Journal of Archaeology in the Low Countries 1-1 (May 2009)Wouter van der Meer: Harvesting underwater meadows, use of eelgrass (Zostera spp.) as indicated by the Dutch archaeological record.
6 Kimswerd – desalinating eelgrass? (Fig. 3:4)

Samples from the excavation of an settled embankment along a tidal creek at Zurich (Friesland) that were examined by the author yielded a large number of waterlogged seeds from both eelgrass species as well as many eelgrass leaves (Van Haaster 2006; Waldus 2007). The samples were taken from a large rectangular pit (2x1.5x1.9 m) that had been dug into clay and was connected to a water supply system. This system consisted of small canals connected to water wells for fresh water, and a canal connected to the tidal creek for salt water or drainage. All features were contemporary and dated to the 12th-13th century AD.

The pit was filled with a compact mass of eelgrass leaves. Among the eelgrass were shells of different molluscs, seeds of local vegetation and ‘settlement noise’. Many of the mollusc shells were eroded and belonged to subterraneous species (Kuijper 2007). This probably means that the leaves were gathered on the beach.

The eelgrass seems to have been purposely stacked below groundwater level. Taking the fresh water supply system into consideration, this might indicate a desalination process. If the sea salt is not removed from the eelgrass its hygroscopic properties will cause it to attract moisture and start fermenting, producing a very strong smell and rendering the leaves unfit for a number of purposes.

Desalinated eelgrass can be used in several ways such as thatch, stuffing and isolation. The way in which the leaves at Zurich were compressed, however, would make desalination difficult. Perhaps the material was just put there for storage. Storing underwater may have been a way to keep it fresh, for example to make it a more attractive fodder, as a kind of silage. Other known agricultural uses for eelgrass are: green fertilizer, bedding for livestock and mulch (Wyllie-Echeverria & Cox 1999; Alm 2003).