Role of elevated organic carbon levels and microbial activity in coral mortality

Role of elevated organic carbon levels and microbial activity in coral mortality

David I. Kline, Neilan M. Kuntz, Mya Breitbart, Nancy Knowlton, Forest Rohwer

Marine Ecology Progress Series, Vol. 314 (May 22 2006), pp. 119-125

Stable URL:

PDF available

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.

‘Nuff said!

But the whole article is available, so as usual – click through and read it!

The Ecological Role of Water-Column Microbes in the Sea

The Ecological Role of Water-Column Microbes in the Sea
Marine Ecology Progress Series, January 1983
DOI: 10.3354/meps010257

PDF Available


This article gives some insight into the ecology we are missing when we try to control algae blooms with carbon dosing.

It’s not even close to a simple bacteria vs algae contest, or bacteria-to-skimmer export that gets reported in hobby literature.

A few quotes:

There is evidence that bacteria show kinesis [movement] in a field 10 to 100 µm from algal cells, close enough to take advantage of DOM (Azam, in press). Under laboratory conditions in natural sea- water, bacteria were observed to remain at distances of the order of 10 pm from algal cells, possibly being repelled by antibiotics produced by healthy algae. They attach mainly to moribund algae.

[…]it follows that the supply of either carbon for energy, or other nutrients may limit bacterial growth.  However, in phytoplankton blooms DOM is often produced, and bacteria with their large surface:volume ratio are adapted to scavenging nutrients from the water at very low concentrations.  The difficulties experienced in quantifying the release of DOM by algae are almost certainly due to its rapid uptake by bacteria.  The same argument applies to nutrient cycling.  If bacteria are so well adapted to
scavenging DOM and nutrients at low concentrations, what limits their population size to the biomass levels given in Table I ? Fenchel (1982a,b, c, d, in press) has shown that heterotrophic microflagellates in the size range 3 to 10 pm are effective bacteriovores in the sea, capable of filtering 12 to 67 % of the water column per day (see also Sorokin, 1979; Sieburth, 1982).These are principally choanoflagellates and colourless chry- somonads[…]


The toxic benthic dinoflagellates of the genus Ostreopsis in temperate areas: a review

The toxic benthic dinoflagellates of the genus Ostreopsis in temperate areas: a review

Stefano Accoroni, Cecilia Totti

Advances in Oceanography and Limnology, 2016; 7(1): 1-15

DOI: 10.4081/aiol.2016.5591

Key Points:

  • Correct ID of Ostreopsis species in the field (distinguishing between them) is “highly problematic” requiring a comparison of precise anatomical measurements and experience comparing strains from different regions.  Even genetic ID has been complicated.  They are now referring to some Ostreopsis as species-complexes and clades.
  • Either P- or N-depletion has been shown to lower Ostreopsis ovata toxicity.  (Strain, growth phase and salinity all figure it too.)
  • Turbulence affects growth rate/cell-size.
  • Cell counts were consistently lower in exposed sites vs sheltered ones.
  • Dino’s are easy to dislodge, which is why they show a preference for calm areas
  • Turbulence is most effective against them at the peak population levels when they are mat-forming.
  • While it appears there is a general preference for higher temperatures during the peak bloom (77ºF+) they tend to range widely and some strains appear to have multiple optimal ranges.
  • N:P around the Redfield ratio and temperatures of at least 77ºF seems necessary to allow cell proliferation.
  • Temperatures to stop a bloom were much lower, however – around or under 60ºF.
  • Blooms appear to be initiated under low-N/low-P conditions and then spike with a flush of nutrients.
  • It’s also suggested that Ostreopsis toxins might be intended for survival under low-N/low-P conditions while waiting for conditions to become ideal.  (Which seems to be an elevation in temperature along with a spike in nutrients.)
  • At least one strain of Ostreopsis showed a very strong demand for P in depletion tests, which was remarkable among dinoflagellates.
  • It’s suggested that Ostreopsis may share the habit known of other dinoflagellates for resorting bacterivory/mixotrophy under low-P/low-nutrient conditions.
  • Most Ostreopsis species exhibited lowered growth rates at light intensities around 250 PAR and higher….sometimes only slightly lowered, sometimes significantly.
  • Higher light levels may also be related to mucus formation (for photodamage protection) and settling from their planktonic stage.
  • However, being motile, they are also capable of migrating from brighter to shadier areas.
  • Although recorded in the wild on a variety of substrates, there are many reports that they prefer to be epiphytic on macroalgae, which as an environment is known to have low light availability.
  • Interestingly, living substrates like macroalgae support the lowest cell densities of all sampled substrates.
  • All investigated seaweed types exhibited a negative effect on Ostreopsis counts: brown, red and green algae.  The brown algae Dictyota dichotoma had the strongest effect….a red algae the weakest.

A review on the effects of environmental conditions on growth and toxin production of Ostreopsis ovata

A review on the effects of environmental conditions on growth and toxin production of Ostreopsis ovata

R. Pistocchi, L. Pezzolesi, F. Guerrini, S. Vanucci, C. Dell’Aversano, E. Fattorusso


For the same strain, both nitrogen and phosphorus limitation determined a decrease in cell toxicity showing different behaviour with respect to many other toxic dinoflagellates.

There’s more to mine from this PDF, but I’m out of reading time.

Phosphatase activities of a microepiphytic community during a bloom of Ostreopsis cf. ovata in the northern Adriatic Sea

Phosphatase activities of a microepiphytic community during a bloom of Ostreopsis cf. ovata in the northern Adriatic Sea

Stefano Accoronia, Cecilia Tottia, Emanuela Razzaa,
Roberta Congestrib, Alessandra Campanellic, Mauro Marinic, Neil Thomas William Ellwoodd

“Ostreopsis seems to have an adaptation that lets it thrive in P-poor environments where organic phosphate is the main source of P.”

This is contrary to most dino’s we see.

Effects of N and P availability on carbon allocation in the toxic dinoflagellate Ostreopsis cf. ovata

Effects of N and P availability on carbon allocation in the toxic dinoflagellate Ostreopsis cf. ovata

Harmful Algae 55:202-212, May 2016

DOI: 10.1016/j.hal.2016.02.011

Laura Pezzolesia, Silvana Vanuccib, Carmela Dell’Aversanoc, Emma Dello Iacovoc, Luciana Tartaglionec, Rossella Pistocchi

Blooms of the toxic dinoflagellate Ostreopsis cf. ovata are usually associated with shallow and calmcoastal waters, characterized by low nutrient concentrations. The algal cells typically cover the benthicsubstrates, such as the macroalgal and invertebrate communities and rocks, forming a mucilaginous film.

The obtained results strongly suggest that in the environment toxin production is steadily sustained by a low and constant nutrient supply, able to maintain appropriate cellular C:N (>12) or C:P (>170) ratios for a long period.

That’s just from the abstract….still need to digest the details on this one.

Nitrogen cycling in corals: the key to understanding holobiont functioning?

Nitrogen cycling in corals: the key to understanding holobiont functioning?

Nils Rädecker, Claudia Pogoreutz, Christian R. Voolstra, Jörg Wiedenmann, Christian Wild

Trends in Microbiology, Vol. 23, Issue 8, p490–497

  • Nitrogen cycling in reef-building corals is a function of all holobiont members.
  • Control of nitrogen cycling may stabilize holobiont functioning under oligotrophic and eutrophic conditions.
  • Anthropogenic change may sway the control of nitrogen cycling, promoting coral decline.
  • Elevated nitrogen fixation rates may foster coral bleaching and disease.

Point for point comments:

  • In aquariums this is what makes corals resilient to our manual attempts to re-create oligotrophic conditions in an overstocked tank.
  • Witness the threads on paling corals and other issues.  KNO3 dosing is often seen these days.  Corals are apparently healthier when some NO3 is present.
  • In the ocean, anthropogenic NO3 additions cause bad PO4 limiting among other things….corals and everything else tend to decline under PO4 starvation.
  • There’s no free lunch…even within successful ecosystems, higher bio-loads come with a higher risk.

The rest of the article is a great read too….tons of more reading is linked within the article too.