Laboratório de Ecologia e Conservação Marinha, Instituto do Mar, Universidade Federal de São Paulo, Rua Dr. Carvalho de Mendonça 144, Santos, 110-070, Brazil.
Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão 915, Rio de Janeiro, 22460-030, Brazil.
Mar Environ Res. 2021 Dec;172:105490. doi: 10.1016/j.marenvres.2021.105490. Epub 2021 Oct 6.
Emerging evidence have been supporting the idea that the better known South Atlantic coral reefs (located between 18°S and 24°S) are now essentially senescent structures that have experienced little or no additional vertical reef growth over the past millennia. This has often coincided with a shift to a dominance of non-coral calcifying organisms becoming the main CaCO producers in these high latitude and marginal marine settings. Here, we used Calcification Accretion Units (CAUs) and census-based methods to measure non-coral rates of CaCO production on the geologically senescent reef and adjacent rhodolith beds within the southernmost subtropical Atlantic reef (i.e., Queimada Grande Reef, QGR). The reef habitat is currently producing CaCO at rates of ∼126 g m yr. In contrast, fragments of dead corals skeletons deposited adjacent to the reef over the last ∼2000 years are now colonized by crustose coralline red algae. These form a rhodolith bed that produces CaCO at rates of 858 g m yr. Our results indicate that, whilst not sufficient to promote active net framework accumulation, CaCO production by coralline algae and bryozoans on the QGR appears to be sufficient to at least limit net large-scale erosion of the underlying reef structure, allowing the reef structure to persist in a state close to budgetary stasis. Finally, our results are also of relevance for providing insights regarding the balance of CaCO production/dissolution/erosion processes in coral reefs, especially in these less understood marginal reefs.
新出现的证据支持这样一种观点，即众所周知的南大西洋珊瑚礁（位于南纬 18°至 24°之间）现在基本上已经衰老，在过去几千年中几乎没有或没有额外的垂直珊瑚礁生长。这通常与一种转变相吻合，即在这些高纬度和边缘海域，非珊瑚钙化生物成为主要的 CaCO3 生产者，从而占据主导地位。在这里，我们使用钙化堆积单元（CAU）和基于普查的方法来测量南大西洋最南端亚热带珊瑚礁（即 Queimada Grande 礁，QGR）中地质上衰老的珊瑚礁和相邻的石莼床上非珊瑚的 CaCO3 生产速率。该珊瑚礁生境目前的 CaCO3 产生速率约为 126 g m yr。相比之下，在过去约 2000 年中沉积在珊瑚礁旁边的死珊瑚骨骼碎片现在被石莼状珊瑚藻定殖。这些形成了一个石莼床，其 CaCO3 产生速率为 858 g m yr。我们的结果表明，虽然不足以促进活跃的净框架积累，但 QGR 上的珊瑚藻和苔藓虫的 CaCO3 生产似乎足以至少限制对下面珊瑚礁结构的大规模净侵蚀，从而使珊瑚礁结构保持在接近预算平衡的状态。最后，我们的结果还为了解珊瑚礁中 CaCO3 生产/溶解/侵蚀过程的平衡提供了重要依据，特别是在这些了解较少的边缘珊瑚礁中。
