Solitary graminoid herb growing in dense or loose tussocks with branching outside leaf sheaths (extravaginal). Almost all leaves basal. Culms several per tussock, up to 18–20 cm, moderately stout (0.6–1.2 mm broad), ascending (typically gently curving upwards from base to top), weakly trigonous with strong, pale ribs, smooth but scabrous beneath the inflorescence, distinctly papillose on and between ribs, with 2–3 prophylls (reduced basal leaves without, or with a short blade) and 3–5 leaves on the lower part of the culm, leaves increasing in length upwards on culm.

Leaves flat or folded, 4–10 cm long, shorter than culms, narrow, 1.0–1.4 mm broad, with mid vein raised on the lower surface and weakly impressed on the upper surface, margins minutely serrate for much of their length, densely papillose, bluish or greyish green.

The flower in Carex is unisexual (either male or female), without perianth, and supported by a scale (the bract of the single flower). The male flower consists of 3 stamens. The female flower consists of a gynoecium of 2 or 3 fused carpels, with a single style and 2 or 3 stigmas, and with a single seed. The gynoecium is surrounded by a perigynium, a container with a narrow apical opening through which the style and stigmas emerge. The perigynia (and nuts) are either lenticular (when two carpels/stigmas) or trigonous (when three). The inflorescences are spikes, one or more per culm. If two or more spikes, all except for the uppermost are supported by more or less leaf-like bracts. Spikes may be unisexual or bisexual, and bisexual spikes may have the female flowers at base (basigynous) or at top (acrogynous). Flowers are wind pollinated and usually cross pollinated because the male flowers reach anthesis before the female flowers (protandry). Cross pollination predominates among sedges investigated in alpine Norway (Berggren & Haugset unpubl.), either due to the protandry or to genetic incompatibility. Seeds are spread inside their perigynia.

Inflorescence a dense cluster, 0.8–1.2 × 0.3–0.5 cm, of 2–3 spikes, all bisexual with female flowers at top (acrogynous). The spikes are short, almost rounded, and if 3, the lowermost spike is often at some distance from the two upper ones. The top spike is larger than the others and may be club-shaped. All spikes have sheath-like bracts 1–3 × 0.6–1.5 mm, broadly ovate, subacute, pale to medium brown, with broad (ca. 0.3–0.4 mm), white hyaline margin, with a paler mid vein, usually not continuing into a blade. Scales similar in male and female flowers, 1.8–2.5 × 1.3–1.6 mm, broadly ovate, obtuse, pale to medium brown with a paler midvein and ca. 0.3 mm broad, white hyaline margins. Perigynia lens-shaped (lenticular, with one nearly flat and one slightly convex surface), elliptic, 1.8–2.1 mm, tapering at base into a short foot, apically obtuse (without any beak), truncate at the aperture, with distinct, reddish veins, bluish green, densely and distinctly papillose. Stigmas 2.

Fruit a lenticular nut enclosed in the perigynium.

Sexual reproduction by seeds; no vegetative reproduction. We have not observed mature fruits in Svalbard but assume, from the stage of the inflorescence at end of season and from the presence of several distinct plants in the stands, often at some distance, that it sometimes sets fruit. This is not a plant that can survive for centuries without reproduction.

Fruits (within perigynia) are dispersed by surface water (within the mires) and probably by birds.

The two Svalbard species most closely related to C. marina (in section Glareosae) are C. glareosa and C. lachenalii. For differences from C. glareosa, see that species. Carex marina differs from C. lachenalii in nearly globular (or club-shaped) pale spikes and in perigynia without beak. Carex lachenalii has oblong brown spikes and perigynia with a distinct (0.2–0.4 mm) beak.

Shallow mires on plains or very gentle slopes, with percolating water from melting permafrost during the entire growth season. Always (in Svalbard) on substrates with a more or less basic soil reaction (pH), and usually associated with one or more other demanding mire plants with restricted distributions, e.g., Carex parallela, C. saxatilis, C. simpliciuscula, Juncus albescens, J. leucochlamys.

Thermophilous. Restricted to Spitsbergen, to the middle arctic tundra zone and the weakly continental section, and to a very few sites in two valleys: Sassendalen (Sabine Land, one stand in Nordenskiöld Land) and Gipsdalen (Bünsow Land) by the innermost parts of Isfjorden. The species has been rumoured to occur also in a few other places but voucher documentation is absent (and mistaken identities probable).

Carex marina s. lat. is circumpolar, in the European sector only found in the arctic zones but elsewhere also in the northern boreal zone. Two subspecies are recognized and discussed (especially by Böcher in Halliday & Chater 1969). Our ssp. pseudolagopina is restricted to Svalbard and to Greenland where it is the predominant race. All other arctic regions are occupied by the other race, ssp. marina, from European Russia throughout Asia and North America to a very small area in W Greenland (inside the range there of ssp. pseudolagopina).

Several authors have accepted the two subspecies of Carex marina (e.g., Böcher in Halliday & Chater 1969; Böcher et al. 1978; Chater 1980). The case is extensively discussed by Halliday & Chater but mainly in relation to another relative, C. heleonastes (not present in Svalbard). Egorova (1999) cited the differences as (2)3(4) spikes in ssp. pseudolagopina, vs. 2(3) in ssp. marina, and more distinct foot (stipe) and narrower leaves in ssp. pseudolagopina.Toivonen (2002) commented on the variation but did not accept two taxa. We accept them here for Svalbards flora and enter the Svalbard plant as ssp. pseudolagopina, but the differences between the two races are rather obscure.

The range in Svalbard is very restricted and difficult to interpret. If the species had occurred in only one valley, it could be due to one successful long distance dispersal event by birds, followed by expansion within the valley system. However, it is found in two valley systems, separated by a fjord and by glaciers, and retraction from a previously larger range may be the more likely theory. The two valleys are among the most favourable places for mire plants in Svalbard in terms of (relatively) high temperatures, basic substrates, well-developed mires, and somewhat stable soil conditions, being plausible growth sites for relict populations of formerly more widespread species adapted to a less harsh environment. Today, the recruitment by seeds is missing or inefficient, and the occurrence of several, well separated stands in both valleys, combined with no means of vegetative reproduction, vouches for a more efficient seed-set in earlier times.

Böcher, T.W., Fredskild, B., Holmen, K. & Jakobsen, K. 1978. Grønlands flora. Ed. 3. – P. Haase & Søns Forlag, København.

Chater, A.O. 1980. Carex L. – In: Tutin, T.G. et al. (eds.), Flora Europaea. 5. Alismataceae to Orchidaceae (Monocotyledones): 290–323.

Egorova, T.V. 1999. The sedges (Carex L.) of Russia and adjacent states. – St.-Petersburg State Chemical–Pharmaceutical Academy, St.-Petersburg, and Missouri Bot. Gard. Press, St. Louis.

Halliday, G. & Chater, A.O. 1969. Carex marina Dewey, an earlier name for C. amblyorhyncha Krecz. – Feddes Repertorium 80: 103–106.

Toivonen, H. 2002. Carex Linnaeus sect. Glareosae G. Don. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 23. Magnoliophyta: Commelinidae (in part): Cyperaceae: 311–321.