| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | February 5, 2014 |
| Latest Amendment Date: | August 17, 2016 |
| Award Number: | 1259043 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Henrietta Edmonds
hedmonds@nsf.gov (703)292-7427 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | February 1, 2014 |
| End Date: | July 31, 2019 (Estimated) |
| Total Intended Award Amount: | $1,458,464.00 |
| Total Awarded Amount to Date: | $1,699,804.00 |
| Funds Obligated to Date: |
FY 2015 = $971,209.00 FY 2016 = $241,340.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
4202 E FOWLER AVE TAMPA FL US 33620-5800 (813)974-2897 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Estacion de Investig. Marinas Porlamar, Edo. Nueva Espar VE |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Chemical Oceanography |
| Primary Program Source: |
01001516DB NSF RESEARCH & RELATED ACTIVIT 01001617DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
This award will provide three more years of support to three U.S. institutions -- University of South Florida, University of South Carolina at Columbia, and Stony Brook University -- for the CARIACO Basin Ocean Time-Series, located in the anoxic Cariaco Basin on the Venezuelan continental margin. In continuous operation since November, 1995, the scientific goal of CARIACO is to understand the relationships between hydrography, plankton community composition, primary production, microbial activity, terrigenous inputs, particle and other fluxes, and other processes of element cycling in the water column, and how their variation is preserved in seafloor sediments. The program strives to serve the ocean carbon and biogeochemistry (OCB) and the paleoclimate research communities by maintaining an observing facility in the Cariaco Basin that provides core observations and samples, and facilitates researcher access to a unique, world-renown tropical continental margin setting.
A central tenet of CARIACO is that the data stream produced there aids in the interpretation of oceanic carbon fluxes and global climate variability. Understanding processes that affect sinking material is key to understanding the "biological carbon pump" and processes that transfer materials from the surface ocean and adjacent land to the bottom. Since the Cariaco Basin only exchanges surface waters with the adjacent Caribbean Sea above a shallow (< 140 m) sill, anoxia prevails below ~250 m. These conditions preserve an excellent varved sediment record that is used by the international community to study Holocene and late Pleistocene climate change.
The OCB community recognizes that we are approaching a "state shift" in the global biosphere due to interactions between natural climate variability and human activities. Ocean time series like CARIACO play a critical role in documenting and evaluating the mechanisms whereby marine ecosystems respond to subtle changes in climate. Indeed, the research team has documented dramatic changes in the Cariaco Basin over the past 17 years that reflect transformations over larger space and time scales. They attribute many of these ecosystem and biogeochemical changes to a northward migration of the Intertropical Convergence Zone.
Broader impacts: The CARIACO Ocean Time-Series owes its success to strong collaborations established with scientists in Venezuela, the US, and other countries. It contributes to development of a growing global observatory focused on measuring ecological processes and understanding impacts of large-scale changes in the Earth system. CARIACO is an IGBP-LOICZ program relevant to international carbon cycle and broader oceanographic research. By providing climate proxies that improve the accuracy of past climate assessments, CARIACO directly addresses the goals of the CLIVAR and PAGES initiatives of the World Climate Research Programme and the International Geosphere-Biosphere Programme. The science also helps understand socio-economic impacts of ecosystem variability, such as the collapse of the sardine fishery and catastrophic weather events seen in the last decade in the region.
CARIACO nurtures international scientific cooperation. Venezuelan funding for local scientists to participate in this joint effort is an important incentive to continue this program. CARIACO has had a significant impact on technology transfer and capacity building in Latin America, by providing regional scientists with opportunities to participate in a project that addresses issues of global relevance. CARIACO also exposes U.S. students and scientists to an international research community and to the cultures of the Caribbean and Latin America. The research team intends to continue proactive efforts to develop scientific and technical links between CARIACO, BATS, HOT, and various other OCB Program efforts.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The CARIACO Ocean Time-Series Program station program carried out 21 years of field work (November 1995-January 2017) in the Cariaco Basin in the southeastern Caribbean Sea off Venezuela. The CARIACO oceanographic station (located at 10.50°N-64.66°W) produced climate-quality data from highly productive surface waters, and from suboxic and anoxic habitats. The legacy of the program is knowledge about ocean chemistry, physics, biology, and geology, relating the ecology of the region to the settling of material to the bottom of the Cariaco Basin. Important scientific findings include:
- A longer period of coastal upwelling than previously reported, with sea surface temperatures between 23-25°C. A primary upwelling occurs between December-April. A second upwelling pulse occurs regularly in the middle of the year (June-August) over a shorter period (~5 weeks).
- In addition to seasonality, there is strong interannual variability in the upper 400 m in the Cariaco Basin. This is controlled by changes in the wind and in the intensity of the geostrophic Caribbean Current, reflecting large-scale changes in the Atlantic Basin. The seasonality and range of the mixed-layer depth varied little, from less than 10 m during the rainy season (August-October) to 35 m during the primary upwelling season (December-April).
- The length of the time-series was key to capture interannual variations, with some variability spanning over a decade. A decrease in upwelling intensity from 2003 to 2013 provided an opportunity to observe changes in the ecology of the Cariaco Basin. Changes led to an increase in zooplankton biomass and increased grazing pressure on the phytoplankton, which in turn resulted in a major shift in phytoplankton community composition and feedback loops that affected higher trophic levels, including the sardine fishery.
- A defining characteristic of the Cariaco Basin subsurface anoxia. The time series advanced our understanding of low-oxygen environments. Dissolved oxygen decreases with depth and reached values <5 μM between about 250 and 300 m. The depth of O2 disappearance and the depth of first appearance of H2S defined the boundaries of the oxic-anoxic interface. The thickness of this interface ranged 0-66 m, depending on ventilations.
- Cyclonic and anticyclonic eddies that interacted with the continental shelf can force denser, oxygenated water from the Caribbean Sea over the sill and into the Cariaco Basin, ventilating the waters bellow the oxycline (200-350 m) and stimulating biogeochemical reactions.
- CARIACO fully characterized the unique microbial community and structure of hypoxic and anoxic waters, and the processes that affect the composition and amplitude of the flux of particulate carbon to deeper waters and deposition on the ocean bottom. A novel ciliate class, Cariacotrichea, was identified based on phenotype and molecular phylogenies.
- The anaerobic decomposition of the settling organic matter particulate flux is as efficient as aerobic remineralization of organic matter. In spite of the high biological productivity in this region (320-628 g C m−2 y−1) and large vertical fluxes of particulate organic matter, only 1-3% of primary production fall to the bottom sediments at ~1310 m.
- The deepest waters of the Cariaco Basin (~1310 m) exhibited positive trends in temperature, salinity, hydrogen sulfide, ammonia, phosphate, methane, and silica. Temperature and salinity at the bottom are increasing due to the sinking of salty, warm water from the surface. Nutrients are increasing because of the continuing settling flux of organic particulates from the surface. Metabolism of organic matter is the process driving the increase of sulfide and methane; however, sulfide concentrations were highly diminished after water ventilations and after the dislodging of coastal sediments caused by earthquakes.
- CARIACO contributed to our understanding of ocean acidification. The station showed trends toward acidification (decreasing pH) comparable to those at other ocean time series around the world. The increasing trend of surface partial pressure of carbon dioxide (pCO2, +2.79 ± 0.37 μatm yr-1) was one of the highest measured. The decreasing trend in pH and increasing trend in dissolved inorganic carbon (DIC) concentration was observed from the surface to the bottom of the basin, with a higher rate of increase in deep waters.
- CARIACO advanced the development and refinement of paleoclimate proxies and helped improve the interpretation of climate signals recorded in the ocean′s sediments. Foraminiferal δ13C records from sediment cores extended the record of aquatic 13C concentrations back to the year 1700, showing changes in dissolved inorganic carbon in the marine carbon reservoir, including increases in anthropogenic CO2. Sea surface temperature in the Cariaco Basin had increased approximately 2°C since the end of the Little Ice Age. The Cariaco Basin had rapid millennial-scale changes in nitrogen cycling 35,000-55,000 years ago, synchronous with changes recorded in Greenland ice cores.
The CARIACO data are publicly available via several Internet-based servers. The legacy of CARIACO will continue as its data and results are combined with future observations to help generate new discoveries.
Last Modified: 07/03/2019
Modified by: Frank E Muller-Karger
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