I have some comments about protein skimmers skewing specific bacteria populations. First only microbes in bulk water are removed. Second, not all microbes in bulk water are attracted to foam fractionators bubbles. Ken Feldermen articles in Advanced Aquaria on carbon dosing & protein skimmers focused on this point in the conclusion section of peer reviewed research papers. I have pasted two points of interest.
The frequency with which nutrient enrichments are supplemented has the potential to exert a significant effect on bacteria populations. Nutrient regimes of different periodicities have been shown to result in mixed heterotrophic bacterial communities with distinct physiological properties. It also was observed that the interplay between various bacterial strains and other participants within the microbial community may be equally as important as the selective forces of the environment in structuring microbial communities. Perhaps most interestingly, when replicate bacterial cultures were subjected to identical nutrient supplementation, the microbial community functionality was conserved despite the fact that community compositions were significantly different (Carrero-Colon, 2006). Thus, there appears to be a great deal of bacteria community plasticity in response to environmental changes, one of the hallmarks of bacteria as a successful species over evolutionary time.
Disruptions within a coral’s holobiont have the potential to negatively impact the coral’s health. Altered bacterial community structures have been linked to both coral disease and bleaching (Kvennefors, 2010). Coral bleaching occurs if the endosymbiosis between corals and their symbiots disintegrates during stress (Ainsworth, 2008). Even so, shifts in the holobiont’s bacterial community component may not be a direct cause of coral bleaching. While bacterial communities play important roles in coral stasis and health, environmental stressors appear to be the primary triggers for coral bleaching, and bacterial involvement in patterns of bleaching appear to be the result of opportunistic colonization (Ainsworth, 2008).
PS: Second paragraph in conclusion
Aquaria subjected to active filtration via skimming present water column bacteria populations that are approximately 1/10 of those observed on natural reefs. The consequences of this disparity on the long-term health of the tank’s livestock are not known. How do reef tank organisms adapt to such a bacteria-deficient environment? Is the whole food web in an aquarium perturbed, or are there compensatory mechanisms that maintain an appropriate energy transduction through all of the trophic levels? Is “old tank syndrome” related to possible nutritional deficiencies stemming from this bacteria “gap”? Alternatively, could “old tank syndrome” be symptomatic of a gradual decrease of bacterial diversity as a consequence of selective skimmer-based removal of only bubble-susceptible bacteria? At present, it is not possible to go beyond speculation on these points – further research is needed.
Bacterial Counts in Reef Aquarium Water: Baseline Values and Modulation by Carbon Dosing, Protein Skimming, and Granular Activated Carbon Filtration
What are the bacteria populations in the water column of reef tanks, and how does that value compare with bacterial counts in authentic reef water? Does carbon dosing indeed increase water column bacteria populations (i.e., is growth carbon limited)? Does mechanical filtration (protein skimming...
reefs.com
Manipulating Bacterial Growth
A “limiting nutrient” is a nutrient that has the ability, though its presence or absence, to restrict the utilization of other nutrients. Bacterial growth rates, bacterial carbon production, and bacterial growth efficiency all increase with the addition of organic carbon supplements in certain groups of marine bacteria (Carlson, 1996). The presence of a readily assimilated carbon source has been demonstrated to increase the uptake of ammonium in certain groups of marine bacteria (Goldman, 2000). The availability of a particular nutrient can not only affect a bacterial population’s growth rate, but also the metabolic functioning of the population. The availability of organic carbon has been shown to not only limit the growth rate of denitrifying bacteria, but also to limit the rate at which denitrification takes place (Brettar, 1992). Chemical entities other than organic carbon, such as inorganic phosphate, also can function as limiting nutrients (Rivkin, 1997). Indeed, given the rapid and dynamic shifts in marine bacteria metabolic behavior over time in response to changing nutrient availability, it may be inappropriate to describe marine bacteria as being limited by a single nutrient.The frequency with which nutrient enrichments are supplemented has the potential to exert a significant effect on bacteria populations. Nutrient regimes of different periodicities have been shown to result in mixed heterotrophic bacterial communities with distinct physiological properties. It also was observed that the interplay between various bacterial strains and other participants within the microbial community may be equally as important as the selective forces of the environment in structuring microbial communities. Perhaps most interestingly, when replicate bacterial cultures were subjected to identical nutrient supplementation, the microbial community functionality was conserved despite the fact that community compositions were significantly different (Carrero-Colon, 2006). Thus, there appears to be a great deal of bacteria community plasticity in response to environmental changes, one of the hallmarks of bacteria as a successful species over evolutionary time.
The Coral Holobiont
A coral’s holobiont is comprised of close associations between the coral animal itself, its symbiotic zooxanthellae, and a diversity of associated microbes including bacteria, archaea, algae, and fungi. These associations can take place in the coral’s immediate environment, on its surface, within its tissues, and within its skeleton (if present). This paradigm emphasizes the potential contributions of each component to the overall function and health of the coral (Rypien, 2010). The dynamic nature of these relationships can be seen in a comparison between freshly collected corals from the Red Sea region that were then placed into marine aquaria. A microbial community shift in the bacteria inhabiting the surface mucus layer was documented for collected corals when placed into the captive marine aquarium. The differences that emerged between corals from natural and captive environments suggested an adaptation of the mucus bacterial communities to the different conditions (Kooperman, 2007).Disruptions within a coral’s holobiont have the potential to negatively impact the coral’s health. Altered bacterial community structures have been linked to both coral disease and bleaching (Kvennefors, 2010). Coral bleaching occurs if the endosymbiosis between corals and their symbiots disintegrates during stress (Ainsworth, 2008). Even so, shifts in the holobiont’s bacterial community component may not be a direct cause of coral bleaching. While bacterial communities play important roles in coral stasis and health, environmental stressors appear to be the primary triggers for coral bleaching, and bacterial involvement in patterns of bleaching appear to be the result of opportunistic colonization (Ainsworth, 2008).
PS: Second paragraph in conclusion
Aquaria subjected to active filtration via skimming present water column bacteria populations that are approximately 1/10 of those observed on natural reefs. The consequences of this disparity on the long-term health of the tank’s livestock are not known. How do reef tank organisms adapt to such a bacteria-deficient environment? Is the whole food web in an aquarium perturbed, or are there compensatory mechanisms that maintain an appropriate energy transduction through all of the trophic levels? Is “old tank syndrome” related to possible nutritional deficiencies stemming from this bacteria “gap”? Alternatively, could “old tank syndrome” be symptomatic of a gradual decrease of bacterial diversity as a consequence of selective skimmer-based removal of only bubble-susceptible bacteria? At present, it is not possible to go beyond speculation on these points – further research is needed.
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