period in culture tanks or calm coastal waters until they reach several centimeters in length. Some species of Porphyra can
regenerate the foliose phase directly through asexual reproduction, which suggests that the time, infrastructure, and costs associated
with conchocelis culture might be avoided by seeding nets with asexual spores. Here, we present work from a short-term
mariculture study using nets seeded with asexual spores (neutral spores) of a native Maine species of Porphyra. Porphyra
umbilicalis (L.) Kützing was selected for this proof of concept research because of its reproductive biology, abundance across
seasons in Maine, and evidence of its promise as a mariculture crop. We studied the maturation, release, and germination of the
neutral spores to develop an appropriate seeding protocol for nets, followed by development of a nursery raceway to provide an
easily manipulated environment for the seeded nets. Neutral spores were produced throughout the year on the central Maine coast;
however, there was a temporal variability in the number and survival of released neutral spores, depending upon thallus position in
the intertidal zone. Small thalli were strictly vegetative, but most thalli reproduced by neutral spores; sexual reproduction was
absent. Neutral spores germinated quickly at 10 and 15 °C, but germination was delayed at 5 °C. Unlike some algal zygotes and
spores, neutral spores of P. umbilicalis required light to germinate; however, irradiances of 25 and 100 μmol photons m−2 s−1 were
equally sufficient for germination. Rafts of seeded nets were deployed in Cobscook Bay, Maine, at two distances from salmon
aquaculture pens and at a control site on a nearby, fallow aquaculture site (no salmon). There was no difference in nitrogen content
of harvested thalli; however, both the density and the surface area of harvested thalli were different among the sites. The possible
causes of these differences are discussed in the context of potential use of P. umbilicalis in IMTA.
© 2007 Elsevier B.V. All rights reserved.