Title: Advancing from pattern to process in Hawaii’s near-shore pelagic ecosystem
Abstract: Micronekton comprising a near-shore sound-scattering layer around the Hawaiian Islands have been shown to exhibit diel horizontal migrations, moving onshore until midnight and them moving offshore into deep waters where they remain in the day. The reasons for this daily movement pattern have remained unexamined. Moored echosounders were used to describe micronekton migration over a 5-week period. A moored acoustic Doppler current profiler (ADCP), thermistor chains, point current meters, and an autonomous vertical profiler provided a description of the physical circulation. Periodic four-frequency echosounder and ADCP surveys were used to further characterize the micronekton’s movement along with water column physics. During surveys, vertical profiles measured zooplankton abundance using the Tracor acoustic profiling system (TAPS) and integrated net tows, micronekton identity and size using an optical imaging system, and primary productivity with a fluorometer. It was found that micronekton are not simply tracers of water mass movement indicating active migration. Near-shore waters had significantly higher biomass of zooplankton during nighttime hours than offshore waters, suggesting micronekton have greater access to food resources as a result of their migration. Primary productivity was also significantly higher inshore, indicating bottom-up control of this system. These results suggest the underlying reasons behind this daily horizontal movement.
Publication Year: 2005
Publication Date: 2005-09-01
Language: en
Type: article
Indexed In: ['crossref']
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