Relatively little is known about the life cycles of ascidians in temperate seas. Here, we investigated the biological cycle of the colonial ascidian Didemnum fulgens, a dominant species in some shallow localities of the NW Mediterranean Sea. Growth rates and frequencies of fission/fusion events were calculated over a period of 13 months, and the reproductive cycle determined after 32 months of observation. For analyses of reproduction, zooids were dissected in the laboratory and classified into five reproductive categories; these data were used to calculate a maturity index. For growth analyses, underwater photographs of marked colonies were used to estimate the surface area of D. fulgens colonies, calculate monthly growth rates, and document fusion and fission events. Clear seasonal patterns in reproduction and growth were observed, with distinct periods of investment into each function. Gonad maturation started in winter and larval release occurred in early summer, just before maximal sea temperatures were reached. After reproducing, colonies shrank and aestivated during the warmer summer months. Growth occurred during the cooler months, with maximal and minimal growth rates observed in winter and summer, respectively. Fusions and fissions occurred year‐round, although fissions were more frequent in fall (coincident with high growth rates) and fusions in spring (coincident with reproduction). These results add to the mounting evidence that ascidian life cycles in temperate seas are characterized by a trade‐off between investment in reproduction and growth, triggered by seasonal temperature shifts and constrained by resource availability during summer.

Abstract:The surface of the snowpack is the bottom boundary layer for air movement, and its roughness influences aerodynamics. The presence of aeolian deposits on a snowpack decreases its albedo and is shown to decrease the roughness of the surface. During snowmelt in the Lake Limnopolar basin on Byers Peninsula of Livingston Island of the South Shetland Islands, Antarctica, wind moved coarse soil grains (1-4 mm particles) from a bare, dry and snow-free area to an adjacent snowpack. This addition of large soil particles rapidly changed the snowpack surface characteristics. Within several days, the sun-cups, initially present on the melting snow surface, had been smoothed out in areas where soil was deposited on the snow surface. The differences in the snowpack surface were assessed using digital imagery of a roughness board inserted into the snow, both parallel and perpendicular to the dominant wind direction. The random roughness was twice as variable for the clean snow compared to the snow with soil; it was 27% more and 26% less perpendicular versus parallel to the wind for the clean snow and snow with soil, respectively. Variogram analysis showed that the clean snow had up to four different scales of roughness over the 55 ð 55 cm area of analysis, with fractal dimensions varying from 1Ð33 to 1Ð83. The snow with soil did not vary substantially from 0Ð1 to 55 cm with fractal dimensions of 1Ð65 in parallel and perpendicular to the wind.