Improving Survival Rates of Young Seaweed in Tank Systems
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Hi fellow seaweed enthusiasts,
We have a setup where we seed around 4 km of sugar kelp line per year and about the same with Chorda filum, and everything works quite well.
However, we keep running into the problem that when the seaweed reaches a certain size in our tanks, around 3–4 mm, it starts to die off in some areas of the rollers. At the moment, we assume it has something to do with the flow in the tanks — that the water isn’t circulating well enough. But do you have other experiences with whether the flow needs to be increased as the blades grow? Could it be a lack of light or something else entirely? Let me know what you think.
@simon_weber7356
we’ve seen this with most fast growing kelp species where they tend to need lots of nutrients, don’t tolerate high nutrient levels though, and their health becomes volatile, dissolving and dying off almost over night. (Species like bull kelp and giant kelp). Can’t speak for Chorda, but with our we have to keep nutrients low (25% strength f/2) with high exchange or dosing rates to better simulate the ocean conditions. Good low turbulent flow can drastically improve nutrient uptake here too. Possible that some type of missing micronutrient could be an issue too that becomes limiting as growth enters exponential.
It can take some troubleshooting to get the microscopic to macroscopic transition correct with the right water turnover. I’ve generally found Saccharina to be quite weedy and resilient compared to other species which seem to require a lot more careful observation and maintenance. Maybe play around with nutrient concentration vs exchange rates, and increase flow and aeration to ensure you’re getting good CO2 replenishment and nutrient uptake?
@simon_weber7356 when you have die offs, do they go green first? Or pale from the tips first and dissolve?
@maisie_roymusor It’s actually a bit of both, now that I think about it!
At the moment they turn green and die, and sometimes when they’ve grown a bit bigger (the ones that survive), the tips turn white and they die slowly.
@simon_weber7356 interesting, so the green rot is usually from light not being high enough. The optimal light intensity increases as the thalli get larger, so we typically step our lights up as they transition from microscopic to macroscopic. Other folks step their lights up a little bit each week as things grow in more of a ramp up.
The blades paling, going white, and dissolving, especially at the tips first is much more likely nutrient related, if things like your water temps are stable!
@maisie_roymusor The water is stable in temperature. The reason I suspect flow is that it happens a lot in “zones.” First, the whole side facing away from the light dies, and then the side facing the light dies. There is no pattern, except that the flow has often turned out to be poor in the areas where it dies.
The N is about 1/3 F2 most of the time.
@maisie_roymusor It’s actually a bit of both, now that I think about it!
At the moment they turn green and die, and sometimes when they’ve grown a bit bigger (the ones that survive), the tips turn white and they die slowly.
@simon_weber7356 interesting, so the green rot is usually from light not being high enough. The optimal light intensity increases as the thalli get larger, so we typically step our lights up as they transition from microscopic to macroscopic. Other folks step their lights up a little bit each week as things grow in more of a ramp up.
The blades paling, going white, and dissolving, especially at the tips first is much more likely nutrient related, if things like your water temps are stable!
@simon_weber7356 when my sporophytes reach 2mm I add a few drops of Transition Elements (by ESV) which has more iron, zinc & manganese in addition to more frequent 100% water changes with full F/2 replenishment. I try to make sure my nitrate levels don’t drop below 20ppm nor above 75 ppm. I’m not sure if this is helpful with your species of kelp, but it helps me with Saccharina.
@simon_weber7356 when my sporophytes reach 2mm I add a few drops of Transition Elements (by ESV) which has more iron, zinc & manganese in addition to more frequent 100% water changes with full F/2 replenishment. I try to make sure my nitrate levels don’t drop below 20ppm nor above 75 ppm. I’m not sure if this is helpful with your species of kelp, but it helps me with Saccharina.
@elizabeth_savage19 Thanks for that answer, and can they then grow larger than if you don’t add it?
How big are they at the time of release?
What do you experience if you don’t add it?
@simon_weber7356 I find that if I don't add more nutrients and water changes the sporophytes bleach quickly. The tips turn clear and brittle, then the spools quickly decline. I have had more success keeping spools alive in open water (hanging off my dock) after they are 6+mm (photo).
@elizabeth_savage19 Thanks for that answer, and can they then grow larger than if you don’t add it?
How big are they at the time of release?
What do you experience if you don’t add it?
@maisie_roymusor The water is stable in temperature. The reason I suspect flow is that it happens a lot in “zones.” First, the whole side facing away from the light dies, and then the side facing the light dies. There is no pattern, except that the flow has often turned out to be poor in the areas where it dies.
The N is about 1/3 F2 most of the time.
@simon_weber7356 I find that if I don't add more nutrients and water changes the sporophytes bleach quickly. The tips turn clear and brittle, then the spools quickly decline. I have had more success keeping spools alive in open water (hanging off my dock) after they are 6+mm (photo).
