Seasonal abundance and vertical distribution of mesopelagic calycophoran siphonophores in Monterey Bay, CA |
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Authors: | Silguero JMB; Robison BH |
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Institution: | Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106 and
1 1Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA, 95039, USA |
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Abstract: | The seasonal abundance and vertical distribution patterns ofa group of small calycophoran siphonophores (principally Chuniphyesmultidentata and Lensia conoidea) were investigated using aremotely operated vehicle (ROV) deployed in Monterey Bay, California.Abundance was assessed along 295 horizontal transects coveringa depth range of 1001000 m over a three and a half yearperiod. The vertical distribution of the study animals changedseasonally, coupled to the onset and cessation of upwellingin the bay. While numerical abundance peaked after upwelling,there was no significant difference between seasons. The siphonophoreswere more broadly distributed over the depth range sampled duringthe upwelling or Shallow Mixed Layer (SML) period, than duringthe non-upwelling or Deep Mixed Layer (DML) period. There wereno significant differences in abundance or distribution patternsbetween years except in 1993, when there were significantlymore siphonophores observed during the SML period than duringthe DML period. This may reflect effects resulting from the19921993 El Niño event. The abundance of thesesiphonophores was negatively correlated with that of Nanomiabijuga, a physonect siphonophore of similar size and feedingbehavior found in the bay. The siphonophores studied here appearfrom preliminary data to migrate vertically, possibly with twoseparately migrating groups. |
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