Proportion of life cycle stages of Chondrus crispus and its population structure: A comparison between a marine and an estuarine environment

The spatial variation in the proportion of gametophytes to tetrasporophytes of the red alga Chondrus crispus Stackhouse was investigated in two areas, Tjarno and Idefjorden, on the Swedish west coast. Tjarno represents a marine environment and Idefjorden an estuarine, polluted environment, where C. crispus on the regional scale is close to the limits of its distribution. The life-cycle stages were identified by the use of the resorcinol method. The ratio of gametophytes to tetrasporophytes significantly differed from I : I in both areas. The proportion of gametophytes was significantly larger at Idefjorden, the population consisting of 79% gametophytes, compared to Tjarno where it was 62%. This is in contrast to theory and earlier work on red algae which suggest that the proportion of tetrasporophytes should increase in marginal populations. There were no significant differences in the proportion of gametophytes between sites within areas on a spatial scale of 0.5 to 2 km, but partitioning the variation into its components suggested large variation between replicates on a scale of 1 to 50 m. There were also significant differences between the two areas in dry mass per individual and density, the estuarine individuals being larger but fewer. Within patches with C. crispus, the standing crop was not different between the two areas but the distribution was more patchy in the estuary resulting in a much lower standing crop when sampling was done over the whole shore. Fertile individuals were rare at Idefjorden, and in both areas individuals with tetrasporangia were more common than those with carposporangia. The result suggests that differences between the areas are due to differences in survival of spores and/or juvenile stages.