Mapping Kelp Dynamics: Fine-Scale Insights into Saccharina latissima Distribution in the Gulf of Maine

Lexi Wilkes¹, Jarrett Byrnes¹

¹University of Massachusetts, USA

Kelp are ecosystem engineers, creating three-dimensional habitats that support species and ecosystem services worldwide. As climate change warms the oceans, multiple kelp species race to follow their ideal environments, shifting their natural ranges. Many studies have investigated how the future climate will cause kelps to shift their distributions, but these studies tend to focus on broad spatial scales with temperature as the main driver; they overlook other factors that may drive kelps now or as they change in the future.To truly understand how climate change is going to affect kelp distribution, we need to understand the ecological mechanisms dictating where kelp can and cannot survive. These mechanisms can only be investigated at fine spatial scales, as small-scale oceanography can create mismatch between large-scale data layers and what kelps actually experience. We propose to test these ideas across New England in the US. This region has historically contained dense populations of the sugar kelp, Saccharina latissima. From the US border to S. latissima’s southern range edge in Long Island, we see a 10ºC summer temperature gradient. Further, the region hosts hundreds of small islands generating differences in small-scale temperature, wave exposure, nutrient regimes, and more. Using this as our study system, we combined in situ observations, machine learning, and causal modeling to compare the abundance and distribution of kelp from two locations at Saccharina’s southern range edge and mid-range. We find that variations in environmental drivers between these locations may influence kelp abundance and distribution, highlighting the importance of fine-scale ecological factors in shaping kelp dynamics. Additionally, we identified a kelp population at S. latissima’s southern range edge, suggesting potential resilience to warming conditions, which could have important implications for understanding kelp persistence under future climate change scenarios.