Salinity and pH variations in the nearshore Arctic Ocean : implications for benthic species physiology and biodiversity
Benthic communities are formed by species-specific tolerances to environmental factors and further shaped by biological interactions that inhibit or enhance post-settlement processes. Abiotic conditions affect species differently, and one example of this in the marine world is the influence of ocean...
| Main Author: | |
|---|---|
| Other Authors: | , , , , |
| Format: | Thesis |
| Language: | English |
| Published: |
2020
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/2152/87024 https://doi.org/10.26153/tsw/13974 |
| Summary: | Benthic communities are formed by species-specific tolerances to environmental factors and further shaped by biological interactions that inhibit or enhance post-settlement processes. Abiotic conditions affect species differently, and one example of this in the marine world is the influence of ocean water carbonate chemistry on calcifying organisms. Crustose coralline algae (CCA) are dominant space occupiers, ecosystem engineers that often shape community structure are early responders to water chemistry changes, and are prevalent benthic species in the Stefansson Sound Boulder Patch. The Boulder Patch is located off the north coast of Alaska and receives large pulses of freshwater each spring from the Sagavanirktok River, reducing salinities to less than five on the benthos in certain locations. Continuous pH, temperature and salinity data (including under-ice data) revealed seasonal variability and the influence of the Sagavanirktok River runoff, which caused short (3-5 week) pulses of highly buffered pH (>8), low A[subscript T] (<1900 μmEq L⁻¹) and low salinity (<5) waters into the Boulder Patch. Through manipulative laboratory experiments we noted that low salinity waters (10) negatively affected CCA physiology and likely drive their distributions within the Boulder Patch, which range from 77% cover to completely absent on rock substrata at nearshore sites where river runoff is prevalent during break-up in spring. Samples were collected and analyzed for algal and invertebrate species and biomass when CCA were present and absent, with a specific focus on the effects on population densities of the Arctic endemic kelp, Laminaria solidungula, an important foundation species. Areas with CCA had significantly higher densities of L. solidunugla adults (4.72 m⁻¹) than the site without CCA (0.36 m⁻¹). Experiments with early life history stages of L. solidungula raised in culture showed that low salinities (10) prevented recruitment. However, during winter, when early microscopic stages are present in the Boulder Patch, salinity levels are consistently high (32). These results point to other post-recruitment processes affecting the distribution of L. solidungula. In our system, CCA outcompeted turf and fleshy algal and other invertebrate species, creating more habitable space for kelp recruitment. This competitive interaction facilitates L. solidungula recruitment and survival and highlights the importance of abiotic factors in structuring benthic marine communities. The role of CCA in facilitating recruitment of a major foundation species and its susceptibility to low salinity events is critical to our understanding of this complex benthic ecosystem Marine Science |
|---|