Impact of North Brazil Current Rings on Local Circulation and Coral Reef Fish Recruitment to Barbados, West Indies

Early observations of the flow environment around the island of Barbados
indicated frequent occurrence of strong current reversals associated with
surface salinity fronts. Higher resolution spatial and temporal measurements of
the flow regime in 1996 and 1997 provided a comprehensive view of the local
surface circulation (0-100 m), revealing that external forcing by North Brazil
Current (NBC) rings plays a dominant role int he near-field flow variability
surrounding the island. NBC ring forcing had comparable effects on the velocity
field during both years, indicating that the ring structure was retained while
interacting with topography. In the present study, the interaction of NBC rings
with coastal flow dynamics and the biological response of the system as
measured by recruitment of coral reef fishes is examined. Our observations
show that NBC rings can remain quite coherent as they pass the Tobago-Barbados
ridge. Further, the flow direction and associated residence time in the
vicinity of the island appear to vary depending on the orientation of the rings
as they collide with the island. Concurrent biological samples revealed complex
responses to the presence of rings in that during some of the events, larval
fishes appeared to be rapidly advected away, resulting in a failure of larval
settlement, whereas under other conditions larval retention was enhanced and
was followed by a settlement pulse. Impingement by a ring did not alter the
concentration of water column chlorophyll a (Chl a), but it did influence the
depth of the Chl a maximum. Simultaneous changes were observed in the vertical
distribution of fish larvae. Larval fish encountering ring waters exhibited
reduced growth rates and longer larval periods, both potentially reducing
survival and, ultimately, recruitment success. Overall, results demonstrate
that NBC rings interfere with the island-scale flow dynamics around Barbados
and interject considerable variability in the local recruitment signal of coral
reef fishes. Contribution to the book, Interhemispheric Water Exchange in the
Atlantic Ocean Summary of prior research with descriptions of models developed
by C.B. Paris. Primarily written by C.B. Paris, although cited as third author.

Spatial Data Organization Information -
Indirect Spatial Reference: Barbados, West Indies; Lesser Antilles;
Tobago-Barbados ridge
Direct Spatial Reference: Raster Raster Object Type: Grid Cell Spatial
Reference
Information - Horizontal Coordinate System Definition - Geodetic Model: