70
Historical aerial photography shows that the area was already in regeneration by
1957, when tidal channels were crossing formerly reclaimed agricultural lands
(Fig. 2.18).
The bottom 26 cm of the core were black silty clay and the upper 18 cm were
brown silty clay with burrows of polychaetes.
2.6.3.1 Paleoenvironmental Interpretation
The benthic foraminiferal content was high except for the basal 12 cm. In general,
although present, calcareous forms were very scarce in this core and foraminiferal
assemblages were almost entirely made of agglutinated forms (only E. macrescens
was dominant throughout). Three DIs were distinguished in this core (Table 2.3;
Fig.  2.19). The lowermost 12  cm (DI 3) contained very scarce tests (mean 31
tests/50g)  and species percentages were not produced. Species number was very
low (average 2 species). This deepest interval represents the agricultural reclamation period. The following 19 cm (DI 2) were characterized by moderate numbers
(mean 1317 tests/50 g) of upward-increasing foraminiferal tests. Assemblages were
highly dominated by E. macrescens (average 94%), while S. moniliformis (average
3%), and T. inflata (average 2%) appeared as secondary species. Species number
Fig. 2.17 General view of the Isla salt marsh dominated by H. portulacoides vegetation. Location
of core (yellow dot) in the Urdaibai estuary is shown (top left). Scale bar, 1 km
A. García-Artola et al.