SMAYDA: NET PHYTOPLANKTON IN UPWELLING WATERS 



20 40 60 80 100 % 



Coscmodiscus 



Loudena 



00 % 



Figure 2. — The mean vertical distribution at all stations of 

 Actinoptychus undulatus, Ditylum brightwelli, Lauderia 

 annulata , Planktoniella muriformis , and P. sol, and for the com- 

 bined Ceratium and Coscinodiscus species. Abundance is given 

 as percent of the maximum mean abundance for each species 

 presented in Table 4. 



below the euphotic zone differs between species of 

 phytoplankton. 



BIOGEOGRAPHICAL COMMENTS 



Planktoniella muriformis 



Loeblich et al. (1968) described Coenobiodiscus 

 muriformis as a new genus and species from north 

 San Diego Bay, Calif., where blooms occur, and 

 where it was reported to be in every sample col- 

 lected since its first sighting in July 1966. Cul- 

 tures were also established at 23° to 25°C. This 

 unique, colonial diatom comprised up to 530 cells 

 embedded in a one-cell thick gelatinous matrix 

 which linked the cells in the girdle region. The 

 circular to subcircular colonies have concave- 

 convex shape and can be at least 500 yu m in diame- 

 ter. Round (1972) recently described a similar or- 

 ganism from the harbor at Tema in Ghana, Africa. 

 (Environmental data were not given.) It differed 

 from the San Diego population in the presence of 

 considerably fewer cells per colony and slight mi- 

 crostructural variations. Nonetheless, Round 



concluded that these taxa were similar, and trans- 

 ferred this species to the genus Planktoniella. 



This unique organism was conspicuous in the 

 present survey, both in the vertical net tows and 

 quantitative samples along the approximately 

 700-km track at temperatures ranging from about 

 11.5° to 16°C. In experiments to be described else- 

 where in greater detail (Smayda in press b), the 

 growth rate for colony increase was 2.9 and 2.0 

 "doublings" per day at ca. 15° to 18°C. These com- 

 pare with daily colony doubling rates of 1.3 to 1.6 

 for cultured populations at 23° to 25°C calculated 

 from data presented in Loeblich et al. (1968). The 

 principal value of these data is the indication that 

 active growth occurred under the upwelling condi- 

 tions. Loeblich et al. and Round disagree as to 

 whether all cells in the colony divide to produce a 

 new colony, or whether growth without new col- 

 ony formation can also occur. 



The maximum recorded abundance of 

 Planktoniella muriformis was 205 colonies/liter at 

 the surface at Station 18. It was very common in 

 the net tows. Thus, given its relative abundance at 

 this time, its noteworthy appearance, and the 

 long-term program of frequent net collections 

 (especially during this time of year) in the coastal 

 waters of southern and Baja California (including 

 this survey area), carried out by Allen and Cupp, 

 their failure to comment in any fashion on its 

 presence is puzzling. Nor is it cited in any way in 

 their periodic species lists for these waters (Cupp 

 1934; Allen 1938), or for the Gulf of California 

 (Cupp and Allen 1938; Gilbert and Allen 1943), 

 where floristic similarities are evident. Neither 

 does Round (1967) mention it in his recent report 

 on the net phytoplankton in the Gulf of California. 

 Further, only this species and Thalassiosira 

 rotula, of those found during this survey, were not 

 found in the Gulf of Panama (Smayda 1966). Thus, 

 the present observations suggest that 

 Planktoniella muriformis is presently distributed 

 in the Pacific Ocean from San Diego south to 

 Punta Abreojos. But it is uncertain whether its 

 presence and/or distribution in these coastal wa- 

 ters are relatively recent phenomena. Its apparent 

 general rarity in nature and intriguing global dis- 

 tribution (off Baja California and Ghana) are also 

 puzzling, although possibly an artifact of sam- 

 pling. (The recent discovery of another remark- 

 able colonial diatom, Thalassiosira partheneia, in 

 the upwelling waters off Cape Blanc, Africa may 

 also illustrate this latter problem (Schrader 



45 



