Calcium carbonate production, growth, and spatial extent of Lithothamnion glaciale in a Newfoundland rhodolith bed along environmental gradients

Teed, Laura L. (2019) Calcium carbonate production, growth, and spatial extent of Lithothamnion glaciale in a Newfoundland rhodolith bed along environmental gradients. Masters thesis, Memorial University of Newfoundland.

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Abstract

Rhodolith beds are highly diverse benthic ecosystems that are distributed worldwide and contribute significantly to global carbon budgets. Discovery of rhodolith beds in Newfoundland has stimulated research on Northwest Atlantic rhodolith (Lithothamnion glaciale) CaCO₃ production and the factors that influence rhodolith beds. The present study estimated CaCO₃ production rate in a rhodolith bed off the coast of St. Philip’s, Conception Bay, Newfoundland using compared methodological approaches of extension and weight change. This study also examined bioturbator influence on rhodolith extension and CaCO₃ production rate. Applying weight change to rhodolith densities yielded gross and net CaCO₃ production rates of approximately 806 and 196 g CaCO₃ m⁻² y⁻¹, respectively. Applying extension to rhodolith biomass yielded a net CaCO₃ production rate of 163 g CaCO₃ m⁻² y⁻¹. Bioturbator presence did not impact extension or CaCO₃ production. Regarding the spatial distribution and abundance of rhodoliths, one prevalent paradigm is that rhodoliths occur in areas where water motion is strong enough to prevent burial by sediments, but not so strong as to cause fragmentation. A drop camera survey estimated rhodolith abundance in a Newfoundland bed and estimated the influence of several environmental parameters, including water motion. Rhodoliths were found to occur further south in St. Philip’s than previously reported. Rhodolith abundance was highly influenced by slope, temperature, and light where abundance increased with light, temperature and decreasing slope. Flow acceleration (water motion) did not vary with depth and remained low, challenging the long-standing paradigm that water motion is a main factor determining rhodolith bed boundaries.

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