Dataset: Masirah Island Time Series: copepod abundance

Half-meter ring net. Collections of surface zooplankton were made daily (five days per week) at a station roughly 1.5 km east of the southwestern end of Masirah Island (20o 13’N, 58o 45’E) during intensive sampling periods (April-June of 2007 through 2011). At other times (May, late June, early August) samples were collected three times per week. Occasionally a vertical sample from bottom to surface, roughly 50-0 meters, was collected. The net was fitted with a 153um mesh net and a General Oceanics 2030R flowmeter. Boat speed was ~2 knots and each tow lasted five minutes. Local time at the time of sampling was between 8am and 10am. The sample was preserved in 5% neutral formalin. Sea surface temperature and a sample of surface phytoplankton were collected at the same time during intensive periods. Sampling was impossible at the height of the SW Monsoon (July) when breaking swell closes the mouths of all embayments on the southern side of Masirah Island.

Laboratory analysis. Subsamples were removed with a calibrated pipette; two to four percent was analyzed immediately (generally the same day as collection) using a Zeiss Stemi2000 stereomicroscope. All Calanoides cf. carinatus and Eucalanidae were removed and kept for additional measurements at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. A second subsample of four to seven percent was removed and sent to Dr. Irina Prusova at the Institute of Biology of the Southern Seas (IBSS) in Sevastapol, Russia, for full taxonomic analyses. Treatment of the samples at IBSS depended on the amount of plankton present in each sample. When the sample contained only a small amount of plankton, the entire subsample was analyzed for all species. In most cases, however, organisms smaller than ~1.5mm were identified and counted in smaller subsamples collected with a 1 or 2 ml Stempel pipette. Two replicate subsamples were withdrawn and counted and the data were averaged for calculation of abundance; generally 1 - 40 individuals per taxon were identified and sometimes more when a taxon was particularly abundant. Organisms ranging in size from ~1-2mm were counted in another part of the subsample collected with a 5ml Stempel pipette or by splitting the subsample into two or four equal parts. The entire subsample was then analyzed for abundance of organisms larger than 2mm, including copepods, euphausiids, amphipods, fish larvae, ostracods and any rare, large organisms. A total of 300 to 500 organisms per entire split were identified and counted.  The identifications were performed with the aid of Leningrad Optic-Mechanics Company (LOMO) binocular microscopes using various magnifications depending on the sizes of the individuals being identified. Copepod species are listed in alphabetical order. All copepod adult stages, copepodite stages and nauplii found in each sample are listed. The taxonomic notations are: c1 = copepodite stage I of the species; c2 = copepodite stage II of the species; c3 = copepodite stage III of the species; c4 = copepodite stage IV of the species; c5 = copepodite stage V of the species; c = undetermined copepodite stage of the species; m = adult males of the species; f = adult females of the species. Total length of the copepods is the average length in mm measured microscopically for that taxon.

 The remainder of the original sample was given to the Marine Science and Fisheries Department (College of Agriculture and Marine Science) of Sultan Qaboos University in Muscat, Oman, at the end of the intensive sampling season.