Abstract Controlled cultivation of marine macroalgal
biomass such as Ulva species, notably Ulva lactuca, is
currently studied for production of biofuels or functional
food ingredients. In a eutrophic environment, this macrophyte
is exposed to varying types of nutrient supply,
including different and fluctuating levels of nitrogen
sources. Our understanding of the influences of this varying
condition on the uptake and growth responses of U. lactuca
is limited. In this present work, we examined the growth
response of U. lactuca exposed to different sources of
nitrogen (NH4
+; NO3
−; and the combination NH4NO3) by
using photo-scanning technology for monitoring the growth
kinetics of U. lactuca. The images revealed differential
increases of the surface area of U. lactuca disks with time
in response to different N-nutrient enrichments. The results
showed a favorable growth response to ammonium as the
nitrogen source. The NH4Cl and NaNO3 rich media
(50 μM of N) accelerated U. lactuca growth to a maximum
specific growth rate of 16.4±0.18% day−1 and 9.4±0.72%
day−1, respectively. The highest biomass production rate
obtained was 22.5±0.24 mg DW m−2·day−1. The presence
of ammonium apparently discriminated the nitrate uptake
by U. lactuca when exposed to NH4NO3. Apart from
showing the significant differential growth response of U.
lactuca to different nitrogen sources, the work exhibits the
applicability of a photo-scanning approach for acquiring
precise quantitative growth data for U. lactuca as exemplified
by assessment of the growth response to two different
N-sources.