Palmaria palmata was integrated with Atlantic halibut Hippoglossus hippoglossus on a commercial farm for one year starting in November, with a temperature range of 0.4 to 19.1°C. The seaweed was grown in nine plastic mesh cages (each 1.25 m 3 volume) suspended in a concrete sump tank (46 m 3 ) in each of three recirculating systems. Two tanks received effluent water from tanks stocked with halibut, and the third received ambient seawater serving as a control. Thalli were tumbled by continuous aeration, and held under a constant photoperiod of 16 : 8 (L : D). Palmaria stocking density was 2.95 kg m -3 initially, increasing to 9.85 kg m -3 after a year. Specific growth rate was highest from April to June (8.0 to 9.0°C), 1.1% d -1 in the halibut effluent and 0.8% d -1 in the control, but declined to zero or less than zero above 14°C. Total tissue nitrogen of Palmaria in effluent water was 4.2 to 4.4% DW from January to October, whereas tissue N in the control system declined to 3.0-3.6% DW from April to October. Tissue carbon was independent of seawater source at 39.9% DW. Estimated tank space required by Palmaria for 50% removal of the nitrogen excreted by 100 t of halibut during winter is about 29,000 to 38,000 m 2 , ten times the area required for halibut culture. Fifty percent removal of carbon from the same system requires 7,200 to 9,800 m 2 cultivation area. Integration of P. palmata with Atlantic halibut is feasible below 10°C, but is impractical during summer months due to disintegration of thalli associated with reproductive maturation.Key Words: bioremediation; IMTA; integrated multi-trophic aquaculture; nutrient removal; Palmaria INTRODUCTIONMany aquaculture businesses are intent not only on maximizing productivity and profitability, but also accomplishing this using environmentally responsible practices. Efficient use of energy (e.g., pumping of water) and natural resources (surrounding environment, ambient water supply, and waste streams) are key elements in this approach. Land-based recirculating aquaculture systems facilitate greater control over culture water and waste discharge than flow-through systems (Blancheton et al. 2009). Though the surrounding environment may be enhanced by moderate volumes of aquaculture discharge (White et al. 2011), the trend toward larger land-based facilities (e.g., 1,000 metric tons finfish production per year) and the associated effluent waste may pose a risk of local eutrophication. Alternatively, integration of seaweed and land-based marine finfish culture can convert these nutrients to a usable product. Previous investigations into land-based seaweed integration have included Gracilaria For this study, integration of Palmaria palmata and Atlantic halibut was established within a land-based recirculating aquaculture facility for one year to evaluate the growth and nutrient uptake characteristics of the seaweed in a commercial application. This study was essential to compare the bioremediation capacity of P. palmata under both lab and small-scale applied conditions...

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Thirty populations of Chondrus crispus Stackhouse from Nova Scotia were collected during the years 1993 to 2011. Taken from estuaries, wave exposed open coasts, high intertidal rock pools and shallow subtidal habitats, the populations were evaluated for relative abundance of tetrasporophytic and gametophytic life history phases. Over 2,800 thalli were characterized using the resorcinol-acetal test to distinguish the kappa-and lambda-carrageenan containing fronds of gametophytes and tetrasporophytes, respectively. These populations had 77 ± 5% gametophytes (mean ± 95% confidence interval), with most populations having gametophyte : sporophyte ratios ranging from 2 : 1 to 9 : 1. No population had a dominance of tetrasporophytes, although two populations had 1 : 1 ratios. A meta-analysis of our data along with previously published accounts showed no significant changes in gametophyte dominance with respect to hypothesized gradients of wave exposure, salinity, or water depth. Significant changes occurred in ratios at five sites where replicate sampling occurred in different years. We conclude that C. crispus in Maritime Canada has a natural ratio of 3 : 1 or greater in stable conditions, and that lower ratios represent recovery from disturbance in which bare substratum is created that is subsequently colonized by carpospores from remaining gametophytic thalli.

To evaluate the nutrient removal capabilities of two red macroalgae, apical blades were cultured in the lab for 4 weeks at either 6, 10, or 17°C and nitrate at either 30 or 300 μM, typical of the seasonal range of conditions at a land-based Atlantic halibut farm. Stocking density was 2.0 gL −1 , irradiance 125 μmol photons m −2 s −1 , photoperiod 16:8 (L:D), and nitrogen to phosphorus ratio 10:1. For both species, the highest growth rate was at 300 μM NO 3 − with Palmaria palmata growing fastest at 6°C, 5.8% day −1 , and Chondrus crispus growing best at 17°C, 5.5% day −1 . Nitrogen and carbon removal by P. palmata was inversely related to temperature, the highest rate at 6°C and 300 μM NO 3 − of 0.47 mg N and 6.3 mg C per gram dry weight per day. In contrast, C. crispus removal of N was independent of temperature, with mean removal of 0.49 mgN gDW −1 day −1 at 300 μM NO 3 − . The highest carbon removal by C. crispus was 4.4 mgC gDW −1 day −1 at 10°C and 300 μM nitrate, though not significantly different from either 6 or 17°C and 300 μM nitrate. Tissue carbon:nitrogen ratios were >20 in both species at 30 μM nitrate, and all temperatures indicating nitrogen limitation in these treatments. Phycoerythrin content of P. palmata was independent of temperature, with means of 23.6 mg gFW −1 at 300 μM nitrate. In C. crispus, phycoerythrin was different only between 6°C and 17°C at 300 μM nitrate, with the highest phycoerythrin content of 12.6 mg gFW −1 at 17°C. Morphological changes were observed in P. palmata at high NO 3 − concentration as curling of the fronds, whilst C. crispus exhibited the formation of bladelets as an effect of high temperature.