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Posted by / 02-Jul-2017 23:05

Caush dating coral 301

While dramatic changes have been observed over the most recent decades, historical, archaeological and paleontological data reveal the antiquity of human disturbances to Caribbean reefs.Fishing and land clearing activities appear to have been altering reef communities and environments for centuries to millennia: exploitation of Caribbean reef megafauna, fishes and invertebrates began centuries before the arrival of Columbus in 1492 (refs 2, 17, 18, 19, 20, 21, 22), and early intensive agricultural activities had degraded coral and mollusk communities on some reefs one to four centuries before disease and bleaching outbreaks.These results confirm the critical role of parrotfish in maintaining coral-dominated reef habitat and the urgent need for management actions to maintain and restore parrotfish populations to enable reef persistence in the Caribbean. AP=Airport Point, CA=Cayo Adriana, PD1 and PD2=replicate cores from Punta Donato. Stars indicate population centers, including Smithsonian Tropical Research Institute (STRI)’s research station.Turquoise=AP, blue=CA, pink and green=PD1 and PD2, respectively.At each site, declines in accretion rates and parrotfish abundance were initiated in the prehistorical or historical period.Statistical tests of direct cause and effect relationships using convergent cross mapping reveal that accretion rates are driven by parrotfish abundance (but not vice versa) but are not affected by total urchin abundance.The Flex Pass is the ultimate in convenience and choice because it allows you to sample the best the BSO has to offer on your schedule.

Since systematic reef monitoring began in the 1970s, researchers have documented a dramatic ‘phase shift’ on Caribbean reefs whereby habitats previously dominated by reef-building corals (in many locations, primarily branching corals from the Acropora genus) are now dominated by macroalgae and low-relief corals tolerant of lower water quality (higher turbidity and nutrient) conditions.

The debate about the relative importance of historical and local versus recent and regional or global anthropogenic causes of reef declines (and the magnitude of their interactive effects—see ref.

35) has important management consequences, as the complexity of approaches is increased with the geopolitical scale of anthropogenic drivers.

Coupled with a recently developed technique that assesses time-delayed causal relationships, convergent cross mapping (CCM), our approach allows us to (1) produce the first historical reconstruction of reef fish communities from abundant fish teeth subfossils, (2) track changes in reef accretion rates from a continuous millennial-scale record of coral-dominated reef sediment accumulation and (3) quantify the causative relationship between reef accretion rate and the abundance of major reef herbivores—parrotfish and urchins.

CCM analyses revealed that accretion rates were driven by parrotfish abundance (but not vice versa) but were not affected by total urchin abundance. A previous analysis of change in coral and molluscan subfossil assemblages spanning from approximately 1900 AD to present from pits excavated at Punta Donato revealed that this site first experienced significant declines in reef water quality at least a century ago(a) Reef matrix cores (n=4) analysed for subfossil and sediment composition and U–Th dates (n=23) obtained (in year AD) along length of cores.

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