|Coralline algal and coral formation at Rose|
Atoll (Photograph by Cristi Richards)
Joseph writes: What types of corals did you see at Rose Atoll that are different from those at Johnston Atoll?
That’s an excellent question! Rose and Johnston Atoll are located in distinct geographical regions and as such, they exhibit unique coral faunas. For example, the table coral Acropora cytherea and the rice coral Montipora capitata are quite common and abundant on the shallow reticulate reefs at Johnston Atoll lagoon. In contrast, corals of the genera Montastrea, Coscinaraea, and Astreopora which are absent at Johnston, are quite common around Rose Atoll. However, regardless of how far away are Rose and Johnston from each other (>1000 miles), there are a few, shared coral faunal elements, including the cauliflower coral Pocillopora mendrina, and the corrugated coral, Pavona varians.
- Dr. Bernardo Vargas-Angel
Lita writes: How come there are different species around the rose atoll island when it’s just a small remote island?
It is difficult to answer why the corals are so different at Rose compared to Tutuila, although distance (240 km from Tutuila), differences in geomorphology (Rose is a low lying atoll compared to a mountainous island), island size and shape (Rose has a land area of 21 hectares and a height of 4 meters, while Tutuila has a land area of 14,181 hectares and a maximum elevation of 653 meters) likely contribute. Many of the corals that are found around Tutuila are also found around Rose Atoll, although there are not as many coral species that inhabit Rose. Also, the relative abundance of species is very different between the areas. Tutuila likely harbors more species of coral because there is more reef area and thus more chance for different types of habitat to develop, which can provide homes for corals. Certain corals like a lot of water motion from waves, while others prefer very calm waters. Some corals like a lot of sunlight, so they live in the shallows, while others prefer deeper darker waters. Since Tutuila also has mountains, waterfalls, and streams, lots of sediment and nutrients may flow into the sea creating another habitat that is not found at Rose since the island is so short! Also, due to Rose Atoll's tiny size, wave swells originating from far away can impact almost all sides as the waves wrap around the atoll. Whereas ocean swells which approach Tutuila will likely be blocked by the shores of the island in certain areas which create more protected habitats. Likely a combination of these factors and potentially others result in the difference in coral communities between the islands.
- Jason Helyer
While Jason’s answer speaks mostly about corals, this same reasoning can be used to explain the differences in the species of fish, algae, and other invertebrates.
Motina writes: How would you compare the Rose Atoll with the other atolls you have visited? Was the Rose Atoll the best view of the underworld you have ever seen? Are there any changes of the Rose Atoll?
Every one of the atolls we visit is different from the rest. A lot of this has to do with what geographic region it is located in. Rose Atoll is pretty spectacular and is unlike many of the other places we visit due to the incredible abundance of the crustose coralline algae. It’s this algae that give the reef its vibrant pink color! The vivid pink color combined with the clear blue water and the various other colors found among the corals, fish and algae certainly make it a beautiful place and fantastic for underwater photography!
As far as changes to Rose Atoll from previous years I did not observe any noticeable differences from my visit to Rose Atoll in 2008. However, sometimes differences can be quite small and may not be realized until we take a deeper look into the data and comparing it to years past.
- Kerry Grimshaw
Soshana writes: How long have you guys been visiting the Rose Atoll Island?
We (NOAA’s Coral Reef Ecosystem Division) have been visiting Rose Atoll since 2002 during our biennial American Samoa Reef Assessment and Monitoring Program cruise. This year was our 5th trip to Rose Atoll.
- Paula Ayotte
Thank you for all of your questions and we will continue to answer them in the upcoming days!