Meeting Abstract
The earliest, newly settled juvenile stages are a critical phase in the life cycles of sessile marine invertebrates. Individuals must grow quickly to avoid lethal predation, yet they may be stuck in low flow boundary layers where obtaining food for rapid growth is challenging. Colonial marine invertebrates such as ascidians, cnidarians, and bryozoans, all grow via the addition of replicated small filtering units however particle capture mechanisms differ among these taxa. Ascidians with internal filters are comparatively understudied in early growth rate dynamics. Here, early growth of a highly successful invader the colonial ascidian, Botrylloides violaceus, is compared across habitats with characterized environmental variation (temperature, salinity, food availability, and flow rate). Newly settled zooids growing with little to no competition on PVC plates were measured initially every 2-7 days for over a month to estimate rate changes through early colony establishment. Growth rates, measured as surface area and zooid counts, showed increased rates over the 5 week period in 3 habitats. Zooid addition rate changes were observed to occur roughly around the 3rd day (3-5 zooids) and 10-14 days (10-15 zooids) with some exceptions. Surface area rate changes were often observed to occur roughly around 10-14 days and 22-23 days post settlement, as two separate rate increases. Variation around this pattern included additional rate changes observed among sampling intervals or a longer time interval to the first rate increase. Overall, this data may be used to consider if the most successful invaders show a growth rate advantage particularly at the earliest and most vulnerable stages in the life cycle.
