There’s loads about DOC on the web, I first came across it during my algal derived insomnia, a long time ago now, here’s one;
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SUMMARY
The following collection of studies supports the idea that the microbial and macrobial community are strongly interrelated and subjected to positive feedback loops in which contribute to phase shifts from coral to algal dominance.
Microbes inhabiting coral surfaces are subjected to shifts in community composition and elevated activity in response to increased availability of algae derived DOM. This increased microbial activity, facilitated by bioavailable algae derived OM, has been identified as a key mechanism leading to coral mortality. First, Kuntz et al. (2005) and Kline et al. (2006) showed that elevated concentrations of organic compounds were more detrimental to coral health than increased availability of inorganic nutrients. Concurrently, Smith et al. (2006) conducted an empirical study which demonstrated that coral mortality was mediated by algal released dissolved compounds which induced microbe facilitated hypoxia. Supporting results have been provided by Barott et al. (2009) and a recent study by Morrow et al. (2012) who identified consistent patterns in physiology and microbial community differentiation across different types of coral-algal competitive interactions. Here turf- or macroalgae interactions with corals created a zone of hypoxia and altered pigmentation in the coral tissue. In the companion articles (Haas et al., 2010a; Haas et al., 2010b) we can provide the first direct visualization of oxygen gradients originating from corals and algae, as well as at the interfaces. The study shows 2 dimensional images of
Haas et al. (2013), PeerJ, DOI 10.7717/peerj.108 21/28
oxygen gradients over time in varying flow conditions and can thereby provide compelling evidence for the existence of hypoxic zones in coral-algae interaction processes. By using oxygen optodes as biological sensors, Gregg et al., 2013, revealed that in these processes the source of DOC, rather than the microbial community is the driving factor for microbial oxygen drawdown.
On a larger scale Dinsdale et al. (2008) described an increase of the microbial density by an order of magnitude from islands dominated by hermatypic corals and coralline algae towards islands dominated by fleshy macro- and turf algae. This study also demonstrated that on islands with high cover of fleshy macro- and turf algae the microbial community was dominated by heterotrophs, including a large percentage of potential pathogens. Adding to this, Nelson et al. (2013) showed that, in contrast to coral exudates, which facilitated high microbial diversity with few virulence factors, macroalgal exudates selected for less diverse communities heavily enriched in copiotrophic lineages, containing pathogens with increased virulence factors.
