FISHERY BULLETIN: VOL. 74, NO. 4 



different subareas being dissimilar in a season. In 

 particular, it was found that: 1) in the spring, 

 subareas IB and 2A were significantly different on 

 both strata, while only stratum 2 in those subareas 

 was significantly different in the summer; 2) both 

 strata in subareas IB and 3A and subareas 3A and 

 4A were significantly different throughout all 

 seasons; and 3) stratum 1 of subareas 2A and 4A 

 were significantly different only in the spring, 

 while stratum 2 in these subareas was different in 

 each season. 



The K-S procedure (« = 0.10) was used to test 

 sediment composition homogeneity both between 

 the strata of a given subarea and among the three 

 seasons for a single stratum. Over half of these 

 null hypotheses were accepted. Therefore, 

 sediment composition of the strata remained 

 largely stable throughout the three seasons and 

 apparently lacked a consistent zonation perpen- 

 dicular to the water. 



Polychaetes 



Table 2 shows that the dominant polychaete 

 species vary according to season and sediment 

 type. These species were found to be: Lumbrineris 

 bicirrata, Dorvillea japonica, Scohplos pugetten- 

 sis, Cirratidiis cirratus, and Capitella capitata. In 

 this study the dominant species is the species with 

 the largest number of individuals. 



Spatial and temporal dominance patterns may 

 be seen. In subarea 2A, the dominant organism is 

 generally D. japonica (in all seasons on stratum 2 

 and in the winter and spring on stratum 1). 

 Capitella capitata is usually the dominant species 

 in subarea 3A (S. pugettensis being dominant 

 there only in the winter on stratum 1). The in- 

 crease in this species during the summer, as 

 compared to the spring, on both strata of subarea 

 3A may have been influenced by the presence of a 

 dense algal mat of Enteromorpha sp. which 

 covered large intertidal areas. Subarea 4A has the 

 greatest fluctuation with respect to the dominant 

 species. On stratum 2 of subarea 4A, C. capitata is 

 dominant in the spring and summer, replacing L. 

 bicirrata, the winter dominant. Capitella capitata 

 is dominant only in the spring on stratum 1 of 

 subarea 4A; C. cirratus is dominant in both winter 

 and summer. Subarea IB shows the smallest 

 seasonal fluctuation of any subarea in both total 

 polychaete assemblage and dominant species. 

 Cirratuliis cirratus is dominant on both strata in 

 the spring and summer, replacing the winter 



dominants S. pugettensis (on stratum 1) and L. 

 bicirrata (on stratum 2). 



No simple seasonal pattern is discernible on the 

 strata of the various subareas (see Table 2). 

 Stratum 1 in both subareas IB and 3A shows a 

 steady increase in total number of individuals 

 between spring and summer. In the cases of 

 subarea IB (stratum 2), subarea 2A (strata 1 and 

 2), and subarea 4A (stratum 2), the largest number 

 of individuals is present in the spring. Subarea 3A 

 (stratum 2) and subarea 4A (stratum 1) have the 

 largest number of individuals in the winter, due to 

 Cirratnlus capitata and Capitella cirratus, re- 

 spectively. However, there is insuflRcient data to 

 conclude that stratum 2 is uniformly sustaining 

 the greatest total numbers of individuals season- 

 ally (perhaps due to the small horizontal distance 

 separating the strata in each subarea). 



Table 2 shows that it is possible to rank the 

 subareas, in descending order, with regard to 

 number of species present: subareas IB, 4A, 2A, 

 and 3A; as well as with respect to the total number 

 of individuals: subareas IB, 2A, 4A, and 3A. There 

 are occasional seasonal reordering of these ranks. 



Statistical analysis using the chi-square 

 procedures (a = 0.05, 33 df) confirmed the exis- 

 tence of a within season polychaete distribution 

 (for the 12 groups used in the analysis) on iden- 

 tically numbered strata, between the four sub- 

 areas in five of these six comparisons. The one 

 exception was the comparison of stratum 1, 

 between the four subareas, during the winter. In 

 that instance, a "no decision" result was reached. 



To investigate the sources of this difference in 

 distribution, the polychaete assemblage on 

 similarly numbered strata, all combinations of 

 subarea pairs and season were examined using 

 chi-square tests (a = 0.05, 11 df). Eleven of these 

 36 null hypotheses (2) resulted in a "no decision" 

 conclusion while the remaining 25 were rejected 

 using this analysis. In the case of stratum 2, the 

 null hypotheses comparing subareas IB and 2A, IB 

 and 3A, IB and 4A, 3A and 4A, and 2A and 4A were 

 rejected in all seasons. The fluctuation of this 

 biotic distribution in time (season) and space 

 (sample area) is apparent. 



The homogeneity (2) of the polychaete assem- 

 blage between the three seasons for a single 

 stratum was examined using chi-square tests 

 (a = 0.05, 22 df). Of the eight null hypotheses of 

 homogeneity (2), six were rejected (i.e., both strata 

 1 and 2 in both subareas IB and 3A, and stratum 2 

 in both subareas 2A and 4A). The two remaining 



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