Since I was invited to post I felt free to bring along my soap box.
There's a ton of research showing increased labile DOC, aka carbon dosing causes problems for corals ranging from chronic to acute. Even the DOC a coral produces, when concentrated and reapplied to the coral can cause problems. One way it negatively affects corals is it allows the heterotrophic in a coral's holobiont to use refractory DOC as a food source and proliferate but these bacteria consume oxygen in the process and create anoxic conditions in the coral's surface boundary layer. Excess labile DOC also has been shown to cause pathogenic shifts in coral microbiomes.
Cryptic sponges in a reef system, fortunately, are able to moderate these processes to some degree by converting labile DOC into nitrogen rich detritus and DIC. These sponges have been shown to do this 1000X faster than the bacterioplankton (only a portion of the bacterioplankton is removed by skimmers). Unfortunately, these sponges are a double edge sword and process DOC from algae differentially from coral DOC and potentially can create a feedback loop the promotes increased algae growth at the cost of corals.
(Short answer - Yup, not surprised.)
Here's a data bomb:
Maintenance of Coral Reef Health (refferences at the end)
"Coral Reefs in the Microbial Seas " This video compliments Rohwer's book of the same title. Used copies are available on line and it may be free to read on Internet Archive. both deal with the conflicting roles of the different types of DOC (carbon dosing) in reef ecosystems and how it can alter coral microbiomes. While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems and are an excellent starting point to understand the conflicting roles of Dissolved Organic Carbon (DOC, aka "carbon dosing") in reef ecosystems.
Bacteria and Sponges
DOC stuff:
FYI: DOC can be roughly seperated into three catagories, Labile, Semirefractory and Refractory. Most of the following papaers are looking mainly at Labile DOC. This will raise the hackles on some reefers but keep in mind Labile DOC and Carbon Dosing are synonamous. Jasper deGeoij's work shows cryptic sponges remove labile DOC about a thousand times faster than bacterioplankton. Included are links to some of the research showing what cryptic sponges are doing as well. Also, researchers tend to use DOM (Dissolved Organic Matter) and DOC (Dissolved Organic Carbon) interchangebly.
long-term stony coral survival in the Coral Reef Exhibit at Reef HQ Aquarium, Townsville, Australia with an ATS was measured in days, not years. (See figure 3) (This page may have been removed, I can send you a copy of the .PDF if you're interested)
www.burgerszoo.com
Indirect effects of algae on coral: algae‐mediated, microbe‐induced coral mortality
Influence of coral and algal exudates on microbially mediated reef metabolism.
Coral DOC improves oxygen (autotrophy), algae DOC reduces oxygen (heterotrophy).
Benthic primary producers in tropical reef ecosystems can alter biogeochemical cycling and microbial processes in the surrounding seawater. In order to quantify these influences, we measured rates of photosynthesis, respiration, and dissolved organic carbon (DOC) exudate release by the dominant...
peerj.com
Role of elevated organic carbon levels and microbial activity in coral mortality
Effects of Coral Reef Benthic Primary Producers on Dissolved Organic Carbon and Microbial Activity
Algae releases significantly more DOC into the water than coral.
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...
journals.plos.org
Pathologies and mortality rates caused by organic carbon and nutrient stressors in three Caribbean coral species.
DOC caused coral death but not high nitrates, phosphates or ammonium.
Visualization of oxygen distribution patterns caused by coral and algae
Planar optodes were used to visualize oxygen distribution patterns associated with a coral reef associated green algae (Chaetomorpha sp.) and a hermatypic coral (Favia sp.) separately, as standalone organisms, and placed in close proximity mimicking coral-algal interactions. Oxygen patterns were...
peerj.com
Biological oxygen demand optode analysis of coral reef-associated microbial communities exposed to algal exudates
Exposure to exudates derived from turf algae stimulated higher oxygen drawdown by the coral-associated bacteria.
Algae-derived dissolved organic matter has been hypothesized to induce mortality of reef building corals. One proposed killing mechanism is a zone of hypoxia created by rapidly growing microbes. To investigate this hypothesis, biological oxygen ...
www.ncbi.nlm.nih.gov
Microbial ecology: Algae feed a shift on coral reefs
Human pressures on coral reefs are giving macroalgae a competitive advantage over reef-building corals. These algae support larger, and potentially pathogenic, microbial populations that are metabolically primed for less-efficient, yet faster, carbohydrate remineralization, perpetuating a...
www.nature.com
Coral and macroalgal exudates vary in neutral sugar composition and differentially enrich reef bacterioplankton lineages.
Increasing algal cover on tropical reefs worldwide may be maintained through feedbacks whereby algae outcompete coral by altering microbial activity. We hypothesized that algae and coral release compositionally distinct exudates that differentially alter bacterioplankton growth and community...
www.ncbi.nlm.nih.gov
Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching
Elevated ammonium delays the impairment of the coral-dinoflagellate symbiosis during labile carbon pollution
(here's an argument for maintaining heavy fish loads if you're carbon dosing)
Labile dissolved organic carbon (DOC) is a major pollutant in coastal marine environments affected by anthropogenic impacts, and may significantly con…
www.sciencedirect.com
Excess labile carbon promotes the expression of virulence factors in coral reef bacterioplankton
Coastal pollution and algal cover are increasing on many coral reefs, resulting in higher dissolved organic carbon (DOC) concentrations. High DOC concentrations strongly affect microbial activity in reef waters and select for copiotrophic, often potentially virulent microbial populations. High...
www.nature.com
Unseen players shape benthic competition on coral reefs.
Recent work has shown that hydrophilic and hydrophobic organic matter (OM) from algae disrupts the function of the coral holobiont and promotes the invasion of opportunistic pathogens, leading to coral morbidity and mortality. Here we refer to these dynamics as the (3)DAM [dissolved organic...
www.ncbi.nlm.nih.gov
Allelochemicals Produced by Brown Macroalgae of the Lobophora Genus Are Active against Coral Larvae and Associated Bacteria, Supporting Pathogenic Shifts to Vibrio Dominance.
Diverse microbial communities associate with coral tissues and mucus, providing important protective and nutritional services, but once disturbed, the microbial equilibrium may shift from a beneficial state to one that is detrimental or pathogenic. Macroalgae (e.g., seaweeds) can physically and...
www.ncbi.nlm.nih.gov
Macroalgae decrease growth and alter microbial community structure of the reef-building coral, Porites astreoides.
With the continued and unprecedented decline of coral reefs worldwide, evaluating the factors that contribute to coral demise is of critical importance. As coral cover declines, macroalgae are becoming more common on tropical reefs. Interactions between these macroalgae and corals may alter the...
www.ncbi.nlm.nih.gov
Macroalgal extracts induce bacterial assemblage shifts and sublethal tissue stress in Caribbean corals.
Benthic macroalgae can be abundant on present-day coral reefs, especially where rates of herbivory are low and/or dissolved nutrients are high. This study investigated the impact of macroalgal extracts on both coral-associated bacterial assemblages and sublethal stress response of corals. Crude...
www.ncbi.nlm.nih.gov
Biophysical and physiological processes causing oxygen loss from coral reefs.
Global microbialization of coral reefs
DDAM Proven
Analysis of 60 sites in three ocean basins suggests that overgrowth of fleshy algae on coral reefs supports higher microbial abundances dominated by copiotrophic, potentially pathogenic bacteria via the provision of dissolved inorganic carbon.
www.nature.com
Coral Reef Microorganisms in a Changing Climate, Fig 3
Coral reefs are one of the most diverse and productive ecosystems on the planet, yet they have suffered tremendous losses due to anthropogenic disturbances and are predicted to be one of the most adversely affected habitats under future climate ...
www.ncbi.nlm.nih.gov
Ecosystem Microbiology of Coral Reefs: Linking Genomic, Metabolomic, and Biogeochemical Dynamics from Animal Symbioses to Reefscape Processes
Sponge stuff:
Element cycling on tropical coral reefs.
This is Jasper de Geoij's ground breaking research on reef sponge finding some species process labile DOC 1000X faster than bacterioplankton. (The introduction is in Dutch but the content is in English.)
Sponge symbionts and the marine P cycle
Phosphorus sequestration in the form of polyphosphate by microbial symbionts in marine sponges
Differential recycling of coral and algal dissolved organic matter via the sponge loop.
Sponges treat DOC from algae differently than DOC from corals
A Vicious Circle? Altered Carbon and Nutrient Cycling May Explain the Low Resilience of Caribbean Coral Reefs
Coral reefs are economically important ecosystems that have suffered unprecedented losses of corals in the recent past. Why have Caribbean reefs in particu
academic.oup.com
Surviving in a Marine Desert The Sponge Loop Retains Resources Within Coral Reefs
Dissolved organic carbon and nitrogen are quickly processed by sponges and released back into the reef food web in hours as carbon and nitrogen rich detritus.
Natural Diet of Coral-Excavating Sponges Consists Mainly of Dissolved Organic Carbon (DOC)
Coral-excavating sponges are the most important bioeroders on Caribbean reefs and increase in abundance throughout the region. This increase is commonly attributed to a concomitant increase in food availability due to eutrophication and pollution. ...
www.ncbi.nlm.nih.gov
The Role of Marine Sponges in Carbon and Nitrogen Cycles of COral Reefs and Nearshore Environments.
Explore millions of resources from scholarly journals, books, newspapers, videos and more, on the ProQuest Platform.
search.proquest.com
Microbially mediated nutrient cycles in marine sponges
