Seasonal and diel patterns in sedimentary flux of krill fecal pellets recorded by an echo sounder
Type
ArticleAuthors
Røstad, Anders
Kaartvedt, Stein

KAUST Department
Biological and Environmental Sciences and Engineering (BESE) DivisionMarine Science Program
Red Sea Research Center (RSRC)
Date
2013-10-21Online Publication Date
2013-10-21Print Publication Date
2013-11Permanent link to this record
http://hdl.handle.net/10754/554358
Metadata
Show full item recordAbstract
We used a moored upward-facing 200 kHz echo sounder to address sedimentation of fecal pellets (FPs) from dielly migrating Meganyctiphanes norvegica. The echo sounder was located on the bottom at 150 m depth in the Oslofjord, Norway, and was cabled to shore for continuous measurements during winter and spring. Records of sinking pellets were for the first time observed with an echo sounder. Seasonal patterns of sedimentation of krill FPs were strongly correlated with data from continuous measurement of fluorescence, which illustrate the development of the spring bloom. Sedimenting particles were first observed as fluorescence values started to increase at the end of February and continued to increase until the bloom suddenly culminated at the end of March. This collapse of the bloom was detected on the echo sounder as a pulse of slowly sinking acoustic targets over a 2 d period. Prior to this event, there was a strong diel pattern in sedimentation, which correlated, with some time lag, with the diel migration of krill foraging at night near the surface. Pellet average sinking speeds ranged between 423 m d−1 and 804 m d−1, with a strong relation to pellet target strength, which is an acoustic proxy for size. This novel approach shows that echo sounders may be a valuable tool in studies of vertical pellet flux and, thereby, carbon flux, providing temporal resolution and direct observation of the sedimentation process, which are not obtained from standard methods.Citation
Seasonal and diel patterns in sedimentary flux of krill fecal pellets recorded by an echo sounder 2013, 58 (6):1985 Limnology and OceanographyPublisher
WileyJournal
Limnology and OceanographyAdditional Links
http://doi.wiley.com/10.4319/lo.2013.58.6.1985ae974a485f413a2113503eed53cd6c53
10.4319/lo.2013.58.6.1985