It does not flourish in shallow water and grows best in moderately sandy substrate. Blades are most often linear and ribbon-like, but can vary with environmental conditions such as water depth and current speed. For instance, in shallow areas with high current flow, the blades may take on a short, narrow morphology, while in less exposed, deeper waters, they may be long and wide to promote better light absorption. In contrast, R. maritima can be found in salinities ranging from 5 ppt to 40 ppt. It usually is found in sand or soft mud, and is more tolerant of fluctuating environmental conditions than Z. marina .
Blades are thin and fragile and, as a result, commonly are found in sheltered, shallow areas.
Mesohaline and polyhaline SVP, particularly Z. marina , exhibit an annual life history pattern characterized by a growing season between April and October. Increases in maximum seasonal biomass vary with latitude due to differences in temperature and photoperiod. In estuaries between New Jersey and North Carolina, the peak biomass increase occurs between May and June. After October, cooler temperatures affect Z. marina growth. It suffers respiratory losses at temperatures outside that range, and is thereby characterized by a bimodal growth pattern.