On the jetty at Radio Island, NC, the 

 brown seaweeds Dictyota dichotoma , Padina 

 qymnospora (formerly f\_ vickersiae ) , and 

 Dictvopteri s membranacea overwinter as 

 early developmental stages (Richardson 

 1978). Of these three species, Dictyota 

 has been studied in greatest detail 

 (Richardson 1979). Dictyota is visibly 

 present from mid-April to December and 

 releases propagules continuously during 

 this growing season; in most instances, 

 these spores rapidly germinate and grow 

 into mature plants. Neither spore release 

 nor attachment are affected by temperature 

 or photoperiod. However, germination and 

 establishment are temperature dependent. 

 Spores cannot germinate in winter. 

 However, if there is an initial warm 

 period of 5-6 days, the spores germinate 

 and the resulting sporlings can survive 

 several months of winter conditions. 

 Thus, microscopic sporlings produced at 

 the end of the growing season, overwinter 

 and assure the continuation of the 

 population when warmer conditions return. 



The red alga Dasya baillouviana is 

 apparent on the jetty between February and 

 May (i.e., the opposite of the pattern 

 shown by Dictyota ) . In April or May it 

 reproduces and disappears. Like Dictyota , 

 it persists as a young developmental stage 

 during those times of year when it is not 

 evident (Richardson 1981). Each winter, a 

 single generation of plants grows, 

 reproduces, and releases spores that 

 settle but do not develop into visible 

 plants until the following growing season. 

 In Cape Cod, D. baillouviana persists 

 through winter as a sporeling but produces 

 multiple generations during its growing 

 season (Sears 1971). In the tropics, 

 D. baillouviana grows year round as a 

 visible plant (Mathieson and Dawes 1975). 



The green alga Bryopsi s pi umosa 

 exhibits a pattern somewhat similar to 

 Dasya and Dictyota . It is visibly present 

 from January until May, and persists 

 through the summer and fall as a prostrate 

 microthallus stage (Richardson 1982). 



Amsler and Searles (1980) 

 investigated the distribution of algal 

 spores in a 20 m water column 30 km off 

 the coast of North Carolina. Spores of 

 green algae were distributed throughout 

 the column and spores of bangiophycean red 



algae (the simpler red algae like 

 Porphyra ) were present at all depths but 

 concentrated in greatest abundance near 

 the bottom. Spores of brown and 

 fl orideophycean red algae (the more 

 complex red algae like Hypnea and 

 Chondria ) occurred almost exclusively near 

 the bottom. Green and bangiophycean red 

 algae tended to be more opportunistic than 

 brown and fl orideophycean red algae, 

 suggesting that this distribution of 

 spores is adaptive in that it allows for 

 wide dispersal of the opportunistic 

 species (carried with the surface curents) 

 and keeps the less opportunistic species 

 near habitats where the parents were 

 successful . 



Epiphytic Algae 



Several species of algae can use 

 other seaweeds as substrates for 

 attachment (Figure 7). A host of small 

 algae (diatoms, filamentous blue-green, 

 red, brown, and green algae) and several 

 larger macrophytes (such as Hypnea , 

 Spyridia , Enteromorpha , Chaetomorpha , and 

 Dictyota ) commonly occur as epiphytes. 

 Growing epiphytically can provide a 

 mechanism for circumventing competitive 

 exclusion when all primary substrate is 

 occupied (Hay 1981a; Hawkins and Harkin 

 1985). Epiphytes may also avoid 

 herbivorous fishes, which visit large 

 unpalatable plants less often than they do 

 smaller, more palatable ones (Hay 1985). 

 Some specialized epiphytes may obtain 

 nutrients from the host (Harlin 1973; Goff 

 1976). 



In situations where consumption by 

 fishes does not severely reduce their 

 numbers, small crustaceans that graze 

 epiphytes can occur at densities of 

 several thousand/m 2 in stands of 

 macroalgae. In some cases, grazing by 

 these small crustaceans can keep larger 

 seaweeds relatively free of fouling 

 epiphytes (Brawley and Adey 1981a, b) . 

 These highly productive epiphytes are very 

 important in maintaining the high density 

 and turnover rate of small crustaceans 

 that are such an important component of 

 the diet of fishes on rubble structures 

 (see later sections) . 



14 



