These reports note parenthetically that susceptibility to disturbance by anchor ice apparently varies among species: at McMurdo Sound, sponges are disturbed most, whereas abundances of some other sessile epibenthic organisms (anemones, alcyonarians, actinians, stoloniferans, and ascideans) seem unaffected by the presence of anchor ice (Dayton, 1989; Gutt, 2001).
Due both to the extreme conditions of the environment in which it occurs (August--December in Antarctica) and to the apparently episodic nature of the process (Dayton et al., 1969; Dayton, 1989; Gutt, 2001), the formation of anchor ice on benthic organisms has not been directly observed in nature.
The presence or absence of visible ice growth originating on the tissue was recorded as a gross measure of propensity to form anchor ice. Differences among species were analyzed using a Kruskal-Wallis rank sum test and multiple comparison tests implemented in R, ver.
To recreate more of what would be encountered in nature, we observed the interaction of anchor ice with whole organisms in tanks containing natural substratum collected from the field.
This encouraged preferential formation of anchor ice on the uninsulated bottom of the tank, which was more rapidly cooled by conduction of heat to the cold table below.
In the tank containing sediment and organisms, anchor ice first formed on the substratum (not surprising, as the bottom surface of the tank cooled more rapidly than the interior).
Only under unusual circumstances can anchor ice accumulate on the seafloor.
Thus, even in the absence of benthic algae and animals, anchor ice can form when supercooled water is present.
First, as noted, we have no direct evidence as to whether anchor ice is deleterious or beneficial to sponges.
A second caveat is that buoyant disturbance by anchor ice depends both on the amount of ice an organism accumulates and on the ability of the organism (and the substratum to which it adheres) to remain attached to the seafloor.
Further research on how anchor ice affects organisms over longer time periods and under more natural conditions is needed to draw conclusions about the ecological impacts of our findings.