Doggett 1978a). As many as 12,000 oligochaetes/m have been found at a single 

 cobble beach station. 



The estuarine intertidal zone differs from the marine intertidal zone largely 

 in the upper reaches of estuaries where the salinity of the overlying waters 

 at high tide is much lower than that of sea water. Two examples of the effects 

 of estuarine hydrography on the distribution of intertidal benthic 

 invertebrates are given. In estuaries with high tidal volumes and low fresh- 

 water input, benthic invertebrate species live farther upestuary in the 

 intertidal subsystem than in the subtidal subsystem. This is because during 

 low tide the benthic invertebrates, which prefer waters of higher salinity, in 

 the intertidal zone would not be covered by fresh waters coming down the 

 estuary from the river (Milne 1940; and Sanders et al. 1965). In estuaries 

 that have high freshwater inputs, it is hypothesized that any intertidal 

 species may occur progressively lower in the intertidal zone as the head of 

 the estuary is approached. This is because of stratification of the water 

 column. Fresher water floats on top, so that the surface waters, those that 

 will contact the intertidal invertebrates at high tide, are less saline toward 

 the head of the estuary. 



The differences between the epifaunal and infaunal distribution of benthic 

 invertebrates in estuarine areas parallels those in the subtidal marine 

 benthos. On rocky substrata, the distance upestuary in which a species can 

 survive is limited by the salinity regime. Epifaunal animals in the upper 



Table 5-8. Invertebrate Species Common to All Estuarine Intertidal Areas 

 of Coastal Maine^ 



Order 



Taxonomic name 



Common name 



Neraatoda 



round worms 



Nemertea 

 Annelida 



Oligochaetes 

 Nereis virens 

 Eteone longa 

 Polydora sp. 



ribbon worms 



same group as earthworms 

 sand worm (polychaete) 

 polychaete worm 

 polychaete worm 



Mollusca 



Arthropoda 



Littorina littorea 

 Littorina obtusata 

 Mytilus edulis 

 Modiolus modiolus 

 My a arenaria 



Balanus balaniodes 

 Jaera sp. 



Gamma rus oceanicus 

 Carcinus maenas 



common periwinkle 

 smooth periwinkle 

 blue mussel 

 horse mussel 

 soft-shelled clam 



barnacle 



isopod (looks like sowbug) 



amphipod (scud) 



green crab 



^Larsen and Doggett 1978a, 



5-93 



10-80 



