In situ decrease in rhodolith growth associated with Arctic climate change

Rhodoliths built by crustose coralline algae (CCA) are ecosystem engineers of global importance. In the Arctic photic zone, their three-dimensional growth emulates the habitat complexity of coral reefs but with a far slower growth rate, growing at micrometres per year rather than millimetres. While climate change is known to exert various impacts on the CCA’s calcite skeleton, including geochemical and structural alterations, field observations of net growth over decade-long timescales are lacking. Here, we use a temporally-explicit model to show that rising ocean temperatures over nearly 100 years were associated with reduced rhodolith growth at different depths in the Arctic. Over the past 90 years, the median growth rate was 85 µm yr-1 but each °C increase in summer seawater temperature decreased growth by a mean of 8.9 µm (95% CIs = 1.32 - 16.60 µm °C-1, p < 0.05). The decrease was expressed for rhodolith occurrences in 11 and 27 m water depth but not at 46 m, also having the sho..., , , # Data from: In situ decrease in rhodolith growth associated with Arctic climate change

[https://doi.org/10.5061/dryad.4j0zpc8m7](https://doi.org/10.5061/dryad.4j0zpc8m7)

This dataset contains all data necessary to support the findings of the study

**Methods**

**Study area**

The rhodolith samples were obtained during the MSM 55 expedition (ARCA) of *RV Maria S. Merian* from 11th to 29th June 2016 in Mosselbukta (‘shellfish bay’). The bay is 5 km long and up to 8 km wide, located at the mouth of the Wijdefjorden along the west shore of Mosselhalvøya peninsula at the northern end of Ny-Friesland, Spitsbergen Island, Svalbard archipelago (79°53’N, 15°55’E). Mosselbukta is a classical site for geo-biological research on carbonate production by benthic communities in Svalbard waters and was first surveyed in 1883, with reported rhodolith beds several square kilometres in extent. The carbonate production rates of the beds appear most pronounced at around 45 m water depth with 119.8 g (...