The Green Thumb Approach to Growing Shellfish at Darling Marine Center
Contact: Dana Morse at (207) 563-3146, a member of the UMaine Marine Extension Team, a collaboration of Maine Sea Grant and Cooperative Extension
WALPOLE — As anyone who has tended plants will tell you, it can be a lot of work to keep your crop healthy and thriving. You need a lot of light, the right nutrients, and attention to detail. At the University of Maine’s Darling Marine Center (DMC), in Walpole, the problem is much the same, except the plants are only about one-hundredth of a millimeter in size.
The tiny plants in question are marine microalgae, and the ones raised at the DMC are used to feed small oysters and other shellfish. Species such as Isochrysis galbana, Tetraselmis chui, Chaetoceros calcitrans and Rhodomonas sp. are commonly raised in shellfish hatcheries the world over, and they require every bit as much care as the most delicate orchid. To help with this tricky and time-consuming task, funds from the 2006 Marine Research Fund, administered by the Maine Technology Institute, have been used toward the installation of a state-of-the-art greenhouse and algal system at the DMC. These improvements will boost production, lower labor costs, and have great impact on the cooperative research done by University of Maine faculty and others throughout the region.
The grant application was written by Christopher Davis of the Maine Aquaculture Innovation Center, together with Paul Rawson of UMaine School of Marine Sciences, and Scott Feindel, shellfish hatchery manager at the DMC. Over $94,000 was awarded to build an energy-efficient greenhouse and install SeaCAPS (Seasalter Continuous Algal Production System) equipment, a system that relies on a sterile environment and carefully controlled inputs to keep algae growing in continuous culture.
Small shellfish like oysters, clams and mussels eat a lot of food, and their principal food is microalgae. To give the young shellfish a balanced diet, hatchery operators grow several species of algae, to get the right mix of carbohydrates, lipids (fats) and protein. The algae are grown in the hatchery greenhouse and raised in transparent containers, so that light can penetrate. Typically, each container is emptied, as the algae are fed to the small shellfish (usually referred to as ‘seed’). Then the culture containers are cleaned, filled with water, nutrients and some of the algae, which are left to grow. The algae divide over time, and the better the conditions, the faster they divide.
Growing microalgae is not easy. The conditions for optimum growth are often hard to maintain, and it is very labor- and time-intensive. Worse, batches sometime get contaminated and go through a rapid downturn, or crash. The new system keeps the algae in balance with their nutrients, so they always grow at an optimum rate, and once the system is set up, the production is continuous, keeping labor at a minimum.
The main components of the new system include a series of culture units, a network of glass- and silicon-tubing to carry nutrients to the culture units and to harvest the algae, and a bank of controls to maintain fluid levels and to conserve heat. Most importantly however, the system installation and maintenance focuses on cleanliness and sterilization to prevent contamination and culture crashes. Once they are all put together, the result is growth of microalgae in what’s called the ‘log phase,’ where cell divisions are the most rapid, and biomass production is at a maximum.
The MTI grant also provided funds for a new greenhouse, in which the algal system sits. The structure was added to the west side of the existing shellfish hatchery, and measures 20 feet square. The greenhouse is important because it allows the algal cultures to be exposed to a maximum of sunlight, rather than use expensive artificial lighting. Given that shellfish hatcheries are hardest at work in the early months of the year, the greenhouse also helps with the expenses of heating.
The algal system and the greenhouse are important to the continued operation of the shellfish hatchery. The current hatchery sits in the Marine Culture Laboratory of the DMC, completed in 2002. There, Rawson and other researchers work with shellfish growers around the state and elsewhere, and the hatchery supports work from other universities and groups.
One such project is the Maine Oyster Broodstock Program (http://www.marine.maine.edu/~rawsonp/oyster_broodstock/start.htm). This work is the continuation of a collaboration between UMaine and shellfish growers that began back in the 1980’s. The program has greatly improved the ability of Maine’s oyster farmers to grow crops quickly, and with better disease resistance. In recent years, Maine oyster growers have donated over $25K in cash to the program, and have invested a similar amount though in-kind services, such as labor and vessel time.
Feindel and Davis recently finished the greenhouse construction and algal system installation, and they are now testing the system and adjusting the controls. The end result will be a more productive facility, and an improved capacity to spawn and rear juvenile shellfish. Though the Darling Center has a rich history in aquaculture research, the new technology is a great addition, and one that will keep the future looking decidedly green for shellfish in Maine.
Photos of the greenhouse construction and installation of the algal system can be found at: http://flickr.com/photos/24015261@N08/sets/72157605248967409/