Apa mekanisme pengusiran zooxanthella dari karang ?--T-REC-komunitas reptil-semarang--KSE-komunitas satwa eksotik

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Apa mekanisme pengusiran zooxanthella dari karang ?

Pemutihan karang , yang sering terjadi di kematian massal karang dan runtuhnya ekosistem terumbu karang , telah menjadi isu penting di seluruh dunia , dengan jumlah terumbu karang menurun setiap tahunnya . Sebuah kelompok riset telah menunjukkan bahwa karang lebih aktif mencerna dan mengusir simbiotik perusak zooxanthellae dalam kondisi stres termal , dan bahwa hal ini mungkin menjadi mekanisme yang membantu karang untuk mengatasi perubahan lingkungan .....read more

What are
mechanisms of zooxanthella expulsion from coral?

Date:

December 29, 2014

Source:

Hiroshima University

Summary:

Coral bleaching, which
often results in the mass mortality of corals and in the collapse of coral reef
ecosystems, has become an important issue around the world, with the number of
coral reefs decreasing annually. A research group has demonstrated that corals
more actively digest and expel damaged symbiotic zooxanthellae under conditions
of thermal stress, and that this is likely to be a mechanism that helps corals
to cope with environmental change.

..............................

coral bleaching, which
often results in the mass mortality of corals and in the collapse of coral reef
ecosystems, has become an important issue around the world, with the number of
coral reefs decreasing annually. Associate Professor Kazuhiko Koike and Ms. Lisa
Fujise of the Graduate School of Biosphere Science at Hiroshima University and
their collaborators have proposed mechanisms that might cause coral bleaching
and damage. This research group demonstrated that corals more actively digest
and expel damaged symbiotic zooxanthellae under conditions of thermal stress,
and that this is likely to be a mechanism that helps corals to cope with
environmental change. On the other hand, if the stressful conditions prevail,
accumulation of the damaged symbiotic zooxanthellae may not maintain the
expulsion, which will gradually accumulate in coral tissues. These researchers
consider that this loss of zooxanthellae and the accumulation of damaged cells
results in coral bleaching. These results were published as an article in PLOS
ONE.

The symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium)
form the foundation of coral reef biology. The aforementioned research group
demonstrated that the expulsion of zooxanthellae at 27°C (non-thermal stress
conditions) is part of a regulatory mechanism that maintains zooxanthellal
density and a stable carbon concentration with expulsion of digested or normal
forms of symbionts. However, at 30°C (moderate thermal stress), Symbiodinium were
damaged, and corals selectively digested the damaged cells or immediately
expelled them without digestion by exocytosis, which is most likely to reflect
an adaptive mechanism in response to moderate thermal stress to avoid the
accumulation of damaged cells. However, under thermal stress, the accumulation
of damaged cells may exceed the increased rate of expulsion of digested
zooxanthella. More photosynthetically damaged zooxanthellae were observed upon
prolonged exposure to thermal stress, and were released by corals without digestion,
therefore preventing their accumulation. This response may be an adaptive
strategy to moderate stress to ensure survival, but the accumulation of damagedSymbiodinium,
which causes subsequent coral deterioration, may occur when this response
cannot cope with the magnitude or duration of environmental stress, and this
might be a possible mechanism underlying coral bleaching during prolonged
moderate thermal stress.







Story Source:

The above story is based on materials provided by Hiroshima
University. Note: Materials may be edited for content and length.







Journal Reference:

1.    Lisa Fujise, Hiroshi Yamashita, Go
Suzuki, Kengo Sasaki, Lawrence M. Liao, Kazuhiko Koike. Moderate
Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically
Damaged Zooxanthellae (Symbiodinium) from Corals. PLoS ONE, 2014;
9 (12): e114321 DOI:10.1371/journal.pone.0114321

http://www.sciencedaily.com/releases/2014/12/141229092600.htm

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