A survey of coastal environments in the vicinity of Nain, Labrador

Authors

  • Robert Gilbert Department of Geology, Queen's University, Kingston, Ont. K7L 3N6
  • Alec Aitkin Department of Geology, McMaster University, Hamilton, Ont. L8S 4M1
  • Brian McLaughlin Department of Biology, Queen's University, Kingston, Ont. K7L 3N6

DOI:

https://doi.org/10.4138/1582

Abstract

On the coast of Labrador in sheltered locations, broad intertidal flats have developed despite isostatic rebound of about 0.3 metres per hundred years. The action of sea Ice Is a major process controlling the distribution of boulders on the surface, which in turn determines the nature of the substratum and the biota which inhabits it. The stability of the surface, the abundance of boulders and the number and diversity of plants and animals increases from a barren zone near shore to luxuriant growths of algae (especially Fucus sp.), barnacles and molluscs (dominated by Mytilus edulls) at the boulder barricade and associated tide pools near the outer edge. A number of the burrowing molluscs (especially Macoma balthica) and polychaetes (including Arenicola marina) prefer the finer, softer sediments of the inner and middle intertidal flats. The subtidal environment on exposed coasts and channels consists of a lag of gravel, cobbles and boulders. Encrusting, calcified algae cover the surfaces along with green and brown algae. In protected areas where sand and mud have accumulated, polychaetes dominate to about 15 to 20 m depth on sand, and molluscs and echinoderms are found on the finer sediments below. On exposed, moderately and steeply sloping bedrock shores above high water, a prominent barren zone occurs. Elsewhere the sand ridges and coastal sand dunes associated with beaches are thickly colonized by grasses, especially Elymus mollis. Blowouts are common behind these areas. Salt marshes occur on shores of low slope. These are small compared to marshes to the south and are made up of turf of grasses dominated by Puccinellla phryganodes which terminates on the barren surface of the intertidal flats. RÉSUMÉ En dépit d'un relèvement isostatique d'environ 0.3 mètres par siécle, de vastes zones d'estran se sont formées dans les secteurs abrités de la côte du Labrador. L'action des glaces marines constitue l’élément majeur qui y limite la distribution des blocs en surface et, ce faisant, détermine la nature du subtrat et son benthos. À portir d'une zone littorale dénudée, la stabilitié du substrat, l'abondance des blocs ainsi que le nombre et la diversity des plantes et des animaux augmentent pour enfin former les thalles riches en algues (plut spécialement Fucus sp.), anatifes et mollusques (dominés par Mytilus edulis) que L’on voit sur l'encorbellement rocheux et dans les mar mites. Nombre de mollusques fouis-seurs (surtout Macoma balthica) et d'annfilides polychètes préfèrent cependant les sédiments plus fins et plus tendres du haut et du milieu de plage. L'environnement infracotidal des points exposés et des chenaux consiste en un foods de blocs, cailloux et graviers qui sont couverts d'algues calcaires incrustantes et d'algues vertes ou brunes. Les sables et les vases se sont accumulés dans les secteurs abrités: Id, les 15 ou 20 m supérieurs sont des sables à polychètes, en contrebas desquels on trouve des sédiments plus fins où vivent mollusques et échino-dermes. La où la plate-forme rocheuse est exposée et en pente forte ou modérée, on trouve un zone dénudée import ante. Ailleurs, Elymus mollis forme d'épais herbus couvrant les crètes sableuses et les dunes côtières alliées aux plages, et derrière lesquels les décapages éoliens sont numbreux. Les plages en faible pente renferment des marals salants d'étendue molndre, cependant, que ceux plus au sud. Elles prennent la forme d'un schorre dominé par Puccinellla phrygarnodes et borné par une zone d'estran stérile. [Traduit par le journal]

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Published

1984-12-12

How to Cite

Gilbert, R., Aitkin, A., & McLaughlin, B. (1984). A survey of coastal environments in the vicinity of Nain, Labrador. Atlantic Geoscience, 20(3). https://doi.org/10.4138/1582

Issue

Vol. 20 No. 3 (1984)

Section

Articles

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