Integrating the Brite-Box Technology into a Shellfish Hatchery

L’Étang Ruisseau Bar Ltée

Table of contents

• 1. Introduction
• 2. Physical layout of Brite-Box and supporting systems
• 2.1 Pasteurizer System
• 2.2 Incubator Carboy Area
• 2.3 Brite-Box Units
• 3. Production Performance: Brite-Box vs KAWAL systems
• 4. Economic performance
• 4.1 Carboys
• 4.2 KAWAL
• 4.3 Brite-Box
• 4.4 Comparative analysis
• 5. Conclusion
• 6. Ackowledgements

1. Introduction

The production of phytoplankton in shellfish hatcheries is critical to the success and reliability of the seed-producing operation. Large-scale hatcheries require a consistent supply of algal biomass for the feeding of juvenile bivalves, broodstock and larval stages. Of equal importance to the biomass output are key quality variables such as low bacterial loads and contaminants in order to insure the best possible nutritive conditions for the delicate larval and metamorphosis stages. It is not surprising therefore that algal production represents a significant proportion of the cost to produce hatchery seed, reportedly 40-50%. Hence, any technologies which will decrease the cost of production while achieving high productivity and quality would be highly desirable.

The field of intensive phytoplankton production is relatively new and little is known about the effect of various environmental conditions (temperature, light intensity, light spectra, pH, photoperiod cycle) on the physiology of the algae and ultimately, their nutritive value for the various stages of bivalve species. In general, commercial shellfish hatcheries tend to have poor pH and temperature control management in their algal culture operations. Most algal culture systems tend to be light-limited which necessitates having a large surface area dedicated to the production of algal biomass which in turn creates problems for heat regulation. Access to a technology which would allow the undertaking of a meaningful research program on defining the set of parameters to produce the best quality algae will become an asset in the future development of this industry.

This report will describe the first integration of a novel phytoplankton-producing technology, the Brite-Box, into a shellfish hatchery located in northern New-Brunswick which is owned by L’Étang Ruisseau Bar Ltée (ERB). The Brite-Box technology has been operated for several years by the National Research Council at the Marine Research Station in Sandy Cove, Nova Scotia, and this project has triggered a renewed interest in the further development of this technology. Substantial refinements have recently been made and this report will describe the present capabilities and the future options with respect to this phytoplankton-growing technology.

2. Physical layout of Brite-Box and supporting systems

The production of phytoplankton in a shellfish hatchery requires several interacting elements such as the production of the stock cultures, inoculating flasks for carboys, carboys, and other larger volume production containers. A substantial labour input is required to insure the execution of a production schedule for the continuous output of high quality algae. Having a technology that can output algae reliably for an extended period could translate into a substantial saving in labour cost.

2.1 Pasteurizer System

In our operation, the pasteurizer system is used to deliver filtered pasteurized seawater to the Brite-Box system by means of a continuous loop. On the first fill, hot seawater at 75°C is used to fill the Brite-Box units in order to complete the sanitation process. For the subsequent harvest and refill, the pasteurized seawater is heated to 75°C, held at this temperature for 2-3 hours, and then cooled by a secondary plate heat exchanger. Presently, these operations are done manually, but a controlled system installed in the fall 2009 will execute these operations automatically. A CPVC loop with 3-way valves is presently used to deliver the heated seawater from the loop to each of the Brite-Box units.

2.2 Incubator Carboy Area

An incubator is used to maintain the 125-mL stock cultures and the 500-mL inoculating flasks for the carboys under constant light. The incubating temperature is maintained at 20°C. The carboy area consists of a set of shelves which can hold a maximum of thirty 20-L carboys. These carboys are prepared using pasteurized seawater enriched with nutrients, inoculated with 500-mL flasks and are ready to use for a Brite-Box within 5 to 7 days. Generally, one carboy is used to inoculate one Brite-Box; these carboys are pre-screened for TCBS-positive bacteria and for the presence of other contaminants.

2.3 Brite-Box Units

Four 250-L and four 750-L Brite-Box units have been installed in the shellfish facility with a central control panel. Each Brite-Box has a cooling titanium loop coupled to a solenoid valve which is activated when the water temperature is above the desired temperature. Each Brite-Box is also equipped with a pH controller and pH probe. When the pH exceeds a preset level, a solenoid valve is activated and CO2 is injected into the airline. Finally, three switches are used to activate different banks of fluorescent lights to augment the light intensity gradually.

3. Production Performance: Brite-Box vs KAWAL systems

KAWAL vs. Brite-Box comparison trials (1-wk duration) were conducted from June 9 to August 10.  For each trial, three carboys of either Isochrysis galbana (TISO) or Chaetoceros mulleri (CHGRA) were mixed to provide a standardized inoculum for one Brite-Box at our facility (ERB) and one or two KAWAL tubes set up at the Coastal Zone Research Institute (CZRI) in Shippagan. On Day 0, Day 3 and Day 7 biomass levels were quantified in terms of cell counts, fluorescence and algal dry weights.

The typical protocol at the IRZC is to grow algae in the KAWAL tubes over a 7-d period and to fully harvest the tubes at the end of this cycle. Final cell counts at Day 7 varied from 6.0 to10.0 million cells/mL. Over a 21-day production cycle at the IRZC, approximately 85 g dry wt of TISO would have been harvested from one KAWAL tube, or 4 g dry wt per day. Over the same 21-d period, 274 g dry wt and 330 g dry wt were harvested from two Brite-Box units, or 13 and 15 g per day, respectively. In other words, four KAWAL tubes would be required to match the production capacity of one 250-L Brite-Box over the same time period.

4. Economic performance

The comparative cost of producing phytoplankton in different production systems has been a topic generally neglected by researchers, even though it is believed to represent one of the major costs in the operation of a shellfish hatchery. This section translates the data into an economic perspective by comparing the cost of producing one kg dry weight of algae from the various systems. Estimates of capital, operating, and labour costs will be made and coupled to the estimates of productivity that were obtained in the production trials.

4.1 Carboys

The steps involved in the preparation of a carboy at ERB include the cleaning, filling with pasteurized seawater, adding of nutrients, their transfer to the carboy area and inoculating with a 500-mL flask. The projection is that one person will be able to do a maximum of 16 carboys per day, which includes the time to propagate the stock culture and the production of the inoculating flasks.

4.2 KAWAL

The production protocol of phytoplankton from KAWAL tubes varies among hatcheries, but the production scenario at the CZRI will be used for comparative purposes. Basically, the KAWALs are inoculated, grown and entirely harvested at the end of the production cycle. If only KAWAL tubes were being prepared in a working day, it is estimated that a total of 32 KAWALs could be prepared and inoculated, or a total of 160 KAWALs/wk by one person. However, carboys are required for the inoculation of a KAWAL, and if one uses ½ carboy per KAWAL (one full carboy is used per KAWAL at the CZRI), then a maximum of 16KAWALs/day can be prepared by one person, or 80 KAWALs per week.

When the KAWAL system is compared to the carboy system, there is a substantial decline in the cost of producing one kg dry weight of algae. In terms of volume equivalency, one KAWAL is equal to 8.5 carboys, and being able to set-up and inoculate 16 KAWALs per day is equivalent to setting 135 carboys per day, an impossible task for one person.

4.3 Brite-Box

Each Brite-Box unit has independent temperature or pH controls; under these conditions, CO2 utilization should be controlled by the algal demand and thus be more efficient than in a KAWAL system where an approximate amount is being incorporated into the air. The preparation of the Brite-Box for inoculation is one of the most time-consuming activities for this operation. For this activity, many parts of the Brite-Box must be taken apart and thoroughly cleaned in order to insure that any build-up of material from the previous runs has been eliminated. The other time-consuming activity is the harvesting and refilling of the Brite-Box, because it is being done repeatedly over a production cycle. Over a typical run of 30 days, 50% of the labour cost is directed at this task.

4.4 Comparative analysis

There are generalities that can be drawn from the comparison of these three production systems for microalgae. Basically, the larger Brite-Box system has a lower cost per litre of growing volume to produce algae. This is related to the lower capital cost per unit volume – for example, the same pH and temperature systems and the same fixtures (eg titanium coil) are used in the smaller and larger Brite-Box units. Also, in comparison to other algal production system, the Brite-Box utilizes the least labour and with further automation of the processes such as harvesting, the labour cost should decrease over time.

5. Conclusion

A successful integration of the Brite-Box into a shellfish hatchery facility was effected in this project. The algal production from the Brite-Box system was used to produce both bay scallop and Eastern oyster seed. Substantial research remains to be carried out in terms of defining the best operating procedures for the production of various algal species, but this technology provides a means of precisely adjusting temperature and pH levels for each species. Preliminary economic assessment suggests that a substantial reduction in algal production cost will be generated from this technology.

6. Ackowledgements

The Brite-Box is a proprietary technology owned by the National Research Council. This project was made possible through a technology enhancement licence agreement between Mallet Research Services Ltd and the National Research Council.