Microalgae: Different types of algae provide vital nutrients to rotifers, copepods and larvae of...

Microalgae are the foundation supporting much of the marine food chain, and they are the natural food of filter-feeding organisms. Algae are therefore essential for production of live feeds for larviculture

of finfish and shrimp. Thousands of species of microalgae are known to science. They present an enormous range of cell sizes, cell structures, biochemical constituents that determine their nutritional value and digestibility, and they also vary widely in ease of culturing. Microalgae can be very difficult, even impossible to identify to species based on light microscopy alone, and different strain isolates that appear identical may exhibit very different biochemical profiles or behavior in culture. Careful consideration is therefore necessary in order to select the most suitable strains for different larviculture applications. Although many microalgae strains have been tested as feeds, only about 20 are in widespread use. What follows can be no more than a brief overview of the how these algae are most commonly used in larviculture.

RotifersThe rotifers used in aquaculture (species of the genus Brachionus)

are capable of ingesting particles as small as bacteria and as large as 10–30 µm; larger rotifers are capable of ingesting correspondingly

larger particles. Bacteria are too small to provide a significant source of nutrients, with the possible exception of vitamins (e.g. B12). Rotifer digestive systems are equipped with a unique grinding apparatus (mas-tax) that can mechanically disrupt yeast or algae cells, enabling rotifers to thrive on algae that may not be digestible by other filter-feeders. Rotifers can ingest inert particles, and yeast has often been used as an inexpensive feed to maintain rotifer cultures. But the nutritional value of rotifers as live feed for larval fish or shrimp is determined by the quality of the feed used to produce the rotifers, and only algae feeds can support high-density rotifer populations with optimal nutritional profiles.

Many of the algae commonly used in aquaculture have been used to successfully culture rotifers, at least for experimental studies, but by far the most commonly used algae are strains of Chlorella, Nannochloropsis, and Tetraselmis. These algae can be produced reliably and at relatively low cost, but none can produce rotifers with an optimal nutritional profile for many larvae. Their most conspicuous shortcoming is the essential HUFAs (Highly Unsaturated Fatty Acids) content, in particular EPA and DHA, which for many fish are particularly important for nerv-ous system development. Chlorella in particular lacks HUFAs, although it can support excellent growth of rotifers. Nannochloropsis contains high levels of EPA, and Tetraselmis moderate levels; both can support excellent rotifer growth, but neither contains DHA. A Japanese com-

MicroalgaeDifferent types of algae provide vital nutrients to rotifers, copepods and larvae of finfish, shellfish and shrimp

by Dr Eric Henry, PhD, Research Scientist, Reed Mariculture Inc

30 | INTERNATIONAL AQUAFEED | September-October 2015

FEATURE

pany offers Chlorella that has been infused with DHA. However, the sterol profile of Chlorella, like many other green algae such as Dunaliella and Haematococcus, lacks cholesterol. Rotifers produced to feed shrimp or crab larvae should instead be fed Nannochloropsis, which will provide the cholesterol that is essential for these crustaceans.

CopepodsA diverse array of different copepod species are used in larviculture,

and they vary in their capacity to thrive on different algae. Some require different algae at different stages of development. The most commonly used algae are strains of the flagellates Isochrysis and Tetraselmis, and the diatoms Thalassiosira and Chaetoceros. Some strains of Isochrysis (most often the “Tahitian strain” or “T-Iso,” which has been recently recognised as the new genus Tisochrysis) have supported growth and development of some copepods through the entire life-cycle, but other copepods require additional strains in their diet. This may be explained by the fact that although Tisochrysis is widely used in aquaculture due to its high levels of DHA, it lacks cholesterol, and some copepods have the specific requirement for cholesterol that has been documented in many other crustaceans.

Diatoms, especially strains of Thalassiosira and Chaetoceros, have seen wide use in copepod culture, although some studies have concluded that “diatoms” can harm copepods, or that a diatom diet requires supplementation with cholesterol. Such broad generalisations ignore the great biochemical diversity among diatoms; for example, very few contain significant cholesterol, but some of these can have high levels.

BivalvesAlthough bivalve aquaculture relies on natural phytoplankton for

market production, cultured algae are essential for larviculture in hatcheries. Cultured algae are also often used for “nursery” culture

of spat and later juvenile stages, and for improving the condition of broodstock for spawning. The algae most widely used for bivalves include strains of Nannochloropsis (mostly for mussels), the diatoms Thalassiosira and Chaetoceros, and the flagellates Tetraselmis, Isochrysis (including Tisochrysis) and Pavlova.

Pavlova strains are known to have a high HUFA content. In addition, there is a widespread impression among bivalve hatchery operators that Pavlova imparts an unknown “special” benefit as a larviculture feed,

and hatcheries expend extra effort to provide Pavlova despite frequent culture difficulties. It may be that the peculiar beneficial effects are not due to the HUFA content, which is not markedly different from what can be provided by combinations of other algae. Different Pavlova strains contain a remarkably diverse range of unusual sterols. Research with scallop larvae indicates that several Pavlova strains produce a sterol

ANDRITZ Feed & Biofuel A/SEurope, Asia, and South America: [email protected] and Canada: [email protected] www.andritz.com

Your global technology process supplier for the aqua feed industry

ANDRITZ is one of the world’s leading suppliers of technologies, systems, and services relating to advanced industri al equipment for the aqua feed industry. With an in-depth knowledge of each key pro-cess, we can supply a compa-tible and homogeneous solution from raw material intake to finished feed bagging.

September-October 2015 | INTERNATIONAL AQUAFEED | 31

FEATURE

that is a structural analog of an arthropod molting hormone, ecdysone, and it induces metamorphosis in larvae. This is a very unexpected phenomenon, and it is a reminder that there remain many gaps in our knowledge of how microalgae may affect the biology of bivalves.

ShrimpShrimp aquaculture exploits a variety of shrimp and prawn species,

many of which have been the subject of larval feeding studies. Caution is therefore required when generalising findings to all shrimp, but some useful conclusions can be drawn.

Larvae of shrimp naturally feed primarily on microalgae, and use of algae as sole feed or co-feed with larger prey can often be ben-eficial well into postlarval stages. The most commonly used algae are strains of Isochrysis Tetraselmis, Thalassiosira and Chaetoceros. Because most shrimp production is carried out in very large-scale culture systems, very large amounts of algae are required, putting a premium on algae capable of maintaining high growth rates under mass-production conditions. Diatoms have proved to perform particularly well in shrimp facilities. This may be attributable in large part to the fact that the silica cell wall of diatoms functions as a pH buffer at the cell surface, enhancing the activity of extracel-lular carbonic anhydrase, the enzyme that converts bicarbonate to carbon dioxide. This mechanism greatly enhances photosynthesis in the relatively high pH (8.5 and above) prevailing in vigorous algae cultures.

FinfishWhen larval fish consume live zooplankton prey, they are gaining

nutrition that origi-nated from the feed consumed by the live prey, most often algae. However, an addition-al, often overlooked contribution from algae is direct con-sumption of algae by the larvae. No doubt some of the beneficial effects of “greenwa-ter” (addition of algae to larviculture tanks) can be attributed to consumption and assimilation of algae by

larvae, as has been demonstrated in cod, turbot, halibut, and clownfish. Other beneficial effects of algae have been reported, such as stimula-tion of digestive activity and immune responses. Suppression of toxic Vibrio bacteria by Tetraselmis and Isochrysis has also been reported.

Nannochloropsis is the most commonly used greenwater alga, because of its low cost and small cell size that imparts a low sinking rate, which ensures that it remains in suspension. It is also an excel-lent feed for the rotifers often used as first-feed for larvae, helping to maintain the nutritional value of the rotifers until the larvae can con-sume them. But Nannochloropsis contains no DHA, and is difficult for many organisms to digest, so other larger-celled and more digestible algae such as Tisochrysis with its high DHA content, or algae such as Tetraselmis with its significant taurine content, may prove to function as more effective as feeds for larvae.

How to choose optimal algal feeds?Although various nutritional components have been documented in

many algae strains, complete nutritional profiles are known for very few of them, so it can difficult to predict which strains are the best choices for a particular application. It is unfortunate that so many studies of the nutritional performance of microalgae have tested only one or two strains in each trial, because one or two strains are unlikely to provide an optimal nutritional profile comparable to that provided by the natural mixed phytoplankton assemblages that filter feeders have evolved to exploit.

It is equally unfortunate that so many feeding studies have failed to clearly identify the particular strains of the algae that were used. Although the HUFA contents of many strains have by now been well-documented, sterol profiles have been more challenging to character-ize because there is far more strain-to-strain variation, even among strains supposedly of the same species. Additional uncertainties arise because the nutritional profiles of even well-known strains of micro-algae can be strongly influenced by culture conditions, including light regime, temperature, nutrient (e.g. nitrogen, phosphate) availability, and the growth phase of the culture (exponential, stationary, declining) when harvested. All these sources of variability in the nutrient value of algae can lead to apparently contradictory findings among studies using ostensibly the same algae.

Nevertheless, these findings are not useless. Reports of the efficacy of certain strains of algae are likely to indicate the most promising can-didates for subsequent trials. Successful trials establish that the strains can provide good nutrition. Contradictory negative results are then most likely to indicate that failure was caused by some unidentified factors in the trials, not the intrinsic qualities of the strains. Much work remains to be done, but well designed feeding studies will continue to refine our understanding of how algae can be used more effectively in larviculture.

www.reedmariculture.com.


FEATURE

Reed Mariculture Inc (RMI) was founded in 1995 by Tim Reed to grow "tank raised" bivalve shellfish. Tim's concept was to produce the

first commercially available shellfish that was raised on land, not in the ocean, producing a product that would be completely safe from toxins such as red tide algae, bacteria blooms, viruses, sewage run-off, and toxic metals.

Reed Mariculture developed tank raised shellfish technology for three years and during this same time developed and refined the technology for large-scale grow out of marine microalgae, which is the feed for shellfish.

In 1998 RMI determined that there was a more lucrative market in selling the microalgae directly to other hatcheries and shut down all shellfish operations. RMI's core technology is a proprietary closed-system photobioreactor design that allows microalgae to be grown in laboratory sterile conditions. This technol-ogy is radically different than the open-pond technology used for growing freshwater spe-cies of microalgae such as Spirulina, Chlorella, Haematococcus, and Chlamydomonas.

In 2003, RMI expanded its product focus from microalgae to a broader range of larvi-culture products with the introduction of live zooplankton (rotifers, copepods, and Mysid shrimp) and by distributing products such as ClorAm-X® (for ammonia control) and Otohime Feeds (Japanese weaning diets).

In 2004, RMI entered the home aquarium market with the introduction of the Phyto-Feast® products. Phyto-Feast is a super con-centrate of marine microalgae formulated for feeding exotic filter feeders such as clams, corals, sponges, and tunicates that are popular in marine reef tanks.

In 2005, RMI expanded their offerings

into the Marine Ornamental industry with the Reef Nutrition product line. This product line includes marine microalgae, macroalgae, rotifers, copepods, mysid shrimp.

Reed Mariculture is now the world's larg-est producer of marine microalgae concen-trates. The Instant Algae® larviculture feeds are used by over 500 hatcheries, universities, and marine ornamental operations in more than 70 countries around the world. We also produce zooplankton, copepods, and weaning feeds.

I was able to talk at some length with RMI founder, Tim Reed about what captivated his interest in aquaculture and how his passion has been the main driver behind the expan-sion of Reed Mariculture Inc from its origins in 1995 to where it is today.

IAF: Could you tell us a little bit about your background and what sparked an interest in the aquaculture industry? TR: What sparked my interest was discovering the amazing taste of razor clams! After college I was working on a factory trawler and on a trip to Chile I was introduced to razor clams. That fueled a dream to start a land-based farm to grow high-value bivalves to sell into the San Francisco market, which required large amounts of marine microalgae.

IAF: You set up and founded Reed Mariculture in 1995. The company is now the world’s largest producer of marine microalgae concentrates used by over 500 hatcheries in more than 90 countries. Can you tell us a bit more about the genesis of the company and its evolution? TR: When Reed Mariculture Inc (RMI) was founded in 1995, my goal was to produce the

first commercially available, biosecure shellfish raised on land. We developed tank-raised shellfish technology for three years, and during this same time we developed and refined the technology for large-scale grow-out of marine microalgae - the feed for shellfish. RMI's core technology was and remains to this day a proprietary, closed-system photo-bioreactor design that allows microalgae to be grown in controlled conditions. In 1998 we determined that selling our microalgae directly to other hatcheries was a more lucrative market, and we shut down all shellfish opera-tions. We innovated a line of refrigerated microalgae concentrates for hatcheries called Instant Algae® that provide “algae when you need it™.” In 2003 we expanded our larviculture product line with the introduction of live zooplankton (rotifers, copepods, and mysid shrimp), and by distributing products for ammonia control and Japanese weaning and juvenile diets. In 2004 RMI entered the home aquarium market with the introduction of the Phyto-Feast® prod-ucts-super-concentrates of marine microal-gae formulated for feeding coral, clams and other popular, marine reef tank filter feeders. We expanded into the marine ornamental industry with the Reef Nutrition® prod-uct line, which includes marine microalgae, macroalgae, rotifers, copepods, Mysis shrimp and other feeds. In 2011 Reed Mariculture launched a new product line, APBreed™, to provide customised solutions for the unique needs of aquarists, propagators and breeders based on our advanced hatchery products.

IAF: A passion for the uses and applications of algae in aquaculture obviously lies at the heart of your work. Can you tell us more

Q&A with Reed Mariculture

Inc founder and President Tim Reed

by Olivia Holden, International Aquafeed Magazine

Microalgae


FEATURE

about the process of how microalgae is grown?TR: Unlike traditional algae systems, we use proprietary, closed, recirculating photobio-reactor design that allows microalgae to be grown in controlled conditions, miles from any vectors of contamination. Our proprietary harvest and concentration processing then retains intact whole cells that retain all their nutritional value, while at the same time ren-dering them non-viable.

IAF: What comprises your current product range and applications?TR: We are the plankton people - both microalgae and zooplankton. We grow and supply hatcheries with a variety of marine microalgae-based feeds for many types of larvae, including finfish, bivalves, crustaceans and ornamentals. We also supply microalgae for rotifers and copepods to nourish finfish and other larvae. In addition, we grow and supply three strains of live rotifers and three strains of live copepods, and supply mysid shrimp and artemia.We are known for our Instant Algae prod-ucts that provide “algae when you need it.” Instant Algae has all the advantages and characteristics of live algae without the large investment of infrastructure, time and labor required to grow it yourself. These biosecure

concentrates and custom blends of the most effective algae for larvae growth and survival can be used as a complete feed replacement or as a nutritional supplement, and provide insurance against a crash. The algal cells are non-viable but intact whole cells that retain all their nutritional value, which in turn provides maximum nourishment to the larvae. We also supply eight species of algae including four species of diatoms, plus Isochrysis, Tetraselmis, Pavlova and Nannochloropsis.For finfish, our RotiGrow® product line includes three all-in-one growth and enrich-ment feeds with varying levels of DHA. The nutrition from the algae in these products is incorporated into the tissue of the rotifers, not merely the gut, and the whole, intact cell of the microalgae encapsulates all of the nutrients, resulting in a cleaner tank, less waste and greater value. For bivalves, we produce Shellfish Diet®, a superior feed that is a blend of algae for broodstock maturation, first feed-ing larvae, setting and spat grow-out.As a complement to the feeds we grow and produce, we also carry a number of support products including Otohime - a high quality Japanese larval weaning and juvenile feed, TDO Chroma Boost™, a pellet fish food "top-dressed" with Haematococcus for vibrant color and superior nutrition, as well as ClorAm-X® for ammonia control and a small

assortment of specialty zooplankton growing equipment.

IAF: What products do you offer specifically for shrimp, one of the biggest exports in Asia-Pacific?TR: Several of our single-species Instant Algae concentrates are used in shrimp produc-tion: Thalassiosira weisflogii and pseudo-nana, Chaetocerous “B” and calcitrans, and Tetraselmis. All provide “algae when you need it,” in the form of clean, bio-secure nutrition for shrimp. Instant Algae is currently most often used as a biosecure supplement to algae grown on site, but we are currently working on the development of blended algal products nutritionally optimised to be available as a complete algae replacement.

IAF: You also supply to the home and com-mercial aquarium market. What is exciting about this for you?TR: Not everyone realises that the needs of home and public aquariums are very similar to the needs of hatcheries. They all need microalgae and zooplankton, which is what we specialise in. We provide clean, biosecure, microalgal and zooplankton feeds that are convenient and easy for home hobbyists and aquariums to use. What is really exciting is how our feeds are helping cutting-edge fish


FEATURE

and ornamental breeders, who are trying to commercialise various hard-to-raise animals and expand the markets for them. Their suc-cesses will ultimately result in greatly reducing or eliminating the need for wild capture and its devastation of natural habitats.

IAF: In what way does Reed Mariculture work with academics and Universities to further and share knowledge?TR: We supply feed to hundreds of university programs that are pushing the envelope in aquaculture technology. They are never shy about giving us feedback on how we can improve our products and telling us what their

unmet needs are. We have developed and maintained close, collaborative relationships with these programs for decades.

IAF: Client care and technical support lies at the heart of any successful business. How does Reed ensure this is achieved?TR: We pride ourselves on our customer service and are committed to going above and beyond to support our customers - whether it’s to get the product out in a timely way to hard-to-reach locations, providing technical assistance in emergency situations, or collaborating with customers to develop

custom blends to meet their animals’ specific nutritional requirements. We refer all techni-cal questions to our phycologists and live feed specialists who take the time to answer questions. We also solicit feedback from our customers to ensure that we are meeting or exceeding their needs.

IAF: Sustainability is obviously a very press-ing issue as the demand for more food grows. How is Reed Mariculture engaging with sustainability?TR: As the supply of fish and shellfish, and more importantly larvae and seed from the wild, become harder to come by,

aquaculture is going to increasingly turn to land-based hatchery larviculture for tradi-tional food sources and new species. Reed Mariculture has the clean, highly nutritious feeds that are needed to support this transi-tion. We also see ourselves playing a role in a future with healthier reef ecosystems. When ornamentals aren’t predominately collected from the wild, creating massive damage to delicate reef life, but are increasingly raised in hatcheries and farms, reefs can be saved from destruction, opening up the possibility of restoration.In terms of our own production from a sus-

tainability point of view, our closed, recirculat-ing systems are highly efficient. We have near -0- wastewater, and no discharge. Traditional open pond and batch culture systems lose considerable amounts of water through evap-oration, and there are not always effective means for cleaning residual water and making it reusable. As aquaculture grows to meet the requirements of the coming decades, the ability to produce algae sustainably will be critically important.

IAF: What do you perceive to be the biggest challenges facing the aquaculture industry today?

TR: The biggest challenges across all sectors of aquaculture are: increasing hatchery produc-tion, improving hatchery technology, and the availability of high quality, healthy, clean larvae/seed that will perform well in grow-out.

IAF: And finally, what is the one piece of advice you would give anybody looking to work in the aquaculture field? TR: Aquaculture is a special community of “scientist farmers” who thrive on innovating, nurturing and getting their hands wet. If this kind of thing is your passion, aquaculture can be the most rewarding adventure of a lifetime.

"Aquaculture is a special

community of “scientist farmers”

who thrive on innovating,

nurturing and getting their

hands wet. If this kind of thing

is your passion, aquaculture

can be the most rewarding

adventure of a lifetime"


FEATURE


FEATURE

AQUA RANGE

Providing proficient tools to achieve cost-effective and sustainable

aquaculture practices

Is your fish ready?

T. +34 91 501 40 41 [email protected] www.norel.net

Die and roll re-working machines

O&J Højtryk A/SØrnevej 1, DK-6705 Esbjerg ØCVR.: 73 66 86 11

Phone: +45 75 14 22 55Fax: +45 82 28 91 41

mail: [email protected]

www.oj-hojtryk.dk

OJ_qp_new.indd 1 23/01/2015 14:51

AE2015 Gold Sponsor

AE2015 JOIN US IN THE NETHERLANDS

Imag

es c

ourte

sy o

f Rot

terd

am M

arke

ting,

the

Dutc

h M

usse

l Pro

mot

ion

Boar

d an

d Ho

lland

Aqu

a B.

V.

Organised by the European Aquaculture Society in cooperation with IMARES Wageningen UR

easonline.org

Microalgae: Different types of algae provide vital nutrients to rotifers, copepods and larvae of...

Science

Transcript of Microalgae: Different types of algae provide vital nutrients to rotifers, copepods and larvae of...