[Coral-List] Kakaban Island - anchialine lake wiith a low pH environmental setting

[David Blakeway]

Interesting! That is very low pH and salinity (& high temp). With those
values I think dissolved oxygen will also be very low. Yet the Halimeda is
doing great.
There are similar atolls in the Pacific, including apparently earlier and
later stages, e.g. Puka-Puka -14.82 -138.82 and Teraina 4.68 -160.38.
Kakaban looks a lot more accessible though.


On Wed, Nov 23, 2022 at 10:44 PM Tomas via Coral-List <
coral-list at coral.aoml.noaa.gov> wrote:

> Dear colleagues,
>
> For those working on ocean acidification and looking for new exciting
> natural field laboratories where to study how calcifying flora and fauna
> may cope in low pH environments under high temperature conditions,
> please have a look at the one pager in the following link:
>
>
> https://www.researchgate.net/publication/365515214_Presence_of_Alveopora_tizardi_Scleractinia_Acroporidae_as_an_epibiont_on_molluscan_shells_in_an_anchialine_lake_of_a_raised_atoll_Kakaban_Island_East_Kalimantan_Indonesia_An_opportunist_or_a_survivor
>
> Considering the wide interest in ocean acidification, as a result of
> climate change, the low pH anchialine marine lake on Kakaban Island
> offers a unique natural laboratory that has been greatly underutilized
> by both the Indonesian and international coral reef scientific community
> thus far. We decided to publish the short “Photogallery” note in Galaxea
> with the hope that it will generate new interest in this unique
> anchialine marine lake before the environmental conditions are changed
> by tourism and introduced species.
>
> Kakaban Island is located on a depositional basin stretching from the
> Mangkalihat peninsula (East Kalimantan) to the Simporna peninsula
> (Sabah, Malaysia) along the northeast coast of Borneo. The atoll is
> located on a relatively flat submarine platform that is 200 to 300 m
> deep. It is located 60 km east of the Berau River delta, in a
> delta-front setting. While the origin of Kakaban remains unresolved, it
> has been suggested that the island represents a lagoonal reef of a
> former barrier reef complex that was located on the edge of the shelf
> off the coast of East Kalimantan. As the shelf slowly subsided it
> carried the barrier reefs further offshore, and as a result of the
> subsidence the atoll was formed in a Darwinian manner. Based on
> sedimentation rate estimates from the Moluccas, and the seafloor
> bathymetry around Kakaban, it has been suggested that the formation of
> the atoll took about 1-2 million years. At some point in recent geologic
> history the slowly sinking platform under Kakaban must have curved
> upwards and consequently raising the atoll 60 m above present-day sea
> level. During the uplift, the former atoll lagoon lost all surface
> connections with the sea, thus making it anchialine. The lake (i.e., old
> lagoon) is now connected to the sea only through a network of
> underground fissures, caves and solution channels. The 11 m deep lagoon
> (about 1.5 km wide and 2.6 km long) is surrounded by a densely vegetated
> coral ridge rising to a height of 45-60 m above present-day sea level.
> Kakaban Island is roughly 2.5 km wide and 6 km long.
>
> I hope that some of you will find this unique setting exactly what you
> have been looking for and will try to establish rewarding research
> partnerships with universities and researchers in Indonesia (e.g.,
> Universitas Diponegoro - UNDIP).
>
> For those of you who are interested to learn more about Kakaban please
> have a look at:
>
>
> https://www.researchgate.net/publication/236849592_Recently_discovered_landlocked_basins_in_Indonesia_reveal_high_habitat_diversity_in_anchialine_systems
>
> and
>
>
> https://www.researchgate.net/publication/259286986_The_ecology_of_'Halimeda_Lagoon'_an_anchialine_lagoon_of_a_raised_atoll_Kakaban_Island_East_Kalimantan_Indonesia
>
> Cheers,
> Tom
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