The effect of sedimentation on spore settlement and recruitment of the endemic Arctic kelp, Laminaria solidungula

Abstract

The Arctic is experiencing rapid rates of environmental change due to ramifications of a warming climate and human development. Environmental changes can enhance the impact of abiotic stressors, such as sedimentation from enhanced river discharge, permafrost melt, coastal erosion, or construction activities on Arctic nearshore ecosystems. Diverse habitat types, such as kelp beds that populate nearshore systems, are especially vulnerable to these environmental impacts. High sedimentation rates can be detrimental to kelp abundance and distribution, possibly due to increased mortality at the spore dispersal and settlement stages. This study aimed to examine sedimentation effects on spore settlement and viability of the endemic Arctic kelp, Laminaria solidungula, through a series of lab-based experiments. We hypothesized that spore settlement, gametophyte development, and spore viability would decrease under increasing sediment loads. Reproductive L. solidungula individuals were collected from the Stefansson Sound Boulder Patch in the Alaskan Beaufort Sea and cultured until the induction of spore release. Spores were exposed to increasing sediment loads in three experimental designs simulating different sedimentation scenarios: depositing sediments on top of settled spores, settling spores on top of sediment-covered substrate, and spores and sediments suspended simultaneously before settlement. Spores were enumerated at the end of the experiment as total and germinated spores. A duplicate set of slides from these treatments was exposed to light after sediments were removed to allow for spore development into gametophytes, and gametophytes were counted after the growing period. In all three types of sediment exposure, increased sediment load led to decreased spore settlement and gametophyte development. However, increasing amounts of sediment had no significant effect on spore viability in any of the three experiments, indicating that the spores that did settle under treatment conditions were viable. These results suggest that increased sedimentation due to rapid advances of climate change and human activities will affect L. solidungula recruitment, and, thus, may affect the long-term persistence of a diverse and productive benthic habitat.