Primary production of edaphic algal communities in a Delaware salt marsh1

Gross primary production of edaphic algae was estimated for five areas in a high salinity tidal marsh near Lewcs, Delaware. Salt pan and bare bank (free of angiosperms) algal production did not vary significantly from one part of the year to another. Algal productivity in the tall Spartina alterniflora and Distichlis spicata areas was greatest from midJanuary to mid-May. In the short S. alterniflora area algal productivity did not decrease in the warmest part of the year as it did in the two other grass areas. Annual cycles of light, tcmpcrature, and salinity were measured. Gross algal production was about a third of the angiosperm net production. Since much of the algal production occurs when angiosperms are dormant, it complements the pattern of angiosperm energy fixation. Primary production in the salt marsh has three components: angiosperms, planktonic algae, and attached algae. Many investigators have examined aerial angiosperm production (e.g. Keefe 1972). Phytoplankton productivity in the major stream channels of a Georgia marsh system was measured by Ragotzkic (1959) and Pomeroy ( 1959) examined the edaphic algal productivity in the same marsh. Production of the soil algae was greatest at low tide in winter and highest at high tide in summer, but total daily production (high and low tide values combined) was not significantly different at different seasons. WC believed that edaphic algal production in a more northern salt marsh would differ from that in Georgia. In addition to affecting algal activities directly, the differcnt climatic conditions would indirectly affect the algae through their influence on the angiosperms. This study was undertaken to measure the algal primary produc1 Part of a thesis submitted for the degree of Ph.D. at the University of Dclawarc. This rcscarch was supported in part by Pittman-Robertson funds made available to the State of Delaware’s Division of Fish and Wildlife, Department of Natural Resources and Environmental Control. 2 Present address : Marine Institute, The University of Georgia, Sapelo Island 31327. tion in a Delaware salt marsh and to examine the potential relationships between the algae and some environmental factors. Materials and rmthods Algal communities associated with five areas in Canary Creek near Lewes, Delaware, wcrc studied for a year. The areas were: a tall (ca. 145 cm) Spartina alterniflora Loisel. stand along a creek, a short (ca. 25 cm) S. alterniflora stand in the higher marsh, a bare bank between the two S. alterniflora stands, a Distichlis spicata L. Greene stand, and a salt pan. Randomly selected samples of the edaphic marsh communities were taken from each area 15 times during the year, and data on illuminance, temperature, salinity (surface and interstitial water ) , surface water pH, and the height of spcrmatophytc cover were collected using standard equipment. Soil for interstitial water salinity samples was obtained by coring with plastic tubing. Water movement during transport was not significant since the average water pcrcolation rates for these saturated soils (57% water) was 0.37 ml hr-l cm-2 (SE = 0.08). Evaporation was reduced by lightly stoppering the coring tubes. Interstitial water samples were obtained by wrapping soil in LIMNOLOGY AND OCEANOGRAPHY 390 MAY 1974, V. 19(3) Marsh edaphic algal production 391