If I recall correctly, Kaneohe's
Dictyosphaeria problem was initially implicated as nutrient-sourced, but subsequent cleanup efforts have been done. Or at least there has been some cleanup with the
point-source discharges. If there HAS been marked reductions in nutrient loadings, then algal vacuuming is viable. All those overflowing dams aren't going to help in the near term.
Many recently algal-overgrown coral reefs defy normal explanation. Take the Bahamas for instance, which is being methodically covered over by a native?
Microdictyon variety. Many of these reef sites are on remote out-islands, with small human footprints, and thus inconsequential anthropogenic nutrient exports. If the algae is thriving due to an initial-point event (i.e. post-hurricane reef trauma, temporary loss of herbivores, mass coral bleaching or disease outbreak), physical removal in large applications may be effective for long term recovery efforts.
Hard corals can't grow on, much less recruit upon, fleshy algae. Similarly, fleshy algae can't grow on healthy hard coral. Some species can however, grow
over hard coral. Those are the particular nasties, which kill hermatypics corals by shading. Overgrowing algae are susceptible to rapid growth via nutrient pulses. But if the pulse abates, the algae don't die off, but merely slow their growth down. For conditions like this, weed vacuuming can be thought a viable solution. Once the overgrowth is removed, new coral recruits are at less a disadvantage against algal recruits, and may be able to recolonize. I would *assume* that the Kaneohe researchers wouldn't have invested in their project unless they were confident that water column nutrient loading was reverting to lower levels. Otherwise, you're right Hank, all they're doing is the equivalent of "mowing the lawn".
The vacuuming can also be effective in removal of intrusive exotics, such as that Mediterranean
Caulerpa. I imagine the technology is adaptable to non-coral reef habitats, which would make it a great option removing intrusive submergent exotics from freshwater rivers and lakes.
