. They are considered one of the
most efficient, environmentally friendly, relatively low-cost
and simple alternative wastewater treatments compared to
conventional wastewater treatment techniques [37].
5. Algal toxins
Algal toxins are organic molecules produced by a variety of
algae in marine, brackish and fresh waters [38]. They are a
problem in aquaculture when they are produced in sufficient
quantities, with sufficient potency, to kill cultured organisms,
decrease feeding and growth rates [39]. The production of algal
toxins is normally associated with algal blooms. Some blue-
green algae, particularly Anabaena and Microcystis, produce
toxins (cyanotoxins) poisonous to fish. For example
neurotoxins are organic molecules that can attack the nervous
systems of vertebrates and invertebrates. Neurotoxins are
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International Journal of Fisheries and Aquatic Studies
produced by several genera of cyanobacteria including
Anabaena, Aphanizomenon, Microcystis, Planktothrix,
Raphidiopsis, Arthrospira, Cylindrospermum, Phormidium
and Oscillatoria. Neurotoxins produced by Anabaena spp.,
Oscillatoria spp. and Aphanizomenon flos-aquae blooms have
been responsible for animal poisonings around the world [40,
41]. Hepatotoxins are produced by many genera of
cyanobacteria and have been implicated in the deaths of fish,
birds, wild animals, livestock and humans around the world [40,
41]. Symptoms of poisoning in fish include flared gills because
of difficulty breathing and weakness or inability to swim.
Blooms of Prymnesium parvum have been responsible for fish
kills and significant economic losses in Europe, North
America and other continents. The P. parvum ichthyotoxin
affects gill-breathing aquatic animals such as fish, brachiated
tadpoles and mollusks [42]. Relatively recent research has
confirmed that Euglena species produce an ichthyotoxin in
freshwater aquaculture [43]. Like E. sanguinea –this species
killed with reddening of gill tissue laboratory-reared channel
catfish, tilapia (Oreochromis niloticus) and striped bass.
6. Conclusion
This review shows the practical importance of microalgae for
aquaculture, but among these were traced and negative aspects
of the excessive development. The possibility of combined use
of a microalgae for wastewater treatment and their subsequent
using for food is a very perspective direction in which
direction the studies should continue.
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