HANSON and BELL: SUBTIDAL AND INTERTIDAL MARINE FOULING 



Settlement by barnacles (Figure 4) was the most 

 rapid during late May. Barnacle density peaked in 

 June, but subsequently there was a general de- 

 crease in the density — probably due to intra- 

 specific competition for the limited growing area. 

 Barnacle settlement was most successful at the 

 -0.6-m level. There was limited settlement at the 

 — 1.2-m level and at the 0.0-m level. No barna- 

 cles successfully settled at the +0.6-m level. 



Settlement by barnacles at the —1.2-m level ap- 

 peared to be limited by heavy siltation and 

 diatomaceous growth. The absence of barnacles at 

 the -1-0. 6-m level was principally caused by the 

 extensive exposure of the organisms to sunlight. 

 Successful settlement at the -0.6-m level was the 

 result of a limited exposure to sunlight and of the 

 moderate wave action limiting the silt/diatom 

 buildup. 



Settlement by M. edulis was predominant at 

 the -0.6-m level, where maximum density was 

 l.S/cm^. Mytilus edulis were present in lower 

 densities at the 0.0-m and -1.2-m levels. The 

 same factors affecting settlement by barnacles — 

 exposure to sunlight and the silt-diatom build- 

 up — affected settlement by M. edulis. Mussels 

 were observed to attach primarily in the late 

 summer and in the fall (July-October); a few in- 

 dividuals were observed in April and May. 



Seasonal Distribution of 

 Fouling Organisms 



The seasonal distribution of the major sessile 

 fouling organisms found in the Kiket Island area 

 is presented in Figure 5. Conclusions about the 

 distribution of these organisms are based on data 

 collected during a iy2-yr study of intertidal 

 settlement and an 8-mo study of subtidal foul- 

 ing. Comparable conclusions were reached by 

 DePalma (1966) for Admiralty Inlet. 



The first diatoms to appear on the study plates 

 were those of the genus Melosira. These diatoms 

 remained dominant throughout the study period. 

 Navicula and Fragilaria, as well as a large 

 number of unidentified diatoms, also settled on the 

 plates, but were not nearly as abundant as Melo- 

 sira. Although the spores of many diatom spe- 

 cies were present all year, settlement occurred pre- 

 dominantly from early spring to midsummer. 



Four dominant forms of algae settled on the 

 study plates. Fucus distichus and Ulva lactuca 

 were dominant in the intertidal zone, while Ulo- 



FlGURE 4. — Mean density o{ Balanus glandula attached to 

 concrete substrata exposed in the intertidal zone of Kiket 

 Island (tidal level relative to mean sea level). 



Diatoms 



Algae 



B glandula 



B. cariosus 



B. crenatus 



C. dalli 



M. edulis 



— c 



€Z 



>- 

 I>- 



— <~zzME:y — 



jrr 





1972 



Figure 5. — Seasonal distribution of predominant subtidal and 

 intertidal fouling organisms. 



thrix sp., Cladophora sp., and Ulva lactuca were 

 dominant in the subtidal zone. The algae was 

 abundant seasonally — in the spring and summer 

 there was an extensive algal cover on the plates, 

 yet in the fall and winter months the abundance of 

 algae decreased substantially. Many small crusta- 

 ceans, including copepods, cladocerans, and am- 

 phipods, were observed inhabiting the diatoms 

 and algae covering the test plates. 



Although barnacles of the genus Balanus were 

 present throughout the year, their rate of settle- 

 ment varied greatly with the different seasons. As 

 a general rule, maximum settlement occurred 

 during the late spring (April-June) and in early 

 fall (mid- August-October). For example, B. glan- 

 dula settled in the intertidal zone from February 



381 



