As we approach the beginning of the coral spawning season for many of Hawaii’s coral species, we wanted to feature the once very common and critically important habitat architect, Pocillopora meandrina, commonly known as cauliflower coral. This beautiful, small branching coral species is usually light tan to brown in color, but can sometimes have a green or purple hue. Branches are textured with bumps, called verrucae, and have a bit of a stubby end that resembles the shape of cauliflower. Tiny tentacles on each coral polyp usually emerge at night.
Cauliflower coral on a shallow reef (Image by the author).
Cauliflower coral is a member of the Pocilloporid family, and can be found in the eastern, central and Indo-Pacific ocean. Pocilloporids are known for their (need-based) long larval duration, meaning that if the larvae don’t detect suitable reef habitat, they can drift and survive in the plankton for a long time (up to several weeks). Pocilloporid corals are also known to travel (or “raft”) on drifting debris, allowing them to colonize remote reef areas. This ability to survive a long journey allowed cauliflower coral to colonize our remote Hawaiian Island chain several million years ago.
If you look closely within the textured branches of cauliflower coral, you might notice cryptic reef fish species, including these endemic Speckled scorpionfish (Sebastapistes coniorta) (Image by the author).
This once abundant species prefers shallow, wave-swept reef areas with lots of open basalt. Its affinity to open reef space allows cauliflower coral to be one of the first colonizers of newly created, volcanic reef areas (e.g., look for it offshore of the new shoreline at Kapoho on the Big Island!)
Unfortunately, we learned in 2015 that cauliflower coral is highly susceptible to heat stress and bleaching. Bleaching occurs when a coral expels its symbiotic plant cells, called zooxanthellae, during periods of extreme thermal or UV stress. Without its colorful plant cells, a coral becomes pale to bright white. Corals can survive in a bleached state for up to a couple of months, but eventually will die if water temperatures do not cool down to a normal level. In 2015, surface seawater temperatures exceeded 90° F (or 32° C) in some areas, and a massive, regional scale bleaching event occurred in West Hawaiʻi and Maui. In the months following the bleaching event, cauliflower coral lost a significant portion of its population in West Hawaiʻi (> 75% loss initially, followed by continued slow decline). Since then, cauliflower coral has been gradually recovering in depleted areas through spawning events and slow regrowth.
Remnant cauliflower coral “skeletons” became common on West Hawaiʻi reefs after the 2015 bleaching event. Spring spawning events are critical to the recovery of this species (Image by the author).
Cauliflower corals spawn or reproduce in the springtime each year. During spawning events, gametes (coral eggs and sperm) are broadcast into the water column, where they mix with gametes from neighboring colonies. Fertilized eggs become larvae over the next day or two, and larvae then search for the best available new habitat for resettlement. For cauliflower corals, peak broadcast spawning usually occurs in May. Lunar or moon cycles and resulting tides play a critical role in cueing cauliflower corals to spawn at the same time as their neighbors. Be sure to watch for cauliflower coral spawning in the early mornings after the May full (hoku) moon, just after sunrise the following day!
To view and read more about last year’s prolific coral spawning event in South Kohala check out:
https://www.wildhawaii.org/the-hawaiian-coral-spawning-season-begins/
and
https://www.youtube.com/watch?v=k-o4nKTQuXo
This year, our friends at the Kohala Center, County of Hawaiʻi and the Division of Aquatic Resources have planned a closure of Kahaluʻu Beach Park from May 5th to 12th, with the goal of giving the corals space to successfully spawn. Read more about the upcoming closure here: www.bigislandvideonews.com/2023/04/01/kahaluu-beach-to-close-for-coral-spawning-in-may/.
You may also have heard about a new draft resolution to minimize human interactions during coral spawning events for other critical areas around the state (SC 113). Please consider supporting this resolution to help minimize disturbance to larval corals in your area. More info at: https://www.capitol.hawaii.gov/session/measure_indiv.aspx?billtype=SCR&billnumber=113&year=2023
And finally, learn even more about cauliflower coral at:
www.coralsoftheworld.org/species_factsheets/species_factsheet_summary/pocillopora-meandrina/
Cauliflower coral (Pocillopora meandrina) is a favorite home for numerous reef fish species, including these endemic Hawaiian domino damselfish (Dascyllus albisella) (Image by the author).
