One of the most significant memories from my early diving excursions was the night dive on the Town Pier in Boniare. Yes, that was a long time ago. The orange cup coral in full bloom blew me away. It still does when I see it on the wrecks or Aquarius Reef Base.</p><p>But Tubastrea coccinea is an invasive species. While lionfish get all the attention and are subjected to extraction derbies and are appropriately placed on a platter, orange cup coral silently keeps on growing. </p><p>Fortunately it is much more selective than lionfish. So far it has specialized on artificial reefs, dock pilings and oil rigs. Isn&#x92;t it funny [peculiar] that two of the most visually attractive species of our waters are invasive aliens?</p><p>In the REEF coral identification book, there is a two-page spread devoted to orange cup coral. In a study by Douglas Fenner and Kenneth Banks, they note the spread of orange cup coral is quite similar to the pattern of die-off of Diadema urchins. Basically the orange cup coral larvae follow water movements, settle, release larvae, settle, and so on. This process has been progressing for about 60 years, rather than only one year for the Diadema tragedy. </p><p>Based on that thinking, they postulate it takes about 18 months from settlement to larval release for orange cup coral.</p><p>Interestingly, a study in the Red Sea of an artificial reef over 100 years old showed that structural differences between natural reefs and artificial reefs are important. For horizontal surfaces, the mix of life on both the artificial and natural reefs was similar. </p><p>Vertical structure on the artificial reef differs from horizontal on both types, as well as vertical on the natural reef for the composition of the community. The importance of this study was the time element &#x97; a shipwreck over one hundred years in age &#x97; and how the structural features play a grater role than age in determining the mix of life that builds on the artificial reef.</p><p>On the vertical surfaces, water movement, distance above the sea floor and less sedimentation than horizontal surfaces favor orange cup coral growth. Since most of our local reef structure does not have significant vertical wall structure, the artificial reefs will be the prime targets for orange cup coral colonies. Is that good or bad? See the Florida Keys National Marine Sanctuary page that lays the foundation for discussion at this link: http://floridakeys.noaa.gov/artificialreefs/effects.html</p><p>While artificial reefs contribute economically &#x97; earlier studies for the Spiegel Grove and Vandenburg have quantified the economic lift to the Florida Keys &#x97; the additional divers can contribute to more stress on the surrounding natural reefs. What a conundrum. And an interesting discussion for the sanctuary over the next couple years as the zones of activity are examined.</p><p>According to Tonya Shearer, of the Georgia Institute of Technology, expansion of this species can be quite rapid, as Tubastraea can proliferate through sexual and asexual means. The larvae settle well locally, but also have a two week span to travel on the water column to the next destination. It&#x92;s a mixed bag &#x97; comprehensive local coverage, but a slower gait to the next destination. That&#x92;s why it has taken decades to spread. But on the local scene, only two polyps are needed to reproduce, and they also send out runners to find new space for the larvae to attach.</p><p>Dr. Shearer says the potential ecological impacts include decreased biodiversity, increased mortality of native species, reduced native coral settlement and spatial dominance. There are some spaces on the Duane, for example, that are almost entirely composed of orange cup coral.</p><p>This type of coral is ahermatypic (does not build reef structure like other stony corals) and azooanththeee (does not live in conjunction with algae &#x97; it won&#x92;t &#x93;bleach&#x94;).</p><p>The recent invasion in Brazil involves two species of Tubasteraea. One species is the same as what is here, and the other is slightly larger with a different polyp structure. Both have been verified as producers of chemicals that reduce predation by fish and affect the settlement of neighboring species. This gives them an advantage in invading new space. The main point is, with chemical mechanisms like that in place, the spread will be enhanced and damaging, as Dr. Shearer documented.</p><p>Tubastraea stakes a claim and puts up an ever-expanding chemical boundary. The chemicals are called allelopathic, which means they inhibit or kill the larvae of other species that try to settle nearby. Google the Brazilian Journal of Oceanography with the term Tubastraea, and you can see this article.</p><p>The combination of no natural predators, allelopathic chemical production and small colony size required for reproduction means once it lands, it establishes itself in a localized area quite well.</p><p>But Brazil has a different take. It&#x92;s relatively new there and they don&#x92;t like it. They even have a nonprofit set up to eradicate Tubastraea. Cup Coral Derby, anyone?</p><p>The wrecks are some of my favorite dives, as is Aquarius Reef Base. Would they be in my top 10 without orange cup coral? Yes, but it wouldn&#x92;t be the same. One of the attractions on both of those sites is the orange cup coral. I guess one of the shots I need to get will be a lionfish in the middle of orange cup coral. Recently I did see them both on one dive, just not together. Perhaps I should not be seeing them at all. And, as always, the real question is, what&#x92;s next?</p><p><i>Tim Grollimund is a freelance photographer and PADI divemaster based in Key Largo. He can be reached at tim@timgimages.com or through his web site at www.timgimages.com. Tim is actively involved with the Coral Restoration Foundation and the Aquarius Foundation.</i>