It was located on
the edge of a large dead sponge which allowed us to distinguish and
measure it in the subsequent time series of images. Its surface area
(measured in two-dimensional top view from single still images)
increased from 2.9 cm2 in October 2009 to 11.6 cm2 in October 2010
and 74.8 cm2 in November 2011. The diameter of the sponge body
(also measured in two-dimensional top view from single still images)
increased from 1.9 to 3.8 and subsequently to 9.8 cm over the
same time period resulting in growth rates of 1 and 3 cm/year in
first and second year, respectively. Sponge growth appeared to be
seasonal: diameter increase averaged 15 ± 20.6% (mean ± SD, n ¼ 3)
over fall and winter (October to February) and 87 ± 6.3%
(mean ± SD, n ¼ 2) over spring and summer (February to October).
Note, however, that fall-winter growth was measured over 5
months, whereas spring-summer growth was measured over 7
months due to the spacing of our surveys.