CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

156 CALIFORNIA COOPERATIVE OCEANIC FISHERIES INVESTIGATIONSespecially for the years 1961 and 1963) ; as upwellingceases fog also decreases, and with sunnier weatherand little turbulence a thermocline often developswhich tends to preserve a temperature gradient, Alsoduring these months, flushes of warmer oceanic waterfrom offshore may flow in on the surface of the bay.The Davidson Current period of the winter monthsis clearly indicated in Figures 1A and 1B by themarked decline in surface temperatures, the closesimilarity of average monthly maximum and minimumsurface temperatures, and the nearly uniformtemperature conditions prevailing in the upper 50meters as a result of mixing.In Figure 1C the phytoplankton volumes representmonthly averages of wet settled volumes of phytoplanktonper haul, 15 meters to the surface, taken ina 2 meter net of 173 meshes/inch. Larger diatomsand dinoflagellates are retained, but not nannoplankton.Major increases in standing crop occur in springand summer. For the 13-year period 1954-1966, maximumcrops appeared most frequently in June, butin different years peaks fell in all months fromMarch through July. Chuetoceros is usually the predominantgenus in the bay in spring and earlysummer.The most notable irregularity in the general seasonaltemperature pattern shown in Figure 1A is theunusual warm peak which occurred in February1963. This unseasonal warming, one phenomenonamong many in a winter of unusual weather, appearsin the records of shore temperatures taken along muchof the temperate Pacific coast (Scripps Institution ofOceanography, 1964). February temperatures at mostshore temperature stations in California, Oregon, andWashington exceeded temperatures recorded for thatmonth in any year through 1966 since the warm years1957-1959. In Monterey Bay this warm pulse wasaccompanied by conspicuous red tides and luminescence; the phytoplankton was dominated by Peridiwium,with lesser numbers of Ceratium and Gonyuzc-Zaz (Hopkins Marine Station, 1963). Red tides extendedat least as far north as Point Montara and insouthern California were prevalent from near SanDiego to Santa Barbara (California Marine ResourcesOperations, 1963). No unusual mortality of fishesor other marine organisms was noted, in MontereyBay or elsewhere in California, but phytoplanktonvolumes obtained in Monterey Bay rose sharply inMarch.A less compicuous warm pulse during the DavidsonCurrent period occurred in February 1961 (Figure1A) , and was reflected in shore temperatures taken atmany points along the coast (Scripps Institution ofOceanography, 1962). In contrast to the situation in1963, dinoflagellates formed less than 2% of the phytoplanktonbloom accompanying and following thewarm conditions. Instead, the phytoplankton consistedof a mixed population of diatoms characteristic ofcoastal waters ; Chaetoceros and Skeletomnza predominated,accompanied by lesser numbers of Asterionella,Thalassiosira, Nitzschia, and other forms. The characterof the phytoplankton in the March bloom of 1963suggests the growth of organisms brought in fromoceanic waters offshore, while the March bloom of1961 represents growth of resident populations characteristicof Californian coastal waters.REFERENCESBolin, R. L., and D. P. Abbott. 1963. Studies on the marineclimate and phytoplankton of the central coastal area ofCalifornia, 1954-1960. Calif. Coop. Oceanic. Fish. Invest.,Rept., 9 : 23-45.Calif. Marine Resources Operations. 1963. Monthly reports :February, 14 p.; hhrch, 12 p. Calif. Dept. Fish and Game,Terminal Island. (multilithed)Hopkins Marine Station. 1963. Quarterly report of the CCOFIinvestigations, Jan. 1-Mar. 31, 4 p. Stanford University,Pacific Grove. (mimeo.)Scripps Institution of Oceanography. 1962. Data report, surfacewater temperatures at shore stations, United States westcoast and Baja California, 1961. SI0 Ref., 62-11 :141.Scripps Institution of Oceanography. 1964. Daily surface watertemperatures and salinities at shore stations, California,Oregon, and Washington coasts, 1963. Preliminary unofficialreport.