Marsh arrowgrass – Seaside arrowgrass
	Triglochin palustre – Triglochin maritimum
	n = 1
	III.B.3.d. Halophytic Herb Wet Meadow
	Ecosystem: Tidal

Related seaside arrowgrass (Triglochin maritimum) types are well known for Alaska (Batten, et. al., 1978; Ritchie, et. al., 1978; Racine, 1978b).  Individual plant preferences along a gradient from saltpannes to upland are readily observable in the tidally influenced zone, and delineation of communities is somewhat arbitrary (cf. Vince and Snow, 1984). 

Marsh arrowgrass – seaside arrowgrass communities are uncommon.  We visited one site, in a recently formed lagoon (post-1964 earthquake) north of Nikiski.  The locale is unusual: A beach berm was breached post-quake, and a peatland was invaded by the tides, forming a lagoon.

Seaside arrowgrass, and its cogener, marsh arrowgrass (Triglochin palustre), occur in the zone between goosetongue (Plantago maritima) and slender glasswort (Salicornia maritima) below, and alkaligrass (Puccinellia spp.) above.  Communities of arrowgrasses mixing with these adjacent plants are common (e.g. the seaside arrowgrass – goosetongue of Batten, et. al. (1978) and seaside arrowgrass – alkaligrass of Racine (1978b)).  The near equal representation of both arrowgrasses is rare, usually marsh arrowgrass is a minor component.    Some Nutka alkaligrass (Puccinelia nukaensis) is present.

On the Susitna Flats, seaside arrowgrass was most abundant in Vince and Snow's (1984) 'Inner mudflat, Zones 4 and 5', which flood a minimum of 8-13 and 6-13 times per summer (average = 11 and 8), respectively. 

On the north Nikiski lagoon site, a silty mineral layer 50 cm thick, with a high organic content, overtops a deep peat layer.  The marsh arrowgrass – seaside arrowgrass community covers 35% of the silty substrate.  The site is a jurisdictional wetland.

Table 1.  Summary of plant cover.

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