Is growing algae for nutrient export a bad idea?

[spotlessaqua]

I like to also think of terrestrial plants that are halophytes! no not mangroves.... more like salicornia Pacifica or dare I say caulerpa taxapholia instead of eel grass! My opinion is nature finds a way depending on the condition and algae will come and go but keeping a proper ion balance is the main goal. testing quality may not always be an accurate measurement on what is actually in the tank, taking into consideration bonds that happen like aluminum and phosphate making the phosphate non bio available and really what does that mean? Is it there or not? And what other reactions release or prolong these bonds that aren't being tested within the water column?

 

[brandon429]

Your rock is awesome Pete

people pay top $$ for diversity

 

[robert]

I started this thread because many think that macroalgaes have no risk or consequences...which in my experience is not the case. Red Sea's knock against refugium export is that dead and dying macros can release allelotoxic substances...so they have it half right. Triton advises to leave dead and dying macros in the system to feed your corals...IMO they have it totally wrong...

Allelopathy can be many things - in the case of macro and algae - they take up nutrients and produce dissolved organic carbons - corals do too...but these are nitrients too and they often go unrecognized. As I remember, algaes are a net contributor of DOC on the reef. They produce more than they consume - even in the dark cycle. So they do take down N and P and in doing so produce complex carbons - which also contain N and P - which you may not be able to detect - and release these back into the water column.

On the reef, a portion of these DOCs produced by algaes, are consumed by bacteria and some ingested by corals where they feed the bacteria in the coral itself. This disregulates the corals nutritional relationship with its resident bacteria resulting in one study of a 40% reduction in growth. Closer, more direct contact - resulted in coral mortality.

Does it depend on the coral and the macro tested? Yes, but all four of the macros tested had a negative impact of varying degree. Could there be macros that don't exhibit this allelopathic strategy - maybe.

Corals practice allelopathy against each other as well, but this is common knowledge and widely accepted.
I wouldn't be surprised to find that some corals use the same bacterial disruption strategy.

I personally don't think any "in system" nutrient export system is a good idea. This includes carbon dosing.
And I prefer the size of my export system to be slightly smaller that the systems production rate, ensuring that nutrients always are building.

Why do I want to see N building constantly? I want this because I then can be sure that my system is running carbon limited. Carbon limitation is what corals need to maintain their control of their own interal bacterial populations.

Corals have some mechanisms to control internal carbon - slime (SCM) is the most obvious. If you've ever seen large strings of slime drifting in you water after a cleaning, its the coral throwing off the particulate organic carbon you've stired into the sysytem. They can't have it as it will cause them to lose control of their interal bacteria - so they expend great resources to push it back out. POC is easy to throw off - DOC not so much so. Sugars - many the same ones you eat and some dose, will kill corals and cause STNs in controlled studies. N and P won't.

Elevated POC was seen to cause bleaching while DOCs resulted in band diseases STN/RTN.

 

[robert]

Organic Carbon and Microbial Activity
Andreas F. Haas ,Craig E. Nelson,Linda Wegley Kelly,Craig A. Carlson,Forest Rohwer,James J. Leichter,
Alex Wyatt,Jennifer E. Smith

Published: November 18, 2011
Abstract
Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata – Ochrophyta; Amansia rhodantha – Rhodophyta; Halimeda opuntia – Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h−1 dm−2), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h−1) and concomitant oxygen drawdown (0.16±0.05 µmol L−1 h−1 dm−2). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial dynamics and biogeochemical parameters (i.e., DOC and oxygen availability, bacterial abundance and metabolism) in coral reef communities.

Proceedings of the 12th International Coral Reef Symposium, Cairns, Australia, 9-13
July 201211C
Seaweed-coral competition

Contact with macroalgae causes variable coralmortality in Montastraea faveolata
Alexander T. Wolf, Christian Wild, Maggy M. Nugues

Coral Reef Ecology Group (CORE), Leibniz Center for Tropical Marine Ecology (ZMT), Bremen,Germany

USR 3278 CNRS-EPHE, Laboratoire d’Excellence "CORAIL", Perpignan, France

Caribbean Research and Management of Biodiversity (CARMABI), Willemstad, Curaçao.Corresponding author: [email protected]

Abstract
Shifts in benthic reef community structure often involve the replacement of corals by macroalgae. Weinvestigated the response of a scleractinian coral to direct contact with different macroalgae during an in situ interaction experiment on Curaçao, southern Caribbean. The macroalgae Dictyota pinnatifida, Lobophoravariegata, Halimeda opuntia and Cladophora spp. were placed onto healthy Montastraea faveolata coloniesand coral condition was monitored over a period of 15 d. Rapid coral tissue mortality was observed in coloniesinteracting with D. pinnatifida and Cladophora spp. In contrast, mortality in the H. opuntia and L. variegata treatments appeared slowly. At day 3, coral tissue in contact with D. pinnatifida and Cladophora spp.experienced 55 and 71% mortality, respectively, whereas mortality remained less than 2 % in the H. opuntia and L. variegata treatments. At day 15, mortality reached 38 % in the L. variegata treatment, whereas all otheralgae caused ≥ 88 % coral mortality. All algae except L. variegata caused mortality outside the area overgrownby the transplants, suggesting white plague disease-like processes beyond the area of direct interaction. Suchdifferential coral mortality could be attributed to variable algal-induced exudation of allelochemicals and/orDOC release rates by means of direct toxicity or by fueling microbial activity with ensuing oxygen deficiency.

 

[robert]

In situ release of coral mucus byAcropora and its influence on the heterotrophic bacteria
Ryota Nakajima, Teruaki Yoshida, Bin Abdul Rahim Azman, Kassim Zaleha,Bin Haji Ross Othman, Tatsuki Toda

Abstract
In situ mucus release by Acropora nobilis and degradation of mucus from A. nobilis and Acropora formosa, by heterotrophic bacteria were investigated at Bidong and Tioman Island, Malaysia. Mucus release rate for A. nobilis was on average 38.7 ± 35.2 mg C m−2 h−1, of which ca. 70% consisted of dissolved organic carbon (DOC) and 30% particulate organic carbon (POC). In the mucus degradation experiment, seawater-mucus mixtures were incubated and compared with control runs for 24 h. Bacterial abundance in the seawater-mucus mixture increased significantly and coincided with a decline in DOC concentration. In controls, bacteria and DOC did not significantly change. The coral mucus had a high content of inorganic phosphate. It is suggested that the coral mucus rich in DOC and phosphate can induce the high bacterial growth.

 

[robert]

Role of elevated organic carbon levels and microbial activity in coral mortality
David I. Kline, Neilan M. Kuntz, Mya Breitbart, Nancy Knowlton, Forest Rohwer

Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography,
University of California, San Diego, La Jolla, California 92093, USA
Department of Biology, LS301, San Diego State University, 5500 Campanile Dr, San Diego, California 92182, USA
Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Republic of Panama
Center for Microbial Sciences, San Diego State University, San Diego, California 92182, USA


ABSTRACT:
Coral reefs are suffering a long-term global decline, yet the causes remain contentious. The role of poor water quality in this decline is particularly unclear, with most previous studies providing only weak correlations between elevated nutrient levels and coral mortality. Here we experimentally show that routinely measured components of water quality (nitrate, phosphate, ammonia) do not cause substantial coral mortality. In contrast, dissolved organic carbon (DOC), which is rarely measured on reefs, does. Elevated DOC levels also accelerate the growth rate of microbes living in the corals’ surface mucopolysaccharide layer by an order of magnitude, suggesting that mortality occurs due to a disruption of the balance between the coral and its associated microbiota. We propose a model by which elevated DOC levels cause Caribbean reefs to shift further from coral to macroalgal dominance. Increasing DOC levels on coral reefs should be recognized as a threat and routinely monitored.

KEY WORDS: Coral reef decline · Dissolved organic carbon · Coral · Montastraea · Bacteria · Caribbean · Nutrients

 

[robert]

Obviously I can't reprint the articles here...search them out for yourselves and read the whole articles as methods are often everything.
If your still interested...follow the citations...many good refrences.

Note - the last article in the text has the DOC levels observed over the reefs in many parts of the world...good data.

 

[reeferKen]

From your reading, are total and dissolved organic carbon the same measurement? How would hobbiets measure
either? I see advancedaquarist has an interesting article testing reef tanks with a Shimadzu Total OC Analyzer.
but from 2008. Thanks.
http://www.advancedaquarist.com/2008/9/aafeature2/

 

[brandon429]

I kept scanning that for any link or significance between toc and sandbed/no sandbed and I found none that was great read

surely less cleaned sandbeds and older ones may contribute to the load through nutrient sinking and isolation from export. feed and export variables seemed most important to toc unless I totally misread the charting per tank

 

[Randy Holmes-Farley Verified Community Expert]

Do the last two articles have a bearing on macroalgae in a refugium causing harm?

From your reading, are total and dissolved organic carbon the same measurement? How would hobbiets measure
either? I see advancedaquarist has an interesting article testing reef tanks with a Shimadzu Total OC Analyzer.
but from 2008. Thanks.
http://www.advancedaquarist.com/2008/9/aafeature2/

No, they are not the same.

Total organics will include particulates, bacteria, viruses, detritus, plankton, etc.

 

[robert]

Do the last two articles have a bearing on macroalgae in a refugium causing harm?
.

Yes - of course - both indirecty as foundation and specifically - but you have to read them and not just the abstarct.

For example from the last: Role of elevated organic carbon levels and microbial activity in coral mortality

"Other human activities can indirectly raise organic
carbon levels on reefs. Removal of herbivores by over-
fishing, aggravated in the Caribbean by an epizootic of
the sea urchin Diadema antillarum (Lessios et al. 1984),
has led to increasing amounts of macroalgae. Algal
growth is promoted by increasing nitrate and phosphate
levels (Hatcher & Larkum 1983, Littler & Littler
1984, McManus & Polsenberg 2004). Because macroalgae
release labile DOC from both living and dead
tissue (Khailov & Burlakova 1969), increasing coverage
by macroalgae could also contribute to mortality by
increasing DOC and thus causing overgrowth of the
SML-associated microbial community. The dead coral
can then serve as substratum for further macroalgae
growth, resulting in additional increases in DOC and a
positive feedback loop (Fig. 4) that could rapidly lead
to a phase shift from coral to macroalgal dominance."

 

[Randy Holmes-Farley Verified Community Expert]

Thanks.

Another reason to skim and use GAC in a reef tank, whether you use macroalgae or not.

 

[robert]

Thanks.

Another reason to skim and use GAC in a reef tank, whether you use macroalgae or not.

I agree.

What appears to emerge, is that the reef can be described as a biphasic system of autotrophs and hetrotrophs, pelagic and benthic, Which phase, coraline or algeal, that expresses is determined by the coposition and concentration of the dissolved organic carbon that predominates in the water column.

Macroalgaes produce a form of DOC which tends to push the algeal phase, these DOCS are damaging to the coral holbiont, which can result in coral stunting and death.

 

[robert]

All the above to get to the point that "what you grow" can infuence "what else you can grow". That growing macros is probably working against your corals and in favor of that algae that your trying to eliminate.

That N and P aren't everything, if fact they may not mean too much at all, and that the forms and levels of DOC are really what you need to control.

Cuts against the grain - doesn't it?

But I want to hear opposing voices, see opposing evidence, get some challenging data, ideas or questions...

What methods do we use to control nutrients that don't result in algae promoting DOCs? How do we remove DOCs from the system? Is this the role of ozone, UV or peroxide dosing - GAC and skimming - what other methods are available?

 

[robert]

So I figure for most it was TLDR....

For you all....here's a video summary...the key is dissolved organic carbon and its disruption of the bacterial balance within the coral...carbon dosing/macroalgaes?

 

[mcarroll]

Great thread....great links.

Need more sources to provide full article access (like these)...or a reasonable cost for temporary access, like $0.99.

 

[blackgate]

I think I will do a before and after experiment as I intend to get rid of my macros (cheato, dragon's breath) and just run UV. I will put up some pics and take some notes as well

 

[mcarroll]

I'm willing to bet that "Role of elevated organic carbon levels and microbial activity in coral mortality" explains a lot about the so-called "burnt tips" phenomena that bothers carbon-dosers (sometimes also known as "ULNS-folk" ) who also try elevated alkalinity, which also has the effect of adding excess C (dioxide) ions to the water - continuously. Would love to have seen "Fig 1" inlcude sodium bicarb. as one of their doses, as well as a parallel set with sodium bicarb+each of their additives.

There's no such thing as a free lunch and that's what folks' usage of carbon dosing has always brought to my mind. I actually spent some time googling for a paper like this....but came up dry at the time. THANK YOU FOR POSTING!

This makes me also question how much of the elevated CO2 in our tanks (which appears at least somewhat common and is thought of as "inorganic" and inert or at least transient) is getting converted to DOC via respiration and photosynthesis processes (and associated food webs) and if that condition (elevated CO2) might be related to similar coral issues (tissue loss, etc). But that's a different tangent on this.

Thank you for being someone who looks outside the box! Keep it up!

 

[Randy Holmes-Farley Verified Community Expert]

I'm willing to bet that "Role of elevated organic carbon levels and microbial activity in coral mortality" explains a lot about the so-called "burnt tips" phenomena that bothers carbon-dosers (sometimes also known as "ULNS-folk" ) who also try elevated alkalinity, which also has the effect of adding excess C (dioxide) ions to the water - continuously. There's no such thing as a free lunch and that's what folks' usage of carbon dosing has always brought to my mind. I actually spent some time googling for a paper like this....but came up dry at the time. THANK YOU FOR POSTING!

I don't think we know what causes burnt tips, but one prevailing idea told to me be Charles Delbeek is that the high alk causes skeletal growth faster than low nutrients will allow good tissue growth. So the tissue at the growing tip gets very thin and susceptible to damage, such as by light.

As I understand it, burnt tips can come about from other ways of reducing nutrients, such as GFO, which do not have a bacterial or CO2 component.

 

[mcarroll]

Interestingly GFO has a lowering effect on alkalinity. I do not think that is a coincidence.

More to come later.