Calcium carbonate production in the southernmost subtropical Atlantic coral reef.

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 CaCO3 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 CaCO3 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 CaCO3 at rates of ∼126 g m-2 yr-1. 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 CaCO3 at rates of 858 g m-2 yr-1. Our results indicate that, whilst not sufficient to promote active net framework accumulation, CaCO3 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 CaCO3 production/dissolution/erosion processes in coral reefs, especially in these less understood marginal reefs.

Traditional Ecological Knowledge and the mapping of benthic marine habitats.

Traditional Ecological Knowledge (TEK) is the empirically accumulated knowledge of local communities whose livelihoods depend directly on natural resources. TEK has a considerable potential as a reliable, rapid and low cost information source. However, its use for decision making in environmental management is frequently challenged due to the lack of scientific validation and the multiple and poorly understood biases deriving from measurement and analytical errors, as well as from political, cultural and religious sources. During the planning stage of a Marine Protected Area (MPA) in Southeastern Brazil we assessed fisherfolk TEK regarding seabed features, comparing it with results from a conventional oceanographic assessment. TEK was acquired and synthesized during a survey involving 19 fishing villages and a consensus analysis that minimized variation among individual fisherfolks and communities. The oceanographic survey included high resolution benthic habitat mapping tools such as sidescan sonar and ground-truthing with SCUBA near the interfaces of benthic features identified by fisherfolk. Nearly 3000 km(2) of seafloor were mapped by local fisherfolk as "gravel", "sand", "mud" and "reef structures", while side-scan sonar surveys covered approximately 360 km with an average 400 m swath. Analyses of overlap and proximity showed that TEK is relatively cost-effective and accurate for large-scale benthic surveys, especially as a starting point for planning oceanographic surveys. Moreover, including TEK in the planning stage of MPAs may increase communities' participation and understanding of the costs and benefits of the new access and fishing effort regulations.

Mechanisms of speciation and faunal enrichment in Atlantic parrotfishes.

Relationships based on mtDNA and nDNA sequences were used to assess effects of two major geographic barriers (the >30 myo Atlantic ocean and the approximately 11 myo Amazon-Orinoco outflow) on speciation among Atlantic parrotfishes (Sparisoma and Nicholsina). Allopatric distributions of sister taxa implicate isolating actions of both barriers in all recent speciation in these fishes, with no clear indications that any speciation resulted from other mechanisms. Molecular clock estimates of the timing of lineage splits indicate that both barriers acted by limiting dispersal well after they formed, although the Amazon barrier also may have been a vicariance agent. Fluctuations in sealevel, climate, and ocean-current dynamics over the past approximately 10 my likely produced marked variation in the effectiveness of both barriers, but particularly the Amazon barrier, allowing intermittent dispersal leading to establishment and allopatric speciation. A dynamic Amazon barrier represents a major engine of West Atlantic faunal enrichment that has repeatedly facilitated bidirectional dispersal, allopatric speciation, and remixing of the Caribbean and Brazilian faunas.