12.) Echinoderm larvae 



Echinoderm larvae were most abundant in Penobscot Bay from early May 

 to late July (Bertrand 1977) . Larvae of sea urchins and brittle stars were 

 found in almost equal abundances (Bertrand 1977). Another echinoderm larva, 

 of the holothurian Psolus fabricii was present in the bay in low numbers 

 from April to July (Bertrand 1977) . Echinoderm larvae were not a significant 

 part of the coastal zooplankton (Sherman 1968) . 



13.) Appendicularia 



Appendicularia made up over 27.4% of the zooplankton in the summer in 

 coastal waters of Maine in 1966 (Sherman 1968). However, in the summer of 

 1965 this group accounted for only 2.1% of the zooplankton population (Sherman 

 1968). In Penobscot Bay, Bertrand (1977) reports the appendicularian, 

 Fritillaria borealis as present in May and June in low numbers. He suggests 

 that appendicularians and their discarded houses may play a biologically 

 important role in the plankton ecology of the bay because phytoplankton and 

 protozoans were found embedded in what appeared to be discarded houses of 

 this group. Zooplankton grazers are thought to find the phytoplankton 

 that are concentrated on the houses and, the houses also are thought to 

 provide miniature habitats on which zooplankton may rest (Alldredge 1976) . 



14.) Sagitta elegans 



Sagitta elegans is the only species of chaetognath reported from the 

 coastal waters of Maine. In coastal waters of the Gulf of Maine, summer 

 highs were recorded during 1963 to 1966 (Sherman and Schaner 1968) . A summer 

 population maxima was also reported by Bertrand (1977) in Penobscot Bay; 

 however, small peaks were noted in the fall and spring. This seasonal 

 pattern for S^. elegans was just the reverse of the population trend found in 

 Montsweag Bay. 



S^. elegans was noted by Bigelow (1926) as one of the characteristic 

 zooplankters of the Gulf of Maine and has suggested that the Gulf of Maine 

 is probably the northernmost center of reproduction for this species. 

 Densities of this species in Penobscot Bay (Bertrand 1977) were found to be 

 higher than those recorded by Sherman and Schaner (1968) in the coastal 

 waters of the Gulf of Maine. Bertrand (1977) suggests that the topography 

 of the bay (i.e., confined), high salinity water and abundant food supply 

 are among the factors supporitng a large population in the bay. Sagitta 

 elegans prefers low temperatures, and Russell (1932) indicated that reproduc- 

 tion may not occur at temperatures >57°F (14°C). Bigelow and Sears (1939) 

 gave a temperature range of 39 to 61° F (3.6 to 16.1°C) for S^. elegans in 

 the Gulf of Maine, and 64 to 68° F (18 to 20° C) as the upper limit for 

 survival. Because S^. elegans , including immature stages, is present year 

 round in Penobscot Bay and the species has similar seasonal patterns as the 

 coastal population, Bertrand (1977) feels that there is a population of £. 

 elegans which is endemic to the bay. Possibly the lowered water temperatures 

 from Penobscot Bay east allow this species to maintain nearshore populations 

 in the summer . 



(Continued) 



4-F-6 



