Inherent tolerance of extreme seasonal variability in light and salinity in an Arctic endemic kelp (Laminaria solidungula)

Abstract

The kelp Laminaria solidungula is an important foundation species in the circumpolar Arctic. One of the largest populations of L. solidungula in the Beaufort Sea occurs in Stefansson Sound, off the north coast of Alaska. We surveyed kelp populations in the Stefansson Sound Boulder Patch and found that inshore sites in close proximity (3.5 km) to river input and increased turbidity exhibited lower sporophyte densities (0.36 ± 0.44 · m−2) than more offshore sites (>7 km) to the west (0.72 ± 0.48 · m−2) and east (4.72 ± 1.51 · m−2). We performed culture experiments to examine the possible combined effects of salinity and light on microscopic sporophyte production. Gametophytes cultured in the low salinity treatment (10) were unable to produce sporophytes regardless of light level. The highest light level tested (40 µmol photons · m−2 · s−1) produced the greatest sporophyte densities (0.037 ± 0.08 · mm−2) at a salinity of 30. Subsequent experimental work on the effect of salinity on microscopic stages revealed that haploid stages were not capable of producing sporophytes at a salinity of 10, but 3‐month‐old microscopic sporophytes were able to persist in the lower (10 and 20) salinity treatments. Although L. solidungula sporophytes have apparently acclimated to extreme salinity (<5–33) and light variations, the vulnerability of haploid microscopic stages to reduced salinity has the potential to affect future populations as the timing and magnitude of freshwater input to the Arctic Ocean changes.

High‐frequency pH time series reveals pronounced seasonality in Arctic coastal waters

“…Projections for a rapidly warming Arctic include increased river discharge (Peterson et al 2002) are likely to only exacerbate the effects of decreased salinity and total alkalinity values. In the Boulder Patch kelp community, crustose coralline algae and kelp are co‐occurring foundation species that are strongly sensitive to lower aragonite saturation levels and salinity, respectively (Muth et al 2020, 2021). The co‐dependency of both species on each other is responsible for maintenance of the most diverse benthic assemblages on the inner shelf of the Beaufort Sea (Dunton et al 1982; Bonsell and Dunton 2021).…”

“…Coastal areas of the Arctic are also undergoing rapid transformation in response to regional climatic warming. We measured pH, salinity, temperature, and total alkalinity from discrete water samples and estimate aragonite saturation levels to further understand water chemistry effects on both kelp and calcifying organisms in Stefansson Sound (see Muth et al 2020Muth et al , 2021. To our knowledge, this is the first continuous, high-frequency biennial time series of pH data from the Arctic Ocean.…”

Decreased Salinity Offsets the Stimulation of Elevated pCO2 on Photosynthesis and Synergistically Inhibits the Growth of Juvenile Sporophyte of Saccharina japonica (Laminariaceae, Phaeophyta)

“…The separate effects and the interaction of salinity or pCO 2 with the other parameters such as light intensity, temperature and nutrient availability on the growth and physiological properties of macroalgae have been extensively discussed [ 9 , 11 , 26 , 33 , 34 , 35 ]. However, the possible interaction between elevated pCO 2 and decreased salinity has been poorly investigated [ 22 , 27 ].…”

Video survey of deep benthic macroalgae and macroalgal detritus along a glacial Arctic fjord: Kongsfjorden (Spitsbergen)

“…As this species requires low light, low temperature and high salinities for the completion of its life cycle (Tom Dieck 1992;Roleda 2016;Muth et al 2021), it may possibly disappear in Kongsfjorden if seawater temperatures and freshwater input will further rise. Interestingly, in our study no Saccorhiza dermatodea was visually obvious.…”