5-32 



Obel'ia long-issima 



Distribution and seasonal abundance patterns of O. longissima 

 remained consistent at Now Haven harbor over the period studied. Maxi- 

 mum coverage was reported from late winter through spring with peaks in 

 February, March and April. "Die-off" of colonies at all sites with 

 increasing temperatures usually occurred after May/ June (Figure 5-10) . 

 The short-term, month-to-month variability observed was probably a 

 function of colony growth rate. During spring settlement, the number of 

 polyps in a growing colony doubles every 2-3 days, allowing for rapid 

 colonization of substrate (Grave, 1933). The colony consists of hun- 

 dreds of thousands of individuals before it becomes sexually mature. 

 The normal longevity of a colony is less than one year (Grave, 1933). 



Seasonal abundance patterns of Obelia were consistent in New 

 Haven Harbor and followed patterns similar to those observed in the 

 Woods Hole region. At Long Wharf and Harbor Station, the inner harbor 

 sites, numbers were slightly lower than at Fort Hale in the outer har- 

 bor. Grave (1933) described lower Obelia densities in areas siibject to 

 higher levels of suspended matter at Woods Hole. He postulated that the 

 reduction in growth was related to contamination of Obelia by bacterial 

 populations associated with the suspended matter. In New Haven higher 

 levels of suspended matter generally occur in the inner harbor (NAI, 

 1978) , possibly accounting for the lower Long Wharf and Harbor Station 

 densities. Degeneration of colonies at all sites when temperatures 

 increased after May /June was observed in New Haven Harbor (Figure 5-10) 

 and by Grave (1933) in Woods Hole. Subsequent new growth occurred in 

 September at Woods Hole from vegetative remains of spring populations . 

 At Niantic Bay, Obelia occurred throughout 1973 with lower densities 

 in August. Obelia settled on short-term panels at Niantic primarily in 

 June (Battelle, 1974). 



