Experimental studies have shown that marsh sandwort propagates readily from vegetative cuttings, using single shoots bearing adventitious roots at the base. Experimental transplantation has been successful at one site with suitable habitat, using 1 gallon containers. Twenty plants were established in 2003 at one site, of which sixteen have survived. Studies of plants at the Santa Barbara Botanic Garden have provided mixed results regarding the breeding system. Overall, flowers are weakly self-compatible, but seed set, relative to a larger number of ovules, is not enhanced by augmented pollination, suggesting the possibility of inbreeding depression. Observations of its growth at the Santa Barbara Botanic Garden and an experimental planting at a freshwater spring in San Luis Obispo County confirm its need for a constant source of fresh water. Studies of soil seed banks at one locality demonstrated a viable natural seed bank, based on observations of germinating seedlings, but seed age could not be determined (Mazer and Waddell 1994; Mazer 2000; Parikh et al. 1998).

The Santa Barbara Botanic Garden maintains a living collection of plants representing limited genetic diversity from one natural population and another presumed to be extirpated.

Based on an August 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden has collected 13 seed accessions of Arenaria paludicola from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 13 maternal plants

Historically known from 15 disjunct sites along the Pacific coast from southern to northern California and in Washington. The species' two currently known U.S. sites are in San Luis Obispo County, California, with fewer than 10 individuals. The species' habitat has been urbanized at most of the historic sites. The individuals that remain may be threatened by changes in hydrology due to well drilling and water uptake by non-native eucalyptus trees, and by shading and competition from the dense eucalyptus stands. Recently found in Mexico, where its status is little known.

Loss of wetlands and sporadic inundation of stable wetland habitats. Competition from alien invasives. Eutrophication resulting from increased nutrient levels.

Among approximately 10 historic occurrences in Washington and California, only two are known to be extant on public or protected lands. As recently as 2005, the number of individual plants at these sites was collectively estimated to be fewer than 50 plants (Anonymous 2008c). The status on private lands has not been recently ascertained, but relatively few plants have been reported (Anonymous 2008c).

Experimental studies have shown that marsh sandwort propagates readily from vegetative cuttings, using single shoots bearing adventitious roots at the base. Experimental transplantation has been successful at one site with suitable habitat, using 1 gallon containers. Twenty plants were established in 2003 at one site, of which sixteen have survived. Studies of plants at the Santa Barbara Botanic Garden have provided mixed results regarding the breeding system. Overall, flowers are weakly self-compatible, but seed set, relative to a larger number of ovules, is not enhanced by augmented pollination, suggesting the possibility of inbreeding depression. Field studies of potential suitable habitat are being conducted by the US Fish and Wildlife Service.

One natural population at Oso Flaco Lake in San Luis Obispo County occurs on lands owned by the State of California, and is managed by State Park staff. An experimental population is managed by the Morro Coast Audubon Society on a preserve at the south end of Morro Bay, in San Luis Obispo County (Anonymous 2008c). The Santa Barbara Botanic Garden maintains a living collection of plants representing limited genetic diversity from one natural population and another presumed to be extirpated.

Currently the highest priority for further research and management depends on the identification of suitable habitats where experimental recovery projects can be implemented, especially to determine limits and requirements of population stability. Genetic analyses of plants remaining in natural populations and plants held in living conservation collections.

Development of an adequate and representative conservation seed collection.