Intertidal Environment (Littoral) 



141 



(Stevenson, 1954; Stevenson and Emery, 

 1958), and in Baja California (Stewart, 1956). 

 Lowest on the marshes of Newport Bay is a 

 belt of Zostera marina, the thin flexible 

 bright-green eel grass, which is rarely ex- 

 posed even at low tide (Fig. 123). Above 

 this plant is a belt that is usually devoid of 

 attached plants and consists of bare sand or 

 mud. At Mission Bay near San Diego the 

 barren area is hundreds of meters wide 

 locally. Next, in the region of midtide, is a 

 belt thickly covered by a grass, Spartina 

 leiantha, which reaches a height of 30 to 60 

 cm but has its base nearly always under- 

 water. The next belt, which is just above 

 midtide, is dominated by a low succulent, 

 Salicornia herbacea (Fig. 124), although 

 other plants are present. Still higher, but 

 reached by most high tides, is a belt dom- 

 inated by Suaeda californica ya.T. pubescens, 

 but again containing several other plants. 

 Lastly, and reached only by the very highest 

 tides, is a belt of Distichlis spicata, a thin- 

 bladed branched grass usually less than 15 

 cm high. At greater elevations only fresh- 

 water plants are present. The salt-water 

 marsh plants contribute much organic mat- 

 ter to the marsh by growth of roots into the 

 mud as well as by burial of the leaves 

 through undermining by waves and animals 

 and through plastering by mud. Partial 

 oxidation of the organic matter leads to for- 

 mation of hydrogen sulfide and methane 

 and such Iow/jH values, particularly high 



on the marsh, that almost all the calcium 

 carbonate of shells is dissolved away. In 

 addition, the Hving plants serve to trap mud 

 carried by the water at high tide, so that 

 low natural levees are commonly built at 

 the outer margins of the marshes. Ac- 

 companying the grasses are relatively minor 

 amounts of algae, most conspicuous of 

 which are loose blanket-like areas of the 

 black Nostoc commune which occurs mostly 

 in the belts of abundant Salicornia and 

 Sueada. 



The commonest animals in the upper 

 marshes other than polychaete worms are 

 the long tapered snail Cerithidea californica 

 in the belt of Salicornia and several species 

 of clams and crabs in the barren belt. The 

 snail, lying unattached atop the mud, is 

 commonly host to many parasitic trematodes 

 (Martin, 1955) which affect the snail's 

 growth in such a way as to produce a shell 

 more tapering than for unaffected snails. 

 The clams and crabs live in burrows (Fig. 

 125) from which the latter emerge mostly 

 just at night. A wide variety of other ani- 

 mals including sponges, oysters, echinoids, 

 sea pens, isopods, and amphipods occur 

 locally on the marshes and in its channels. 

 Most of these animals are restricted to the 

 marshes and adjoining waters because of 

 the small size of waves, abundance of food, 

 and ease of burrowing, and they have be- 

 come tolerant of changing salinity, temper- 

 ature, and tide level. Indeed, it is believed 



Figure 123. Plant communities and their relationship to tide and substrate on a marsh in the upper part of Newport Bay. 



