sediment-water interface, indicating that N. incisa may perforate sediment at 
all levels down to its size-limited depth. 
Temporal Aspects of Burrowing 
Rate of new burrow formation is temperature-dependent. Figure 20-7 
illustrates both the numbers of new burrows formed per week and its 
reciprocal, duration of burrow occupancy, at Five temperatures spanning the 
annual thermal range. At 0°C, burrow turnover averages one new burrow built 
every two weeks. At 6°, an average of 1.5 burrows are built per week; 3-3.5 at 
12°; 3.5-4 at 18° and 6.5-7 burrows were observed per week at 24°C. 
BURROW FORMATION RATE (PER WEEK) 
K)OJ (Ji CT) -nI 00 CO O 
DURATION OF BURROW OCCUPANCY (DAYS) 
Figure 20-7. Relationship between Nephtys incisa burrow 
formation rate and burrow occupancy to temperature. 
NOTE: Mean and range observed indicated by -0- (range limits refer only to 
burrowing rate axis). N = 6 for each temperature level. 
312 
