 |
| Titel |
Geochemical signatures of benthic foraminifera shells from a heat-polluted
shallow marine environment provide field evidence for growth and
calcification under extreme warmth |
| VerfasserIn |
Danna Titelboim, Aleksey Sadekov, Ahuva Almogi-Labin, Barak Herut, Michal Kucera, Christiane Schmidt, Orit Hyams-Kaphzan, Sigal Abramovich |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144354
|
| Publikation (Nr.) |
 EGU/EGU2017-8166.pdf |
|
|
|
|
|
| Zusammenfassung |
| Shallow marine calcifiers play an important role as marine ecosystem engineers and in the
global carbon cycle. Understanding their response to warming is essential to evaluate the fate
of marine ecosystems under global change scenarios. So far, most data on thermal tolerance
of marine calcifiers have been obtained by manipulative laboratory experiments.
Such experiments provide valuable physiological data, but it remains unclear to
what degree these observations apply to natural ecosystems. A rare opportunity to
test the effect of warming acting on ecosystem-relevant scales is by investigation
of heat-polluted coastal areas. Here we study growth and calcification in benthic
foraminifera that inhabit a thermally polluted coastal area in Israel, where they are
exposed to temperature elevated by 6˚ C above the natural seasonal temperature range
and reaching up to ∼42˚ C in summer. Several species of benthic foraminifera
have been previously shown to persist throughout the year in the heat-polluted
area, allowing us to examine in natural conditions the thermal limits of growth
and calcification under extreme temperatures as they are expected to prevail in the
future.
Live specimens of two known heat tolerant species Lachlanella sp. 1 and Pararotalia
calcariformata were collected over a period of one year from two stations, representing
thermally polluted and undisturbed (control) shallow hard bottom habitats. Single-chamber
element ratios of these specimens were obtained using laser ablation and the Mg/Ca of the
last chambers (grown closest to the time of collection) were used to calculate calcification
temperatures.
Our results provide the first direct field evidence that these foraminifera species not only
persist extreme warm temperatures but continue to grow and calcify. Species-specific Mg/Ca
thermometry indicates that P. calcariformata precipitate their shells at temperatures as
high as 40˚ C and Lachlanella sp. 1 at least up to 36˚ C. Instead, both species
showed a calcification threshold above the local winter temperatures. Calcification
in P. calcariformata only occurred above 22˚ C and in Lachlanella sp. 1 above
15˚ C. Our observations from the heat-polluted area indicate that under future
warming scenarios, growth and calcification in both benthic foraminifera species
will not be inhibited during summer heat and the seasonal temperature window for
their calcification will be expanded throughout much of the year. The observed
inhibition of calcification at low temperatures indicates that the role of heat-tolerant
foraminifera in carbonate production will most likely increase in future decades. |
|
|
|
|
|
|