Coral reefs acclimatized to elevated carbon dioxide concentrations at natural Co2 seeps in Papua New Guinea

The study is based on field investigations of clear-water coral reefs and seagrass communities around three cool volcanic seeps of ~99% CO2 gas, and at three adjacent control sites with similar geomorphology, seawater temperature and salinity, that fringe the D'Entrecastraux Islands, Milne Bay Province, Papua New Guinea.

Co2 has been streaming from the seabed for over 70 years (likely much longer), resulting in localised acidified conditions:

seeps (pCO2 ,500 to 900 ppm, pHTotal 7.8 – 7.9)

adjacent control areas (pCO2 ,390 ppm,pHTotal ,8.0 – 8.05)

Field surveys were conducted from 2010 to characterise seawater chemistry and ecological and physiological conditions in coral reefs control sites and seeps. See Fabricius et al. (2011) for further details.

Environmental parameters (measured: pH, dissolved inorganic carbon, total alkalinity, salinity, and temperature; calculated with CO2SYS software: pCO2 and aragonite saturation state) were obtained across a 4-year period (2010–2013) at 1–5 m depth in both control and seep sites.

A total of 433 colonies were sampled from six species of scleractinian coral: Acropora millepora, Pocillopora damicornis, Seriatopora hystrix, Poritescylindrica, massive Porites sp. and Galaxea fascicularis. Favites pentagona was the only species that occurred in moderate abundance at the extreme seep site and 10 colonies were sampled from the Upa-Upasina seep.

DNA sequencing and statistical analysis was conducted, see Noonan et al. (2013)

Samples of A. millepora, G. fasciularis, P.damicornis, and massive Porites. Analysis were analyised for skeletal porosity, bulk density and micro-density as described in the paper Prada et.al (2021), led by the team at the University of Bologna, Italy.

本研究基于巴布亚新几内亚米尔恩湾省当特尔卡斯托群岛周边三处二氧化碳占比约99%的低温火山冷泉周边的清水珊瑚礁与海草群落野外调查，同时选取了地貌、海水温度与盐度均相似的三处邻近对照位点开展对照研究。

冷泉区域的海底已持续溢出二氧化碳超70年（实际时长可能更久），由此形成局地酸化环境：
- 冷泉位点：二氧化碳分压（pCO₂）500~900 ppm，总氢离子浓度pH（pHTotal）7.8~7.9
- 邻近对照区域：二氧化碳分压（pCO₂）约390 ppm，总氢离子浓度pH（pHTotal）8.0~8.05

2010年开展野外调查，以表征珊瑚礁对照位点与冷泉位点的海水化学、生态及生理状况。详细研究细节参见Fabricius等人（2011）的研究成果。

研究在2010至2013年的4年期间，于对照与冷泉位点的1~5米水深处获取了以下环境参数：实测得到pH、溶解无机碳、总碱度、盐度与温度；借助CO₂SYS软件计算得到二氧化碳分压（pCO₂）与文石饱和状态。

研究人员共从6种石珊瑚（Scleractinian coral）类群中采集了433个珊瑚群落样本，分别为：千孔鹿角珊瑚（Acropora millepora）、指状杯形珊瑚（Pocillopora damicornis）、迷走轴孔珊瑚（Seriatopora hystrix）、圆柱多孔珊瑚（Porites cylindrica）、块状多孔珊瑚属（massive Porites sp.）与丛生盔形珊瑚（Galaxea fascicularis）。其中五边角蜂巢珊瑚（Favites pentagona）是仅在极端冷泉位点以中等丰度出现的物种，研究人员于乌帕-乌帕西纳（Upa-Upasina）冷泉位点采集了该物种的10个群落样本。

本研究开展了DNA测序与统计分析，详细方法参见Noonan等人（2013）的研究。

研究人员采集了千孔鹿角珊瑚（Acropora millepora）、丛生盔形珊瑚（Galaxea fascicularis）、指状杯形珊瑚（Pocillopora damicornis）以及块状多孔珊瑚属（massive Porites sp.）的样本。参照意大利博洛尼亚大学团队在Prada等人（2021）发表的论文中所述方法，对上述样本的骨骼孔隙率、体密度与微密度开展了分析。