I do not need to provide anyone with examples of how awful the Covid-19 pandemic has been.  There have been a few bright spots, though, such as all the time we have been able to spend at home with our dogs.

One negative thing that had a slightly positive aspect was having to put the slug system on hold.   I took the remaining slugs home, hoping that they would be the parents of the next generation.  They did remarkably well for about a year living on the Bryopsis pennata that was growing in the reef and seagrass tanks.

Last slug from the last brood raised in the USG system. They came home last spring, and held out for over a year. 3/13/21

Over the course of the summer, the last one has faded and shrunk as she reached old age and lost the ability to eat algae and to maintain her chloroplasts.

After about 16 months, the last of the Elysia that grew up in the system is just about gone. As they fade away and use their tissues for energy, they get increasingly small and yellow. This one is about the size of a pea. 8/11/21.

After at least five generations, it is sad to say goodbye to the last of the progeny.  Nonetheless, the lack of slugs meant that I could clean the USG system thoroughly.

During the years that I have been trying to culture Bryopsis, I have managed to introduce at least half a dozen invasive and undesirable species of algae, some of which were outcompeting the desired species.  Valonia (bubble algae) and a coarse red alga were thriving under the same conditions as Bryopsis.  Also, Bryopsis plumosa, the finer species that is a favorite of the hatchlings, was being overrun by B. pennata, which the babies will not eat.  I had been trying to push the balance toward Bryopsis by manually removing the other species, or introducing grazers that prefer the nuisance species, but I was not winning.  It was a wet mess.

Enter the pandemic.  The system was unoccupied, allowing for a fresh start.  Even if I will not be able to keep the system as an absolute monoculture, it would be worth getting rid of as many pests as possible, and maybe eliminate some of the bristleworms and flatworms that prey on the babies in the process.

Step one was to dismantle the system, scrub out the tanks, and clean as much of the plumbing as possible.  Drainpipes, pumps, powerheads etc. were soaked in warm bleach solution, then scrubbed and left to dry.

Trying to eliminate at least some of the unwanted algae species by bleaching plumbing and equipment. 3/2/21

Once everything was clean and dry, it was reassembled, and left dry for a few months.  Then it was filled with fresh water to flush out remaining debris and organisms, and to check for leaks.

Tanks back in place after scrubbing (center shelves). The tanks to the left contain crayfish for the neurobiology lab.  3/9/21

With the tanks in place and plumbing reassembled, I let it run for a couple of months to see what grew.  The good news was that almost none of the species of pest algae has made a reappearance.  There was little Ulva and some diatoms, but none of the worst characters had come back.  It was time for new algae.

Elysia system filled with saltwater and circulating. There is a small amount of residual algae, but most species seem to have been eradicated. 3/25/21

This time around, my goal was as pure a culture of B. plumosa as possible.  Hatchlings eat it, adults eat it, everybody eats it, so there is no need for other species.  I contacted Michael Middlebrooks at the University of Tampa to find out if he would be able to send me a small amount as a starter.

At last, we found a time that he could send the algae and I would be here to receive it.  It arrived last week, having survived near-record heat here in MD, and looked great.

Bryopsis freshly arrived from Florida. Ready for the first treatments to reduce predators, parasites and pathogens. Hopefully, I can get rid of some of the non-Bryopsis algae as well. 8/11/21

Under the microscope, you can see dark filaments full of green cytoplasm, indicating good health and growth potential.

Bryopsis plumosa, close up. Many of the filaments appear uniformly green, which is a good sign that much of the algae arrived healthy. 8/11/21

The wild intertidal zone is a complex environment, so there were other algae in the mix.  There are a few species of red algae that grow closely with B. plumosa, often intertwined at the site of attachment to the rock.

Red macroalgae mixed in with Bryopsis. The green “fingers” to the left are part of a healthy growth of Bryopsis plumosa. Unfortunately, the red stuff likes to grow in and among it. 8/11/21

I removed as much of the non-Bryopsis algae as possible, and will try to be vigilant about removing whatever crops up as the new algae take hold in the tanks.

Meantime, the algae are settling in and growing.  It is remarkable how quickly Bryopsis will find a place to anchor itself and start growing.

Filaments of Bryopsis plumosa extending from a clump that arrived on 8/12/21. Photo 8/17/21

Healthy Bryopsis plumosa growing on a powerhead. 8/17/21

Some algae are making small adherent spots on the tiles that I added as a substrate, along with the glass and silicone sealant.  At this point, it is impossible to know whether it is a species I want or a pest, but let’s keep our fingers crossed.

Dots and threads of small unidentified algae stuck to ceramic tiles. 8/17/21

If all goes well, it will be time to add some slugs in a month or so.