Scripps Institution of Oceanography, University of California San Diego, San Diego, California, United States of America.
PLoS One. 2011;6(11):e27973. doi: 10.1371/journal.pone.0027973. Epub 2011 Nov 18.
Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata--Ochrophyta; Amansia rhodantha--Rhodophyta; Halimeda opuntia--Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h⁻¹ dm⁻²), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h⁻¹) and concomitant oxygen drawdown (0.16±0.05 µmol L⁻¹ h⁻¹ dm⁻²). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial dynamics and biogeochemical parameters (i.e., DOC and oxygen availability, bacterial abundance and metabolism) in coral reef communities.
海洋生态系统中的底栖初级生产者可能会显著改变其周围环境中的生物地球化学循环和微生物过程。为了研究这些相互作用，我们研究了法属波利尼西亚莫雷阿泻湖礁中的优势底栖分类群的溶解有机质释放及其随后的微生物再矿化作用。我们评估了来自后礁生境的几种常见底栖礁生物的光合作用、呼吸作用和溶解有机碳 (DOC) 释放率。我们通过测量两天黑暗稀释培养孵育中细菌浮游生物的生长、呼吸和 DOC 消耗来评估每种底栖生产者的溶解分泌物对微生物群落的反应。实验针对六种底栖生产者进行：三种大型藻类（每种代表不同的藻类门：Turbinaria ornata——褐藻；Amansia rhodantha——红藻；Halimeda opuntia——绿藻）、混合的藻坪藻类、一种有孔虫珊瑚（Hydrolithon reinboldii）和一种优势造礁石珊瑚（Porites lobata）。我们的结果表明，所有五种藻类都会向周围环境中分泌大量的易溶解有机碳，但珊瑚不会。一般来说，光合作用速率最高的初级生产者释放的 DOC 最多，产生的细菌浮游生物生长最多；藻坪藻类单位表面积产生的 DOC 几乎是其他底栖生产者的两倍（14.0±2.8 µmol h⁻¹ dm⁻²），刺激了细菌浮游生物的快速生长（0.044±0.002 log10 细胞 h⁻¹）和相应的氧气消耗（0.16±0.05 µmol L⁻¹ h⁻¹ dm⁻²）。我们的结果表明，底栖礁藻类可以将其光合作用固定的碳的很大一部分作为 DOC 释放出来，这些释放速率因物种而异，并且这些 DOC 可被珊瑚礁相关微生物利用和消耗。这些数据提供了令人信服的证据，表明底栖初级生产者会以不同的方式影响珊瑚礁微生物动态和生物地球化学参数（即 DOC 和氧气的可用性、细菌丰度和代谢）在珊瑚礁群落中。
