Kenneth R. Tenore

Tidal resuspension in Buzzards Bay, Massachusetts: I. Seasonal changes in the resuspension of organic carbon and chlorophyll a

Abstract Greater than 50% increases in the amount of particulate organic carbon and chlorophyll a per square meter occurred in a 13-m water column of Buzzards Bay during tidal cycles. The composition and quantity of the resuspended material varied seasonally. Greater percentages of the carbon in the water column were resuspended during the summer and winter months while more resuspension of chlorophyll a occurred during spring and summer. Increases in the amount of primary production in the water column occurred with the resuspension of chlorophyll a , indicating that the resuspended cells were viable. The contribution of this resuspended phytoplankton to the total yearly primary productivity can be significant. The tidal resuspension of phytoplankton and detritus from the mud bottom of Buzzards Bay, if utilized by the zooplankton community, could provide significant food resources for secondary production.

Inorganic nitrogen removal in a combined tertiary treatment—marine aquaculture system—I. Removal efficiences

Abstract The increasing awareness that nitrogen is often a key nutrient controlling algal growth in coastal marine waters has led to a concerted effort to find ways to remove ammonia and nitrate from wastewaters. A novel approach to this problem involves the combining of algal and seaweed nutrient stripping processes with a marine aquaculture. Not only is nitrogen removed from wastewater, but important commercial shellfish and seaweeds are produced. A prototype process consisting of growth systems for marine algae, oysters and seaweed, joined in series, was fed secondarily treated wastewater, diluted 1:4 with seawater, for 11 weeks during the Summer of 1972. During this time 95 per cent of the influent inorganic nitrogen was removed by algal assimilation. The oysters in turn removed 85 per cent of the algae, but regenerated as soluble ammonia 16–18 per cent of the nitrogen originally bound in the algal cells. All of the regenerated nitrogen was removed in the seaweed system so that the total inorganic nitrogen removal efficiency of the system was 95 per cent. Phosphorus removal on the other hand was not nearly as complete as only 45–60 per cent was removed. The process has the capability of being expanded to include additional trophic levels in an integrated and highly controlled food chain system to serve the dual function of tertiary wastewater treatment and waste recycling through the production of shellfish and seaweeds.

The food chain dynamics of the oyster, clam, and mussel in an aquaculture food chain

Abstract The food chain dynamics of the edible mussel Mytilus edulis L., the American oyster Crassostrea virginica (Gmelin) and the hard clam Mercenaria mercenaria (L.) were investigated in large experimental tanks with flowing, filtered sea water and controlled addition of phytoplankton. The feeding rate of the mussel (5.36 μg carbon removed/l/g C animal was higher than that of the oyster (3.92) and clam (3.03) but the ecological efficiencies (net production/ingested food) × 100 of the clam (23.69 %) and the oyster (18.38 %) were higher than that of the mussel (10.01 %). The food chain efficiencies (net production/available food) were lower than the ecological efficiencies, suggesting under-exploitation of the available food. The clam, although having a lower feeding rate, was more efficient in utilizing the food it filtered and so showed the highest net production. The rates (μg-at/l/g C animal) of regeneration of nutrients, especially total inorganic nitrogen (mussel, 2.1723 × 10 −3 ; oyster, 7.4270 × 10 −3 ; and clam, 8.1750 × 10 −3 ) along with reported high biodeposition rates of bivalves suggest that multi-species aquaculture systems would be more efficient and productive than one-species systems.

Comparison of rates of feeding and biodeposition of the American oyster, Grassostrea virginica Gmelin, fed different species of phytoplankton

The feeding and biodeposition rates of small (2.4 cm) and large (5.2 cm) Crassostrea virginica were differently affected in experiments using flowing systems by moderate (292 μ C/1 sea water) and high (487 μ C/1 sea water) concentrations of the following phytoplankton: the diatoms, Thalassiosira pseudonana (Hasle & Heindal) (Cyclotella nana), Skeletonema costatum (Greville) Cleve, Nitzschia closterium (Ehrenberg) Wm. Smith, and the green alga, Dunaliella tertiolecta Butcher. The average feeding rate of the oysters on the different phytoplankton was: Dunaliella < Nitzschia < Skeletonema < Thalassiosira. In contrast, oysters fed on Thalassiosira had the lowest rate of biodeposition (1.626 × 10−3 g ash-free dry wt/g dry flesh wt per day) but oysters cultured on Nitzschia showed the highest rate of biodeposition (2.952 × 10−3 units). The response of the feeding rate of the two sizes of oysters to food concentration differed according to the algal food source. Oysters fed on Thalassiosira and Skeletonema exhibited a higher feeding rate at a higher food level: in contrast, oysters fed on Nitzschia showed no significant differences and those cultured on Dunaliella a depressed feeding rate at the higher food concentration. We observed no differences in feeding rate between small and large oysters fed on Skeletonema and Dunaliella, but small oysters had a higher feeding rate than large oysters when cultured on Thalassiosira and a lower feeding rate when fed on Niitzschia. The smaller size of Thalassiosira and larger size of Nitzschia might account for these differences in the feeding efficiency of small oysters. The biodeposition rates of both sizes of oysters were also affected by food concentration of the different algae. At the high food concentration with Skeletonema, Nitzschia, and Dunaliella, all oysters showed a marked increase in the rate of biodeposition, but oysters fed on Thalassiosira exhibited no great change. On all species of phytoplankton, the larger oysters produced greater biodeposition than the smaller oysters. These differences in response of feeding and biodeposition rates are important to our knowledge of food chain dynamics and may be used to optimize aquaculture systems.

Intensive outdoor culture of marine phytoplankton enriched with treated sewage effluent

Abstract Secondary sewage effluent has been used as a nutrient source for the outdoor mass culture of marine phytoplankton that serve as food for bivalve molluscs in a combined tertiary sewage treatment-aquaculture system. Using a daily harvest rate of 50%, yield in algae ranged from one to five grams carbon/m 2 /day and averaged 2.6 over the four-month experimental period. Under outdoor conditions, the sewage enrichment of sea water in 400-liter tanks stimulated the growth of a variety of microalgae which were usually dominant in the water before enrichment. Several sources and samples of sewage effluent were successfully used for enrichment, and the possible control of species composition was demonstrated using different combinations of nutrients. Changes in the rate of harvest and level of enrichment increased the yield by 37% and further refinements in the growing and harvesting procedure would make possible higher yields of plant material.

Food chain dynamics of abalone in a polyculture system

Abstract The food chain dynamics of three species of commercially important abalone — the red abalone (Haliotis rufescens), the green (H. fulgens) and the Japanese (H. discus) — were measured to determine their relative success in the multispecies aquaculture system at Woods Hole Oceanographic Institution. The abalone were fed sea lettuce (Ulva lactuca) used in the polyculture system to remove nutrients regenerated by the bivalves. This polyculture system was operated on a moderate-sized scale during the summer of 1973. Growth and feeding rates of the abalone were measured during a 112-day period and net growth efficiency was calculated (net production/food ingested). All three species grew during the experiment but H. rufescens had the lowest efficiency of 10.2%, and H. fulgens had the highest efficiency of 22.7%. These differences might be due to the temperature regime (16–23°C) during the experiment. H. rufescens is typically found in colder waters whereas H. fulgens is common in warmer Southern California waters. The results suggest the feasibility of the browsing role of abalone in polyculture systems.

Inorganic nitrogen removal in a combined tertiary treatment-marine aquaculture system—II. Algal bioassays

Abstract Algal bioassays were conducted on samples from various components of the combined tertiary treatment-marine aquaculture process, described in Part I of this study. These assays demonstrated that nitrogen removal is necessary to prevent increasing the algal growth potential of coastal marine waters receiving wastewater discharges. When nitrogen was removed from secondarily treated domestic wastewater, the wastewater in varying dilutions with seawater could not support more algal growth than the seawater alone. By adding nitrogen back to the treated wastewater the algal growth potential was increased to that of the untreated wastewater. This was demonstrated by assaying samples containing both artificially added nitrogen, and nitrogen regenerated by oysters. Assays of the effluent from the seaweed system showed that the removal of regenerated nitrogen reduced the algal growth potential to that of natural seawater.

Growth comparisons of oysters, mussels and scallops cultivated on algae grown with artificial medium and treated sewage effuent

Shell growth, dry-meat weight, and mortality of the American oyster (Crassostrea virginica), the blue mussel (Mytilus edulis) and the bay scallop (Aequipecten irradiens) cultured for 3 months on algae grown in artificial medium and in secondarytreated sewage effluent exhibited no significant differences.

A flowing experimental system with filtered and temperature-regulated seawater

A method of setting up an inexpensive and easily maintained system with flowing filtered and temperature-regulated seawater is described. Filtration is by a combination of filter bags and cartridges of various porosities that results in 1 μ-filtered seawater with particulate carbon concentrations of less than 30 μ-grams/liter. The temperature of the water is regulated by a titanium heat transfer panel. Water is then pumped to a head tank for distribution to experimental trays. Alarm systems for excessive temperature and water level fluctuations are described.

Integrated Systems of Mollusk Culture

Mollusks have two environmental requirements for their growth and commercial culture that may often be mutually exclusive. First, the water temperature must be in the proper range for the animals to pump and filter water; second, the water must contain enough microscopic food organisms of the proper size and composition to provide food for the shellfish. These two prerequisites are often not present simultaneously in the same environment. Tropical and semitropical waters are naturally poor in nutrients and normally lack the level of primary productivity (i.e., phytoplankton growth) for substantial mollusk growth. The more eutrophic temperate and boreal waters have temperatures too low for feeding and growth of bivalves for at least part and often as much as half the year.