Algal genus Spotlight: Bryopsis "hair algae"

[horge]

This was originally going to be submitted to Reefkeeping way back in July. For various reasons I didn’t think it would fit in, and decided my energies better focused on the tedious grind of filling out the online MaBMA (marine benthic macroalgae) catalogue.

I will be posting genus-level articles on TRT and here on RC every couple of weeks, in the hope that readers will contribute their photos of the alga being discussed, as well as contributing their experiences with the same. What follows is a slightly condensed version for RC, the lengthier original remaining on TRT’s forum, angling for the photos and experiences of interested readers, who have also been pointed to this forum.

Whatever the TOS on this board, the article and its excerpts remain my intellectual property. Enjoy.



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TRT MaBMA Algal Spotlight
“Hair Algae� Part 1/10 : Bryopsis
Author: Horge Cortes Jorge Jr.

Introduction
One of the most beloved of macroalgae in reef aquaristics are those rare guests, Bryopsis, one of several genera affectionately dubbed ‘hair algae’. Bryopsis are a vital and much sought-after component of the compleat reef aquarium. Bryopsis can cure cancer, end poverty, and bring about world peace.

But enough sarcasm.
The marine green algae Bryopsis are, to my perception, the most prevalent and problematic sort of ‘hair alga’ around our hobby, colonizing and dominating captive reefscapes with a speed and remorselessness that would make a Spanish conquistador blink.

Why are Bryopsis so common? Why do they spread so fast?
What does one do to rid one’s aquarium of them?
Why not read on, gentle readers?


Taxonomic Background
There are at least 50 species of Bryopsis (including varieties and forms), but only a mere seven species are commonly found in tropical waters, plus three varieties of one of the most commonly cited species:

Bryopsis corticulans
Bryopsis corymbosa
Bryopsis halliae
Bryopsis hypnoides
Bryopsis indica
Bryopsis pennata
(Bryopsis pennata var. leprieurii )
(Bryopsis pennata var. secundata)
(Bryopsis pennata var. secunda)
Bryopsis plumosa
Bryopsis ramulosa

Many of the diagnostics between these species can be subtle to a hobbyist, and furthermore the morphological variance within some species (take just the much-cited B. plumosa for example) can be surprising. It is often practical not to differentiate between them.
What use, then, the list above?
I just wanna name-drop.


God willing, MaBMA will deal with the dirty details of species-level diagnostics.

Morphology & Reproduction
Bryopsis all go through two alternating phases that are starkly different in appearance: as gametophytes and as sporophytes.


Fig 1.1: The gametophyte phase of Bryopsis, likely Bryopsis corticulans, producing male and female gametes which combine to form a zygote, which in turn settles to form the other phase, called a sporophyte:


Fig 1.2: Bryopsis sporophyte is a sometimes lighter-green, filamentous, sparsely-branching and ground-hugging little wretch.
(Cut me slack: a sketch is all I can muster right now. Give me your photos!!! )

Because Bryopsis gametophytes are monoecious, they would seem to value sexual quantity over quality: during sexual reproduction, the chances are very good indeed for girl gametes and boy gametes to meet up and do their thing since they can come from so close to each other --as in, the same algal specimen. This means that ‘self-fertilization’ is likely, and whatever benefit derives from a more catholic genetic lottery are largely lost to any population of Bryopsis.

We must note: that the resulting sporophyte phase (see Fig 1.2 again) is rarely reported in marine aquaria suggests that sexual reproduction is not the usual means by which Bryopsis multiply in aquaria. Also, if there really aren’t any sporophytes, then spore-based reproduction can’t be common in aquaria either. There may be under-reportage involved, but let's just suppose here AREN'T many sporophytes around: how might Bryopsis usually reproduce?

Reef aquarium enthusiasts ought to be familiar with reproduction via fragmentation, and Bryopsis are, by the way, coenocytic –meaning each thallus is technically a single, if multinucleate, cell. Any scrap of Bryopsis --no matter how small-- can regenerate if allowed to settle in a favorable location.

Alas, there’s more:
The gametophyte also reproduces by forming what are called microthalli on the ends of the pinnules, when it isn’t Bryopsis “breeding season� --we did earlier indicate that gametangia and gametes were formed seasonally, yes?. Anyway, each microthallus eventually detaches and drifts freely in the current, just waiting for the right surface to crash into and colonize, as sporophytes. Again, since not too many sporophytes are being reported, then microthalli-formation may not be a serious issue in aquaria, so we’re back to accusing fragmentation as the chief means of reproduction.

In case this reproductive picture has become too contorted for words (and considering the verbal diarrhea preceding, it ought to be), let me share yet another visual crutch to enhance our confusion (see Fig 1.3)


Fig 1.3: Bryopsis Life-Cycle
(Again, cut me some slack: a sketch is the best I can offer right now)

One more time:
Given a paucity of reported sporophytes, we might assume that reproduction via fragmentation is the primary route to Bryopsis' frequent dominance in a marine aquarium. (Or, again, maybe no one is paying attention to the little creeps, leading to severe under-reportage.)

Controls
As I mentioned in another article, the standard threefold plan of attack against a problem alga is as follows:

1. Manual removal of the problem alga
2. Suppression via appropriate herbivores
3. Denial of resources

Given the strength in Bryopsis’ ability to reproduce, there must be an emphasized fourth:

4. Severe curtailment of reproduction

Manual removal of Bryopsis is a tedious task.
The removal itself is easy, as the thalli are small and soft enough to be scraped off. The thallus however is susceptible to severe fragmentation. The challenge is in ensuring that no viable algal material is released into the display environment.

If manual removal is to be attempted in the display, a siphon is most useful for drawing off any fragments that may eventually settle and regenerate, pointed right where the action is taking place. The drawn-off water may be discarded, though I have sometimes filtered such wastewater through calcium hydrochloride powder–which apparently destroys algal cells, and stored the filtrate in bottles for later use as calcium boosters.

If the Bryopsis-infested rock (or other material) can be removed to a separate container for a scrub-down, so much the better. Whatever saltwater was used in that container, during scrub-down, and for the final rinses, should be discarded

More herbivores can adapt to eating Bryopsis than the many horror stories around might suggest. The most reliable are perhaps some sacoglossan slugs (of Genus Elysia, for example) which unfortunately have relatively short lifespans. Other effective herbivores include certain sea urchins. While the commonly-sold herbivorous snails can infrequently take a bite out of Bryopsis, they can be messy eaters and none too thorough, just as many herbivorous fish can be. The viable algal crumbs from their feasting make the problem worse.

Even with herbivorous pressure, there is also the problem of incomplete digestion to consider: viable algal material is often found in the feces of many of these herbivores, and a biodiverse ecosystem, with herbivorous/omnivorous scavengers and recyclers of all sizes (the sort that live on eating the crap of higher herbivores....yechhh), seems the best way to deal with it.

Denying Bryopsis the resources they need (particularly nutrient) is a tricky thing to attempt. Their magnificent, plumose arrays (in the gametophyte phase) spell efficient assimilation of nutrient in the water, likely far more efficiently than anything a rival “scrubber� algae can muster. No harm in trying to introduce competition, though! Obviously, one can try to limit the nutrients imported into the system. A reef aquarium must be fed, and natural, live foods can live on in the display, rather than decomposing and releasing nutrient when left uneaten.

Physical removal can become a repetitious ordeal even with the best efforts at providing herbivorous pressure and at denying resources to the problem alga(e). This is likely because of the impressive reproductive potential that Bryopsis own. The process of obtaining relief can perhaps be speeded up by specifically targeting the avenues that Bryopsis employ to perpetuate their presence. All aforementioned modes of Bryopsis reproduction depend on using the water as a transport medium, and water is among the easiest of a reef aquarium’s components to police, given the circulation systems we use.

A properly-designed UV sterilizer may effect a significant reduction in repeat manifestations of Bryopsis, within the context of physical removal, herbivorous suppression, and resource denial. Those latter three primarily deal with the presence of Bryopsis on substrate, whilst proper application of UV (or other prophylactic filtration) helps deal with the problem’s presence in the water, obliterating many spores, gametes, microthalli and viable fragments. It is also no small benefit that proper use of UV filters also provides rapid oxidation of many dissolved nutrients in the water, reducing one fuel that powers Bryopsis blooms.
Fourfold approach, then.

Of course, patience, humble perseverance and a little prayer go a long way. So does sharing your pain with your brothers and sisters on TRT (and RC).


Summary
Bryopsis are a formidable bunch of algae to deal with, and in no small part due to their reproductive prowess. They can reproduce sexually via gametes, or asexually via spores, fragmentation or dispersal of 'microthalli'.

Bryopsis are often deemed problem algae in the hobbyist reef aquarium. While addressing the physical presence with manual removal and herbivores, and attempting to slow its growth via denial of resources are important, it is likely just as important to restrict reproduction. Prophylactic filtration of the water (for example, via UV devices) may provide the means towards a shortened effort at controlling any outbreak of Bryopsis.


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Please help me:
Contribute your own photos of Bryopsis, and your experiences in dealing with it, what worked and what didn’t, to MaBMA. Post them on this thread and indicate your willingness to let me use them. If the kind of photo you post is just what I don’t already have, I’ll PM you for details (like what name you want to appear on the photo as credit, like in Jim Bednar's photo above, etc.)

After ten genera of hair algae, (every couple of weeks) I’ll move on to finger algae, I guess. Or maybe we'll do random Genera from all across the spectrum of weeds. Lemme know.


Yebaaa,
horge