site. These 12 species account for about 95% of the invertebrate individuals 

 on Maine's mud flats, indicating that the community is homogeneous throughout 

 the characterization area (Larsen and Doggett 1978a). 



Some of the species listed for mud flats have particular requirements that 

 affect their distribution. For instance, the rock barnacle must have 

 substratum on which to attach. It is only found in association with mussels, 

 rocks, and other firm substrata. The common periwinkle also is found most 

 commonly in association with mussels or rocks. Blue mussels tend to aggregate 

 with other mussels and may form mussel reefs. 



The mean number of species per station encountered by Larsen and Doggett 

 (1978a) is 17, which ranks mud flats behind only exposed rocky shores and 

 boulder beaches in species diversity. A total of 75 species was identified on 

 mud flats. The mean number of individuals/m^ was 7345; however, at some 

 stations certain species had very high densities. As many as 24,848 

 oligochaetes, 23,652 gem clams, and 16,660 gastropods, Hydrobia sp . , were 

 found per m^ at individual station locations. 



Since intertidal mussel reefs are found usually on mud flats they are 

 considered as a subhabitat of mud flats. The number and location of mussel 

 reefs varies from year to year. Field (1923), in his study in Long Island 

 Sound, New York, found mussel reefs to be ephemeral, lasting only 2 to 3 

 years. Storm waves, floating ice, suffocation by sand and gravel deposits. 



Table 5-12. The Relative Abundance of the Invertebrate Species Commonly 

 Taken in Samples of Maine's Mudflats as Determined by Rank 

 Score Analysis^ 



Taxonomic name 



Score 



(highest possible 



score 195) 



Common name 



Oligochaeta 



Hydrobia sp. 



Macoma balthica 



Streblospio benedict i 



Nereis virens 



Corophium volutator 



Gemma gemma 



Scoloplos sp . 



Nematoda 



Heteromastus f iliformls 



My a arenaria 



Polydora sp. 



119.5 

 89.0 

 57 

 48 

 41 

 30 

 29 

 24 

 24 

 20 

 15 

 14 



Oligochaete 



gastropod 



Baltic clam 



polychaete 



polychaete 



amphipod 



gem clam 



polychaete 



Nematode 



polychaete 



soft shelled clam 



polychaete 



'Larsen and Doggett 1978^. 



5-106 



