Enhanced production of Pacific dulse (Palmaria mollis) for co-culture with abalone in a land-based system

Palmaria mollis (Pacific dulse) is increasingly being used in land-based marine aquaculture. This work elucidates nutrient, inorganic carbon, light, salinity, and temperature requirements of P. mollis as food for abalone species.; Nutrient additions every 5 to 7 days resulted in no significant difference in P. mollis growth compared with daily nutrient additions. The addition of f medium trace metals (Guillard and Ryther, 1962) significantly increased growth compared with additions of PO₄ − and NO₃− alone. The use of NaNO₃ as an N source was found to be superior compared with NH ₄NO₃. Palmaria mollis growth was most sensitive to phosphorus additions, with a declines in growth above concentrations of 83.3 μM - P d−1.; Palmaria mollis growth was positively correlated with concentrations of dissolved inorganic carbon. A pH of 8.9 produced growth rates that were not significantly different than at pH 8.3. A seawater flushing regime that increased flushing during the light cycle but lowered flushing during the dark cycle resulted in growth rates equal to those obtained by maintaining pH at 8.5 with CO₂.; At a specific light density (SLD) of 0.0048 to 0.036 mol photons g −1[fw]d−1, growth was highly correlated with light. Growth was best at a salinity of 30 ± 1‰ and a temperature of 12°C for low light and 14° to 18°C at high light. Growth under higher temperatures was correlated with increased light. Lowering culture temperature at night from 15°C to 11°C significantly increased growth compared with a constant daily temperature of 15°C.; There was no significant difference in growth of Haliotis discus hannai cultured in seawater compared to seawater supplemented with PO₄−, NO₃−, and 0.75f + Zn (d−1). The Japanese abalone H. discus hannai showed the highest growth when fed on P. mollis supplemented with nitrate loads ranging from 1176 to 2353 μM d−1 NO₃− - N and the red abalone H. rufescens when fed on P. mollis supplemented with nitrate loads of 2353 to 2942 μM d−1 NO₃− - N. Both abalone species grew better on P. mollis supplied with 0.75f + Zn (d −1) trace metal solution (Guillard and Ryther, 1962).